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Reliable optoelectronic switchable device implementation by CdS nanowires conjugated bent-core liquid crystal matrix
Abstract
Enhancing the performance of high luminescent and dielectrically capable cadmium sulfide nanowire (CdS NW) is of great importance, because of their promising ability in analyzing the dimensionality and size. The tuned physical characteristics of semiconductor CdS NWs allowed the manipulation of both electronic and optoelectronic devices at the nanoscale by dispersing a new bent core (BC) liquid crystal (LC) compound. This was derived from a 4-chlororesorcinol central core unit with two terephthalate based rod-like units carrying chiral (S)-3, 7-dimethyloctyloxy (namely ‘CPDB’) terminal chains, which have been synthesized in a pure solvo-chemical process. The mesomorphic properties of the newly-prepared bent-core LC, exhibiting an enantiotropy ‘Sm A’ phase as a result of dispersing 0.005% of CdS NWs, were investigated by several spectroscopic investigations. In addition, the hydrothermal fabrication of CdS NWs with a high-yield was modified with a cationic agent, cetyltrimethyl ammonium bromide (CTAB), which was utilized as a compatibilizer for providing a better interaction with LC molecules and giving a homogeneous solution. This work focused on the experimental investigation and optimization, using a combinational view of bent-core liquid crystal (CPDB) compound dispersion which was achieved in a controllable manner. The product of the resulting composite matrix has a very outstanding and promising behavior, e.g. semiconductor nanostructures emission polarization that can be manipulated using an external bias modulation of the novel switchable device, which was found quite convincing in the recent trends of brand-new technologies. In particular, the electro-optic responses by POM of various mesophases were investigated from the view point of the CdS incorporated bent-core LC matrix formation and transitional phase variants of ‘ON’ and ‘OFF’ states, which were depending on the geometrical parameters of CdS NW’s. Finally, the future challenges and prospects of any other nanomaterials dispersed into CPDB compound which will give rise to an increase of the mesomorphic range by preserving the mesophase type were explored in detail.
... In the nematic phase, molecules of liquid crystal are oriented on average along a common direction, called the director, and their alignment is easily distorted by external electric or magnetic fields due to the weak orientational elasticity. A linear and rigid part of molecule made of several conjugated multiple bonds and aromatic rings ensures the thermal stability of this phase [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Polar, rod-like LC materials have attracted considerable attention as a promising candidate material for next generations of displays as they exhibit new types of nematic phases. ...
... where b is an exponent characteristic of the material, Dn 0 is the birefringence at 0 K, and T C is the N-I transition temperature. The best fit of Equation (1) to experimental data in Fig. 10a was obtained for b = 0.14, close to the value obtained for 5CB [42], and Dn 0 = 0.24. The present results show an enhanced polarization under an electrical field for the short chain 7OBAF molecule that we ascribed to the presence ferroelectric clusters. ...
... In 2020, Asiya et al. dispersed CdS nanowires (NWs) into bent-core LC compounds. CdS is an exceptional material for various electro-optical properties [162]. CdS NWs have various properties such as high melting point, high electronic absorption and well-defined crystal structure. ...
... Along with that, the Structure 43. Redrawn from Ref [162]. Table 12. ...
Bent-core liquid crystals (BLCs) are a class of thermotropic LCs that exhibit chiral and polar superstructures in achiral molecules. Progress in design and synthesis of novel bent-core architectures in search of unconventional properties enriched the field of BLCs. Here, we present a comprehensive review of the recent bent-shaped LCs, discuss relevant simulation and theoretical models, which draws a comparison to experimental results, survey the advances in the molecular design and structure-property correlation, and predict the future directions from chemical and physical perspectives. This review article is dedicated in commemoration of Prof. B K Sadashiva, a pioneer chemist who made a notable contribution to the field of bent-core liquid crystals.
... One of the promising heterojunctions is the semiconductor-semiconductor heterojunction established between TiO 2 and CdS NPs. CdS NPs are not only promising in technological applications, but also in biomedical uses due to their antimicrobial potential [40,41]. Post-treatment procedures have also been investigated as a way to improve the characteristics of metal oxide NPs. ...
Background
Water scarcity is now a global challenge due to the population growth and the limited amount of available potable water. In addition, modern industrialization, and microbial pathogenesis is resulting in water pollution on a large scale.
Methods
In the present study, reusable Co0.5Ni0.5Fe2O4/SiO2/TiO2 composite matrix was incorporated with CdS NPs to develop an efficient photocatalyst, and antimicrobial agents for wastewater treatment, and disinfection purpose. The antibacterial performance of the gamma-irradiated samples was evaluated against various types of Gram-positive bacteria using ZOI, MIC, antibiofilm, and effect of UV-exposure. Antibacterial reaction mechanism was assessed by bacterial membrane leakage assay, and SEM imaging. In addition, their photocatalytic efficiency was tested against MB cationic dye as a typical water organic pollutant.
Results
Our results showed that, the formed CdS NPs were uniformly distributed onto the surface of the nanocomposite matrix. While, the resulted CdS-based nanocomposite possessed an average particle size of nearly 90.6 nm. The antibacterial performance of the prepared nanocomposite was significantly increased after activation with gamma and UV irradiations. The improved antibacterial performance was mainly due to the synergistic effect of both TiO2 and CdS NPs; whereas, the highest photocatalytic efficiency of MB removal was exhibited in alkaline media due to the electrostatic attraction between the cationic MB and the negatively-charged samples. In addition, the constructed heterojunction enabled better charge separation and increased the lifetime of the photogenerated charge carriers.
Conclusion
Our results can pave the way towards the development of efficient photocatalysts for wastewater treatment and promising antibacterial agents for disinfection applications.
... A liquid crystal (LC) is a material state that exists between crystalline solids and amorphous liquids. They are distinguished by the long-order range of the molecular orientation, and as a result, their physical properties are anisotropic [1][2][3][4]. Because of anisotropy in dielectric permittivity or diamagnetic susceptibility, LCs can be oriented in magnetic or electric fields. ...
This work aimed to look into how N-(4-methoxybenzylidene)-4-n-butylaniline (MBBA) liquid crystal's (LCs) electro-optical properties are affected by gold nanoparticles (Au NPs). A sandwich approach has been used to construct LC optical switch cells samples. It has been found that changing the Au NPs concentration can alter the electro-optical characteristics of MBBA LC samples; therefore, liquid crystal doped with 0.1 wt% of AuNPs showed the best concentrate that improves response time from 44 ms for pure LC to 38.96 ms for 0.1 wt %. This is due to the fact that the electric dipole–dipole interaction between Au NPs at 0.1 wt % concentration and the liquid crystal molecules is better than for the others. Moreover, the threshold voltage was around 44% lower than with pure LC.
... QDs have extensive use in targeted and controlled drug delivery and cancer therapy (Zayed et al. 2019;Pourmadadi et al. 2022Pourmadadi et al. , 2023Rahmani et al. 2022), bioimaging (Gupta et al. 2022;Pal et al. 2022), Responsible Editor: George Z. Kyzas light-emitting diodes , solar cells and lasers (Yang et al. 2021), photocatalysts (Ramalingam et al. 2022), and fluorescent probes, markers, sensors, and optoelectronics (Granados-Oliveros et al. 2022;Liu et al. 2019;Asiya et al. 2020;Pal et al. 2021;Hwa et al. 2022) as well as antimicrobial agents . ...
Quantum dots (QDs) with distinctive optical properties have been extensively researched and developed for usage in solar cells, imaging, drug delivery, cellular targeting, etc. But the inevitable production of QDs can lead to their unavoidable release and increased environmental concentration. Depending on morphological and surface properties, QDs at the nano-bio interface considerably impact the activity and structure of bio-molecules. The present study investigates the interaction of metalloenzyme jack bean urease (JBU) and bi-sized CdSe QDs (2.43 nm and 3.63 nm), surface-functionalized to mercaptopropionic acid (MPA) (–COOH), l-cysteine (CYS), l-glutathione (GSH), N-acetyl l-cysteine (NAC) (–COOH, –NH2), and cysteamine hydrochloride (CYST) (–NH2) to assess any alterations in JBU’s binding, microenvironment, structure, exciton lifetime, and activity. JBU catalyzes the hydrolysis of urea to produce ammonia and carbon dioxide; any changes in its properties could threaten the survival of several microbes and plants. Spectroscopy techniques such as UV–Vis, fluorescence, circular dichroism, synchronous, time-resolved fluorescence, atomic force microscopy, and JBU activity assay were studied. Results suggested highly spontaneous and energy-favored interactions, which involved static quenching and hydrophobic forces of varied magnitude, dependent on QDs properties. The size, surface modifications, and dosage of QDs significantly impacted the secondary structure and activity of JBUs. Even though the larger sizes of the relevant modifications demonstrated stronger binding, the smaller sizes had the greatest impact on α-helicity and activity. CYST-capped QDs with an average number of the binding site (n) = 1, reduced α-helicity by 16% and activity by 22–30% at 7 nM concentration. In contrast, MPA-capped QDs with n < 1 had the least effect on α-helical structure and activity. The smaller GSH-capped QDs increased the activity by 9%, via partially restoring JBU’s α-helical content. The study thus thoroughly analyzed the impact of varied-size and surface-functionalized QDs on the structure and function of JBU, which can be exploited further for several biomedical applications.
Graphical Abstract
... In a memory device, the current-voltage (I-V) characteristics are recorded when an electrical stimulus is present [8]. In addition, the photonic stimulus can alter the active switching layer's memristive characteristics [9,10]. A degree of freedom is provided with a photonic stimulus by the synergistic impact of photo-induced memorization [11]. ...
Recently, the nanostructured metal oxides are widely attracted for resistive switching memory devices. In this work, nanostructured ZnO thin films were deposited via simple and cost-effective spray pyrolysis technique (SPT) onto a glass/FTO substrates at 450 °C by varying the solution quantity such as 40, 80, and 120 ml. The structural, morphological, and compositional properties of the deposited ZnO thin films were investigated using XRD, FESEM, AFM and EDAX characterizations. All the deposited ZnO samples showed crystalline nature with nanoflakes-like morphology. The bipolar resistive switching properties of the Al/ZnO/FTO fabricated memristive devices and its mechanism were investigated. The fabricated memristive device showed two-valued charge–flux relation which confirms non-ideal memristor devices. The data retention property of memristive devices was examined by measuring the low-resistance state (LRS) and high-resistance state (HRS) for every 10 s and it can retain data up to 10⁴ s. The ZnO-based memristive device possesses good non-volatile memory properties with reliable device performance that can be advantageous for light-responsive memory, synaptic, sensor devices, etc.
Graphical abstract
Synthesis of nanostructured ZnO thin films by spray pyrolysis technique for resistive switching applications.
... Molecular dynamics (MD) simulation is an essential tool to investigate the interaction mechanism between molecules and atoms of micro-materials. In decades of development, MD simulation has been widely used in aerospace, materials, medicine, engineering, processing and manufacturing [22,23]. Researchers have revealed the diffusion, agglomeration, electrolytes and asphaltenes process as well as mechanism of nanoparticles in liquids through MD simulation, and studied the influence trend of electric field, temperature, pressure and magnetic field [24][25][26][27]. ...
The use of nano-materials can effectively improve the dielectric and heat transfer properties of natural ester insulating oil. However, the migration and interaction mechanism of components in nano-modified insulating oil under electric field is still not clear. Through detailed Molecular Dynamics (MD) simulation, this study revealed the migration and interaction mechanism of Cage Polysilsesquioxane (POSS) and H2O molecules in natural ester insulating oil. The data indicates that POSS and H2O molecules have completely different diffusion properties under electric field. The existence of electric field not only makes the displacement of molecules nonlinear, but also limits the Brownian motion of H2O molecules. On the contrary, POSS molecules under electric field have better diffusion properties. Electric field leads to the extremely uneven distribution of electrostatic potential (ESP) of oil molecules, which makes it easier for H2O molecules with small volume to dissociate near the polarized oil molecular structure and be bound by it, and the interaction energy between oil molecules and POSS molecules under the action of electric field will be weakened, which is the main reason why H2O and POSS molecules have completely different diffusion performance under electric field. The limited displacement of H2O molecules can inhibit the aging of insulating oil and improve its service life. Compared with the electric field effect, temperature has a great influence on the interaction energy between POSS and oil molecules. The results provide useful guidance for the design of the next generation of natural ester nano-modified insulating oil.
... Electro-optics phenomenon of FLC, as described by pseudo cone based optical switching, is well controlled by interface of FLC with alignment layer and exhibit various electro-optical modes of operation such as surface stabilized switching mode [1,18], deformed helix mode [19], V-shaped switching [20], hysteresis free switching [21], switchable device using nanomaterials [22][23][24], electrically suppressed helix mode [25], photoalignment [26], and electroclinic effect [27,28]. Most of the electro-optical modes are controlled by thin polymer layer while some are fascinated by an intrinsic feature of the FLC system [25][26][27][28]. ...
... Currently, NMs are considered the cornerstones of the broad area of nanoscience and technology [4,6]. NMs are attractive as a result of their promising and versatile uses in medicine, electronics, energy, environment, biology, industry, and other fields [7][8][9][10][11][12][13][14][15][16][17]. There are two reasons behind the novel properties of NMs, which are not common in their bulk materials; the first is the relatively-higher surface area, and the second is the quantum effects, which play an essential role in tuning materials' properties at the nanoscale [18][19][20][21][22]. ...
“There’s Plenty of Room at the Bottom: An Invitation to Enter a New Field of Physics” said Richard Feynman in 1959, this lecture opened the way to the new field of science which we know today as nanotechnology. Materials’ manipulation at a very small size, ranges from 1 to 100 nm (nanoworld or the nano-edge) is well-known as nanotechnology. Since then, a lot of investigations and research were devoted by many researchers around the globe to keep an eye on the different properties and behavior of nanomaterials. Materials with at least one nanoscale dimension are called nanomaterials that have outstanding features compared to their bulk counterparts. These exceptional characteristics are due to the relatively-high surface area and the relatively-large surface atoms compared to those in the inner mass. Thus, nanomaterials have attractive chemical, physical, electronic, physiological, and optical properties. In this chapter, we are covering the historical overview and origin of nanomaterials to their recent applications. In addition, types and applications of recycled carbon-based nanomaterials as an example have also been discussed.
... Contrarily, the nanosized particle formation by biological means is a much better approach owing to their advantages in reducing the limitation of physical and chemical approaches (Jeevanandam et al. 2019a). NPs synthesized by biological methods are non-toxic, easy to scale up with consistent unique shape, dimension and composition (Asiya et al. 2019;Deepak et al. 2019). These properties of the nanoparticles are vital in the end user application of nanoparticles. ...
... Luminescence properties of CdS are widely reported with their short emission intensities at 480 nm [11]; besides, enhanced magnetic, dielectric, and magnetodielectric properties were observed for the (10%) Gd: CdS nanorods with a considerable increase in dielectric constant [12]. CdS nanowires sandwiched in liquid crystal bent-core matrix exhibited enhanced high luminescent and dielectric properties, nanostructures were investigated for their geometrical parameters, electro-optic responses when incorporated in LC matrix [13]. A novel green chemistry approach developed toward the synthesis of Au NPs, and an in-depth investigation of the biogenic screening platform was conducted against antimicrobial strains and degradation of Au NPs. ...
Synthesis of Gd doped Srx O: CdO (x = 1.4, 1.6, 1.8) nanostructures (NS) was achieved through the coprecipitation method by using CTAB (cetyl trimethyl ammonium bromide) with the purpose to investigate the effect of Gd doping on the optical, structural, morphological, and photoluminescence properties at room temperature. Mixed phase of tetragonal crystal structure verified via X-ray diffraction technique, no structural variation was observed except lattice distortion. Size of the crystallites (D), morphology studied by SEM (scanning electron microscopy) analysis, nanoparticles (NPs) crystalized roughly flake-like morphology with homogeneous particle distribution centered at ~ 78 nm, ~56 nm, ~65 nm, ~88 nm for pure and Gd (x-1) doped Sr xO: CdO nanostructure, respectively. Fourier transform infrared spectroscopic investigation (FTIR) revealed the presence of Gd–O–Gd, Cd–O, Sr–O, and OH peaks appeared at ~1321 cm ⁻¹, ~1550 cm ⁻¹, ~1400 cm ⁻¹–3300 cm ⁻¹ with small variation in vibration modes due to Gd doping. Optical absorptivity observed in the range of 325 nm–359 nm (redshifted) with absorption edges at 346 nm, 364 nm, and 380 nm for Gd (x-1) doped Sr xO: CdO nanostructure, respectively. This redshift on the bandgap was discussed in terms of new band levels below conduction band. The energy gap was calculated using Kubelka-Munk theory and was found to be in the range of 3.22 eV–2.61 eV. X-ray photoelectron spectroscopy (XPS) performed to determine chemical composition and binding energies of Gd 3d 3/2, Sr 3d 3/2, and Cd 3d 3/2, O1s, and C1s observed at 150.8 eV, 141.6 eV, 411.0 eV, 530.4 eV, and 285.6 eV indicating Gd⁺³ ion replaces Sr⁺² in all concentrations. Our results showed that Gd-doped Sr xO: CdO nanoparticles exhibited enhanced photoluminescence (PL) properties in contrast to the pure Gd2O3 with Gd⁺³ randomly incorporated into crystal structure, probably in tetrahedral sites. The composition of Gd 0.6 doped Sr x O: CdO NS exhibited photoluminescent emission spectra, peaks centered at 433 ± 3 nm, 449 ± 3 nm, and 469 ± 2 nm (λ excitation = 318 nm) and for Gd 0.8 doped Sr x O: CdO nanostructure showed broad emission peak at 412 ± 2 nm to 433 ± 2 nm (λ excitation = 380 nm), which indicates a reduction in defects with an increase in Gd doping. The transitions can be ascertained with shielding of 4f shells of Gd ⁺³ ions by 6s, 5d shells by the interaction of other Gd ⁺³ ions.
... There has been a growing interest in recent years, in physics of porous materials. These systems play an increasingly important role in various technological applications such as electrooptical, nuclear waste storage, switching operation, display modulation, oil recovery, heterogeneous catalysis, glass processing, thermal insulation of refrigerators, and passive solar energy collection devices [33,[45][46][47][48][49] . Also, soft matter-based approaches have been further extended to other advanced applications, such as organic semiconductor-based devices, soft templates for nano-objects trapping and nature-inspired biomedical applications [50][51][52][53] . ...
In this review, we present the phase behaviour of liquid crystals (LCs) confined to Controlled-Pore Glasses (CPG) of various pore sizes. We consider either non-treated or silane-treated CPG pore surfaces, which impose parallel and homeotropic alignment to n-cyanobiphenyl (n-CB) LCs, respectively. The resulting nematic or smectic ordering depends on the characteristic void radii R and is well described in terms of the Landau-de Gennes free energy. Experimental data for different n-CB LCs, 5CB, 8CB, and 12CB, demonstrate phase transitions in orientation and translational degrees of freedom. In the bulk, 5CB and 8CB exhibit on cooling from the isotropic phase (I) the 1st order isotropic-nematic (I−N) phase transitions. In addition, 8CB also exhibits on further cooling a 2nd order nematic-smectic A (N−SmA) phase transition. 12CB, on the other hand, only has a 1st order isotropic-smectic A (I−SmA) phase transition. The bulk LCs exhibit a variety of different phase structures. When LCs are confined to porous media, their phase structures can be modified and even glass transition is possible.
For LCs confined to CPG, the phase transition temperatures are shifted, depending on the pore size and the pore surface treatment. The Landau-de Gennes model predicts that the present phase transition shifts display inversely linear and inversely quadratic contributions in terms of the characteristic pore sizes. Furthermore, for strong enough confinement the phase transitions are replaced by gradual evolution of LCs order. These predictions are in line with nuclear magnetic resonance, small- angle X-ray scattering, and high-resolution calorimetry experimental observations.
... Also, suspension stability, diffusion abilities, hydrophilicity, and hydrophobicity [10]. Moreover, electrical and magnetic properties such as resistivity, semi-conductivity, and superconductivity enabling NPs to be extensively-used in optoelectronics [11,12], electrochemical hydrogen storage [13][14][15][16], environmental remediation [17][18][19], photo-catalysis [20,21], biomedical [22][23][24], industrial [12], and renewable energy applications [10,25]. ...
Surface engineering of energetic particles can offer significant applications; the emergence of surface modification with polydopamine (PDA) can propose novel material science. Even though, nanothermites (metal oxide/metal) can offer surplus heat output; the reaction rate is comparatively-low as it is limited to the interplaner distance between particles. Intimate mixing between metal oxide/metal could be accomplished via surface modification. This study reports on the facile synthesis of MnO2 nanoparticles (NPs) of 5 nm average particle size. On the other hand, Al NPs in the shape of plates of 100 nm particle size were employed. Surface modification of Al NPs with PDA was conducted via in situ polymerization. Colloidal MnO2 NPs integrated into PDA/Al during the polymerization process. DPA layer was effectively-deposited on the aluminium surface and effectively-anchored MnO2 NPs. SEM micrographs of developed MnO2/PDA/Al nanocomposite demonstrated the successful bonding of MnO2 to Al surface via strong PDA chemical bonding. From FTIR spectra, the sharp peaks at 1544 cm⁻¹ and 1389 cm⁻¹ attributed to the C=O and C–O bonds, respectively, and could be due to bond formation between Mn and oxygen in C=O, and C–O in PDA. The developed MnO2/PDA/Al demonstrated the uniform distribution of MnO2 NPs on Al nano-plates. This work dropped the light toward the green production of novel nanothermite hybrid with durable chemical bonding. MnO2/PDA/Al hybrid can offer superior combustion characteristics with intimate mixing between the oxidizer and metal fuel to the molecular level.
... Prominent methods of measuring helical pitch include spectroscopic measurements [38] and measurement of distance between dislocation lines [ 39 , 40 ]. Induced smectic phases [41] , luminescence in hydrogen bond liquid crystals [42] , optoelectronics and biological aspects of liquid crystals [43][44][45] are reported. Influence * Corresponding author. of nano particles in liquid crystal [46,47] along with electro-optic properties [4 8,4 9] is available in the recent literature. ...
A sequence of hydrogen bond ferroelectric liquid crystals (HBFLC), derived from Camphoric acid and alkyloxy benzoic acids display a variety of mosogenic polymorphism with various smectic ordering like C*, X* and G*. FTIR spectra and dielectric relaxations in smectic C* and smectic X* are studied. A new method to elucidate the helicoidal structure variation with temperature through dielectric investigations is discussed. Thermistor which exhibits both positive and negative temperature coefficients is derived from the present liquid crystals and results are discussed.
... In liquid crystal phase, the molecules are with enough disorder that offers flow properties, and some degree of ordering that leads to anisotropy. [1][2][3][4] This phase offers higher degree of orientational order to a liquid and a less positional order to a crystal. The molecules ordering in a liquid crystal phase may be either translational and/or rotational. ...
In this paper, a theoretical study has been carried out on a liquid crystal compound named p-n-propyl cyanobiphenyl (3CB). The different modes of interaction energy values in a polar aprotic solvent (ethyl acetate) for small amount of translation and rotation are calculated. The corresponding probabilities have been calculated at both room temperature (300 K) and transition temperature (303.3 K). The rigidity parameter for stacking and in-plane interactions has been estimated and then the stability of molecule according to probability and rigidity at definite translation and rotation has been concluded. The change in the characteristics and stability of the compound at transition temperature has been observed. The dependence of mesophase behaviour with change in the certain configurations and orientation of the molecules have been discussed. These observed results provide an insight about the process of mesophase structure and its formation. The present compound may guide in establishing the other molecular models with transition temperature nearer to room temperature.
... Contrarily, the nanosized particle formation by biological means is a much better approach owing to their advantages in reducing the limitation of physical and chemical approaches (Jeevanandam et al. 2019a). NPs synthesized by biological methods are non-toxic, easy to scale up with consistent unique shape, dimension and composition (Asiya et al. 2019;Deepak et al. 2019). These properties of the nanoparticles are vital in the end user application of nanoparticles. ...
Plants are the well-known sources for the hyper-accumulation and reduction of metallic ions. Analysis of various plant extracts has justified the presence of different types of phytochemicals that possess the stabilization and reduction functionali-ties of precursors to form nanoparticles. Such characteristics make plants as an attractive source for synthesizing eco-friendly nanoparticles (NPs) with potentially less toxicity to the body. Recently, phytosynthesized nanoparticles have been explored for targeted inhibition and diagnosis of cancer cells without affecting non-cancerous healthy cells. The aim of this review is to discuss the characteristic performance of NPs synthesized from various plant sources for the diagnosis and inhibition of cancer. The mode of action of phytosynthesized nanoparticles for anti-cancer applications are also discussed.
... Nanoscience and nanotechnology is a rapid-developing field which has demanded the technologist to innovate applicable nanomaterials with manipulated shape and size to explore their principal chemical and physical characteristics [1]. In recent years, rare earth phosphates have attracted many researchers because of their technological applications [2,3]. ...
Most of the work has been done on the optical properties of the rare earth doped CePO4, so there are few studies on the effect of metal ion doping on CePO4. The doping improves the properties of the compounds and can lead to new properties. It is the first time, that multi- ionic doping process is used in the CePO4matrix, in order to improve the ionic conductivity and the electrochemical stability. The low percentage of (Cd2+, Li+), Cr3+, Bi3+ dopant affect the structure showing a weak decrease in the lattice parameters compared to the CePO4. Impedance spectroscopy analysis was used to analyze the electrical behavior of samples as a function of frequency at different temperatures. The total electrical conductivity plots obtained from impedance spectra shows an increase of the total conductivity as Li, Cr-content increases. The determined energy gap values decrease with increasingly Li+, Cr3+ and Bi3+ doping content. Electrochemical tests showed an improved capacity when increasing the Li+, Cr3+ and Bi3+ content and a stable cycling performance.
... The demand for plant extracts and matrices rich in natural substances with ovicidal, larvicidal, and skin-repellent effects has increased (Yu et al. 2014), as they are cheap and readily available in several areas of the world (Simas et al. 2004). The development of controlled release larvicides, which provide several months of control after a single application to water storage containers (Pavela et al. 2019b), is an up-and-coming alternative to hydrophobic plant extracts (Guzman et al. 2010), which always can be improved by Nanotechnology (Benelli et al. 2018;Elkodous et al. 2019;Asiya et al. 2020). ...
Dengue is the most important infectious disease in the world and is a severe public health problem. The chikungunya is an arbovirus, in many cases, increased, which is transmitted by the same transmitter dengue vector, Aedes aegypti. The symptoms of both diseases are similar, and infections can be lethal. Although there is no preventive vaccine against any of the two diseases, therefore, it is extremely important to control the mosquito. The eggs of A. aegypti are very resistant and hatch into larvae, which later give rise to mosquitoes in any container with water. Natural plant extracts have come from active substances with larvicidal activity against A. aegypti. However, they tend to be highly hydrophobic and need some strategy to improve its affinity for water. Because of these factors, this research aims to synthesize and characterize polymeric materials with properties suitable for the release of hydrophobic principles with larvicidal action. The synthesized polymers are poly (butylene succinate) (PBS) and PBS block copolymer with polyethylene glycol (PEG). The synthesized polymers were characterized by nuclear magnetic resonance, thermal analysis simultaneous, differential scanning calorimetry, Fourier transform infrared spectroscopy, and diffraction of X-rays analysis. The analysis results showed that the synthesized materials have chemical composition and properties suitable for use in the controlled release of actives substances. Systems were prepared using the Dendranthema grandiflora extract, which has larvicidal activity was incorporated via fusion to polymers, to evaluate its release in aqueous media. The results proved that higher amounts of PEG in the copolymer chain speed up the delivery of the larvicidal extract. Besides that, the larvicidal extract concentration required to cause death larvae of A. aegypti was achieved from the first minutes of dissolution tests, indicating that the materials developed are promising tool to fight dengue and chikungunya. This new system is a vital tool for eliminating vectors, potentially contributing to saving millions of lives worldwide.
... Various nano-materials possess exceptional physical, chemical, and physiological characteristics allowing them to be perfect candidates for many applications (Maksoud et al. 2018(Maksoud et al. , 2019Pal et al. 2018;Thirugnanasambandan et al. 2018;Asiya et al. 2020;Elkodous et al. 2019c;Govindasamy et al. 2019;Pal et al. 2019;Jeevanandam et al. 2020). Biomedical applications of nano-materials have gained significant consideration from numerous researchers across the past decade because of the important role they can perform in improving the public health (Elkodous et al. 2019a, b, d, e;El-Batal et al. 2019;Wong et al. 2019;Abdelhakim et al. 2020;Elkhenany et al. 2020;El-Sayed et al. 2020a, b). ...
Neurodegenerative disorders especially Alzheimer’s disease (AD) are significantly threatening the public health. Acetylcholinesterase (AChE) inhibitors are compounds of great interest which can be used as effective agents for the symptomatic treatment of AD. Although plants are considered the largest source for these types of inhibitors, the microbial production of AChE inhibitors represents an efficient, easily manipulated, eco-friendly, cost-effective, and alternative approach. This review highlights the recent advances on the microbial production of AChE inhibitors and summarizes all the previously reported successful studies on isolation, screening, extraction, and detecting methodologies of AChE inhibitors from the microbial fermentation, from the earliest trials to the most promising anti-AD drug, huperzine A (HupA). In addition, improvement strategies for maximizing the industrial production of AChE inhibitors by microbes will be discussed. Finally, the promising applications of nano-material-based drug delivery systems for natural AChE inhibitor (HupA) will also be summarized.
Key Points
• AChE inhibitors are potential therapies for Alzheimer’s disease.
• Microorganisms as alternate sources for prospective production of such inhibitors.
• Research advances on extraction, detection, and strategies for production improvement.
• Nanotechnology-based approaches for an effective drug delivery for Alzheimer’s disease.
Photodetectors suitable for visible light communication (VLC) technology were fabricated and characterized in this study. The photodetectors were designed using two p-type stacked layers of SeO2 and SiO2, which were coated onto n-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathrm{n}-$$\end{document} type Si thin wafers. These stacked layers were deposited in a vacuum medium under a pressure of 10–5 mbar using the thermal evaporation technique. p-SiO2 thin layer enriched the hole concentration of p-SeO2 layer forming p+n\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\mathrm{p}}^{+}\mathrm{n}$$\end{document} type heterojunction and prevented SeO2 from environmental contaminations. The microstructure, surface morphology, and photoelectrical properties of the n-Si/p-SeO2/p-SiO2 (SSS) detectors were explored. It was observed that the SSS detectors exhibited biasing and light power dependent asymmetry. The asymmetry varied in the range of 77–178 as the light power increased from zero to 77 mW. In addition, the SSS photodetectors demonstrated a current responsivity, external quantum efficiency, and specific detectivity reaching values of 123 mA/W, 15.6%, and 1.3 × 10¹⁰ Jones, respectively. These values are considered adequate for VLC technology. Practical tests have shown that the device can transmit wireless square-wave pulses with frequencies up to approximately 10–100 kHz. The growth and decay response times were found to be 1.15 ms and 0.89 ms, respectively. The features of the SSS detectors make them suitable for use as light-controlled current rectifiers and VLC detectors.
Graphical abstract
The novel series of hydrogen bond liquid crystals were synthesized from the 2-methylglutaric acid (MGA) and 4-alkyloxybenzoic acid (nOBA) compounds. The induced smectic B phase with different texture (spine texture, needle texture, mosaic texture, natural mosaic texture and marble texture) were identified by polarizing optical microscope. Due to breaking of in-plane rotational symmetry within molecular layers, smectic B phase is tempted by suppressing other usual mesophases. The mesomorphic transition temperature, enthalpy and entropy values were calculated by differential scanning calorimeter which strongly proves the existence of mesomorphism. H-bond interaction and functional groups were confirmed by the observed peak between 2910 and 2954 cm-1 in the FTIR spectra. Thermal stability and extended mesophase width (for MGA + 12OBA = 31.1) of Sm B mesophase were reported and it clearly reveals the existence of mono-phase variance in the MGA + nOBA HBLC complex. Due to the steric effect, and the increased molecular core polarity, the highly stabilized Sm B phase with different textures were observed while varying alkyloxy carbon number n = 7 to 12. Further, the origination of Sm B phase and its detailed characteristics were reported.
Polymers of chitosan (Ch) and polyvinyl alcohol (PVA) were combined effectively to create a synergetic property of both. To this composite, BiOCl:Eu³⁺ nanoparticles (NPs) were used as an appropriate filler. Vitamin B2 (VB2) was used as a biosafe coupling agent to modify the surface of NPs. Different weight percentage of BCE (50, 100, and 150 wt %) were then created using a casting/solvent evaporation process after being exposed to ultrasonic irradiations. The compatibility of NPs with the blend polymer were enhanced due to the coupling agent. Optical absorbance and thermal stability of compounds were impacted by inserting the modified NPs into the blend polymer. The hydrophilicity reduced for various ratios of the modified NPs loaded in the blend polymer, according to the contact angle measurements. The characteristic emission peaks of Eu³⁺ ions were observed at 581, 594, 621, 652, and 698 nm after being stimulated by 466 nm. With increased surface modifier concentration, the chromaticity diagram showed that emission colors altered from red to deep red. Reduced space charge polarization of the dipoles was shown to be the cause of the dielectric constant decreasing with frequency. The various resistive and capacitive elements of the produced materials are credited with the non-Debye type relaxation process. The level I-III ridge details are visible in the colorimetric images of fingerprints using the optimized nanofiller in polymer matrix on forensic-related surfaces. The aforementioned results made it abundantly evident that the improved NCs are very beneficial in multidimensional applications.
PVA/CMC/PEG blended polymers loaded with (1-x)CdS/xCuS nanocomposites (x = 0, 0.3, 0.5, 0.7, 1) were formed applying the thermolysis and casting techniques. Rietveld analysis of synchrotron x-ray diffraction data measured for (1-x)CdS/xCuS manifested a single hexagonal phase CuS (x = 1.0) and biphasic structure, hexagonal and cubic, for CdS (x = 0.0); composite samples (x = 0.3, 0.5, and 0.7) exhibited the three phases with varied percentages. Average crystallite size for all nanofillers ranged 4–12 nm. The surface morphology and chemical compositions of the different blends were investigated using SEM and EDS techniques. The effect of loading PVA/CMC/PEG blends with multi phases CdS–CuS nanocomposite on the optical linear and nonlinear behaviors was explored using diffused reflectance technique. The direct and indirect optical band gaps (Eg) values determined for PVA/CMC/PEG are 5.62 and 5.18 eV, respectively, which reduced to (4.2, 4.5, 4.47, 4.56, 3.89) and (3.43, 3.9, 3.74, 3.98, 3.18) eV upon loading with (1-x)CdS-xCuS for x = 0, 0.3, 0.5, 0.7, and 1, respectively. The refractive index of all loaded blends increased non monotonically with (x) reached its highest value for λ ≥ 500 nm upon loading with x = 0.0 (CdS). The fluorescence (FL) intensity of the blended polymers nearly quenched upon loading with CuS (x = 1.0) and greatly enhanced for x = 0.5.
Orientation‐controlled large‐area synthesis of nanowires is key to their direct integration into circuits and devices for functional exploitation. In this report, the vapor‐liquid‐solid process yields planar arrays of tin‐doped CdS NWs with precise crystallographic orientation on flat and faceted sapphire surfaces. The nanopatterned catalyst and epitaxial correlation of each surface determine nanowires’ exact position, yield, and orientation while the graphoepitaxial effect steers their growth along the nanochannels. The incorporation of dopants widens the emission spectrum beyond the bandgap, which facilitates enhanced optical transport in nanowires. Electron‐beam lithography (EBL) is employed to fabricate photodetector on individual NW, which demonstrates high photoresponsivity and fast response. Graphoepitaxial effect‐based assembly of highly ordered horizontal NW arrays and their facile self‐integration into devices for modern applications, including LEDs, biomedical or photoelectric sensors, photovoltaic cells, and visible span integrated optoelectronic and photonic systems, has promising prospects. This article is protected by copyright. All rights reserved.
Magnetite nanoparticles are widely used in current medicine because their magnetite properties allow several uses as drug delivery systems, contrasts in imaging tests, and even for magnetohyperthermia. However, magnetic nanoparticles possess meager Zeta potential, presenting a strong tendency to agglomerate. For clinical use, they must be covered with a biocompatible material to maintain colloidal stability, without, however, altering its magnetic properties. Thus, for biomedical applications in general, magnetic nanocomposites are more interesting than pure magnetite. The present work applies poly(butylene succinate) (PBS), as a coating on magnetite nanoparticles, aiming to increase their biocompatibility. PBS is a polymer obtained from renewable sources, being entirely suitable for pharmacological uses. In this work, the synthesis of ricinoleic acid from natural castor oil is carried out through the saponification method and subsequent acid hydrolysis. In turn, the synthesis of magnetite nanoparticles is performed by coprecipitation. Then, by an acid-base reaction, the nanoparticles are treated with ricinoleic acid. Soon afterward, toluene diisocyanate is used to produce bonding between the modified particles and PBS. Fourier-transform infrared spectroscopy confirms the synthesis of the material. Also, scanning electron microscopy and dynamic light scattering experiments are performed. The obtained results allow inferring the success in the preparation of the pursued hybrid material.
An efficient computational procedure was proposed to study the adsorption of leadonto two surface decorated alumina nanostructures using density functional theory (DFT) calculations. Notably, lead removal of abundantly available low-price decorated γ-alumina compounds was superior over previously studied functionalized 2D graphene nanosheets. The binding energy for adsorption of Pb on the most stable configuration of γ-alumina was −2.96 eV. Evaluation of adsorption energy demonstrated a noticeable increase in the binding energy of Ni- and Pt-decorated nano γ-alumina as −3.40 eV and −4.29 eV, respectively. Enhanced adsorption energy was taken as a sign of the chemisorption process of Pb on decorated γ-alumina surfaces via covalent bond formation. The use of the projected density of states (PDOS) plot elucidated strong hybridization of Pb 6p with Ni 3d orbitals and 5d orbital of Pt atoms. Moreover, the hybridization of Pb with aluminum 3p and oxygen 2p orbitals proved the strong interaction between Pb and Pt-decorated γ-alumina surface. The results of this investigation can shed some light on decontamination of wastewater applying Ni- and Pt-decorated γ-alumina surfaces. The The proposed approach can also be applied in design and manufacture of iefficient solid adsorbents for the removal of lead contaminations.
Wastewater treatment has been drawing more and more attention due to increasing water pollution. The most common sources of water pollution are heavy metals, dyes, plastics, and foods from industries. Animal, agriculture, and farm wastes are other important causes of water pollution. Several adsorbents have been tested for wastewater treatment. Among these, activated carbon (AC) is the best and the most effective adsorbent for a specific class of pollutants because of its abundant starting materials availability, high surface area, surface reactivity, adsorption efficiency, and porosity structure. Although commercial AC has outstanding potential in the industry of water treatment, the usage is limited because of the high cost. The high initial cost and expensive regeneration of AC motivate the search for low cost, disposable ACs from conventional wastes materials to remove dyes, volatile organic compounds, heavy metals, and organic pollutants. The main goal of this chapter is to compare and list the advantages and disadvantages and methods of AC preparation from wastes materials as adsorbents and their application in water treatment to remove pollutants.
Synthesize of materials with desired properties such as harvest wide range of solar spectrum including visible light and better charge transport properties preferred due to its many potential applications such as water hydrogen splitting, photocatalytic dye degradation and photovoltaic application etc. In this present study the CuBi2O4 material successfully synthesized by solution based synthesize method, followed by dried at 150°C and sintered at various temperature such as 300°C, 400°C and 500°C and the variation of its’ optical, structural and electrochemical properties were analyzed. The sample sintered at 500°C exists in pure form and there are no identified incomplete phases of CuO and Bi2O3. However, the sample sintered at higher temperature shows higher charge transfer resistance between electrode-electrolyte interface. CuBi2O4 sintered at lower temperature shows better charge transfer characteristic due to formation of small size of crystal and existence of different incomplete phases of CuBi2O4 such as CuO and Bi2O3 etc. However, the sample sintered at high temperature showed better characteristic properties for visible light-driven photocatalyst such as enhanced in crystallinity, low dislocation density, and enhanced absorption in visible region of the spectrum. Therefore, the higher sintered temperature is more suitable to synthesize the visible light-driven CuBi2O4 photocatalyst.
Topological defects (TDs) arise in phases reached via symmetry-breaking phase transitions. Their behavior displays several universalities and is of interest to all branches of physics, including particle physics, soft-condensed matter, and cosmology. Ideal testing beds to study the physics of TDs are liquid crystals (LCs), where TDs are relatively easily approachable experimentally. In the paper, we perform a numerical investigation of a locally perturbed m=1 line defect core structure in the nematic LC phase confined within a plane-parallel cell. We use the mesoscopic Landau-de Gennes model in terms of the tensor nematic order parameter. Relatively thin LC cells are considered, where a m=1 disclination is enforced by appropriately patterned confining surfaces. We demonstrate that an imposed local melting, which breaks local cylindrical symmetry, could trigger splitting of the disclination into two m=1/2 disclination lines. Such manipulations could enable transformations between qualitatively different defect core structures. Cores of TDs could be also manipulated by nanoparticles which could be exploited in various applications.
Cement materials have good compression strength, but poor tensile resistence. Aiming to improve this property, natural fibers can be applied as reinforcement. However, natural fibers have low adhesion with cement, and surface treatments are needed. In this work, sisal fibers were submitted to a cationization process followed by the grafting of two kinds of nanoparticles, Fe2O3 and MnO2. It is a usual treatment to dye fibers to the fabrics. The fibers microstructural characteristics were evaluated, before and after treatment, by using FTIR, XRD, TGA, DSC, SEM, water absorption, and tensile strength tests. The effect of the nanoparticles on the sisal fiber-cement matrix adhesion was evaluated by single fiber pull-out tests. The results show the cationization process removes part of lignin, increasing the fiber crystallinity, while the grafting of nanoparticles reduces the fiber crystalline degree, which indicates that nanoparticles grafting in the lignin spaces. The nanoparticles grafting acts as a catalyst of cellulose formation during the thermal degradation changing the initial fiber degradation profile. All treatments have caused a reduction in the absorbed water amount, become the fibers more stable dimensionally. They have improved the fiber adhesion on the cementitious matrix, being the sisal fiber grafting with MnO2 the best result.
This manuscript emphasizes the phase behaviour of p-n-Octyloxy Benzoic acid (OOBA) and p-n-Nonyloxy Benzoic acid (NOBA) which are homologues of alkoxy benzoic acid. Fluctuation of the intermolecular interaction energies have been noticed according to rotational and translational co-ordinates for both the compounds in vacuum and under the influence of polar aprotic solvent Dimethyl sulfoxide (DMSO, ε=47). Structures of the molecules have been framed for both the compounds using published crystallographic data. All the charges of atoms and dipole moments of each atom have been estimated on the basis of complete neglect differential overlap (CNDO/2) method. Long-range intermolecular interactions have been considered by modified Rayleigh–Schrodinger perturbation theory and multicentered-multipole expansion method. Short-range interactions have been described by 6-exponential potential function. Theoretical thermodynamic formulations are chosen for the determination of Helmholtz free energies, entropies and internal energies. Existence of liquid crystal phase and its behaviour have been discussed by the combined results achieved from relative free energy (ΔA) and relative entropy (ΔS) data. The possibility of addressing the multi-phase phenomenon is discussed from these relative values. The present data is expected to provide a route to analyze behaviour of molecules in various solvents, and property prediction for thermodynamic applications.
Divalent ion batteries are potential substitutes to existing rechargeable batteries because of the high-energy density, safety, and low cost. However, the applications of divalent batteries are strongly dependent on the availability of efficient electrode materials. We herein report the adsorption and migration mechanism of divalent ions like Mg+2 and Ca+2, on two-dimensional carbon nitride monolayer (C4N). The adsorption of both Mg and Ca ions are much stronegr on C4N saturated with functional groups like hydrogen (-H), hydroxyl (-OH), and carboxylic (-COOH) as compared to the pristine monolayers, which implies the improvement in metal storage caused by the functional groups. On functionalized C4N, the first Mg binds within the binding energy range of 1.5-2.2 eV having migration barrier, at the saturated sites, of around 0.5 eV, which indicates desirable binding and robust diffuse. However, the functional groups tend to act as the trapping sites for Ca ions and the diffusion might get hindered as compared to Mg ions. In addition to binding and diffusion mechanism, charge transfer, electronic structures and open circuit volatges have also been calculated for both Mg and Ca on pristine and functionalized C4N monolayers. We find that -H, -OH, and -COOH play important role for the cyclic performance of C4N as the prospective anode material for divalent ion batteries.
Two-dimensional graphene and its hybrid derivatives combined with liquid crystals, polymers, and nanomaterials enable the formation of hybrid nanocomposites possessing extraordinary and unique properties. Among others, these assemblies could exhibit stimulus-induced optical and electrical changes, which are essential for many new switchable device technologies. The current review deals straight forward and versatile techniques of the fabrication of exclusive graphene self-assembly of liquid crystalline polymer nanocomposite which exhibiting novel emerging equities as well as unique functionalities. Unique design makes hybrid composite matrix multidomain structures serve as both alignment and conductive layers, thus sustaining novel switchable device fabrication mechanism. Exhibited thin-film nanocomposite based smart switchable devices are promising candidates for diverse applications in the field of stretchable electronics, energy storage, photodetectors, high contrast displays, and optoelectronics. Furthermore, these brand new materials have the potentials of cost-effective production, large-area compatibility and scalability, and seamless heterogeneous integration.
For the development of solution-processable functional materials, it is significant to increase the solubilities of the materials for organic solvents, retaining ordered structures of functional π-conjugated units during an evaporation process of solvents. For this purpose, not only a design of π-conjugated functional units but also a design of side chains is indispensable. In addition to alkyl side chains utilized for liquid crystals and conjugated polymers, oligosiloxane, oligoethylene oxide, perfluoroalkyl side chains are discussed in this review. Oligosiloxane side chains remarkably increase the solubilities of π-conjugated liquid crystals and conjugated polymers while the side chains promote self-organization of π-conjugated units to enhance their functions. In the thin films of the liquid crystals and conjugated polymers bearing cycloterasiloxane rings, liquid crystalline nanosegregated structures can be immobilized by an exposure to acid vapors. Oligoethylene oxide chains also promote nanosegregation and coordinate with ionic species. This property provides liquid crystals with electrochemical functions. Perfluoroalkyl side chains reinforce nanosegregated structures to enhance device performances. The electroluminescence devices using π-conjugated liquid crystals and polymers can emit linearly polarized light. Field-effect transistors comprising liquid crystalline active layers provide flexible devices with high performance. Solar cells based on liquid crystalline nanosegregated structures have a potential for high performance devices, due to high carrier mobility in the liquid crystal phases. The π-conjugated liquid crystals bearing oligoethylene oxide chains and ionic moieties form thin films in which electrons and ions are conducted separately, resulting in a new kind of electrochemical devices.
Biomedical applications of nanomaterials have received considerable attention and interest from many researchers over the past decade due to the key role they can play in enhancing public health. Different types of nanomaterials possess both diagnostic and therapeutic potential owing to their outstanding properties compared to their bulk counterparts. Herein, we present, analyze and provide significant insights and recent advances about the promising biomedical applications of nanoparticles including bioimaging of biological environments and its role as a significant tool for early detection of many diseases with respect to traditional means, explaining their types and limitations. In addition, different types of nanoparticles acting as effective bio-sensors and detectors of our body have been analyzed. Moreover, the therapeutic potential of different types of nanoparticles and their attractive antimicrobial effects allowing them to act as powerful and new drug substitutes against multi-drug resistant bacteria and pathogenic fungi. Finally, we introduce some nanoparticles as powerful anti-oxidants and promising candidates in cancer therapeutics. We conclude that this review can give up-to-date information about various biomedical applications of nanoparticles and will be of great value and interest to researchers and scientists of materials science, biology, chemistry, and medicine.
Nanomaterials have received considerable attention due to their unique properties; they have high surface area compared to volume ratio, giving them superior chemical, optical and thermal characteristics. Nanomaterials have also both diagnostic and therapeutic applications. In this mini review, we are highlighting valuable data about human immunodeficiency virus (HIV), its relationship with cancer and its potential treatment with some nanomaterials such as silver nanoparticles (Ag NPs). © 2019, Springer Science+Business Media, LLC, part of Springer Nature.
Precise tailoring of nanostructured cobalt ferrite paves the way to design and develop devices for stress and noncontact torque sensors. Herein, Mn ²⁺ ions are inserted into cobalt ferrite with different ratios using a facile sol–gel method. The as-synthesized ferrites are characterized via energy dispersive X-ray (EDX), Fourier transforms infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), high resolution transmission electron microscope (HR-TEM), thermogravimetric analysis (TGA), electrochemical impedance spectroscopy (EIS), and vibrating sample magnetometer (VSM). EDX analyses affirm the stoichiometry of the synthesized samples with the intended ratios. The FTIR and XRD prove the presence of a single-phase cubic spinel structure for all as-synthesized samples. The dislocation, the inter-chain distance and the distortion parameter values decrease with increasing Mn ²⁺ content, which outweigh the improvement of the crystal structure of the doped CFO samples. SEM micrographs illustrate that the incorporation of Mn ²⁺ significantly soars the porosity of the samples. TEM images reveal that the samples comprise particles in the nanometer range with spherical shape and porous nature. Thermal analyses show that the weight loss is dependent on Mn ²⁺ content in the sample. For instance, at x = 0, a slight variation in the weight loss estimated by 8% is observed while at x = 0.25 the weight loss has reached up to 40%. The dielectric losses (8 × 10 ⁵ ) of Co 0.5 Mn 0.5 Fe 2 O 4 is enough to meet the demands of microwave applications. Finally, a reduction in the magnetization of the pure CFO from 68.419 emu g ⁻¹ to 50.307 emu g ⁻¹ is achieved at x = 0.25. [Figure not available: see fulltext.]. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.
Spinel ferrites (SFs) show high potential in different aspects of modern technology. Particularly, copper ferrite represents a promising electrode material for supercapacitors and lithium based batteries. This paper is devoted to synthesizing and characterizing nanostructured copper substituted cobalt ferrites using an eco-friendly sol–gel method. Energy dispersive X-ray (EDX) and FT-IR analyses confirm the chemical composition and the successful formation of the cubic phase of CuFe2O4, respectively. XRD analyses based on Williamson–Hall (W–H) method indicate that the average crystallite size drops from 25.1 to 12.1 nm dependent on the Cu²⁺ content in the samples. Further, scanning electron microscopy (SEM) reveals that the CoFe2O4 (CFO) has a honeycomb structure, which gradually disappears with the soaring of Cu²⁺ content in the samples and converts to a porous sponge-like shape structure. The investigated copper substituted CFO holds a high specific surface area equals to 102.5139 m² g⁻¹ which satisfies the contaminant adsorption applications. The measured DC resistivity (ρDC = 10⁸ Ω m) is high enough to meet the requirements of transformer cores applications. Due to the difference in the magnetic moment between Cu²⁺ and Co²⁺ cations, the coercivity of the CFO significantly depends on the Cu²⁺ content; it has declined by more than 50% for the system Co0.25Cu0.75Fe2O4 in comparison to the pure CFO (Hc = 1617.30 Gauss).
Development of new liquid crystalline materials exhibiting interesting properties and phases continues to be an enabling enterprise in the forward march of their successful display and non-display applications. The design and synthesis of a homologous series of liquid crystalline bent-core compounds derived from the oxadiazole bisaniline moiety and the phase behavior of three members of the series that exhibit nematic, smectic C, and dark conglomerate phases is reported. The liquid crystalline phases exhibited by these mesogens are characterized using polarized optical microscopy, differential scanning calorimetry and x-ray scattering techniques. All three homologs prepared exhibit the nematic phase. Interestingly, the homolog with short hexyl terminal chains exhibits only the nematic phase that is stable over a very broad, nearly 100 K wide, temperature range. The compound with terminal octyl chains shows the chiral dark conglomerate phase below the nematic phase despite the bent molecules being achiral. The homolog with dodecyl alkyl chains is found to possess the smectic-C and two additional lamellar phases besides the nematic phase. These compounds enrich the library of achiral bent-core materials capable of exhibiting chiral and nematic phases.
This paper reports the electro-optical properties of high resistivity nematic liquid crystals sandwiched between ferroelectric polymer films. Interactions between liquid crystals and the film result in a series of interesting optical and electro-optical features. For example, the visualization of ferroelectric domains by means of liquid crystals has been known for decades. However, here we demonstrate that liquid crystals can also reveal the fractal dimension of multi—domain poly(vinylidene fluoride)-based films. Unidirectionally rubbed films made of poly(vinylidene fluoride)-based (PVDF) materials align liquid crystals (LC) homogeneously, with the pretilt angle on the order of 1–2 degrees. This property was implemented in the design of hybrid cells composed of liquid crystals sandwiched between PVDF-based films. The designed PVDF|LC|PVDF cells exhibit tunable electro-optical performance originating from the presence of the PVDF-based films. More specifically, (i) the threshold voltage characterizing the transition of liquid crystals from a planar to a homeotropic state can be tuned by varying the film thickness, and (ii) total fall time (turn-off time) can be controlled by varying the frequency and amplitude of the driving voltage. This frequency dependence of the fall time is strongly pronounced at a relatively high voltage applied across the cell. In the low frequency regime, an increase in the turn-off time can be approximated as a linear function of the applied electric field. An electric-field induced polarization of the PVDF-based films is considered a major reason leading to the afore-mentioned amplitude and frequency dependence of the switching time.
Nanomaterial shapes can have profound effects on material properties, and therefore offer an efficient way to improve the performances of designed materials and devices. The rational fabrication of multidimensional architectures such as one dimensional (1D)–two dimensional (2D) hybrid nanomaterials can integrate the merits of individual components and provide enhanced functionality. However, it is still very challenging to fabricate 1D/2D architectures because of the different growth mechanisms of the nanostructures. Here, we present a new solvent-mediated, surface reaction-driven growth route for synthesis of CdS nanowire (NW)/CdIn2S4 nanosheet (NS) 1D/2D architectures. The as-obtained CdS NW/CdIn2S4 NS structures exhibit much higher visible-light-responsive photocatalytic activities for water splitting than the individual components. The CdS NW/CdIn2S4 NS heterostructure was further fabricated into photoelectrodes, which achieved a considerable photocurrent density of 2.85 mA·cm⁻² at 0 V vs. the reversible hydrogen electrode (RHE) without use of any co-catalysts. This represents one of the best results from a CdS-based photoelectrochemical (PEC) cell. Both the multidimensional nature and type II band alignment of the 1D/2D CdS/CdIn2S4 heterostructure contribute to the enhanced photocatalytic and photoelectrochemical activity. The present work not only provides a new strategy for designing multidimensional 1D/2D heterostructures, but also documents the development of highly efficient energy conversion catalysts.
CdS with a direct bandgap of 2.42 eV is considered to be an excellent material for various optoelectronic applications in the visible range of the electromagnetic spectrum, like nonlinear optical devices, LEDs and solar cells. CdS nanowires have drawn great attention owing to their novel properties. Here, we focus on recent strategies used to create CdS nanowires and the emergent properties of the one-dimensional CdS nanowires, and discuss their potential applicability in different fields. In particular, the mechanisms of various synthetic methods for the CdS nanowires are discussed detailedly.
Discotic liquid crystals (DLCs) are nanomaterials with sizes ranging from 2 to 6 nm, and they are emerging as one-dimensional organic semiconducting materials. Recently, hybridization of these materials with various metallic and semiconducting nanoparticles (NPs) to alter and improve their properties has been realized. This article provides an overview of the developments in the field of newly immersed discotic nanoscience, a sub-field of liquid crystal (LC) nanoscience. As this field is also of great interest to readers without an LCs background, a brief introduction of the LC field is given first, with special emphasis on DLCs. This is followed by various DLC-NP hybrid systems. Finally, an outlook into the future of this newly emerging, fascinating and exciting field of discotic nanoscience research is provided.
Since the curing process of an epoxy thermoset is thermally-activated and temperature dependent, thermal analysis is the most common method to monitor the process. In addition, many common temperature-dependent properties like heat capacity and modulus change with the degree of cure or extent of cross-linking. Common thermal analysis techniques which are applicable to the study of thermoset cure are reviewed, specifically differential scanning calorimetry (DSC and TMDSC), thermomechanical and dynamic mechanical analysis (TMA and DMA), thermally stimulated depolarization (TSD), and thermogravimetric analysis (TGA).
Bent-core (BC) materials that form nematic liquid crystals (BC nematics (BCNs)) are known only since 2000, but since then they have been intensively studied. In this review we give a comprehensive summary of the main research directions and results. After discussing representative examples of molecules making BCNs, we review theoretical predictions and experimental findings about macroscopic symmetries, such as chirality of achiral and chiral molecules, tetrahedratic symmetry and phase biaxiality versus uniaxiality. Then we describe the properties of smectic nano clusters often observed in BCNs, and discuss rheological properties that reveal unusually large viscosities and small twist and bend elastic constants. Finally, we focus on the electric properties of BCNs, such as dielectric and ferroelectric properties, electroconvection (EC) and electromechanical effects.
Over the last ten years, the nematic phases of liquid crystals formed from bent-core structures have provoked considerable research because of their remarkable properties. This Minireview summarises some recent measurements of the physical properties of these systems, as well as describing some new data. We concentrate on oxadiazole-based materials as exemplars of this class of nematogens, but also describe some other bent-core systems. The influence of molecular structure on the stability of the nematic phase is described, together with progress in reducing the nematic transition temperatures by modifications to the molecular structure. The physical properties of bent-core nematic materials have proven difficult to study, but patterns are emerging regarding their optical and dielectric properties. Recent breakthroughs in understanding the elastic and flexoelectric behaviour are summarised. Finally, some exemplars of unusual electric field behaviour are described.
Shape tuning of CdS nanocrystals (NCs) by controlled growth and stabilization by tetraoctyl ammonium bromide ligands in non-aqueous medium is thoroughly investigated in this report. CdS nanorods and nanospheres were synthesized by manipulating the addition rate of the sulfide precursor. A higher addition rate (10 mL min−1) of the precursor yields nanorods and a lower addition rate (1 mL min−1) of the precursor yields nanospheres whereas an addition rate (7 mL min−1) in between these two addition rate yields a mixture of nanorods and nanospheres. The investigation further revealed that an optimum concentration of stabilising agent decides the shape, whereas the precursor mole ratio does not play any significant role in shape tuning. The band edge and trap state emission of the NCs synthesized were analysed by time resolved emission studies.
In a brief history of the discovery of antiferroelectricity in liquid crystals, the important role played by tristable switching, i.e. an electric field induced phase transition from antiferroelectric SCA* to ferroelectric SC*, has been emphasised and the antiferroelectric herringbone structure of SCA* has been presented. Then we have explained how to identify the subphases in the SC* region, e.g. SCγ*, SCα*; the clarification of the subphase structures is essential for understanding antiferroelectricity in liquid crystals. After summarizing the evidence for the SCA* structure presented, we have suggested the pair formation of transverse dipole moments in adjacent smectic layers as the cause of its antiferroelectricity, showing that the smectic layer is much closer to the usual picture of molecules lying on equidistant planes; the packing entropy due to the sinusoidal density wave character stabilizes ferroelectric SC*. The competition between the interactions stabilizing SCA* and SC* is responsible for the occurrence of several varieties of ferrielectric and antiferroelectric subphases, which constitutes the Devil's staircase. We have further suggested that the essentials of the SCα* phase are its considerably reduced ability to form SCA* and SC*. At least when the spontaneous polarization is zero, SCα* is a smectic C-like phase with molecular tilting that is non-correlated on the visible wavelength scale When the spontaneous polarization is not zero, as suggested by Prost and Bruinsma recently, a novel type of Coulomb interaction between smectic layers due to the collective polarization fluctuations causes the antiferroelectricity in the high-temperature region of SCα*; the competition between this antiferroelectricity and the SC* ferroelectricity may form another staircase, causing the complexity in SCα*. Applications and some future problems have been described in the final section.
Since it was developed in the late 1990s, 1,1-diamino-2,2-dinitroethene (FOX-7), with lower sensitivity and comparable performance to RDX, has received increasing interest. This paper will present our results for the phase changes of FOX-7 using DSC and HFC (Heat Flow Calorimetry). DSC thermal curves recorded at linear heating rates of 0.10, 0.35 and 1.0 C minâ»Â¹ show two endothermic peaks and two exothermic peaks. The two endothermic peaks represent solid-solid phase transitions, which have been observed in the literature at 114 C (β-γ) and 159 C (γ-δ) by both DSC and XPD (X-ray powder diffraction) measurements. The first transition shifts from 114.5 to 115.8 C as the heating rate increases from 0.10 to 1.0 C minâ»Â¹, while the second transition shifts from 158.5 to 160.4 C. Cyclical heating experiments show the endotherms and exotherms for a first heating through the γ phase to the δ phase, a cooling and reversion to the α or β phase, and a second heating to the γ and δ phases. The data are interpreted using kinetic models with thermodynamic constraints.
A novel series of double hydrogen bonded liquid crystals have been isolated. Hydrogen bond was formed between non mesogen chiral ingredient levo tartaric acid (LTA) and mesogenic undecyloxy benzoic acids (11BA) Thermal and electrical properties exhibited by levo tartaric acid and undecyloxy benzoic acid (LTA+11BA) were discussed. Interesting feature of the present investigation was observation of an optical shuttering action in LTA+11BA hydrogen bonded complex on application of a stipulated applied dc bias voltage. By enhancement of the dc bias voltage the mesogen behaves like an optical shutter, thus this hydrogen bonded complex mesogen acts as an effective light modulator. It was noticed that this action of shuttering was reversible, in the sense that when applied bias voltage was removed the original texture was restored. Experimental results relating to textures, optical tilt, dielectric studies and optical shuttering action were presented. This optical shutter property of the mesogen can be exploited for commercial and display device applications.
Large scale high yield cadmium sulfide (CdS) nanowires with uniform diameter were synthesized using a rapid and simple solvo-chemical and hydrothermal route assisted by the surfactant cetyltrimethylammonium bromide (CTAB). Unique CdS nanowires of different morphologies could be selectively produced by only varying the concentration of CTAB in the reaction system with cadmium acetate, sulfur powder and ethylenediamine. We obtained CdS nanowires with diameters of 64-65 nm and lengths of up to several micrometers. A comparative study of the optical properties of ferroelectric liquid crystal (FLC) Felix-017/100 doped with 1% of CdS nanowires was performed. Response times of the order of from 160 to 180 μs, rotational viscosities of the order of from 5000 to 3000 mN s m and polarizations of the order of from 10 to 70 nC cm were measured. We also observed an anti-ferroelectric to ferroelectric transition for CdS doped FLC instead of the ferroelectric to paraelectric transition for pure FLC.
Molecular shape is an important factor in determining the material properties of thermotropic liquid crystals (LCs). We synthesized and investigated several LC compounds formed by asymmetrically bent molecules with a rigid four-ring core in the shape of the letter 'L'. We measured the temperature dependencies of dielectric permittivities, birefringence, splay K 1 and bend K 3 elastic constants, splay viscosity h splay and flow viscosities h || and h t . The bend–splay anisotropy dK 31 ¼ K 3 À K 1 is negative, similar to the case of nematic LCs formed by symmetrically bent molecules of V-shape. The dielectric anisotropy D3 and birefringence are positive in the entire nematic range. The splay viscosity h splay and the flow viscosities h || and h t are smaller than the viscosities measured for the symmetric V-shaped bent-core materials at similar temperatures. The ratio G ¼ h splay /h ||,t is in the range 5–4 that is typical for rod-like LCs. The reported L-shaped bent-core nematic LCs combine the useful features of bent-core LCs (such as a negative dK 31 , suitable for formulation of broad-range blue phases) with the relatively low viscosities, a property typical for rod-like LCs and beneficial for electro-optic switching applications.
Spinel ferrites (SFs) show high potential in different aspects of modern technology. Particularly, copper ferrite represents a promising electrode material for supercapacitors and lithium based batteries. This paper is devoted to synthesizing and characterizing nanostructured copper substituted cobalt ferrites using an eco-friendly sol–gel method. Energy dispersive X-ray (EDX) and FT-IR analyses confirm the chemical composition and the successful formation of the cubic phase of CuFe2O4, respectively. XRD analyses based on Williamson–Hall (W–H) method indicate that the average crystallite size drops from 25.1 to 12.1 nm dependent on the Cu2+ content in the samples. Further, scanning electron microscopy (SEM) reveals that the CoFe2O4 (CFO) has a honeycomb structure, which gradually disappears with the soaring of Cu2+ content in the samples and converts to a porous sponge-like shape structure. The investigated copper substituted CFO holds a high specific surface area equals to 102.5139 m2 g−1 which satisfies the contaminant adsorption applications. The measured DC resistivity (ρDC = 108 Ω m) is high enough to meet the requirements of transformer cores applications. Due to the difference in the magnetic moment between Cu2+ and Co2+ cations, the coercivity of the CFO significantly depends on the Cu2+ content; it has declined by more than 50% for the system Co0.25Cu0.75Fe2O4 in comparison to the pure CFO (Hc = 1617.30 Gauss).
Nanocrystalline spinel ferrite nanoparticles [MxCo(1−x)Fe2O4; (M = Zn, Cu, Mn; x = 0 and 0.5)] like: Cobalt ferrite (CFO), Zinc Cobalt ferrite (ZCFO), Copper Cobalt ferrite (CCFO), and Manganese Cobalt ferrite (MCFO) modified carbon paste electrodes (CPE) were synthesized via sol–gel technique utilizing citric acid and ethylene glycol as a polymerization agent. The synthesized ferrite NPs were used as bi-functional smart biosensor, not only used to determine the drug Anagrelide-HCl (ANDH) in urine and serum samples, but also possesses antimicrobial potential against some pathogenic microbes, founded in the biological samples. The synthesized ferrite NPs were confirmed by XRD, FTIR spectroscopy, SEM, EDX, and elemental mapping images. Antimicrobial activities of ferrite NPs against selected urinary tract infected microbes were investigated. From XRD data and FTIR spectroscopy it is found that the average crystallite size is lies in the range 12.86 to 33.92 ± 1.5 nm, also the bond lengths RA and RB increase from 1.8986 to 1.9145 Å and from 2.0434 to 2.0606 Å respectively and Debye temperature θD lies in the range of 681.52–708.87 K. Our study describes the improvement of a screen-printed sensor, modified with ferrite NPs materials for rapid, sensitive and cost-effective quantification of ANDH present in the real samples such as blood serum samples, urine and in the pharmaceutical formulations. The results obtained postulate a linear regression between the ANDH charge density of peak current and its concentration in the range from (0.64–8.18 μg/ml) with DL 0.31 μg/ml and QL 0.94 μg/ml. Antimicrobial results indicated that ZCFO NPs were a novel antibacterial agent against Klebsiella pneumoniae (28.0 mm ZOI), and multidrug-resistant bacteria Enterococcus faecalis (27.0 mm ZOI). Additionally, ZCFO NPs were active against Candida albicans (18.0 mm ZOI) seems to be a smart antifungal agent. Therefore, ZCFO NPs can be used as applicant resources for industrial, medical, and biological applications.
Mono-dispersed copper nanoparticles (CuNPs) were constructed using cheap polysaccharides (citrus pectin, chitosan, and sodium alginate), and by appropriating aqueous fermented fenugreek powder (FFP) under the action of Pleurotus ostreatus (as reducing and preserving means), through the influence of gamma irradiation. The created CuNPs are described by UV-Vis. spectroscopy TEM, DLS, XRD, and FT-IR. XRD study of the CuNPs confirmed the generation of metallic CuNPs. The nucleation and the production mechanism of CuNPs are moreover explained. TEM unveiled that, the ordinary diameter of CuNPs incorporated by various polysaccharides, and FFP taken in the range of 31.0 and 36.0 nm respectively. CuNPs size is influenced by many parameters such as the variety of stabilizer, pH within the organization and applied gamma dose. Evaluation of the antioxidant and antimicrobial actions of CuNPs was performed against some selected wound pathogens. The results showed that, CuNPs were a strong antimicrobial agents against microbes caused burn skin infection such as Klebsiella pneumoniae, Staphylococcus aureus, and Candida albicans (16.0, 15.0, and 15.0 mm ZOI, respectively). Additionally, CuNPs have a strong antioxidant with 70% scavenging activity against DPPH. So, due to unique characteristics of CuNPs (cost-effective with continued-term stabilization and effective features), they can recover reasonable potential in biomedical, industrial, agricultural, cosmetics, dermal products and pharmaceutical purposes.
Metal-substituted cobalt ferrites [MxCo(1-x)Fe2O4 (M=Zn, Cu, Mn; x =0.0, 0.25, 0.5, and 0.75)] were synthesized via a sol-gel technique. The ferrite structures were confirmed by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, surface analysis using the Brunauer-Emmett-Teller method, and energy-dispersive X-ray spectroscopy. Antimicrobial activity of these ferrites against selected pathogenic microbes was determined. The structures remained cubic spinel phases after substitution of metals. Substitution strongly influenced the microstructure and homogeneous grain distribution. The particle size of the ferrites increased linearly with increase in their annealing temperature. The surface area of zinc cobalt ferrite nanoparticles (ZCFO) was 52.56m²/g, the average pore size was 1.84nm, and pore volume was 0.136mL/g. All ferrites showed antimicrobial activity toward all pathogens selected. Of these, the most powerful was ZCFO, showing zones of inhibition of 13.0mm against Bacillus subtilis and Staphylococcus aureus and 12.0mm against Candida albicans. Gamma-irradiated ZCFO nanoparticles (150.0kGy) maintained higher antimicrobial activity than non-irradiated particles, e.g. being active toward S. aureus (16.0mm). ZCFO is proposed as a candidate material for industrial and biomedical purposes. © 2018 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences.
Novel synthesis and properties of versatile CdS nanostructures (e.g., Nano-brush, nano-cube, nanosphere) dispersed liquid crystals application in chemical friendly medium exploring this article. Most recent studies, CdS nano-wire brush with the stacking fault structures were hydrothermally synthesized through a dissolution-recrystallization approach in concentrated ammonia solvent in one step solution, for the first time. Those structures-property relations with respect to ferroelectric hydrogenbonded liquid-crystalline complex (HBLC; AC+5BAO) controlled and efficient formation of surface relief nanostructures. A successful attempt has been made to form hydrogen bonding between CdS nanostructures and supramolecular LC with p-n-alkyloxy benzoic acids (n-OBA). The formation of an inter-H-bond is evinced through FTIR study, as well as Gaussian simulation also ensures complete formation of intermolecular hydrogen bond optimized geometry. In contrast, a new sensitive response of smectic G ordering observed in this series is investigated by constructing a phase diagram obtained from two binary mixtures of CdS nanostructures influenced by homogeneous liquid crystals. Temperature-dependent dielectric relaxation, tilt angle, electro-optical switching measurements allow for monitoring very unique and useful behavior in that the polarization of the emission from the semiconductor nanostructures can be controlled by an external bias. It reveals electrically tunable interaction of the composites may allow for engineering of practical electro-optic switchable device.
Light-driven phenomena both in living systems and nonliving materials have enabled truly fascinating and incredible dynamic architectures with terrific forms and functions. Recently, liquid crystalline materials endowed with photoresponsive capability have emerged as enticing systems. In this Review, we focus on the developments of light-driven liquid crystalline materials containing photochromic components over the past decade. Design and synthesis of photochromic liquid crystals (LCs), photoinduced phase transitions in LC, and photoalignment and photoorientation of LCs have been covered. Photomodulation of pitch, polarization, lattice constant and handedness inversion of chiral LCs is discussed. Light-driven phenomena and properties of liquid crystalline polymers, elastomers, and networks have also been analyzed. The applications of photoinduced phase transitions, photoalignment, photomodulation of chiral LCs, and photomobile polymers have been highlighted wherever appropriate. The combination of photochromism, liquid crystallinity, and fabrication techniques has enabled some fascinating functional materials which can be driven by ultraviolet, visible, and infrared light irradiation. Nanoscale particles have been incorporated to widen and diversify the scope of the light-driven liquid crystalline materials. The developed materials possess huge potential for applications in optics, photonics, adaptive materials, nanotechnology, etc. The challenges and opportunities in this area are discussed at the end of the Review.
In nanotechnology, the novel creation of nanostructures consistently feeds back into efforts to fabricate novel complex hybrid nanomaterials. Two-dimensional graphene oxide dispersed liquid crystalline materials (GDLC) module assembled with CdS nanowires(NW's) have received widespread unprecedented attention due to their exceptional mechanical, electrical, thermal properties. However, making macroscopic graphene oxide (GO) sheets with average diameter 2.1 μm, CdS nanowires (15–20 nm) requires novel technology to fabricate few layered graphene oxide (FGO)-sheets were uniformly distributed as macroscopically ordered structures. Aqueous GDLC-CdS nanowires are continuously twist to obtain macroscopic GO-sheets. Subsequently chemical reduction gave first macroscopic neat graphene sheets with high conductivity and good mechanical performance. Liquid crystal formation is the most viable approach to produce macroscopic, periodic self-assembled materials from oriented graphene sheets. We discovered well-soluble FLG-sheets can exhibit nematic liquid crystallinity into Dimethyl sulfoxide (DMSO), first established isotropic-nematic solid phase diagram demonstrated by optical microscopy textural evidences of switching and relevant spectroscopic characterizations. GO utilizes light absorption and nanoscale heat source to thermally induced phase transition with LC from homogeneous alignment to isotropic phase. Thus, volume contraction occurred over the surface area of the GDLC-nanowires hybrid complex module due to photothermal effect. Thus, an excellent conductor as well as high contrast electro-optic switchable cell also deserves most promising applications. These novel findings shed focus on microscopically assembled graphene-LC based semiconductor nanomaterial's textural phase behavior, which can only be realized as the field moves forward and makes more significant advances.
In general, a dielectric is considered as a non-conducting or insulating material (such as a ceramic or polymer used to manufacture a microelectronic device). This book describes the laws governing all dielectric phenomena.
Electronic levels and energies of a solid, such as Fermi level, vacuum level, work function, ionization energy or electron affinity, are of paramount importance for the control of device behavior, charge carrier injection and transport. These levels and quantities, however, depend sensitively on the structure and surface morphology and chemical composition of the solid. A small amount of contaminants on a metal surface, or a shift in molecular orientation at the surface of an organic semiconductor, can change work function and vacuum level position by a large fraction of an electron-volt, and significantly impact the electronic structure of interfaces. The goal of this brief focus article is to provide definitions of key concepts and review simple mechanisms that affect these fundamental quantities.
An account is given of the surface forces acting between two solids. Different contributions to the force are outlined, with particular attention paid to the underlying mechanisms, and how they are affected by the nature of the medium between the surfaces. This is followed by a discussion of the areas of ceramic science and engineering in which surface forces play a role.
The influence of gold nanoparticles dispersed in ferroelectric liquid crystals (FLCs) on the properties of the resulting nanocolloids has been investigated by thermoanalytical, electrooptical and dielectric methods. All gold nanoparticles were protected by thiolate capping layers either connected via alkyl groups of different chain length or via flexible spacers bridged to liquid crystalline p-cyano-biphenyl end groups. The colloidal stability of the gold nanocomposites with capping layers consisting of nonyl or octadecylthiolate groups is drastically reduced compared to the stability of those with p-cyano-biphenyl end groups. The present work describes the influence of the kind of capping layers around the gold nanoparticles and the effect of the amount of gold nanoparticles dispersed in such liquid crystal colloids on their electrooptical and dielectric parameters.
Cubic nanocrystalline CdS was hydrothermally transformed into hexagonal CdS in the presence of Na3PO4 at 180 °C for 12 h. The as-prepared CdS samples were characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), BET, electrophoretic analysis, photoluminescence (PL) spectra and UV-Vis absorption spectra techniques. Effects of phosphate concentration, hydrothermal time and Pt loading content were investigated. Their photoactivity was evaluated by hydrogen evolution from aqueous solution containing formic acid as a hole scavenger under visible light (λ ≥ 420 nm) irradiation. Phosphate markedly promotes the phase transformation of CdS from cubic to hexagonal. With 0.050 mol L−1 PO43−, the formed hexagonal phase content reaches a maximum (82%). The as-prepared CdS with a high percentage of hexagonal phase displays excellent activity for photocatalytic hydrogen evolution. Pt is highly dispersed on CdS so that the Pt content for the effective hydrogen evolution is very low. The CdS loaded with 0.025 wt% Pt shows the maximum activity for the hydrogen evolution. The apparent quantum yield at 420 nm amounts to 21.4%. This work highlights a facile and low-cost method for the preparation of a highly-efficient CdS photocatalyst. The possible mechanisms were discussed.
The mechanism for hydrothermal growth of ZnO was studied in ammonium hydroxide solution at pH near 11 (0.3 M NH4OH). The products formed at 20–90 °C and ambient pressure were characterised using Fourier Transform Infrared Spectroscopy (FTIR), X-ray PhotonSpectroscopy (XPS), X-ray Diffraction (XRD) and Secondary Ion Mass Spectroscopy (SIMS). Under these conditions, the growth of ZnO occurs via the initial precipitation of ε-Zn(OH)2 (Wülfingite), which subsequently dehydrates, to form Würtzite ZnO. Isotope tracking experiments show that most of the oxygen atoms do not mix with water during the conversion from Wülfingite to ZnO, and thus that the reaction proceeds primarily in the solid phase rather than through dissolution then reprecipitation. XPS results show that the surface of hydrothermal ZnO consists primarily of zinc hydroxide at lower temperatures, and there is a significant fraction of zinc hydroxide persisting at higher temperatures. Together these results show that much of the solid-solution interface is mainly comprised of zinc hydroxide not ZnO. These findings may have implications for understanding how small organic molecules can be used to control the morphology of zinc oxide crystals grown under hydrothermal conditions.
This article summarizes the results obtained by various experimental methods on the physical properties of a bent-core nematic liquid crystal 4-chloro-1,3-phenylene bis-4-[4′-(9-decenyloxy) benzoyloxy] benzoate (ClPbis10BB). The material exhibits unusual properties in all aspects tested. Its bend flexoelectric coefficient is 1000 times larger than in calamitics; it is viscoelastic with a large, shear-rate-dependent viscosity. Its bend and twist elastic constants are abnormally low; thus the nematic phase can be rendered to be a blue fog phase with a small amount of chiral dopant. It shows very high flow birefringence and unusually small leading Landau coefficient. It has two types of isotropic phases; at lower temperature it is probably tetrahedratic that can be transferred into the nematic phase with magnetic field. ClPbis10BB has a frequency-dependent conductivity anisotropy which is characterized by a double sign inversion. It exhibits various electroconvection (EC) patterns which are currently not understood in the frame of the standard theory of EC.
This paper presents the results of a series of experiments in which a giant pulsed ruby laser is used to study several different nonlinear optical effects arising from an induced optical polarization third order in the electric field strength. The various phenomena studied are special cases of either frequency mixing or intensity-dependent changes in the complex refractive index, including Raman laser action at a focus. A wide range of crystalline and isotropic materials was studied. The theory for these effects is extended to cover resonant interactions. The experimental results are interpreted in terms of simplified models, and quantitative values for the nonlinear polarizability coefficients are given. The rather large experimental uncertainties in these coefficients are discussed.
In this study, cadmium sulfide (CdS) nanocrystal thin films and nanowires have been deposited onto mechanically flexible substrates via dc-electrodeposition, which is a very suitable technique for large area manufacturing. For the first time with this study, flexible CdS nanocrystal thin films were integrated into photoelectrochemical (PEC) cells and their performances were compared with CdS nanowires. It has been demonstrated that PEC performance of both nanocrystal thin films and nanowires were a strong function of production conditions such as deposition time and voltage. The maximum power conversion efficiency of the CdS nanocrystal thin films obtained in this study was 0.3%. On the other hand, higher efficiencies (about 1.4%) were observed for the CdS nanowires. UV–vis analysis confirmed that both transmittance and band gap energies of the CdS nanowires were lower than that of CdS nanocrystal thin films. X-ray diffraction analysis revealed that both nanocrystal thin films and nanowires have a preferred orientation at 26° (2θ), which can be attributed to the CdS (002) structure.
The electrical properties of frustrated twist grain boundary (TGB) phase are a matter of curiosity. Some studies have indicated the existence of soft and Goldstone modes in TGBA and TGBC* phases respectively. However, the experimental results are still not very conclusive. In the present work, we report dielectric studies of wide temperature range TGBA and TGBC* phases of an optically active dimeric compound 4‐n‐decyloxy‐4′‐(cholesteryloxycarbonyl‐1‐butyloxy) chalcone in the frequency range of 1 Hz to 35 MHz for the planar and homeotropic anchoring of the molecules. Two different relaxation processes have been detected for the planar anchoring of molecules in the TGBA and TGBC phases. The soft mode like behaviour is obtained due to tilt fluctuation of molecules in the megahertz region for both TGBA and TGBC* phases. Goldstone mode like behaviour due to phase fluctuation of molecules has been detected for the TGBC* phase in the low frequency region (∼200–300 Hz). Activation energies for DC conductivity have also been determined for various phases of the material.
TGA investigations on the thermal degradation of isotactic polypropylene–vapor grown carbon nanofibers composites in nitrogen are reported. The mass evolution as a function of temperature is a single sigmoid for both polypropylene and polypropylene loaded with carbon nanofibers. The inflection temperature of these sigmoids increases as the concentration of carbon nanofibers is increased. The width of the degradation process narrows as the concentration of carbon nanofibers is increased due to a better homogenization of the local temperature provided by the high thermal conductivity of carbon nanofibers. Thermogravimetric analysis data indicate the formation of polymer–carbon nanofiber interface. Based on TGA data, a two-layer structure is proposed for carbon nanofibers–polypropylene interface. The external layer is soft and has a thickness of about 102nm that confines most polymer molecules in interaction with nanofibers. The core layer is rigid and has a thickness of the order of few nanometers.
Structures and properties of liquid crystalline phases formed by bent-core molecules are reviewed. At least eight phases designated as B1-B8 have been found, being unambiguously distinguished from phases formed by usual calamitic molecules due to a number of remarkable peculiarities. In addition to B1-B8 phases, smectic A-like phases and biaxial nematic phases formed by bent-core molecules are also reviewed. The most attractive aspects of this new class of liquid crystals are in polarity and chirality, despite being formed from achiral molecules. The bent-core mesogens are the first ferroelectric and antiferroelectric liquid crystals realized without introducing chirality. Spontaneous chiral deracemization at microscopic and macroscopic levels occurs and is controllable. Moreover, achiral bent-core molecules enhance system chirality. The interplay between polarity and chirality provides chiral nonlinear optic effects. Further interesting phenomena related to polarity and chirality are also reviewed.
A layer of thin gold film was sandwiched between a silicon substrate and an Al film to form the Al/Au/Si structure. Subsequent anodization leads to formation of a Si-based anodic aluminum oxide (AAO) template (AAO/Au/Si structure) with ordered nanopores. This kind of template has unique electrodeposition properties and can bond well with the deposited materials. The anodic process of the Al/Au/Si structure was investigated in detail by in situ monitoring the current–time curve. As an application, CdS nanowires were fabricated on the silicon substrate using this kind of AAO templates. Light-emitting property from the CdS nanowires was observed. This kind of Si-based light-emitting nanowires are expected to have practical applications in optoelectronic integration.
The dispersion and absorption of a considerable number of liquid and dielectrics are represented by the empirical formula ε*−ε∞=(ε0−ε∞)/[1+(iωτ0)1−α]. In this equation, ε* is the complex dielectric constant, ε0 and ε∞ are the ``static'' and ``infinite frequency'' dielectric constants, ω=2π times the frequency, and τ0 is a generalized relaxation time. The parameter α can assume values between 0 and 1, the former value giving the result of Debye for polar dielectrics. The expression (1) requires that the locus of the dielectric constant in the complex plane be a circular arc with end points on the axis of reals and center below this axis.
If a distribution of relaxation times is assumed to account for Eq. (1), it is possible to calculate the necessary distribution function by the method of Fuoss and Kirkwood. It is, however, difficult to understand the physical significance of this formal result.
If a dielectric satisfying Eq. (1) is represented by a three-element electrical circuit, the mechanism responsible for the dispersion is equivalent to a complex impedance with a phase angle which is independent of the frequency. On this basis, the mechanism of interaction has the striking property that energy is conserved or ``stored'' in addition to being dissipated and that the ratio of the average energy stored to the energy dissipated per cycle is independent of the frequency.
Different contributions to the dielectric permittivity in ferroelectric liquid crystals are discussed, with emphasis on the soft mode and the Goldstone mode and their location in the dielectric spectrum. Experimentally, the complex dielectric permittivity has been studied as a function of temperature and frequency in the range 5 Hz - 13 MHz for three different ferroelectric liquid crystal materials. The main problems encountered in dielectric measurements at low and high frequency are discussed in some detail. The soft mode dielectric behaviour has been studied as a function of temperature, frequency and bias electric field. The applicability of the Curie-Weiss law for the soft mode dielectric contribution in the A phase was analyzed. In the C phase the temperature dependence of the dielectric contribution of the Goldstone mode has been measured. By applying a bias electric field, we have been able to study the soft mode dielectric behaviour also deep into the C phase. In the A and C phases the relaxation frequency and the inverse of the dielectric strength of the soft mode vary linearly with |T-TC|, which can be used to determine the A-C transition temperature to a good accuracy. The ratio of the slopes of the soft mode relaxation frequency vs temperature line and the inverse of dielectric strength vs temperature line in the C and A phases has been calculated for the three compounds and compared with solid ferroelectric systems. The soft mode rotational viscosity in the A phase has been calculated for one of the compounds.
Various modes are being explored for the construction of functional materials out of nanoparticles. Despite these efforts, the assembly of nanoparticles remains challenging with respect to the requirement of multiple component organization on varying dimensions and length scales. We report here a room-temperature, wet chemical-based synthesis route in which silica and gold nanoparticles (10 nm) are cooperatively assembled with lysine−cysteine diblock copolypeptides into robust hollow spheres (diameter microns). The walls of the hollow spheres are composed of two distinct layers of silica and gold nanoparticles, and the hollow center is created without the use of a sacrificial core, emulsion phase, or hollow preformed substrate. Block copolypeptides designed with specific recognition sites for nanoparticles of various compositions provide a versatile approach for the hierarchical organization of nanoparticles into multidimensional composite arrays.
A new type of liquid crystalline side-chain polyacrylate has been built through selective intermolecular hydrogen bonding between H-bond donor and acceptor moieties. Polyacrylate P6OBA with a 4-oxybenzoic acid pendant group attached to its side chain through a hexamethylene spacer has been prepared for use as an H-bond donor polymer. A series of trans-4-alkoxy-4'-stilbazoles nOSz having the linear alkyl chain CnH2n+1 (n = 1-8 and 10) have been used as H-bond acceptors. Self-assembly of the polymer and the stilbazole results in the selective formation of thermotropic side-chain polymeric complexes having well-defined molecular structures. A mesogenic structure that induces a stable mesophase is formed in the polymer side chain through the single hydrogen bond between the benzoic acid pendant group of the polymer and the pyridyl unit of the stilbazole. All polymeric 1:1 complexes exhibit stable and homogeneous smectic A phases. For example, the complex from P6OBA and 2OSz shows a smectic A phase between 89 and 200-degrees-C. The isotropization and melting temperatures show odd-even effects for the terminal alkoxy group. Monomeric 1:1 complexes having the same type of H-bonded mesogen as that of the polymeric complexes have been prepared from 4-(hexyloxy)benzoic acid (6OBA) and the series of stilbazoles. For example, the monomeric 1:1 complex from 6OBA and 2OSz melts at 112-degrees-C and exhibits smectic A and nematic phases. The smectic A-nematic and nematic-isotropic transitions are observed clearly at 128 and 166-degrees-C, respectively. A binary phase diagram of polymeric complex P60BA-2OSz and monomeric complex 6OBA-2OSz shows complete miscibility over the entire range of composition.
Self-assembly of gold nanorods (NRs) with aspect ratio of 4.6 (12 nm in diameter and 50−60 nm in length) has been studied using transmission electron microscopy (TEM). Under appropriate conditions such as nanoparticle concentration, solvent evaporation, narrow size distribution, ionic strength, and surfactant concentration of the parent solution, gold nanorods assemble into one-, two-, and three-dimensional structures. Some of the three-dimensional assemblies extend to superlattices of NRs. The translation and orientation symmetries of the self-assembled structures are determined. The factors affecting the formation of the ordered self-assembly are discussed.
Values of the microwave and infrared dielectric loss epsilon'', the coefficient of the imaginary part of the complex permittivity epsilon* = epsilon' - jepsilon'', in the frequency ranges 0.46-130 GHz and 0.9-6 THz (30-180 cm-1), are reported for acyclic dimethyl carbonate (DMC) dissolved in cyclohexane and (for one solution) in benzene and for cyclic ethylene carbonate (EtC) dissolved in benzene at 25-degrees-C. For the DMC solutions in cyclohexane, the spectral profiles are described by the sum of two Debye relaxation processes and by a Powles-Rocard relaxation process retaining the angular velocity or inertial relaxation time tau(J3). A fourth resonant process centered at 4.1 THz (approximately 135 cm-1) is described by a Gaussian-Lorentzian product function. For the EtC solutions in benzene, the spectral profiles are described by the sum of two Debye and one Powles-Rocard relaxation process. The solvent benzene, however, contributes to the loss with a process centered around 60-70 cm-1 as already reported in the literature. A fourth resonant process for EtC in benzene, centered at approximately 215 cm-1, can be described by a separate Gaussian-Lorentzian product function. The two Debye processes for both solute carbonates are attributed to molecular rotation around two axes of symmetry of the molecules. The Powles-Rocard process is interpreted as arising from molecular librations. The resonant process for DMC at approximately 135 cm-1 has been assigned to molecular torsion. The resonant process for EtC is ascribed to an out-of-plane vibration of the ring or ring puckering also in accord with literature interpretations. An alternate description of the fourth process for DMC in cyclohexane in terms of a second Powles-Rocard process is also offered. Static permittivity data and sodium doublet refractive index values for the above mixtures at 25-degrees-C required to elaborate the data are also reported.