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Influence of mesoporous defect induced mixed-valent NiO (Ni 2+/ Ni 3+ )-TiO 2 nanocomposite for non-enzymatic glucose biosensors

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Influence of mesoporous defect induced mixed-valent NiO (Ni 2+/ Ni 3+ )-TiO 2 nanocomposite for non-enzymatic glucose biosensors

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Abstract

An extraordinary sensitive and selective non-enzymatic glucose sensor has been demonstrated based on the electrochemically highly stable NiO-TiO2 mixed oxide comprising the defect induced mesoporous TiO2 nanoparticles with Ni²⁺ and Ni³⁺ ions scattered on the surface. The defects on TiO2 nanoparticles have been successfully introduced using NiO to investigate the interfacial properties between NiO and TiO2. This defect induced interfacial behavior was characterized using X-ray diffraction, X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy analyses. The obtained mixed oxide NiO-TiO2 nanocomposite dispersion was drop casted on glassy carbon electrode to form a NiO-TiO2/GCE modified electrode for non-enzymatic glucose sensor. The defects along with high surface area of mixed oxide enabled excellent electrocatalytic activity for glucose oxidation with sensitivity of 24.85 μA mM⁻¹ cm⁻² and detection limit of 0.7 μM (S/N = 3). The Ni ions scattered on the surface of TiO2 nanoparticles, enabling effective charge transfer process, circumventing the agglomeration during prolonged detection, and resulting the unprecedented long-term stability and sensitivity. Thus, this defect induced mesoporous metal oxide nanocomposite is an outstanding candidate for application as redox active material in electrochemical biosensors.

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... This suggests that the TiO 2 NPs in the nanocomposite structures are simultaneously deposited and doped with Ni ions due to the comparability of the ionic radii of Ni ions with the Ti ions in the anatase structure [30] and also their formation mechanism (see Scheme 2). As depicted in Scheme 2b,c, it is probable that the Ni ions are trapped in the TiO 2 lattice structure by incomplete phase segregation of the TiO 2 and NiO phases from the alloyed NiTi NPs during the thermal annealing process [30] or because of the presence of many interfaces between TiO 2 and NiO phases in the structure [63]. As will be proved by XPS analysis, a significant amount of Ni 3+ ionic state is present in the structure which is easier to replace Ti 4+ in the lattice space of anatase TiO 2 because of the slight difference in the ionic radius of Ni 3+ (0.070 nm) and the ion radius of Ti 4+ (0.0745 nm) in six-coordained TiO 6 octahedron spaces [22,63]. ...
... As depicted in Scheme 2b,c, it is probable that the Ni ions are trapped in the TiO 2 lattice structure by incomplete phase segregation of the TiO 2 and NiO phases from the alloyed NiTi NPs during the thermal annealing process [30] or because of the presence of many interfaces between TiO 2 and NiO phases in the structure [63]. As will be proved by XPS analysis, a significant amount of Ni 3+ ionic state is present in the structure which is easier to replace Ti 4+ in the lattice space of anatase TiO 2 because of the slight difference in the ionic radius of Ni 3+ (0.070 nm) and the ion radius of Ti 4+ (0.0745 nm) in six-coordained TiO 6 octahedron spaces [22,63]. However, Ag + (0.129 nm) and Ti 4+ (0.0745 nm) have highly different ionic radii, which makes doping of Ag + less significant in the TiO 2 component of the TiO 2 -NiO-Ag nanocomposite structure [64]. ...
... Deconvolution analysis results in Fig. S4b show that 91.7 at% of the Ag atoms are in Ag 0 metallic state, leaving only 8.3 at% of the Ag atoms in Ag + oxidation state. As we did not observe any characteristic peak of silver oxide in the XRD pattern of the structure (see Fig. 1b), this oxide phase is most probably because of the slight oxidation of the surface of Ag NPs during the thermal annealing process [82,83] or structure, but probably exists as an intrinsic defect in the NiO structure or as an extrinsic dopant in the TiO 2 lattice [63]. It is to note that the Ni 3+ ionic state has a very similar ionic radius to the Ti 4+ and can thus be easily doped into the TiO 2 lattice, in agreement with our observations on the XRD results [22,63]. ...
Article
Construction of Schottky heterojunctions with plasmonic metals and p-n heterojunctions with p-type semiconductors have been considered as two effective approaches for boosting photocatalytic activity of TiO2. Here, we report on a magnetically-recyclable TiO2-NiO-Ag p-n/Schottky heterojunction photocatalyst, fabricated by a facile and two-step approach combining spark discharge generation of mixed metallic nanoparticles under a protective argon atmosphere and a suitable thermal annealing process at air. Our comprehensive characterization studies revealed the formation of a mesoporous nano-heterostructure consisting of defective TiO2 nanoparticles that were finely incorporated with well-dispersed p-type NiO and Ag nanoparticles. Thanks to its extremely high surface area (223.07 m2.g-1), reduced optical band gap (~1.88 eV), improved visible-light absorption (~26% within 400-900 nm), and suppressed charge carriers recombination rate, our structure exhibited an enhanced photocatalytic degradation efficiency of 93.8% and a mineralization efficiency of 87.5% within 90 min irradiation towards methylene blue decomposition, superior to those of pure TiO2, NiO, and TiO2-NiO samples. This nanocomposite structure shows a large potential for practical application in the areas of environmental remediation and other photocatalytic applications.
... The detailed experimental procedure and physicochemical characterization techniques used are well described in our recent report [43]. Typically, the mesoporous TiO 2 nanoparticles was prepared by dissolving 30 ml of titanium tetra-isobutoxide in 150 ml of isopropyl alcohol (1:5 ratio) under continuous stirring at 600 rpm followed by the drop-wise addition of 0.5 M citric acid into the colloidal mixture to form gel. ...
... The preparation of mixed-valent mesoporous NiO@TiO 2 nanocomposites has been reported in our recent publication [43]. In a typical experiment, as-prepared mesoporous TiO 2 powder and nickel acetate (9:1) was grounded and then calcined at 450 � C for 3h. ...
... Furthermore, the materials were studied by XPS, Raman, TEM, DRS, and thermal analysis. A detailed report of XRD and XPS data for this material can be found in our recent publication [43]. In brief, Fig. 1(a-d) Raman scattering was measured to examine the structural changes associated with peak position and their intensities in TiO 2 upon insertion of NiO and showed in Fig. 1b, the inset highlights the expansion of intensity. ...
Article
Colourful dyes are primarily used in the textiles, toys, food, inks, paper and plastics. These dyes are water soluble and contaminate the water. The dyes are not bio-degradable and sustain in the water for long time create diseases like bladder tumour and chromosomal damage. Hence dyes are the major cause of pollution and must be removed from domestic and drinking water. The photocatalysts are energy-less technology for dye degradation and expected to solve clean water problems. Most of the photocatalysts are metal oxides and absorbed in the ultra violet region. But, sun light mostly consists of visible light, hence to use the sunlight effectively the absorption spectrum of the photocatalysts must be tuned to the visible region. Herein, we proposed visible light absorbed new TiO2/NiO nanocomposite for methyl orange dye degradation. The integration of NiO modified the TiO2 nanocomposite UV absorption spectrum into visible light region. The photocatalyst was prepared using mechano-thermal method and characterised using PXRD, TGA, FT-IR, HR-TEM, EDS, UV, PL and DRS methods. The photocatalytic property was explored using the degradation of methyl orange and compared the activity with different time intervals and wide range of pH. Within 60 min of irradiation, 98% of degradation was observed. Similarly, at all pH range more than 50% of degradation was observed, but the best performance (98%) was observed at pH = 7 (neural). Thus, the TiO2/NiO nanocomposite catalyst was effective in neutral, acidic and basic polluted water treatment. The synthesized TiO2/NiO nanocomposite is tuneable to visible light and degrade the methyl orange dye in all pH range.
... A large number of electrodes modified with metal-based nano-and composite-materials have been used in the construction of non-enzymatic glucose biosensors. Some noble metal (Au, Pt, Pd and Ag) nanoparticles (NPs) [26][27][28][29], transition metals (Cu-and Ni-NPs) [30,31], metal oxides (NiO, CuO, Co 3 O 4 , NiNPs-ZnO, NiO-TiO 2 ) [32][33][34][35][36], metal hydroxides (Ni(OH) 2 ) [19,20,37], metal sulfides (CuS, CoS, NiS) [38][39][40][41], bimetallic nanoparticles and alloys (Cu-Ni, Co-Ni, Ni-Ag, Ni-Au etc [42][43][44][45], metal organic or zeolitic imidazolate frameworks (Cu-MOF, Ni-MOF, Co-ZIF)) [46][47][48] and transition metal complexes [49][50][51] have been successfully used for this purpose. ...
... The recorded cyclic voltammograms presented in Fig. 4 illustrates that both electrodes have a well-defined reversible redox couple, which is attributed to the reversible oxidation of Ni(OH) 2 , which is formed at electrode surface under alkaline media, into NiO(OH). Similar Ni 2+ /Ni 3+ -based redox pair has also been reported in the case of some others Ni-based modified electrodes [18][19][20]36,53]. These anodic and cathodic peaks increased by the increase of scan rate from 2.5 to 400 mV s − 1 . ...
... This effect is related to hindered diffusion of glucose through Ppy layer towards electro-catalytic NiO(OH) structures, which was electrodeposited at electrode surface. It is well known that Ni-modified electrodes exhibit oxidational electrocatalytic activity towards glucose [18,20,41,36,45,54]. Thus, to observe this electrocatalytic effect at here designed electrode surface, cyclic voltammograms of all modified electrodes were recorded in solution containing 0.10 mol L − 1 of NaOH and different glucose concentrations at a scan rate of 50 mV s − 1 . ...
Article
This study reports non-ezymatic electrocatalytic amperometric glucose biosensor based on a graphite rod electrode (GRE) modified with biomimetic-composite consisting of Ni nanoparticles (Ni-NPs) and polypyrrole (Ppy) prepared by 1 cycle electro polymerization of pyrrole monomer (Ni-NPs/Ppy(1)/GRE). During the modification of GRE, the electropolymerization of pyrrole and the electrodeposition of Ni-NPs onto GRE surface were consequentially performed by potential cycling. Surface morphology of Ni-NPs/Ppy(1)/GRE electrode was evaluated by atomic force microscopy and scanning electron microscopy based imaging, and electrochemical characterization of electrodes was performed by electrochemical impedance spectroscopy and cyclic voltammetry. Cyclic voltammograms recorded in the presence of glucose show that Ni-NPs/Ppy(1)/GRE at +500 mV vs Ag/AgCl exhibits efficient electrocatalytic oxidation activity towards glucose, while the oxidation of glucose was not observed at a bare GRE. Amperometric sensing of glucose was performed by Ni-NPs/Ppy(1)/GRE at constant +450 mV vs Ag/AgCl electrode potential in 0.10 mol L⁻¹ NaOH. Ni-NPs/Ppy(1)/GRE-based sensor, which was characterized by a wide linear glucose determination range between 1.0 and 1000 µmol L⁻¹ with a limit of detection of 0.4 µmol L⁻¹ and a sensitivity of 2873 µA mmol⁻¹ L cm⁻². The applicability of here reported Ni-NPs/Ppy(1)/GRE-based sensor has been demonstrated by the determination of glucose concentrations in real samples.
... The detailed experimental procedure and physicochemical characterization techniques used are well described in our recent report [43]. Typically, the mesoporous TiO 2 nanoparticles was prepared by dissolving 30 ml of titanium tetra-isobutoxide in 150 ml of isopropyl alcohol (1:5 ratio) under continuous stirring at 600 rpm followed by the drop-wise addition of 0.5 M citric acid into the colloidal mixture to form gel. ...
... The preparation of mixed-valent mesoporous NiO@TiO 2 nanocomposites has been reported in our recent publication [43]. In a typical experiment, as-prepared mesoporous TiO 2 powder and nickel acetate (9:1) was grounded and then calcined at 450 � C for 3h. ...
... Furthermore, the materials were studied by XPS, Raman, TEM, DRS, and thermal analysis. A detailed report of XRD and XPS data for this material can be found in our recent publication [43]. In brief, Fig. 1(a-d) Raman scattering was measured to examine the structural changes associated with peak position and their intensities in TiO 2 upon insertion of NiO and showed in Fig. 1b, the inset highlights the expansion of intensity. ...
Article
A noble-metal free and surface defect-induced mesoporous mixed valent NiO decorated TiO2 heterostructure with tuned bandgap has been successfully prepared. Its outstanding visible-light driven hydrogen evolution and its excellent H2 storage ability have been examined and confirmed. The formation of oxygen vacancies by surface defect creates the Ni³⁺ and Ti³⁺ on the interface of the heterostructure induce the efficient H2 evolution, bench-marked by 1200% enhancement in catalytic performance. The underlying chemistries include the near-unity occupancy of eg orbital (t2g⁶ eg¹) of Ni³⁺ which speeds up the electron transfer and significantly promote the excellent electron-hole separation efficiency, establishes the outstanding overall charge-transfer efficiency and long-term photocatalytic activity in the visible light spectrum. Multiple Ti³⁺ adsorption centers in the structure attract multiple intact H2 molecules per each center via a sigma - pi bonding motif - namely the Kubas interaction - which leads to 480% higher H2 adsorption capability against the performance of the pristine mesoporous TiO2. Not only the significant results, the study also provide an air-stable synthetic method on the basis of low-cost and abundant materials, which are strongly favoured for scaling up production.
... However, the unaffordable cost of these metals for the development of NEG sensors has limited their use. Consequently, researchers have commenced designing NEG sensors based on metals and their oxides, and in particular, the focus was given to Ni (Rajendran et al., 2018), Zn (Yang et al., 2016a;Ognjanović et al., 2019), Cu (Shabnam et al., 2017), NiO (Baghayeri et al., 2018b), CuO (Shabnam et al., 2017), NiCo 2 O 4 (Baghayeri et al., 2018b;Rajendran et al., 2018), Fe (Li et al., 2015;Marie et al., 2018), Mn (Li et al., 2015;Xie et al., 2018a), Ti (AL-Mokaram et al., 2017), Ir (Dong et al., 2018a;Dong et al., 2019), and Rh (Dong et al., 2018b) etc. ...
... However, the unaffordable cost of these metals for the development of NEG sensors has limited their use. Consequently, researchers have commenced designing NEG sensors based on metals and their oxides, and in particular, the focus was given to Ni (Rajendran et al., 2018), Zn (Yang et al., 2016a;Ognjanović et al., 2019), Cu (Shabnam et al., 2017), NiO (Baghayeri et al., 2018b), CuO (Shabnam et al., 2017), NiCo 2 O 4 (Baghayeri et al., 2018b;Rajendran et al., 2018), Fe (Li et al., 2015;Marie et al., 2018), Mn (Li et al., 2015;Xie et al., 2018a), Ti (AL-Mokaram et al., 2017), Ir (Dong et al., 2018a;Dong et al., 2019), and Rh (Dong et al., 2018b) etc. ...
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There is an undeniable growing number of diabetes cases worldwide that have received widespread global attention by many pharmaceutical and clinical industries to develop better functioning glucose sensing devices. This has called for an unprecedented demand to develop highly efficient, stable, selective, and sensitive non-enzymatic glucose sensors (NEGS). Interestingly, many novel materials have shown the promising potential of directly detecting glucose in the blood and fluids. This review exclusively encompasses the electrochemical detection of glucose and its mechanism based on various metal-based materials such as cobalt (Co), nickel (Ni), zinc (Zn), copper (Cu), iron (Fe), manganese (Mn), titanium (Ti), iridium (Ir), and rhodium (Rh). Multiple aspects of these metals and their oxides were explored vis-à-vis their performance in glucose detection. The direct glucose oxidation via metallic redox centres is explained by the chemisorption model and the incipient hydrous oxide/adatom mediator (IHOAM) model. The glucose electrooxidation reactions on the electrode surface were elucidated by equations. Furthermore, it was explored that an effective detection of glucose depends on the aspect ratio, surface morphology, active sites, structures, and catalytic activity of nanomaterials, which plays an indispensable role in designing efficient NEGS. The challenges and possible solutions for advancing NEGS have been summarized.
... After adding the Cr into the NiFe-LDH host, a positive shift in the Ni 2þ and Fe 3þ peak is observed, which confirms the doping of Cr into NiFe-LDH [41]. The deconvolution of the Ni 2p 3/2 spin orbit showed Ni 2þ and Ni 3þ peaks at 855.8 eV and 857.1 eV, respectively [42]. In Fig. 3(f), the XPS spectra of Cr 2p reveals the existence of Cr 3þ oxidation state in NiFeCr-LDH [43,44]. ...
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... Table S2 shows the comparison of the analytical performance of state-of-the-art non-enzymatic glucose sensors. Non-enzymatic glucose sensors have overall excellent LOD and sensitivity; however, they require higher operation voltage and are limited in conducting experiments under physiological conditions [42][43][44][45][46][47]. ...
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We developed a new photolithographic method for introducing micro-patterned metal array onto flexible substrates without the substrates being affected by temperature, solvent, or UV exposure. We used SL-03, acrylate copolymer as a separation layer between glass carrier and metal pattern, and transferred the micropattern from the glass to a flexible substrate in the last step of the process. Through the developed micropatterning technology, we successfully fabricated the glucose sensor. The proposed glucose sensor has a LOD of 1.2 μM and a dynamic range from 0.05 to 0.30 mM, which covers the screening of diabetes in sweat. The sensor showed a good stability and reproducibility in mechanical deformation and continuous glucose monitoring conditions. In addition, miniaturized multiple glucose sensors were fabricated in limited area, which provided the exceptional accuracy (R² ≈ 0.9978) compared to the mono glucose sensor. These results confirm that the proposed glucose sensors based on new photolithographic method are highly promising for application as healthcare sensors such as continuous glucose level monitoring on a flexible devices.
... To date, numerous approaches have been successfully used for glucose determination, such as fluorescence , chemiluminescence , spectrometry (Galant et al., 2015), and electrochemical methods (Zhu et al., 2018;Lu et al., 2015b). Among these techniques, electrochemical glucose sensors have attracted the attention of scientists because of the important properties of their detection method, such as sensitivity, rapid response time, simplicity, and low production cost (Rajendran et al., 2018;Huang et al., 2017). ...
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This work reports the synthesis of nickel/nickel hydroxides nanoflakes (Ni/Ni(OH)2-NFs) at room temperature via a novel chemical deposition and exfoliation from a liquid crystal template mixture. The nickel ions dissolved in the interstitial aqueous domain of the Brij®78 hexagonal liquid crystal template were deposited by a reducing agent of sodium borohydride that concurrently reduces the nickel ions and generates extreme hydrogen gas bubbles, that exfoliated the nickel/nickel hydroxide layers. The Ni/Ni(OH)2-NFs crystal structure, morphology, and surface area characterizations revealed the formation of semi-crystalline α-Ni(OH)2 nanoflakes with a thickness of approximately 10 nm and a specific surface area of about 135 m²/g. The electrochemical measurements of cyclic voltammetry, chronoamperometry, and impedance analysis showed that the Ni/Ni(OH)2-NFs exhibited significant performance for the glucose non-enzymatic oxidation in an alkaline solution in comparison to the bare-nickel hydroxide (bare-Ni(OH)2) deposited without surfactant. The Ni/Ni(OH)2-NFs electrode showed superior glucose oxidation activity over the bare-Ni(OH)2 catalyst with a sensitivity of 1.078 mA mM⁻¹ cm⁻² with a linear concentration dependency range from 0.2 to 60 mM and a detection limit of 0.2 mM (S/N = 3). The enhanced electrochemical active surface area and mesoporosity of the 2D nanoflakes make the Ni/Ni(OH)2-NFs a promising catalyst in the application of glucose non-enzymatic sensing.
... By using Kubelka-Munk method, the bandgap values of MTNPs-2 of 3.21 eV, as shown in the inset of Fig. 4b correspond to the commercial TiO 2 bandgap of 3.2 eV. [34][35][36][37] The sensing performance of GCE/MTNPs-2/GOx electrode.-The mechanism diagram of MTNPs-2 immobilized by GOx to detect glucose is shown in Fig. 5a. ...
Article
This study reports on an enzymatic glucose sensor based on mesoporous TiO2 nanoparticles (MTNPs) synthesized by a simple solvothermal method. The unique structure of MTNPs with a fairly homogenous shape, porous, and high crystallinity is the consequence of the use of PVP yang during the synthesis process. PVP plays an important role in creating the uniform morphology and mesoporous structure of MTNPs-2. The success of glucose oxidase immobilization on the surface of MTNPs was proven by FTIR and UV–vis characterizations. The prepared GCE/MTNPs-2/GOx electrode successfully detects glucose molecules with good sensing performance with a sensitivity of 0.4098 μA mM−1 cm−2, a wide linear range of 0.1–1 mM, and a relatively low detection limit of 73 μM.
... T-NTs alone show poor conductivity and lack affinity towards glucose oxidation [29]. Although surface treatment can improve the overall properties of T-NTs, their ability to electrochemically detect glucose is limited [30]. ...
Article
The surface properties of nanostructures play a vital role in defining the electrical and optical properties of nanomaterials needed for various applications. In this study, the TiCl4 surface treatment approach was used to enhance the performance of TiO2 nanotubes (T-NTs) based electrochemical sensors. The TiCl4 treated TiO2 nanotubes and pristine TiO2 nanotubes were deposited with a glucose-sensing mediator (Cu2O nanoparticles (NPs)), and a systematic comparison of their performances using cyclic voltammetry (I-V) curves, Nyquist plot, Mott-Schottky plot, chronoamperometry (I-T) curves, and sensitivity curves are presented. The TiCl4 treated sensors demonstrated 2 times higher sensitivity of 0.4 mA mM-1 cm-2 and 2.5 times lower limit of detection of 80 μM, whereas the untreated nanotubes-based sensors had lesser sensitivity of 0.19 mA mM-1 cm-2 and a higher limit of detection of 200 μM. Further, the treated substrates exhibited a higher donor charge density of 8.79 x 1021 cm-3 in comparison to plain T-NTs (6.5 x 1021 cm-3). The enhanced electrocatalytic performance of the surface-treated sensor was due to the formation of an additional TiO2 layer over the surface of nanotubes which reduced the surface defects and introduced Ti3+ ion in the nanotubes. This resulted in improved electronic contacts of T-NTs with the Cu2O NPs, increasing donor charge density, reduced band-gap, and yielded a three-fold enhancement in electrical conductivity, thereby increased the overall electrochemical sensing performance. Thus, the strategy of TiCl4 surface modification on TiO2 nanotube arrays is effective in enhancing the performance of T-NTs based electrochemical sensors.
... Moreover, FETs of these materials can be processed at moderate temperatures from solutions facilitating deposition on a large scale economically and the conductivity tuned by varying crystal size, morphology, dopant, contact geometry and temperature of operation [46,102,103]. Metal oxides, to date, have been applied as electrochemical and photoelectrochemical transducers for bio/chemical sensing [30,[103][104][105][106] and FET transducer for sensing of gases [107,108]. As mentioned previously, FET gas sensors of metal oxides typically operate at high temperatures, leading to higher energy needs and reliability and safety issues. ...
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... Nowadays, TiO 2 based heterojunction photocatalysts have attracted wide attention and utilized for various application. This is due to the effectiveness of heterojunction photocatalysts in facilitating charge transfer and suppressing the recombination of photogenerated e-/h + pairs, which help to improve the photocatalytic performance [42]. Li et al. [43] explored the potential of TiC x /SiC x heterojunction semiconductor as anode material. ...
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In this work, ZrO2–TiO2 heterojunction photocatalysts were successfully synthesized using sol–gel method. The effect of ZrO2 doped into TiO2 on the retardation of the electron–hole pairs were investigated. The crystalline structure of ZrO2–TiO2 heterojunction photocatalysts was verified through x–ray diffraction (XRD) patterns and the crystallite size were found smaller compared to TiO2 and ZrO2 photocatalysts. Morphological characterization evidenced that the co–doping of ZrO2 into TiO2 has altered the particle size of TiO2 and the shape of the synthesized particle through chemical nucleation and growth process in bulk solution. The small crystallite size of the ZrO2–TiO2 heterojunction recorded the highest surface area with higher incident in the mesopores volume as confirmed by Brunauer–Emmett–Teller (BET) analysis. The adsorption–photodegradation performance of the ZrO2–TiO2 heterojunction photocatalysts on oily wastewater as model pollutant enhanced with the incorporation of small amount of ZrO2 compared to TiO2. The presence of surface adsorbed water peaks and hydroxyl groups as disclosed by Fourier transform infrared (FTIR) supported the finding of the study.
... Nanomaterials and especially nanocomposites showed many advantages due to unique properties and high surface area [21][22][23][24][25][26][27]. The nanocomposite systems are used for various applications like solar cells, biosensors, antibacterial activity including photocatalytic activity [28][29][30][31][32][33][34][35]. In the recent times, the integration of noble metals with metal oxides also suppresses the charge recombination due to shift in fermi level [36]. ...
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Water contamination is increasingly an important issue in developing and under developed countries. The main cause of water contaminations are industrial dyes and toxic chemicals. Hence many technologies are being developed to de-contaminate the toxic materials. The photocatalytic de-contamination of dyes is an effective and simple technology to purify water. Among various photocatalysts, the transition metal based oxides (TiO2, NiO and ZnO) being the state-of art photocatalytic material. But, the metal oxides have large band gap and suffers from the fact that it predominantly absorbs the Ultra Violet region of irradiation. But, any viable photocatalytic technology demands absorption in the visible light region, so as to utilize the cost-free sun light. Herein, we tune and utilize the metal oxides through the integration of Ag metal nanoparticles. The synthesized materials were completely analyzed by PXRD, HRTEM, UV, XPS and BET instruments. All TiO2/Ag, NiO/Ag and ZnO/Ag nanocomposites were subjected to photocatalytic degradation using visible light. The nanocomposites acted as photocatalyst and degrade the colorful methyl orange and colorless toxic 4-chlorophenol. Among the aforementioned three samples, TiO2/Ag exhibited best performance than ZnO/Ag and NiO/Ag. We attributed the enhancement of photocatalytic activity due to Plasmons assistance and nanoscale regime of photocatalyst. In summary, we tuned the metal oxide photocatalytic performance using the Ag nanoparticle surface Plasmon resonance.
... A comparative analytic performance of the NiO nanosheets modified gold with other glucose sensors is shown in Table I. The low applied potential (+0.37 V) of our sensor is comparable with enzymatic glucose sensors 19,20 and better than most of the non-enzymatic glucose sensors, 15,16,18,21,36,[41][42][43][44][45][46][47][48] except one reported by Wang et al. 49 The low applied potential is a crucial parameter of any sensor for their successful implications. 50 Further, we studied the selectivity of the sensor in the presence of common interferents (Fig. 7). ...
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A non-enzymatic electrocatalyst, nickel oxide (NiO) nanosheets was developed via a facile hydrothermal approach and further characterized in detail. To harness the potential of NiO nanosheets as a potential electrocatalyst, the hydrothermally synthesized nanosheets were fixed onto the sensor working electrode for glucose sensing application. The NiO nanosheets providing abundance active sites for non-enzymatic glucose detection showed sensitive (1618.4 μA mM⁻¹ cm⁻²) response in the linear range of 0.25-3.75 mM. The excellent electrocatalytic activity of the NiO modified gold working electrode resulted in a low detection limit (2.5 μM). Moreover, the sensor selectively detected glucose in the solution containing common interferants such as cholesterol, dopamine, uric acid and ascorbic acid, further makes it highly suitable for non-enzymatic glucose detection in near-real samples. © 2020 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited.
... Dip-coating technique was employed to obtain TiO 2 films serving as sensors for microRNA (Wang M. et al., 2019), heme (Çakiroglu and Özacar, 2019), or glucose (Rajendran et al., 2018). The microRNA sensor is based on black TiO 2 deposed on indium tin oxide (ITO) substrate and improved with Au nanopoarticles. ...
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... Structural and morphological studies showed that the bimetallic MOF are electrochemically active than the singular Co-MOF and Ni-MOF. Van der Waals forces, non-covalent interactions between carboxyl groups of H 2 TZB and amino groups of antibodies [83,84], enables the antibodies to bind to the surfaces of deoxynivalenol, and salbutamol results in the efficient response of the materials as sensors through electrochemical interactions. This electrochemical-based immunosensor Co-Ni-MOF showed a better performance compared with the individual metal-organic framework of cobalt and nickel, with a detection limit of 0.05 pg·mL −1 and 0.30 pg·mL −1 towards deoxynivalenol (DON) and salbutamol (SAL), respectively, in the concentration range of 0.001 to 0.5 ng·mL −1 . ...
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... In recent years, many inorganic nanomaterials, such as metals [13][14][15][16], metal oxides [17][18][19][20][21], carbon nanocomposites [22][23][24], have been used as the sensitive materials for enzyme-free glucose sensors. Among them, the bimetallic sensitive materials containing platinum (Pt) are highly popular, such as Pt-Pd [25][26][27], Pt-Au [28,29], Pt-Ag [30], which have excellent electrical conductivity and high electrocatalytic activity toward glucose oxidation. ...
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TiO2 and 10 wt%Ni-ZrxTi1-xO2 (x = 0, 0.1, 0.15, and 0.2) catalysts were synthesized and used for CO2 methanation reaction. The catalyst with 10 mol% Zr addition (10 wt%Ni-Zr0.1Ti0.9O2) exhibited the highest CO2 conversion and CH4 selectivity with highly stable property. The role of Zr addition on enhancing CO2 methanation reaction rate was to tune the electronic property of Ni species by electron transfer from Zr to Ni valence state. From the donating effect of Zr, an appropriate metal-support interaction was then improved which led to higher dispersion of Ni species on catalyst surface which was beneficial to the adsorption of H2 molecules. Moreover, Zr addition also improved the basicity of the catalyst, which can also promote the adsorption of CO2. Therefore, an appropriate H2 and CO2 adsorption ability can enhance catalytic activity. The effect of tuning electronic properties by Zr addition on enhancing the catalytic performance resulted from lowering of C-O bonding dissociation barrier. Upon CO intermediate was adsorbed on Ni electron rich site, the electron of valence d state of Ni was transferred to π* anti-bonding of CO molecule and the C-O bonding was then weakened and easily dissociated to carbon and oxygen to further hydrogenation and formed products.
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Numerous studies suggest that modification with functional nanomaterials can enhance the electrode electrocatalytic activity, sensitivity, and selectivity of the electrochemical sensors. Here, a highly sensitive and cost-effective disposable non-enzymatic glucose sensor based on copper(II)/reduced graphene oxide modified screen-printed carbon electrode is demonstrated. Facile fabrication of the developed sensing electrodes is carried out by the adsorption of copper(II) onto graphene oxide modified electrode, then following the electrochemical reduction. The proposed sensor illustrates good electrocatalytic activity toward glucose oxidation with a wide linear detection range from 0.10 mM to 12.5 mM, low detection limit of 65 µM, and high sensitivity of 172 µA mM − 1 cm − 2 along with satisfactory anti-interference ability, reproducibility, stability, and the acceptable recoveries for the detection of glucose in a human serum sample (95.6–106.4%). The copper(II)/reduced graphene oxide based sensor with the superior performances is a great potential for the quantitation of glucose in real samples.
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NaNbO3 enriched with oxygen vacancies by Ni doping was successfully synthesized via a polymerized complex method and applied as a photocatalyst in the oxidation of cinnamyl alcohol (CA) to cinnamaldehyde in air. Reaction rates as high as 45 μmol h-1 were achieved under visible light with a high apparent quantum efficiency of 67.2% and excellent chemoselectivity larger than 99%. UV-vis, electron paramagnetic resonance, and attenuated total reflectance infrared spectroscopy results indicate that the CA molecules preferentially adsorb at the oxygen vacancies, thus enabling electron transfer between coordinatively bound CA and NaNbO3 under visible light, inducing CA oxidation. The photocatalytic aerobic oxidation of CA is assumed to proceed via the one-photon pathway with H2O2 as the coupled product. The photodeposited Pt nanoparticles on the surface not only enhanced the oxidation rate but also improved the selectivity to cinnamaldehyde substantially because of the fast decomposition of formed H2O2, in this way avoiding its consecutive oxidation by H2O2. The oxygen vacancies on the surface generated by Ni doping are identified to play a decisive role in the chemisorption of cinnamyl alcohol and the interface charge transfer.
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This work reports a one-step synthesis of reduced graphene oxide (rGO) supported platinum-nickel oxide nanoplate arrays (denoted as Pt-NiO/rGO) for nonenzymatic glucose sensing. The prepared Pt-NiO/rGO nanocomposite was characterized by scanning electron microscopy, X-ray energy dispersive spectrometer, and X-ray powder diffraction. The existence of a small quantity of Pt could significantly enhance the catalytic activity of NiO and played an important role in controlling the morphology of Pt-NiO nanoplate arrays. The vertical array structure of Pt-NiO/rGO nanocomposite increased the effective loading of Pt-NiO catalyst on electrode surface to some extent. Therefore, the Pt-NiO/rGO modified glassy carbon electrode (GCE) was successfully used for highly sensitive and selective nonenzymatic glucose detection. The linear range was from 0.008 to 14.5 mM (R2=0.9976, n=41). The sensitivity was 832.95 μA cm−2 mM−1, and the detection limit was 2.67 μM (S/N=3). The good catalytic activity, high sensitivity and stability of the Pt-NiO/rGO/GCE sensor opened up a new kind of hybrid materials in electrochemical detection of glucose.
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A helical TiO2 nanotube (TNT) array modified with cuprous oxide (Cu2O) electrode was fabricated and used for nonenzymatic glucose detection. The structure and morphology of Cu2O/TNT were characterized by X-ray diffraction and transmission electron microscopy. The electrocatalytic performance of Cu2O/TNT electrode for glucose oxidation was investigated by cyclic voltammetry and chronoamperometry. At an applied potential of +0.65V versus SCE, a linear range was obtained within the concentration range of 3.0-9.0mM with a detection limit of 62μM (signal/noise=3). The response time was approximately 3s after adding 0.10mM glucose. Formate and gluconic acid were identified as the main products of the glucose oxidation using (1)H NMR spectrometry. A possible mechanism for continuous glucose oxidation was also proposed.
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In this work, a Ni/CdS bifunctional Ti@TiO2 core-shell nanowire electrode with excellent electrochemical sensing property was successfully constructed through hydrothermal and electrodeposition method. FESEM and TEM were employed to confirm the synthesis and characterize the morphology of the as-prepared samples. The results reveal that the CdS layers between Ni and TiO2 plays an important role in the uniform nucleation and the following growth of highly dispersive Ni nanoparticle on the Ti@TiO2 core-shell nanowire surface. The bifunctional nanostructured electrode was applied to construct electrochemical non-enzymatic sensor for the reliable detection of glucose. Under optimized conditions, this non-enzymatic glucose sensor displays a high sensitivity up to 1136.67 μA mM-1 cm2, a wider liner range of 0.005 mM to 12 mM and a low detection limit of 0.35 μM for glucose oxidation. High dispersity of Ni nanoparticles combined with the anti-poisoning faculty against intermediate derived from the self-cleaning ability of CdS under the photoexcitation are considered to be responsible for these enhanced electrochemical performances. Importantly, favorable reproducibility and long-term performance were also obtained thanks to the robust frameworks. All these results indicate this novel electrode is a promising candidate for non-enzymatic glucose sensing.
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A novel nonenzymatic, amperometric sensor for hydrogen peroxide (H2O2) was developed based on an electrochemically prepared reduced graphene oxide (RGO)/zinc oxide (ZnO) composite using a simple and cost effective approach. RGO/ZnO composite was fabricated on a glassy carbon electrode (GCE) by a green route based on simultaneous electrodeposition of ZnO and electrochemical reduction of graphene oxide (GO). The morphology of the as-prepared RGO/ZnO composite was investigated by scanning electron microscopy (SEM). Attenuated total reflectance (ATR) spectroscopy has also been performed to confirm the ample reduction of oxygen functionalities located at graphene oxide (GO). The electrochemical performance of the RGO/ZnO composite modified GCE was studied by amperometric technique, and the resulting electrode displays excellent performance towards hydrogen peroxide (H2O2) at −0.38 V in the linear response range from 0.02 to 22.48 μM, with a correlation coefficient of 0.9951 and short response time (<5 s). The proposed sensor also has good operational and storage stability with appreciable anti-interferring ability.
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In this report, we presented a new method to fabricate TiO(2) nanotube (TiO(2) NT) arrays modified with cupric oxide (CuO) nanofibers, getting a novel TiO(2) NT arrays composition electrode for sensitive nonenzymatic glucose detection. For the preparation of CuO nanofibers, Cu nanoparticles were firstly electrodeposited onto the TiO(2) NT arrays, and then oxidized to CuO nanofibers followed by annealing in air. The CuO nanofibers modified TiO(2) NT (CuO/TiO(2) NT) arrays electrode for electrocatalytic detection of glucose was investigated by cyclic voltammetry and chronoamperometry in 0.10 M NaOH solution. The linear range of detection of glucose extended up to 2.0mM (R=0.997, n=10) at a potential of 0.50 V (vs. SCE). The sensitivity was 79.79 μA cm(-2)mM(-1), and the detection limit was 1 μM (S/N=3). Significantly, the poisoning by chloride ion and the interferences from ascorbic acid, uric acid, lactose, sucrose, fructose and dopamine were negligible. Particularly, the CuO/TiO(2) NT arrays electrode showed excellent stability and repeatability over 1 month. The sensor was also investigated detecting glucose in human blood serum samples.