[Show abstract][Hide abstract] ABSTRACT: Preparation of nanomaterials with controllable sizes and shapes at ambient conditions, without heating or cooling, is extremely attractive from the perspective of cost and energy efficiency. However, highly reactive precursors must be used to obtain NCs at ambient conditions, and this can make the control of particle formation extremely challenging. Degenerately p-doped copper sulfide NCs have attracted much recent interest based on the observation of localized surface plasmon resonance (LSPR) in these materials. These earth-abundant semiconductor NCs have potential applications ranging from photovoltaics to biomedical imaging. Here, we provide the first report of ambient-temperature preparation of covellite nanoplatelets. The lateral dimensions of these are controllable over a wide range while maintaining a constant thickness of 4 nm. The crystalline phase of the NCs is shown here to be controlled by the oxidation state of the copper reagent, with a Cu(II) precursor required to prepare phase-pure covellite NCs. The NCs exhibit LSPR absorbance that depends upon their aspect ratio (their lateral dimension, at fixed thickness) and can be tuned over a range of more than 600 nm. Their optical absorbance was modeled quantitatively to extract consistent values of free carrier concentration and background polarizability that apply over a wide range of NC sizes.
Full-text · Article · Mar 2015 · Chemistry of Materials
[Show abstract][Hide abstract] ABSTRACT: Random laser (RL) emission in Nd3þ doped potassium gadolinium tungstate—KGd(WO4)2:Nd3þ—
crystal powder is demonstrated. The powder was excited at 813nm in resonance with the Nd3þ
transition 4I9/2!4F5/2. RL emission at 1067 nm due to the 4F3/2!4I11/2 transition was observed and
characterized. An intensity threshold dependent on the laser spot area and bandwidth narrowing
from �2.20 nm to �0.40 nm were observed and measured. For a beam spot area of 0.4mm2, a RL
threshold of 6.5 mJ/mm2 (90MW/cm2) was determined. For excitation intensity smaller than the RL
threshold, only spontaneous emission from level 4F3/2 with decay time in the tens microsecond
range was observed, but for excitation above the RL threshold, significant shortening of excited
level lifetime, characteristic of a stimulated process was found. The overall characteristics measured
show that KGd(WO4)2:Nd3þ is an efficient material for operation of solid state RLs in the nearinfrared.
Full-text · Article · Feb 2015 · Journal of Applied Physics
[Show abstract][Hide abstract] ABSTRACT: The ability to tune the emission color of upconversion nanoparticles (UCNPs) will greatly enhance the scope of their applications, ranging from infrared solar cells to volumetric multiplexed bioimaging. Conventional methods to tune upconversion are to vary the type and/or the concentration of doped rare-earth ions in these nanoparticle formulations. Here, we introduce a different approach to vary the emission colors of the frequently used sensitizer/activator pairs of Yb(3+)/RE(3+) (RE = Ho, Er, Tm) via utilization of a sensitizer/activator-isolated NaYF4 core-shell structure. We show that the typical green, yellow, and blue luminescent colors from Yb(3+)/Ho(3+)-, Yb(3+)/Er(3+)-, and Yb(3+)/Tm(3+)-co-doped NaYF4 UCNPs can be converted into the quasi-white, green, and pink blue, when corresponding core-shell structures of NaYF4:Yb(3+) @NaYF4:Ho(3+), NaYF4:Yb(3+) @NaYF4:Er(3+) and NaYF4:Yb(3+) @NaYF4:Tm(3+) are built. Time-resolved spectra indicate that decay lifetimes of the emission bands from the sensitizer/activator-isolated core-shell structure significantly vary from that of the sensitizer/activator-codoped NaYF4 UCNPs, verifying the strain-induced modulation of emission channels in the core-shell structure. These sensitizer-activator-isolated core-shell UCNPs have implications for a range of biophotonic or photonic applications.
[Show abstract][Hide abstract] ABSTRACT: Opiates act on the dopaminergic system of the brain and perturb 32 kDa dopamine and adenosine 3', 5'-monophosphate-regulated phosphoprotein (DARPP-32) function. The DARPP-32 mediated inhibition of protein phosphatase-1 (PP-1) and modulation of transcriptional factor CREB is critical to the changes in neuronal plasticity that result in behavioral responses during drug abuse. To investigate the role of DARPP-32 mediated signaling on withdrawal behavior in a rat model of opiate addiction, we used intracerebral administration of gold nanorods (GNR) complexed to DARPP-32 siRNA to silence DARPP-32 gene expression and measure its effects on the opiate withdrawal syndrome. We hypothesized that DARPP-32 siRNA will suppress the neurochemical changes underlying the withdrawal syndrome and therefore prevent conditioned place aversion by suppressing or removing the constellation of negative effects associated with withdrawal, during the conditioning procedure. Our results showed that opiate addicted animals treated with GNR-DARPP-32 siRNA nanoplex showed lack of condition place aversive behavior consequent to the downregulation of secondary effectors such as PP-1 and CREB which modify transcriptional gene regulation and consequently neuronal plasticity. Thus, nanotechnology based delivery systems could allow sustained knockdown of DARPP-32 gene expression which could be developed into a therapeutic intervention for treating drug addiction by altering reward and motivational systems and interfere with conditioned responses.
No preview · Article · Jan 2015 · Journal of Neuroimmune Pharmacology
[Show abstract][Hide abstract] ABSTRACT: A simple approach is proposed in which a nanoparticulate agent, readily formed from just two active components, can be used to explore imaging parameters in six modalities. Porphyrin-phospholipid- upconversion nanoparticles (PoP-UCNPs) were generated by coating oleic acid-capped UCNPs, synthesized via thermal decomposition, with phospholipids to render them dispersible in aqueous solutions. Thin films containing PoP-UCNPs with varying ratios of PoP to polyethylene glycol (PEG)-lipid were hydrated with water and sonicated to generate stable and dispersed nanoparticles. Transmission electron microscopy and dynamic light scattering of PoP-UCNPs coated with 80 molar% PoP and 20 molar% PEG-lipid revealed an average particle size of 74 nm. At higher resolution, micrographs revealed a crystal lattice spacing of 0.52 nm. Based on their dense self-packing in a spatially constrained bilayer, PoP bilayers give rise to intense intermolecular porphyrin face-to-face contact and FL self-quenching.
Full-text · Article · Jan 2015 · Advanced Materials
[Show abstract][Hide abstract] ABSTRACT: We review the emerging field of chiral photonics, its applications and corresponding materials. Chiral photonics is a new direction for photonics that encompasses enantio-selective polarization control of linear and nonlinear optical functions. New materials are required to realize the full potential of this field. Specifically, chiral polymers or polymer nanocomposites exhibiting very large optical rotation and third-order optical nonlinearity are needed to make applications of chiral photonics a reality. Multiscale modeling, guiding the synthesis of materials and nanocomposites with custom-tailored photonic functionality, is a necessary strategy. This review describes the necessary multiscale modeling and provides an example of modeling guided synthesis. Characterization methods are also described, together with some demonstrative results. These novel materials would have a broad and transformative impact in many technological areas by enabling on-demand roll-to-roll fabrication of flexible chiral photonic polymer based-materials with unprecedented throughput and manufacturing efficiency.
No preview · Article · Jan 2015 · Nonlinear Optics Quantum Optics
[Show abstract][Hide abstract] ABSTRACT: This paper is a review of the recent research in bio-based materials for electronic applications. It will highlight work on ionic conductivity of deoxyribonucleic acid (DNA) based membranes, enhancement of direct current and photoconductivity of DNA, crosslinking of DNA, electrical and Raman characterization of DNA-based films fabricated by a drawdown bar technique and characteristics of DNA nucleobases. Also included are potential applications in electronics.
No preview · Article · Jan 2015 · Nonlinear Optics Quantum Optics
[Show abstract][Hide abstract] ABSTRACT: We report the operation and characterization of two different three-photon pumped anti-Stokes emission in Random Lasers (RL) in different materials. Using a special dye with a high three-photon cross-section and TiO2 nanoparticles (250 nm diameter), optimized upconverted emission was obtained for particle densities of ~2 x 109/cm3, pumped by a 1350nm femtosecond laser. On the other hand, by exploiting the important and versatile ZnO semiconductor on a ZnOon-Si nanostructured film platform, upconverted RL emission centered at ~390nm was obtained by three-photon excitation at 802nm. We demonstrate characteristic random laser features, as the presence of an intensity threshold and a linewidth narrowing.
[Show abstract][Hide abstract] ABSTRACT: The authors introduce a novel multilayer core/shell design to broadly
upconvert infrared (IR) light at many discrete wavelengths into visible
or near-IR (NIR) emissions. It utilizes hexagonal-phase core/multishell
NaYF 4 :10%Er 3+ @NaYF 4 @NaYF 4 :10%Ho 3+ @NaYF 4 @NaYF 4 :1%Tm 3+ @
NaYF 4 nanoparticles, where the active core as well as each active shell upconvert
a distinct set of IR wavelength. The inert NaYF 4 layers in between these
upconverting domains effi ciently suppress the detrimental cross-relaxation
processes between different types of lanthanide ions, thus yielding about two
times more effi cient upconversion photoluminescence than the counterpart
NaYF 4 :10%Er 3+ @NaYF 4 :10%Ho 3+ @NaYF 4 :1%Tm 3+ @NaYF 4 without the
inert NaYF 4 layers, and about one order of magnitude higher than the core/
shell NaYF 4 :10%Er 3+ , 10%Ho 3+ , 1%Tm 3+ @NaYF 4 nanoparticles without
spatially isolating the Er 3+ , Ho 3+ , and Tm 3+ ions. These core/multishell nanoparticles
can be excited at ≈1120–1190 nm (due to Ho 3+ ), ≈1190–1260 nm
(due to Tm 3+ ), and ≈1450–1580 nm (due to Er 3+ ), collectively covering a broad
spectral range of about 270 nm in the IR range that can be very useful for IR
photosensitization of solar cells.
Full-text · Article · Nov 2014 · Advanced Optical Materials
[Show abstract][Hide abstract] ABSTRACT: Light upconverting nanostructures employing lanthanide ions constitute an emerging research field recognized with wide ramifications and impact in many areas ranging from healthcare, to energy and, to security. The core–shell design of these nanostructures allows us to deliberately introduce a hierarchy of electronic energy states, thus providing unprecedented opportunities to manipulate the electronic excitation, energy transfer and upconverted emissions. The core–shell morphology also causes the suppression of quenching mechanisms to produce efficient upconversion emission for biophotonic and photonic applications. Using hierarchical architect, whereby each shell layer can be defined to have a specific feature, the electronic structure as well as the physiochemical structure of the upconverting nanomaterials can be tuned to couple other electronic states on the surface such as excitations of organic dye molecules or localized surface plasmons from metallic nanostructures, or to introduce a broad range of imaging or therapeutic modalities into a single conduct. In this review, we summarize the key aspects of nanophotonic control of the light upconverting nanoparticles through governed design and preparation of hierarchical shells in the core–shell nanostructures, and review their emerging applications in the biomedical field, solar energy conversion, as well as security encoding.
Full-text · Article · Oct 2014 · Chemical Society Reviews
[Show abstract][Hide abstract] ABSTRACT: To achieve high precision and efficacy in disease treatment, biodegradability and environmental responsivity are highly desired for drug delivery systems. Having a polylactide (PLA)-based biodegradable scaffold conjugated with doxorubicin (DOX) moieties via pH-responsive linkages, a brush polymer-drug conjugate (BPDC) was synthesized and studied. The biodegradable scaffold, PLA-graft-aldehyde/polyethylene glycol (PLA-g-ALD/PEG), was prepared via copper-catalyzed alkyne-azide click reaction. Subsequently, the BPDC was obtained by conjugating doxorubicin with the scaffold through an acid-sensitive Schiff base linkage. Well-controlled structures of the resulting BPDC and its precursors were verified by proton nuclear magnetic resonance and gel permeation chromatography characterizations. As revealed by dynamic light scattering and transmission electron microscopy, the BPDC had well-defined nanostructure with the size of 10-30 nm. Drug release study of the BPDC demonstrated much faster release of DOX at the pH of 5.5 than at the pH of 7.4. Both cell internalization and cytotoxicity studies of the BPDC in MCF-7 breast cancer cells indicated its significant potential for application as a novel anticancer nanomedicine.
[Show abstract][Hide abstract] ABSTRACT: Apoptosis is a dynamic process regulated by mitochondrion critical for cellular respiration and survival. Execution of apoptosis is mediated by multiple protein signaling events at mitochondria. Initiation and progression of apoptosis require numerous apoptogenic factors that are either released from or sequestered in mitochondria, which may transform the biomolecular makeup of the organelle. In this communication, using Raman microspectroscopy, we demonstrate that transformation in biomolecular composition of mitochondrion may be used as apoptosis marker in an individual cell. For the first time, we show that significant changes occur in the concentrations of RNA, DNA, protein, and lipid constituents of mitochondria during apoptosis. The structural analysis of proteins on mitochondria demonstrated a decrease in alpha-helix secondary structure content, and an increase in the levels of random coils and beta-sheets on mitochondria. This may represent an additional hallmark of apoptosis. Strikingly, we observed nearly identical changes in macromolecular content of mitochondria both in the presence and absence of a key proapoptotic protein, Bax (Bcl-2-associated X protein). Increased DNA level in mitochondria corresponded with higher mitochondrial DNA (mtDNA), cellular reactive oxygen species (ROS), and mitochondrial ROS production. Upregulation of polymerase-gamma (POLG), mitochondrial helicase Twinkle, and mitochondrial transcription factor A (Tfam) in response to DNA damage correlated with increased mtDNA and RNA synthesis. Elevated activity of oxidative phosphorylation complexes supports functional mitochondrial respiration during apoptosis. Thus, we define previously unknown dynamic correlation of macromolecular structure of mitochondria and apoptosis progression in the presence and absence of Bax protein. These findings open up a new approach for monitoring physiological status of cells by non invasive single-cell method.
Full-text · Article · Oct 2014 · Cell Death & Disease
[Show abstract][Hide abstract] ABSTRACT: Silica-based nanoparticles are well known for their ease of synthesis, structural robustness, resistance to
biofouling, enhanced storage stability, and multimodality. Organically modified silica (ormosil)
nanoparticles are a special type of hybrid nanoparticle known for encapsulating/conjugating active
agents for applications such as in photodynamic therapy (PDT), gene therapy and diagnostic imaging.
Herein, we report the use of ormosil nanoparticles as a sustained release drug delivery vehicle, using the
well-known anticancer and fluorescent drug doxorubicin (Dox). These drug/dye loaded nanoparticles
have been synthesized within an oil-in-water microemulsion medium, and characterized for their size,
shape, porosity, and optical properties. Nanoencapsulation significantly enhanced the optical stability of
a dye against chemical quenching. Particle-size variation could be achieved by changing the amount of
co-surfactant. However, size variation did not affect their pore size. The release pattern of encapsulated
drug was found to depend on the size of the nanoparticles, with optimal drug release observed for the
50 nm particles at about 70% in a sustained manner over two weeks. Confocal bioimaging was used to
demonstrate the differential pattern of cellular uptake of the free and nanoencapsulated drugs, as the
sub-cellular distribution of nanoencapsulated Dox is guided by the nanoparticles distributing throughout
the cytosol. Cell viability (MTS) and soft-agar colony formation assays in vitro have confirmed the
cytotoxic effects of the drug loaded nanoparticles, but not of the blank nanoparticles. The results
indicate that ormosil nanoparticles can act as a sustained release vehicle of potent lipophilic anticancer
[Show abstract][Hide abstract] ABSTRACT: Fixation of biological sample is an essential technique applied in order to "freeze" in time the intracellular molecular content and permit mapping of cellular molecules. However, fixation induces changes of the cellular molecular structure, which mask physiological distribution of biomolecules and bias interpretation of results. Accurate, sensitive, and comprehensive characterization of changes in biomolecular composition, occurring during fixation, is crucial for proper analysis of experimental data. Here we apply Biomolecular Component Analysis for Raman spectra measured in the same nucleoli of HeLa cells before and after fixation by either formaldehyde solution or by chilled ethanol. It is found that fixation in formaldehyde does not strongly effect the Raman spectra of nucleolar biomolecular components, but may significantly decrease the nucleolar RNA concentration. At the same time, ethanol fixation leads to a proportional increase (up to 40%) in concentrations of nucleolar proteins and RNA, most likely due to cell shrinkage occurring in the presence of coagulant fixative. Ethanol fixation also triggers changes in composition of nucleolar proteome, as indicated by an overall reduction of the α-helical structure of proteins and increase in the concentration of proteins containing the β-sheet conformation. We conclude that cross-linking fixation is a more appropriate protocol for mapping of proteins in situ. At the same time, ethanol fixation is preferential for studies of RNA-containing macromolecules. We supplemented our quantitative Raman spectroscopic measurements with mapping of the protein and lipid macromolecular groups in live and fixed cells using Coherent Anti-Stokes Raman Scattering nonlinear optical imaging.
[Show abstract][Hide abstract] ABSTRACT: Fixation of biological sample is an essential technique applied in order to " freeze " in time the intracellular molecular content and permit mapping of cellular molecules. However, fixation induces changes of the cellular molecular structure, which mask physiological distribution of biomolecules and bias interpretation of results. Accurate, sensitive, and comprehensive characterization of changes in biomolecular composition, occurring during fixation, is crucial for proper analysis of experimental data. Here we apply Biomolecular Component Analysis for Raman spectra measured in the same nucleoli of HeLa cells before and after fixation by either formaldehyde solution or by chilled ethanol. It is found that fixation in formaldehyde does not strongly effect the Raman spectra of nucleolar biomolecular components, but may significantly decrease the nucleolar RNA concentration. At the same time, ethanol fixation leads to a proportional increase (up to 40%) in concentrations of nucleolar proteins and RNA, most likely due to cell shrinkage occurring in the presence of coagulant fixative. Ethanol fixation also triggers changes in composition of nucleolar proteome, as indicated by an overall reduction of the α-helical structure of proteins and increase in the concentration of proteins containing the β-sheet conformation. We conclude that cross-linking fixation is a more appropriate protocol for mapping of proteins in situ. At the same time, ethanol fixation is preferential for studies of RNA-containing macromolecules. We supplemented our quantitative Raman spectroscopic measurements with mapping of the protein and lipid macromolecular groups in live and fixed cells using Coherent Anti-Stokes Raman Scattering nonlinear optical imaging.
[Show abstract][Hide abstract] ABSTRACT: The efficiency of most photovoltaic devices is severely limited by near-infrared (NIR) transmission losses. To alleviate this limitation, a new type of colloidal upconversion nanoparticles (UCNPs), hexagonal core/shell-structured β-NaYbF4:Er3+(2%)/NaYF4:Nd3+(30%), is developed and explored in this work as an NIR energy relay material for dye-sensitized solar cells (DSSCs). These UCNPs are able to harvest light energy in multiple NIR regions, and subsequently convert the absorbed energy into visible light where the DSSCs strongly absorb. The NIR-insensitive DSSCs show compelling photocurrent increases through binary upconversion under NIR light illumination either at 785 or 980 nm, substantiating efficient energy relay by these UCNPs. The overall conversion efficiency of the DSSCs was improved with the introduction of UCNPs under simulated AM 1.5 solar irradiation.
[Show abstract][Hide abstract] ABSTRACT: Controllable 3D assembly of multicomponent inorganic nanomaterials by precisely positioning two or more types of nanoparticles to modulate their interactions and achieve multifunctionality remains a major challenge. The diverse chemical and structural features of biomolecules can generate the compositionally specific organic/inorganic interactions needed to create such assemblies. Toward this aim, we studied the materials-specific binding of peptides selected based upon affinity for Ag (AgBP1 and AgBP2) and Au (AuBP1 and AuBP2) surfaces, combining experimental binding measurements, advanced molecular simulation, and nanomaterial synthesis. This reveals, for the first time, different modes of binding on the chemically similar Au and Ag surfaces. Molecular simulations showed flatter configurations on Au and a greater variety of 3D adsorbed conformations on Ag, reflecting primarily enthalpically driven binding on Au and entropically driven binding on Ag. This may arise from differences in the interfacial solvent structure. On Au, direct interaction of peptide residues with the metal surface is dominant, while on Ag, solvent-mediated interactions are more important. Experimentally, AgBP1 is found to be selective for Ag over Au, while the other sequences have strong and comparable affinities for both surfaces, despite differences in binding modes. Finally, we show for the first time the impact of these differences on peptide mediated synthesis of nanoparticles, leading to significant variation in particle morphology, size, and aggregation state. Because the degree of contact with the metal surface affects the peptides ability to cap the nanoparticles and thereby control growth and aggregation, the peptides with the least direct contact (AgBP1 and AgBP2 on Ag) produced relatively polydispersed and aggregated nanoparticles. Overall, we show that thermodynamically different binding modes at metallic interfaces can enable selective binding on very similar inorganic surfaces and can provide control over nanoparticle nucleation and growth. This supports the promise of bionanocombinatoric approaches that rely upon materials recognition.
No preview · Article · Sep 2014 · Chemistry of Materials