Showing papers in "Langmuir in 2010"
TL;DR: The photodegradation mechanisms for two typical dyes, rhodamine B (Rh B) and methyl orange (MO), are proposed based on comparison experiments and the electron paramagnetic resonance was used to detect the active species for the photodegrading reaction over g-C(3)N(4).
Abstract: Graphitic carbon nitride (g-C3N4) and boron-doped g-C3N4 were prepared by heating melamine and the mixture of melamine and boron oxide, respectively. X-ray diffraction, X-ray photoelectron spectroscopy, and UV−vis spectra were used to describe the properties of as-prepared samples. The electron paramagnetic resonance was used to detect the active species for the photodegradation reaction over g-C3N4. The photodegradation mechanisms for two typical dyes, rhodamine B (Rh B) and methyl orange (MO), are proposed based on our comparison experiments. In the g-C3N4 photocatalysis system, the photodegradation of Rh B and MO is attributed to the direct hole oxidation and overall reaction, respectively; however, for the MO photodegradation the reduction process initiated by photogenerated electrons is a major photocatalytic process compared with the oxidation process induced by photogenerated holes. Boron doping for g-C3N4 can promote photodegradation of Rh B because the boron doping improves the dye adsorption and...
1,495 citations
TL;DR: N nanoparticle-polymer composites are used to demonstrate the anti-icing capability of superhydrophobic surfaces and report direct experimental evidence that such surfaces are able to prevent ice formation upon impact of supercooled water both in laboratory conditions and in natural environments.
Abstract: Superhydrophobic coating compositions are provided. The compositions comprise nanoparticles between 5-100 nm in size and a polymeric binder. The compositions are effective in preventing ice formation on the surface of various substrates.
1,287 citations
TL;DR: The as-prepared new solid-phase biopolymer-based catalysts are very efficient, stable, easy to prepare, eco-friendly, and cost-effective, and they have the potential for industrial applications.
Abstract: Silver and gold nanoparticles have been grown on calcium alginate gel beads using a green photochemical approach. The gel served as both a reductant and a stabilizer. The nanoparticles were characterized using UV−visible spectroscopy, X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), energy dispersive X-ray (EDS), and selected area electron diffraction (SAED) analyses. The particles are spherical, crystalline, and the size ranges for both Ag and Au nanoparticles are <10 nm. It is noticed from the sorption experiment that the loading of gold on calcium alginate beads is much more compared to that of Ag. The effectiveness of the as-prepared dried alginate-stabilized Ag and Au nanoparticles as a solid phase heterogeneous catalyst has been evaluated, for the first time, on the well-known 4-nitrophenol (4-NP) reduction to 4-aminophenol (4-AP) in the presence of excess borohydride. The reduction was very efficient and followed zero-order kinetics for both Ag and Au nanocompos...
886 citations
TL;DR: In this study, ceria nanocrystals with well-defined surface planes have been synthesized and utilized for studying defect sites with both Raman spectroscopy and O(2) adsorption, and the stability and reactivity of these oxygen species are found to be surface-dependent.
Abstract: Defect sites play an essential role in ceria catalysis. In this study, ceria nanocrystals with well-defined surface planes have been synthesized and utilized for studying defect sites with both Raman spectroscopy and O2 adsorption. Ceria nanorods ({110} + {100}), nanocubes ({100}), and nano-octahedra ({111}) are employed to analyze the quantity and quality of defect sites on different ceria surfaces. On oxidized surfaces, nanorods have the most abundant intrinsic defect sites, followed by nanocubes and nano-octahedra. When reduced, the induced defect sites are more clustered on nanorods than on nanocubes, although similar amounts (based on surface area) of such defect sites are produced on the two surfaces. Very few defect sites can be generated on the nano-octahedra due to the least reducibility. These differences can be rationalized by the crystallographic surface terminations of the ceria nanocrystals. The different defect sites on these nanocrystals lead to the adsorption of different surface dioxygen...
848 citations
TL;DR: This simple hydrothermal method could provide the synthesis of nitrogen-doped graphene sheets in large scale for various practical applications and should play an important role in the nitrogen doping and the jellyfish-like graphene formation.
Abstract: Nitrogen-doped graphene sheets were prepared through a hydrothermal reduction of colloidal dispersions of graphite oxide in the presence of hydrazine and ammonia at pH of 10. The effect of hydrothermal temperature on the structure, morphology, and surface chemistry of as-prepared graphene sheets were investigated though XRD, N2 adsorption, solid-state 13C NMR, SEM, TEM, and XPS characterizations. Oxygen reduction and nitrogen doping were achieved simultaneously under the hydrothermal reaction. Up to 5% nitrogen-doped graphene sheets with slightly wrinkled and folded feature were obtained at the relative low hydrothermal temperature. With the increase of hydrothermal temperature, the nitrogen content decreased slightly and more pyridinic N incorporated into the graphene network. Meanwhile, a jellyfish-like graphene structure was formed by self-organization of graphene sheets at the hydrothermal temperature of 160 °C. Further increase of the temperature to 200 °C, graphene sheets could self-aggregate into a...
666 citations
TL;DR: This letter demonstrates that a novel, highly efficient enzyme electrode can be directly obtained using covalent attachment between carboxyl acid groups of graphene oxide sheets and amines of glucose oxidase, suggesting potentials for a wide range of practical applications.
Abstract: This letter demonstrates that a novel, highly efficient enzyme electrode can be directly obtained using covalent attachment between carboxyl acid groups of graphene oxide sheets and amines of glucose oxidase. The resulting biosensor exhibits a broad linear range up to 28 mM·mm−2 glucose with a sensitivity of 8.045 mA·cm−2·M−1. The glucose oxidase-immobilized graphene oxide electrode also shows a reproducibility and a good storage stability, suggesting potentials for a wide range of practical applications. The biocompatibility of as-synthesized graphene oxide nanosheets with human cells, especially retinal pigment epithelium (RPE) cells, was investigated for the first time in the present work. Microporous graphene oxide exhibits good biocompatibility and has potential advantages with respect to cell attachment and proliferation, leading to opportunities for using graphene-based biosensors for the clinical diagnosis.
658 citations
TL;DR: The dispersibility of graphene is measured in 40 solvents, with 28 of them previously unreported, and transmission electron microscopy analysis is used to show that the graphene is well exfoliated in all cases.
Abstract: We have measured the dispersibility of graphene in 40 solvents, with 28 of them previously unreported. We have shown that good solvents for graphene are characterized by a Hildebrand solubility parameter of δT ∼ 23 MPa1/2 and Hansen solubility parameters of δD ∼ 18 MPa1/2, δP ∼ 9.3 MPa1/2, and δH ∼ 7.7 MPa1/2. The dispersibility is smaller for solvents with Hansen parameters further from these values. We have used transmission electron microscopy (TEM) analysis to show that the graphene is well exfoliated in all cases. Even in relatively poor solvents, >63% of observed flakes have <5 layers.
587 citations
TL;DR: Based on the XRD and XPS patterns of the AgI/BiOI composites before and after reaction, AgI was stable in the composites under visible irradiation, indicating that AgI /BiOi composites could be used as stable and efficient visible-light-induced photocatalysts.
Abstract: The nanostructured AgI/BiOI composites were prepared by a facile, one-step, and low temperature chemical bath method with Bi(NO(3))(3), AgNO(3), and KI. Several characterization tools, such as X-ray powder diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), the Brunauer-Emmett-Teller (BET) surface area, photoluminescence (PL) spectra, and UV-vis diffuse reflectance spectroscopy, were employed to study the phase structures, morphologies, and optical properties of the samples. The PL intensity of AgI was greatly decreased when combined with BiOI, indicating the corresponding decreased recombination of the carriers. The photocatalytic properties of the as-prepared products were measured with the degradation of methyl orange and phenol at room temperature under visible light irradiation. The AgI/BiOI composites showed much higher photocatalytic performances over BiOI as well as AgI. It was also found that the AgI amount in the AgI/BiOI composites played an important role in the corresponding photocatalytic properties and the optimized ratio was obtained at 20%. The dramatic enhancement in the visible light photocatalytic performance of the AgI/BiOI composites could be attributed to the effective electron-hole separations at the interfaces of the two semiconductors, which facilitate the transfer of the photoinduced carriers. By the detection of hydroxyl radicals through a fluorescence technique, the photoinduced holes (h(VB)(+)) were considered to be the dominant active species in the photodegradation process, which was also deduced from the theoretical speculations. The photocatalytic performances of the AgI/BiOI composites were maintained for the cycling experiments. In addition, based on the XRD and XPS patterns of the AgI/BiOI composites before and after reaction, AgI was stable in the composites under visible irradiation, indicating that AgI/BiOI composites could be used as stable and efficient visible-light-induced photocatalysts.
530 citations
TL;DR: It is demonstrated that the enzyme immobilization on the GO sheets could take place readily without using any cross-linking reagents and additional surface modification.
Abstract: Graphene oxide (GO), having a large specific surface area and abundant functional groups, provides an ideal substrate for study enzyme immobilization. We demonstrated that the enzyme immobilization on the GO sheets could take place readily without using any cross-linking reagents and additional surface modification. The atomically flat surface enabled us to observe the immobilized enzyme in the native state directly using atomic force microscopy (AFM). Combining the AFM imaging results of the immobilized enzyme molecules and their catalytic activity, we illustrated that the conformation of the immobilized enzyme is mainly determined by interactions of enzyme molecules with the functional groups of GO.
492 citations
TL;DR: The scope of this article covers a variety of semiconductor materials, focusing particularly on TiO(2)-based nanostructures, which have potential applications in the field of energy.
Abstract: Considerable effort has been made to design, fabricate, and manipulate nanostructured materials by innovative approaches. The precise control of nanoscale structures will pave the way not only for elucidating unique size/shape-dependent physicochemical properties but also for realizing new applications in science and technology. Nanotechnology offers unprecedented opportunities for improving our daily lives and the environment in which we live. This review mainly describes our recent progress in the design, fabrication, and modification of nanostructured semiconductor materials for environmental applications. Their potential applications in the field of energy are briefly introduced. The scope of this article covers a variety of semiconductor materials, focusing particularly on TiO2-based nanostructures (e.g., pure, doped, coupled, nanoporous, mesoporous, hierarchically porous, and ordered mesoporous TiO2). The preparation of nanoparticles, hierarchical nanoarchitectures, thin films, and single crystals b...
464 citations
TL;DR: By using a low-power oxygen plasma treatment, the wettability of graphene is improved without additional damage, which can solve the adhesion issues involved in the fabrication of graphene devices.
Abstract: Contact angle goniometry is conducted for epitaxial graphene on SiC Although only a single layer of epitaxial graphene exists on SiC, the contact angle drastically changes from 69° on SiC substrates to 92° on graphene It is found that there is no thickness dependence of the contact angle from the measurements of single-, bi-, and multilayer graphene and highly ordered pyrolytic graphite (HOPG) After graphene is treated with oxygen plasma, the level of damage is investigated by Raman spectroscopy and the correlation between the level of disorder and wettability is reported By using a low-power oxygen plasma treatment, the wettability of graphene is improved without additional damage, which can solve the adhesion issues involved in the fabrication of graphene devices
TL;DR: It is shown that the pitch values of microstructures and density of nanostructures play an important role in real rose petals and artificial surfaces to control their adhesion properties.
Abstract: Certain rose petals are known to be superhydrophobic with high adhesion There also exist rose petals which are superhydrophobic with low adhesion similar to lotus leaf The purpose of this study is to characterize systematically the superhydrophobic rose petal with high and low adhesion surfaces and understand the mechanism for adhesion characteristics Based on these, artificial superhydrophobic surfaces with high and low adhesion are fabricated using a two-step molding process and wax evaporation method It is shown that the pitch values of microstructures and density of nanostructures play an important role in real rose petals and artificial surfaces to control their adhesion properties
TL;DR: The sensitivity toward changes in the local refractive index was found to increase for larger nanostars, though lower figure of merit (FOM) values were obtained because of the larger polydispersity.
Abstract: Gold nanostars are multibranched nanoparticles with sharp tips, which display extremely interesting plasmonic properties but require optimization. We present a systematic investigation of the influence of different parameters on the size, morphology, and monodispersity of Au nanostars obtained via seeded growth in concentrated solutions of poly(vinylpyrrolidone) in N,N-dimethylformamide. Controlled prereduction of Au(3+) to Au(+) was found to influence monodispersity (narrower plasmon bands), while the [HAuCl(4)]/[seed] molar ratio significantly affects the morphology and tip plasmon resonance frequency. We also varied the size of the seeds (2-30 nm) and found a clear influence on the final nanostar dimensions as well as on the number of spikes, while synthesis temperature notably affects the morphology of the particles, with more rounded morphologies formed above 60 °C. This rounding effect allowed us to confirm the importance of sharp tips on the optical enhancing behavior of these nanoparticles in surface-enhanced raman scattering (SERS). Additionally, the sensitivity toward changes in the local refractive index was found to increase for larger nanostars, though lower figure of merit (FOM) values were obtained because of the larger polydispersity.
TL;DR: A simple surface modification method results in strong covalent bonds between α-Al(2)O(3) supports and imidazolate ligands, which promote the heterogeneous nucleation and growth of ZIF crystals.
Abstract: Zeolitic imidazolate frameworks (ZIFs) are hybrid organic-inorganic microporous materials that exhibit zeolite-like structures and can be synthesized with a wide range of pore sizes and chemical functionality. ZIFs as thin films and membranes are of interest for their applications in sensors and gas separation. Here, we report a method for ZIF film and membrane fabrication, based on support surface modification and in situ solvothermal growth, which has potential for general application to other ZIF membranes. Our simple surface modification method results in strong covalent bonds between α-Al(2)O(3) supports and imidazolate ligands, which promote the heterogeneous nucleation and growth of ZIF crystals. The microstructure of ZIF-8 films can be controlled by controlling the pH of the growth solution. ZIF-7 films were fabricated to demonstrate the potential for general applicability of our method. Finally, the separation performance of several ZIF-8 membranes was evaluated, revealing molecular sieving behavior with an ideal selectivity for H(2)/CH(4) of 13.
TL;DR: The PEG-phosphate coated upconverting NPs were used to image a line of ovarian cancer cells (CaOV3) to demonstrate their promise in biological application and overcome the upconversion intensity problem in aqueous environments.
Abstract: We present a technique for the replacement of oleate with a PEG−phosphate ligand [PEG = poly(ethylene glycol)] as an efficient method for the generation of water-dispersible NaYF4 nanoparticles (NPs). The PEG−phosphate ligands are shown to exchange with the original oleate ligands on the surface of the NPs, resulting in water-dispersible NPs. The upconversion intensity of the NPs in aqueous environments was found to be severely quenched when compared to the original NPs in organic solvents. This is attributed to an increase in the multiphonon relaxations of the lanthanide excited state in aqueous environments due to high energy vibrational modes of water molecules. This problem could be overcome partially by the synthesis of core/shell NPs which demonstrated improved photophysical properties in water over the original core NPs. The PEG−phosphate coated upconverting NPs were then used to image a line of ovarian cancer cells (CaOV3) to demonstrate their promise in biological application.
TL;DR: Matériaux de l'Institut Lavoisier (MIL)-100 was found to be completely water stable and was used to adsorb the pharmaceuticals furosemide and sulfasalazine from water with large uptakes achievable at low concentrations, indicating that the adsorption of wastewater contaminants may be a feasible application for these materials.
Abstract: The stability of a variety of microporous coordination polymers (MCPs) to water-containing solutions was studied using powder X-ray diffraction. It was determined that the stability of the MCP is related to the metal cluster present in the structure with trinuclear chromium clusters more stable than copper paddlewheel clusters which are more stable than basic zinc acetate clusters. Zn(2-methylimidizolate)(2) was found to be more water stable than zinc MCPs with carboxylate linkers; however, extended exposure to water led to decomposition of all zinc-based MCPs. Materiaux de l'Institut Lavoisier (MIL)-100 was also found to be completely water stable and was used to adsorb the pharmaceuticals furosemide and sulfasalazine from water with large uptakes achievable at low concentrations, indicating that the adsorption of wastewater contaminants may be a feasible application for these materials.
TL;DR: The results show that the pH of the solution influences the dried deposit pattern, which can be ring-like or more uniform, and a phase diagram is proposed that explains three types of deposits commonly observed experimentally, such as a peripheral ring, a small central bump, or a uniform layer.
Abstract: The shape of deposits obtained from drying drops containing colloidal particles matters for technologies such as inkjet printing, microelectronics, and bioassay manufacturing. In this work, the formation of deposits during the drying of nanoliter drops containing colloidal particles is investigated experimentally with microscopy and profilometry, and theoretically with an in-house finite-element code. The system studied involves aqueous drops containing titania nanoparticles evaporating on a glass substrate. Deposit shapes from spotted drops at different pH values are measured using a laser profilometer. Our results show that the pH of the solution influences the dried deposit pattern, which can be ring-like or more uniform. The transition between these patterns is explained by considering how DLVO interactions such as the electrostatic and van der Waals forces modify the particle deposition process. Also, a phase diagram is proposed to describe how the shape of a colloidal deposit results from the compet...
TL;DR: The result confirmed the earlier belief that the rate-determining step in the charging of a graphitic anode inLi(+) intercalation chemistry relates to the stripping of solvation sheath of Li(+), which is closely interwoven with the interphasial resistance to Li(+) migration.
Abstract: Efforts were made to differentiate the contributions to the so-called "ion transfer" barrier at the electrolyte/graphite junction from two distinct processes: (1) desolvation of Li(+) before it enters graphene interlayer and (2) the subsequent migration of bare Li(+) through the ad hoc interphase. By leveraging a scenario where no substantial interphase was formed on Li(+) intercalation hosts, we were able to quantify the distribution of "ion transfer" activation energy between these two interfacial processes and hence identify the desolvation process of Li(+) as the major energy-consuming step. The result confirmed the earlier belief that the rate-determining step in the charging of a graphitic anode in Li(+) intercalation chemistry relates to the stripping of solvation sheath of Li(+), which is closely interwoven with the interphasial resistance to Li(+) migration.
TL;DR: Metal-organic frameworks for removal of carbon dioxide from gases containing water vapor, such as flue gas, are considered, because of their permanent porous structures, huge surface areas, and potential applications as novel adsorbents and catalysts.
Abstract: Metal−organic frameworks (MOFs) have recently attracted intense research interest because of their permanent porous structures, huge surface areas, and potential applications as novel adsorbents and catalysts. In order to provide a basis for consideration of MOFs for removal of carbon dioxide from gases containing water vapor, such as flue gas, we have studied adsorption equilibrium of CO2, H2O vapor, and their mixtures and also rates of CO2 adsorption in two MOFs: HKUST-1 (CuBTC) and Ni/DOBDC (CPO-27-Ni or Ni/MOF-74). The MOFs were synthesized via solvothermal methods, and the as-synthesized products were solvent exchanged and regenerated before experiments. Pure component adsorption equilibria and CO2/H2O binary adsorption equilibria were studied using a volumetric system. The effects of H2O adsorption on CO2 adsorption for both MOF samples were determined, and the results for 5A and NaX zeolites were included for comparison. The hydrothermal stabilities for the two MOFs over the course of repetitive me...
TL;DR: It is proposed that the defect sites at the surface or the interface of TiO(2) films promote the separation of photogenerated electron-holes, leading to a higher photoactivity of defectiveTiO( 2) films, and indicates that the interface defect sites in TiO (2) could be applied in environmental photocatalysis.
Abstract: TiO2 bilayer films with a normal surface (Ns-TiO2), surface defects (Sd-TiO2), and interface defects (Id-TiO2) were successfully prepared by a combination of cold plasma treatment (CPT) and sol−gel dip-coating technology. The photodegradation of rhodamine B (RhB) over these as-prepared TiO2 films was investigated via UV−vis irradiation. Results indicate that the three kinds of films exhibit very different photodegradation processes for RhB. A mainly N-deethylation reaction over the Ns-TiO2 films, whereas an efficient degradation (cycloreversion) of RhB occurs over the Sd-TiO2 films. In the RhB/Id-TiO2 system, however, efficient N-deethylation concomitant with the highly efficient cycloreversion of RhB is observed. The efficiency of the complete mineralization of RhB dye follows the order of Id-TiO2 > Sd-TiO2 > Ns-TiO2. It is proposed that the defect sites at the surface or the interface of TiO2 films promote the separation of photogenerated electron−holes, leading to a higher photoactivity of defective Ti...
TL;DR: A graphene oxide-polypyrrole composite prepared from this approach exhibited an excellent electrocapacitive performance with a high specific capacitance over 500 F g(-1).
Abstract: We demonstrate a general approach to the preparation of layered graphene oxide structures with sandwiched conducting polymers of different morphologies. The approach is conceptualized on the basis of the electrostatic interactions between negatively charged graphene oxide sheets and positively charged surfactant micelles. A graphene oxide−polypyrrole composite prepared from this approach exhibited an excellent electrocapacitive performance with a high specific capacitance over 500 F g−1. Good rate performance and cycle ability were realized by the composite electrode. The simple method described here opens up a generalized route to making a wide range of graphene oxide-based and graphene-based composite materials for applications beyond electrochemical energy storage.
TL;DR: Although the silver nanoparticles were observed to dissolve in all three electrolyte solutions, the aggregation results were still consistent with classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory.
Abstract: Bare silver nanoparticles with diameters of 82 ± 1.3 nm were synthesized by the reduction of the Ag(NH3)2+ complex with d-maltose, and their morphology, crystalline structure, UV−vis spectrum, and electrophoretic mobilities were determined. Dynamic light scattering was employed to assess early stage aggregation kinetics by measuring the change in the average hydrodynamic diameter of the nanoparticles with time over a range of electrolyte types (NaCl, NaNO3, and CaCl2) and concentrations. From this the critical coagulation concentration values were identified as 30, 40, and 2 mM for NaNO3, NaCl, and CaCl2, respectively. Although the silver nanoparticles were observed to dissolve in all three electrolyte solutions, the aggregation results were still consistent with classical Derjaguin−Landau−Verwey−Overbeek (DLVO) theory. The dissolution of the silver nanoparticles, which were coated with a layer of Ag2O, was highly dependent on the electrolyte type and concentration. In systems with Cl− a secondary precipi...
TL;DR: Three donor-linker-acceptor triphenylamine-based cyanoacrylic acid organic dyes used for dye-sensitized solar cells (DSCs) have been examined with respect to their effect on the open-circuit voltage (V(oc).
Abstract: Three donor-linker-acceptor triphenylamine-based cyanoacrylic acid organic dyes used for dye-sensitized solar cells (DSCs) have been examined with respect to their effect on the open-circuit voltage (V(oc)). Our previous study showed a decrease in V(oc) for DSCs based on dyes with increased molecular size (increased linker conjugation). In the present study, we investigate the origin of V(oc) with respect to (i) conduction band (E(CB)) positions of TiO(2) and (ii) degree of recombination between electrons in TiO(2) and electrolyte acceptor species at the interface. These parameters were studied as a function of dye structure, dye load, and I(2) concentration. Two types of behavior were identified: the smaller polyene dyes show a surface-protecting effect preventing recombination upon increased dye loading, whereas the larger dyes enhance the recombination. How the different dye structures affect the recombination is discussed in terms of dye surface blocking and intermolecular interactions between dyes and electrolyte acceptor species.
TL;DR: The surface chemical modification with n-octadecyl isocyanate allows dispersion of the nanoparticles in organic solvents and may allow processing of nanocomposite films from a casting/evaporation technique for a broad range of polymeric matrices.
Abstract: Cellulose nanocrystals (or whiskers) and microfibrillated cellulose (MFC) were successfully obtained from sisal fibers and modified with n-octadecyl isocyanate (C18H37NCO) using two different methods with one innovation that consists of an in situ solvent exchange procedure. The surface chemical modification was characterized by elemental analysis, as well as FTIR and XPS spectroscopies. The crystalline structure of both unmodified and modified nanoparticles was investigated through X-ray diffraction measurements. It was shown that the efficiency of the chemical modification is strongly dependent on the nature of the nanoparticle with explanation linked to specific area, ability of peeling, and solvent dispersion. The surface chemical modification with n-octadecyl isocyanate allows dispersion of the nanoparticles in organic solvents and may allow processing of nanocomposite films from a casting/evaporation technique for a broad range of polymeric matrices.
TL;DR: Evidence from surface-enhanced Raman scattering (SERS) was obtained for p,p'-dimercaptoazobenzene (DMAB) produced from p-aminothiophenol (PATP) by selective catalytic coupling reaction on silver nanoparticles.
Abstract: Combining experiment and theory, evidence from surface-enhanced Raman scattering (SERS) were obtained for p,p′-dimercaptoazobenzene (DMAB) produced from p-aminothiophenol (PATP) by selective catalytic coupling reaction on silver nanoparticles. The time-dependent SERS spectra of PATP are consistent with the calculated SERS spectra of DMAB, which is the direct evidence for the production of DMAB from PATP by selective catalytic coupling reaction on silver nanoparticles. The so-called “b2 modes” of PATP is the −N═N− related vibrational modes of DMAB. The silver nanoparticles could be assembled together to form different size of aggregates with different concentration of PATP solution. When the concentration of Ag nanoparticle (the radius 40 nm) in colloid is 35 pM, the time-dependent SERS of DMAB reveals that the better experimental conditions for observing SERS signals of DMAB are (1) concentration of PATP is around 5 × 10−6 M in which condition the aggregates consist with about 3−5 silver nanoparticles, wh...
TL;DR: This work rationalizes the different reaction paths and optimize the reaction conditions to obtain as pure as possible succinimidyl ester-terminated surfaces and maps the surface composition after activation was constructed by systematically varying the solution composition.
Abstract: Infrared spectroscopy is used to investigate the transformation of carboxyl-terminated alkyl chains immobilized on a surface into succinimidyl ester-terminated chains by reaction with an aqueous solution of N-ethyl-N'-(3-(dimethylamino)propyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS). The acid chains are covalently grafted at the surface of hydrogenated porous silicon whose large specific surface area allows for assessing the activation yield in a semiquantitative way by infrared (IR) spectroscopy and detecting trace amounts of surface products and/or reaction products of small IR cross section. In this way, we rationalize the different reaction paths and optimize the reaction conditions to obtain as pure as possible succinimidyl ester-terminated surfaces. A diagram mapping the surface composition after activation was constructed by systematically varying the solution composition. Results are accounted for by NHS surface adsorption and a kinetic competition between the various EDC-induced surface reactions.
TL;DR: For the first time, dye-sensitized solar cells based on porous WO(3) nanoparticle films were successfully fabricated with efficiency of up to 0.75% by Raman spectroscopy and X-ray diffraction analysis.
Abstract: In research on alternative photoanode materials for dye-sensitized solar cells (DSCs), there is rarely any report on WO3, probably due to its acidic surface and more positive (vs NHE) conduction band edge position compared to TiO2 and ZnO. For the first time, dye-sensitized solar cells based on porous WO3 nanoparticle films were successfully fabricated with efficiency of up to 0.75%. The multicrystalline structure of WO3 was examined by Raman spectroscopy and X-ray diffraction analysis. It was found that significant performance enhancement can be obtained from treating the WO3 nanoparticle film with TiCl4; the TiCl4-treated WO3 DSCs were recorded with efficiency reaching 1.46%.
TL;DR: Using silica coated NPs, various NPs that are functionalized with antibody, oligonucleotide, biotin and dextran are efficiently used for protein detection.
Abstract: Herein, we describe the synthesis of functional and multifunctional nanoparticles (NPs), derived from our recent work, for bioimaging and biosensing applications. The functionalized NPs involve quantum dots (QDs), magnetic particles (MPs) and noble metal NPs for the aforementioned applications. A diverse silica coating approaches (reverse microemulsion and thin silanization) are delineated for the design of water-soluble NPs. We also review the synthesis of silica-coated bifunctional NPs consisting of MPs and QDs for live cell imaging of human liver cancer cells (HepG2) and mouse fibroblast cells (NIH-3T3). Using silica coated NPs, various NPs that are functionalized with antibody, oligonucleotide, biotin and dextran are efficiently used for protein detection.
TL;DR: CNC properties were reasonably uniform along the entire CNC length, despite variations along the axis of 3-8 nm in CNC height, according to a detailed study of the topography, elastic and adhesive properties of individual wood-derived CNCs performed using atomic force microscopy.
Abstract: Cellulose nanocrystals (CNCs) are gaining interest as a "green" nanomaterial with superior mechanical and chemical properties for high-performance nanocomposite materials; however, there is a lack of accurate material property characterization of individual CNCs. Here, a detailed study of the topography, elastic and adhesive properties of individual wood-derived CNCs is performed using atomic force microscopy (AFM). AFM experiments involving high-resolution dynamic mode imaging and jump-mode measurements were performed on individual CNCs under ambient conditions with 30% relative humidity (RH) and under a N(2) atmosphere with 0.1% RH. A procedure was also developed to calculate the CNC transverse elastic modulus (E(T)) by comparing the experimental force-distance curves measured on the CNCs with 3D finite element calculations of tip indentation on the CNC. The E(T) of an isolated CNC was estimated to be between 18 and 50 GPa at 0.1% RH; however, the associated crystallographic orientation of the CNC could not be determined. CNC properties were reasonably uniform along the entire CNC length, despite variations along the axis of 3-8 nm in CNC height. The range of RH used in this study was found to have a minimal effect on the CNC geometry, confirming the resistance of the cellulose crystals to water penetration. CNC flexibility was also investigated by using the AFM tip as a nanomanipulator.
TL;DR: It was found that rGO is biocompatible with all these cell types, whereas the SWCNT network is inhibitory to the proliferation, viability, and neuritegenesis of PC12 cells, and the proliferation of osteoblasts.
Abstract: Nanocarbon materials, including single-walled carbon nanotubes (SWCNTs) and graphene, promise various novel biomedical applications (e.g., nanoelectronic biosensing). In this Letter, we study the ability of SWCNT networks and reduced graphene oxide (rGO) films in interfacing several types of cells, such as neuroendocrine PC12 cells, oligodendroglia cells, and osteoblasts. It was found that rGO is biocompatible with all these cell types, whereas the SWCNT network is inhibitory to the proliferation, viability, and neuritegenesis of PC12 cells, and the proliferation of osteoblasts. These observations could be attributed to the distinct nanotopographic features of these two kinds of nanocarbon substrates.