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Electrochemical water splitting stands as a promising avenue for sustainable hydrogen production, with the oxygen evolution reaction (OER) playing a pivotal role. Efficient and durable electrocatalysts are crucial for expediting the sluggish kinetics of OER. In this work, we investigate the synthesis and performance of a novel CaMoO4/polyaniline (CaMoO4/PANI) composite catalyst for OER. In situ growth of CaMoO4 has been done after the electropolymerization of polyaniline on nickel foam (NF), offering advantages such as improved structural integrity, increased surface area, and enhanced electroconductivity. Electrochemical characterization reveals that CaMoO4/PANI exhibits superior catalytic activity, with an overpotential of 233 mV at 10 mA cm-2, outperforming pristine CaMoO4, PANI, and certain current similar non-noble-metal electrocatalysts. Electrochemical studies reveal that the exceptional activity can be attributed to reduced charge transfer resistance, underscoring the catalyst's enhanced efficiency. Furthermore, multistep chronopotentiometry confirms excellent robustness of the catalyst electrode as well as its excellent mass transportation. This work highlights the potential of inorganic oxide/conductive polymer composites as efficient catalysts for OER, offering insights for future developments in sustainable energy technologies.
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We have studied the structural and interfacial properties of CTAB/isooctane/alcohol/aqueous urea reverse micelles (RMs) for the first time using time-resolved fluorescence and small-angle X-ray scattering techniques. The chain length of alcohol, used as cosurfactant, has been varied to design three microemulsion systems: CTAB/1-butanol, CTAB/1-hexanol, and CTAB/1-octanol/isooctane/water, at a fixed water loading ratio, w0 = 12. Time-resolved fluorescence anisotropy studies indicate that urea induces micellar aggregation in CTAB/1-butanol and CTAB/1-hexanol RMs but breaks down RM aggregates in CTAB/1-octanol RMs. Urea addition slows down solvation dynamics inside RMs at higher urea concentrations, evident from the longer lifetimes of solvent correlation decay. The underlying changes in microemulsion structure and intermicellar interactions are studied using small-angle X-ray scattering studies. The significant intermicellar interactions were modeled using the sticky hard sphere (SHS) for the CTAB/1-butanol and CTAB/1-hexanol RMs and by using the Macroion model for the CTAB/1-octanol RMs. The two different structural factors highlight the dominance of attractive and repulsive forces, respectively. Although there is no change in RM shape, the combination of urea addition and chain length variation in cosurfactants significantly alters the size and interface in these pseudoternary RMs.
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Ternary transition metal chalcogenide (Cu2WS4) is a semiconductor with a band gap of 2.1 eV and could be a promising candidate for photoelectrochemical water splitting and solar energy conversion applications. Despite numerous reports on ternary transition metal chalcogenides, this semiconductor's ultrafast charge transfer dynamics remain unknown. Here, we report on charge carrier dynamics in a pristine Cu2WS4 system with the aid of ultrafast transient (TA) pump-probe spectroscopy and a hot carrier transfer process from Cu2WS4 to multi-walled carbon nanotubes (CNTs) and FeOOH has been observed. Furthermore, we have explored Cu2WS4-FeOOH having a type-II composite for photo-electrochemical (PEC) water oxidation and modified this with the addition of multi-walled carbon nanotubes to expedite the charge-transfer processes and photo-anodic performance. The photo-electrochemical studies demonstrate that the Cu2WS4-CNT, Cu2WS4-FeOOH, and Cu2WS4-CNT-FeOOH provide nearly 3-, 8- and 12-fold enhancement in photocurrent density relative to the bare Cu2WS4 photo-anode at 1.23 V vs. RHE. These photo-electrochemical studies support the results obtained from the TA investigation and further prove the higher charge separation in the ternary composite system. These studies probe the excited states and provide evidence of longer charge separation in the binary and ternary composites, responsible for their remarkable photo-electrochemical performance.
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Correction for 'Understanding the charge transfer dynamics of the Cu2WS4-CNT-FeOOH ternary composite for photo-electrochemical studies' by Preeti Dagar et al., Phys. Chem. Chem. Phys., 2023, https://doi.org/10.1039/D3CP03498D.
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Transamidation reactions catalyzed by boronic acid derivatives and metal catalysts are well known nevertheless their requirement for elevated temperatures and long reaction times were considered major obstacles in converting amides to N-alkyl amides with the coupling of primary amides and amines. The acidic-basic co-existence of ceria nanoparticles is considered a perfect choice for different catalytic activities. Mesoporous silica on the other hand is well known for its use as a supporting material for catalysts owing to its excellent characteristics like large surface area, good absorption capacity, and high-temperature stability. The SiO2-CeO2 hybrid nanocomposite was prepared by solvothermal route followed by annealing and the formation of the catalyst was confirmed by XRD, EDX, FTIR, and TEM characterization techniques. The hybrid catalyst shows high catalytic activity towards transamidation reaction at very low temperatures and in solvent-free conditions compared to pure ceria nanoparticles. The SiO2-CeO2 catalyst showed more than 99% selectivity and a remarkable catalytic activity of above 90% for the conversion of N-heptyl amine with acetamide to N-heptyl acetamide at a very low temperature of 120 °C for 3 hours. Furthermore, the catalyst remains stable and active for repeated catalytic cycles. It established 80% catalytic activity even after 4 repeated cycles making it suitable for multiple-time usages.
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Upconversion materials have attracted considerable research interest for their application in bioimaging due to their unique optical properties. NaREF4 (RE = Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) based host lattice, which is widely used for upconversion, requires expensive rare-earth elements and tedious reaction conditions. Hence there is a need to develop environmentally friendly and cost effective materials for upconversion. In this study, we propose NaBiF4 as a host material for upconversion which is based on environmentally friendly and cost-effective bismuth. NaBiF4 has not been explored as an imaging probe before. We report efficient Yb3+/Tm3+ doped NaBiF4 based upconversion submicron particles which exhibit a photostable, wide upconversion emission range (NIR-to-NIR and Vis) under NIR (980 nm) excitation, and in-vitro non-cytotoxic uptake by mammalian cancer cell lines as well as bacterial cells with a high signal to background ratio. The synthesis of the chosen host material co-doped with Yb3+/Tm3+ has not been reported earlier through such a non-aqueous quaternary reverse micelle route. Here, we functionally validate these submicron particles as viable alternatives to currently available upconversion nanomaterials and highlight their potential as luminescent probes for bioimaging.
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Metais Terras Raras , Nanoestruturas , Animais , Luminescência , MamíferosRESUMO
Tailoring the characteristics of anisotropic nanostructures like size, morphology, aspect ratio, and size dispersity is of extreme importance due to the unique and tunable properties including catalytic, optical, photocatalytic, magnetic, photochemical, electrochemical, photoelectrochemical, and several other physical properties. The reverse microemulsion (RM) method offers a useful soft-template and low-temperature procedure that, by variation of experimental conditions and nature of reagents, has proved to be extremely versatile in synthesis of nanostructures with tailored properties. Although many reports of synthesis of nanostructures by the RM method exist in the literature, most of the research studies carried out still follow the "hit and trial" method where the synthesis conditions, reagents, and other factors are varied and the resulting characteristics of the obtained nanostructures are justified on the basis of existing physical chemistry principles. Mechanistic investigations are scarce to generate a set of empirical rules that would aid in preplanning the RM-based synthesis of nanostructures with desired characteristics as well as make the process viable on an industrial scale. A consolidation of such research data available in the literature is essential for providing future directions in the field. In this perspective, we analyze the literature reports that have investigated the mechanistic aspects of growth of anisotropic nanostructures using the RM method and distil the essence of the present understanding at the nanoscale timescale using techniques like FCS and ultrafast spectroscopy in addition to routine techniques like DLS, fluorescence, TEM, etc.
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The role of ionic flux in controlling the polarity of the surfaces of ZnO was evaluated, both experimentally and theoretically. Zinc oxide was synthesized by controlled decomposition of zinc oxalate nanorods in the presence of ionic flux. The degree of preferred orientation for a specific plane, for the ZnO structures, was observed by calculating the texture coefficient. The presence of flux (NaCl, KCl, a mixture of NaCl-KCl and Na2SO4) during decomposition of the oxalate precursor led to the preferential growth of (112[combining macron]0) planes. The value of texture coefficient was found to be high for the (112[combining macron]0) plane when the decomposition was carried out in the presence of a mixture of NaCl and KCl when compared to their counterparts. A decrease in the value of texture coefficient for the (112[combining macron]0) plane was observed when Na2SO4 was used as a flux, which was similar to the value obtained for ZnO synthesized in the absence of flux. The observations from the analysis of texture coefficient were correlated with the photocatalytic degradation of rhodamine B dye, by making use of the fact that the nature of exposed surfaces influences the catalytic activity of a material. On-site Coulomb correlation corrected density functional theory (DFT + U)-based computational studies were performed to get theoretical insight into the role of the ionic flux in surface reconstructions. The surface energies for different ZnO surfaces were computed in the presence and absence of the ionic flux. It was revealed that the pristine (101[combining macron]0) surface is more stable compared to pristine (112[combining macron]0) by 0.04 J m-2 (surface energy), however the scenario changes in the presence of the ionic flux and (112[combining macron]0) becomes more stable by 0.03 J m-2. This indeed corroborated with our experimental observations and explained the fundamental role of ionic flux on the polarity of exposed surfaces of ZnO.
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DyPdBi (DPB) is a topological semimetal which belongs to the rare-earth-based half-Heusler alloy family. In this work, we studied the thickness-dependent structural and magneto-transport properties of DPB thin films (20 to 60 nm) grown using pulsed laser deposition. The DPB thin films show (110) oriented growth on MgO(100) single crystal substrates. Longitudinal resistance data indicate metallic surface states dominated carrier transport and the suppression of semiconducting bulk state carriers for films ≤40 nm. We observe the weak antilocalization (WAL) effect and Shubnikov-de Hass (SdH) oscillations in the magneto-transport data. The presence of a single coherent transport channel (αâ¼ -0.50) is observed in the Hikami-Larkin-Nagaoka (HLN) fitting of WAL data. The power law temperature dependence of phase coherence length (LØ ) â¼ T-0.50 indicates the observation of the 2D WAL effect and the presence of topological nontrivial surface states for films ≤40 nm. The 60 nm sample shows semiconducting resistivity behavior at higher temperature (>180 K) and HLN fitting results (αâ¼ -0.72, LØ â¼ T-0.68 ) indicate the presence of partial decoupled top and bottom surface states. The Berry phase â¼π is extracted for thin films ≤40 nm, which further demonstrates the presence of Dirac fermions and nontrivial surface states. Band structure parameters are extracted by fitting SdH data to the standard Lifshitz-Kosevich formula. The sheet carrier concentration and cyclotron effective mass of carriers decrease with increasing thickness (20 nm to 60 nm) from â¼1.35 × 1012 cm-2 to 0.68 × 1012 cm-2 and from â¼0.26 me to 0.12 me, respectively. Our observations suggest that samples with a thickness ≤40 nm have transport properties dominated by surface states and samples with a thickness ≥60 nm have contributions from both bulk and surface states.
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Chemosensing plays a very important role in the detection of essential/pollutant ions in aqueous media. In this manuscript, two tripodal ligands, i.e., 1-(2-hydroxybenzyl)-3-(4-nitrophenyl)-1-phenylurea (ligand 1) and 1-(2-hydroxybenzyl)-3-(4-nitrophenyl)-1-phenylthiourea (ligand 2) have been synthesised, which differ in the linker molecule, i.e., urea and thiourea in ligand 1 and ligand 2, respectively. The ligands were characterised by NMR, IR and mass spectroscopic techniques. Ligands 1 and 2 (2 mM) were further employed for the generation of their organic nanoparticles (ONPs) (0.01 mM) of size 20-25 nm and 30-35 nm, respectively, by the reprecipitation method. The chemosensing properties of 1-ONP and 2-ONP solutions were investigated. 1-ONP showed simultaneous recognition behaviour towards Cs(i) and Al(iii) with the limits of detection of â¼220 and â¼377 nM, respectively, in an aqueous medium, while 2-ONP did not show any recognition behaviour towards any ion.
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Correction for 'Understanding the role of co-surfactants in microemulsions on the growth of copper oxalate using SAXS' by Sunaina et al., Phys. Chem. Chem. Phys., 2019, 21, 336-348.
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Reverse micelles (RMs) as soft templates have been successfully used in tailoring the structural characteristics (size and morphology) of nanomaterials that in turn have been used in various applications. In this work, we have focused on the local perturbations in the different interior domains of the cetyltrimethylammonium bromide-reverse micelle-based soft template en route to nanorod formation by monitoring the solvation response of coumarin-based solvatochromic probes (C343 and C153). We have observed an appreciable retardation of the solvent coordinate during the initial phases of nanorod growth, which we have attributed to the reorientational motion of the water molecules lodged in the interfacial region. Moreover, these rigid nanostructures leave their imprints on the soft interfacial layer as was observed from the direct correlation in the solvation response of RM-containing nanostructures and respective surfactant aggregates in supernatant solution. Supporting data from time-resolved anisotropy studies further reinforced our conclusions from the solvation experiments. Our study proves that the hydration dynamics can be a promising tool in tracking the heterogeneous growth evolution of nanostructure formation in RMs since solvent reorganization provides insights into the intrinsic, molecular-level features of the micellar assemblies.
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Self-organization of nanoparticles into one-dimensional (1D) nanochains leads to new unpredicted physiochemical properties, which are further exploited to develop photonic or electronic devices. Thus, the controlled fabrication of 1D nanochains requires nanotemplate, which acts as building blocks for the self-assembly of nanoparticles. To address this issue, we designed a hydrotrope (sodium salicylate)-based CTAB/ n-hexanol/water/heptane reverse micellar system. Hydrotrope, herein, modulates electrostatic interactions between reverse micellar droplets and paves the way for the formation of self-assembled structures. Small-angle X-ray scattering studies were performed on the CTAB/heptane reverse micellar system by varying hydrotrope concentrations and water-to-surfactant ratios (W x). The aqueous content of the reverse micellar pool is determined from the W x value, where W x = [H2O]/[CTAB] and [CTAB] = 0.05 M. SAXS studies were performed for CTAB/heptane reverse micellar systems at three different W x values, that is, 6, 12, and 16 and represented by W6, W12, and W16, respectively. All SAXS profiles were modeled with a spherical form factor and a Baxter sticky hard sphere structure factor. The interaction between droplets was predicted in terms of stickiness parameter. The effect of W x on the formation of self-assembled structures and forces governing the assembly has been discussed in detail. For the W6 system, the electrostatic repulsion between reverse micellar droplets decreases, resulting in the formation of the 1D chain-like assembly of nanodroplets. In the case of the W12 system, the dual feature of the hydrotrope has been observed, it increases the size of the reverse micellar system and reduces electrostatic repulsion between droplets because of which the formation of chain-like assemblies cannot be determined with accuracy. For the W16 system, the decrease in micellar size with the increase in the hydrotrope concentration has been observed. Thus, our reverse micellar templates may provide a comprehensive method for the fabrication of high aspect ratio 1D nanochains of a variety of materials and harnessing their collective properties for magnetic, catalytic, and opto-electronic applications.
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Increase in industrialization as a tool to become global leader has led to an exponential rise in environmental pollution. The present study describes a process developed to extract nanocrystalline sodium carbonate from chemical industry effluents, which contributes to wealth creation from hazardous waste. Sodium carbonate is a high demand product because of its applications in detergents, dyeing, glass, and paper manufacturing. In the present work, we have extracted nanostructured sodium carbonate using industrial waste (alkaline solution of silicates, obtained from ceramic industry) and carbon dioxide (a major component of flue gas effluent from power plants). Here we have collected waste from ceramic industries, which is highly corrosive (pH 13-14) and disposal of such waste is dangerous to the environment and needs to be taken special care. Pure carbon dioxide has been purged in collected industrial waste to get nanoparticles and flakes structure of sodium carbonate at room temperature. The use of the nanostructured sodium carbonate in the dyeing of textiles was encouraging. Significantly, higher dyeing efficacy was observed compared to the fabric dyed in the absence of sodium carbonate (Na2CO3). The nanocrystalline particles show much better color strength than bulk sodium carbonate when K/S value was compared. Na2CO3 with the minimum particle size (26â¯nm) results in the maximum color strength (K/Sâ¯=â¯14.49).
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Indústria Têxtil , Poluentes Químicos da Água , Carbonatos , Cerâmica , Corantes , Resíduos Industriais , Eliminação de Resíduos LíquidosRESUMO
This study is an effort to understand the mechanism of the effect of the chain length of co-surfactants on the growth of copper oxalate inside the core of reverse micelles using small angle X-ray scattering (SAXS). In this study, we have used two different kinds of co-surfactants viz. 1-butanol (C4) and 1-octanol (C8) for the formation of the microemulsions. Time-dependent SAXS studies were carried out for these two systems. The data were analyzed using both the model-independent approach and model-dependent approach. For microemulsions containing only water inside the core of reverse micelles (no ions), the shape of the reverse micelles was observed to be ellipsoid and spherical in nature for 1-butanol and 1-octanol respectively. For a system containing copper oxalate nanostructures, the fitting was carried out using the ellipsoidal core-shell model for reverse micelles and spheres, ellipsoids and cylinders for copper oxalate nanostructures with 1-butanol as the co-surfactant. With 1-octanol as the co-surfactant, the two contributions that were used were the spherical core-shell model for reverse micelles and spheres for copper oxalate nanostructures. Based on the analysis of SAXS data, a growth mechanism has been proposed. The study discussed here could open the field of understanding the growth mechanism of complex nanostructures formed using the microemulsion route.
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Here, we report the fabrication of a new Z-scheme based core/shell/shell heterostructure of NaNbO3/CuInS2/In2S3 (core/shell/shell) for photoelectrochemical (PEC) water splitting and also for degradation of organic pollutants. We have also performed a comparative study with a modified heterostructure of NaNbO3/In2S3/CuInS2 having Type II band alignment. The PEC measurements under visible light irradiation show increased photocatalytic performance for the NaNbO3/CuInS2/In2S3 heterostructures as revealed by a high current density of â¼6.72 mA/cm2 at -1.0 V versus Ag/AgCl and low photocurrent onset potential of â¼ -110 mV in comparison to the Type II system (â¼1.63 mA/cm2 and -180 mV vs Ag/AgCl). Mott-Schottky plots confirmed the n-p-n type heterojunction formation in the NaNbO3/CuInS2/In2S3 heterostructure which reduces the charge carrier recombination (revealed by PL intensity and short lifetime). The Z-scheme based system also exhibits excellent degradation efficiency (â¼99.6%) of organic pollutants. This work shows that the Z-scheme charge separation mechanism in NaNbO3/CuInS2/In2S3 nanostructures is more efficient than the Type II based on NaNbO3/In2S3/CuInS2.
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Hydrogen fuel is among the cleanest renewable resources and is the best alternative to fossil fuels for the future. Hydrogen can be best produced by means of electrolysis or photoelectrolysis of water among the various routes available for hydrogen production. So far, Pt has been recognized as the best electrode material for electrochemical hydrogen production. However, the cost of the catalyst, activity, and durability make Pt-catalyzed hydrogen production unsuitable on a commercial scale. It has hence become imperative to explore low-cost, highly active and durable HER catalysts to replace platinum as a catalyst. This perspective provides key concepts and the current status of the research on the properties of nanocatalysts that influence the hydrogen evolution reaction. Important structural features controlling the surface chemistry (i.e. facets, defects, dopants), nature of supports (graphene, CNTs, black phosphorus), role of heteroatoms, media and morphology are the key points of discussion in this perspective.
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Potential impacts of inevitable leaks of silver nanoparticles (AgNPs) into environment on human beings need attention. Owing to the vitality of photosynthesis in maintaining life and ecosystem functioning, impacts of exogenously applied nanoparticulate and Ag+ on photosystem (PS)II function, which governs overall photosynthesis, in wheat and sunflower were evaluated. PSII efficiency and related Chl a fluorescence kinetics of these two plants remained unaffected by AgNPs. However, Ag+ caused a significant decline in the PSII activity and related fluorescence steps in wheat, but not in sunflower. Electron flow between QA and PQ pool was found most sensitive to Ag+. Number of active reaction centers, electron transport, trapping of absorbed light for photochemistry, and performance index declined, while dissipation of absorbed light energy as heat significantly increased in wheat exposed to Ag+. Total antioxidant activity in sunflower was least affected by both Ag and AgNPs. In contrast, in the case of wheat, the antioxidant activity was declined by Ag+ but not by AgNPs. Further, the amount of silver absorbed by plants exposed to Ag+ was higher than that absorbed by plants exposed to AgNPs. While wheat retained majority of Ag in its roots, sunflower showed major Ag accumulation in stem. Photosynthetic events in sunflower, unlike wheat, were least affected as no detectable Ag levels was recorded in their leaves. Our findings revealed that AgNPs seemed non/less-toxic to light harnessing photosynthetic machinery of wheat, compared to Ag+. Photosynthetic events in sunflower were not affected by Ag+, either, as its translocation to leaves was restricted.
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Helianthus/fisiologia , Fotossíntese/efeitos dos fármacos , Prata/farmacologia , Triticum/fisiologia , Clorofila/metabolismo , Helianthus/metabolismo , Íons/farmacologia , Nanopartículas Metálicas/química , Complexo de Proteína do Fotossistema II/efeitos dos fármacos , Complexo de Proteína do Fotossistema II/metabolismo , Folhas de Planta/metabolismo , Triticum/metabolismoRESUMO
Designing nanostructures of desired morphology calls for development of new synthetic protocols to stimulate structural alterations in templates, modulating the architecture of nano-metric structures. The present study is an endeavor to investigate structural modifications in reverse micellar nanotemplates of a cationic surfactant system, CTAB/butanol/water/isooctane, as a function of hydrotrope concentration (sodium salicylate) and amount of water loading, Wx, in the micellar pool by synchrotron small-angle X-ray scattering. The micellar structural transition from a one-dimensional cylinder to a prolate ellipsoid can be controlled by tuning the water-to-surfactant molar ratio while the hydrotrope modulates growth of the micellar droplets. The inter-micellar interactions in these systems could be best represented by the Polymer Reference Interaction Site (PRISM) model at lower water content in the reverse micellar pool and by the Macroion model at higher water loadings. The location of the hydrotrope inside the micellar assembly and its interaction with different components of the reverse micellar system is probed with the help of 1H NMR studies. The formation and tuning of anisotropic cylindrical/ellipsoidal reverse micellar droplets suggest promising application of such aggregates as "tunable soft templates" for fabricating fascinating nanostructures.
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In this combined experimental and theoretical research, magnetic nano-particle (mNP) mediated energy transfer due to high intensity-focused ultrasound (HIFU) sonication has been evaluated. HIFU sonications have been performed on phantoms containing three different volume percentages (0%, 0.0047%, and 0.047%) of mNPs embedded in a tissue mimicking material (TMM). A theoretical model has been developed to calculate the temperature rise in the phantoms during HIFU sonication. It is observed from theoretical calculation that the phonon layer at the interface of the mNPs and TMM dominates the attenuation for higher (0.047%) concentration. However, for a lower concentration (0.0047%) of mNPs, intrinsic absorption is the dominating mechanism. Attenuation due to the viscous drag becomes the dominating mechanism for larger size mNPs (>1000 nm). At a higher concentration (0.047%), it is observed from theoretical calculations that the temperature rise is 25% less for gold nano-particles (gNPs) when compared to mNPs. However, at lower concentrations (0.0047% and 0.002%), the difference in temperature rise for the mNPs and gNPs is less than 2%.