Precursor Salt Concentration Research Articles

Green synthesis, characterization and antibacterial activity of copper nanoparticles using <i>L</i>-ascorbic acid as a reducing agent

Synthesis of Cu nanoparticles using chemical route offers a competitive alternative approach over the common biological and physical procedures. In this study, simple, economical, convenient and environmentally-friendly chemical reduction technique was used for the production of Cu nanoparticles from CuCl2.2H2O solution using L-ascorbic acid as reducing and capping agent. The effects of concentration of precursor salt and ascorbic acid, reaction time and reaction temperature on the synthesis of Cu nanoparticles were studied. The optical properties of the synthesized Cu nanoparticles were characterized by UV-Vis Spectroscopy while the crystallinity of synthesized Cu nanoparticles was verified with the help of X-ray diffraction analysis. The antimicrobial activity of Cu nanoparticles was determined by Agar disc diffusion method against some selected species of bacteria: two gram positive (Staphylococcus aureus, Streptococcus pyogenes) and two gram negative (Escherichia coli, Pseudomonas aeruginosa). The UV-Vis spectrum of solution of Cu nanoparticles showed a characteristic peak at 423 nm that confirms the preparation of Copper nanoparticles. Moreover, FT-IR spectroscopy was performed to detect the binding effect of ascorbic acid on Cu nanoparticles, and its result indicated that ascorbic acid could prevent oxidation and agglomeration. The findings revealed that Cu nanoparticles formed at a concentration of 3mM Cu- Cl2.2H2O solution and 4 mM ascorbic acid exhibited an excellent zone of growth inhibition for both gram-negative and gram-positive bacteria, 16.83+0.42 and 15.50+0.89mm, respectively.Keywords: - Green synthesis, Copper nanoparticles, Chemical reduction, Optical properties, Antibacterial activity

Bifunctional Oxygen Reduction/Evolution Reaction Electrocatalyst Based on MnO2 for Rechargeable Alkaline Metal-Air Batteries and Regenerative Fuel Cells: Challenges and Opportunities

Development of non-PGM bifunctional electrocatalysts with high electrocatalytic activity and durability for both oxygen reduction and evolution reactions (ORR and OER) is of outmost importance to realize the full potential of rechargeable metal-air batteries (e.g., Zn-air, Al-air, Mg-air, Li-air) and regenerative H2-O2 fuel cells. Manganese oxides have been in the spotlight especially as alkaline ORR electrocatalysts, due to low cost and natural abundance. Regarding the bifunctional ORR and OER electrocatalytic performance of MnOx, further improvements in activity and durability are required for implementation in commercial energy storage and conversion systems. The aim of this study is to enhance the bifunctional activity and durability by investigating the role of MnOx morphology, co-catalyst addition, potassium ion doping and support effect (e.g., graphene and graphitized carbon). The experiments were performed in 6 M KOH, 293 K and 1 atm(abs) over a wide potential window encompassing the ORR and OER polarization regions. Results obtained with both flooded dissolved O2 and gas (O2 or air)-diffusion cells are presented. The combination of MnO2 with a structurally different oxide co-catalyst such as perovskite (LaCoO3) or fluorite-type oxide (Nd3IrO7) produces a synergistic catalytic effect improving both the activity and durability compared to the individual oxides. Doping of the oxide catalyst with potassium ions, either by long-term exposure to 6 M KOH or potential driven insertion (PDI), increases further the activity and durability as revealed in accelerated degradation experiments.1,2 The effect of MnO2 morphology on the bifunctional performance was investigated by carrying out a statistically designed MnO2 electrodeposition study. Four main variables were studied through factorial experiments: a) anodic MnO2 electrodeposition potential, b) surfactant type (non-ionic, cationic and anionic) and concentration, c) Mn(II) precursor salt concentration and d) temperature. Fig. 1 shows the surface plots for three different responses: ORR and OER mass activities, and ORR/OER onset potential window.3 Fig. 1. Effect of MnO2 electrodeposition conditions on the ORR and OER bifunctional electrocatalytic performance. Surface plots for the 24-1+3 factorial design showing the three responses: A) ORR mass activity, B) OER mass activity and C) OER/ORR onset potential window. Legend: E - anodic MnO2electrodeposition potential (mV vs. Hg/HgO/0.1 M KOH), S - surfactant (Triton X-100) concentration in the deposition bath (%vol.), T - electrodeposition temperature (K). As shown by Fig. 1, optimizing the MnOx electrodeposition conditions can produce nanostructured morphologies that are favorable for bifunctional activity. The activity metrics compare favorably to either commercially obtained MnO2 sampled or literature reported activities for various catalysts including CoMn2O4 and core-corona structured bifunctional catalyst. The electrochemical results are discussed in conjunction with extensive surface analysis (SEM, TEM, XPS, EDX, EELS) and the modern prevailing theory of ORR and OER electrocatalytic activity based on the scaling relationship between the binding energies of HO* and HOO*.

Facile control of ZnO nanostructures by varying molar concentration of zinc acetate

This paper reports the synthesis of ZnO nanostructures (nano-bullets, nanorods, nanospheres) by a facile and novel modified polyol method without surfactants, varying only the molar concentration of precursor salt (Zinc acetate dihydrate) using ethylene glycol and deionized water. At a constant temperature of 160°C, nano-bullets were obtained at a concentration of 0.6M, whereas at 0.8M nanorods were observed while at 1.0M only nanospheres appear. X-ray Diffraction, Scanning Electron Microscopy, High-Resolution Transmission Electron Microscopy and Room-Temperature Photoluminescence properties were used to characterize the nanostructures. Based on the results it is suggested a high dependence between morphology and molar concentration of the precursor salt as well as a mechanism of crystallization of the different nanostructures. The nanostructures may be used to produce optoelectronic devices.

In-situ upgrading of reservoir oils by in-situ preparation of NiO nanoparticles in thermal enhanced oil recovery processes

In-situ combustion (ISC) in the presence of catalytic metal oxide nanoparticles is a promising enhanced oil recovery process for heavy oil reservoirs. A proper method for uniform distribution of the nanoparticles in the reservoir fluids is in-situ synthesis of the nanomaterials. Precursor metal ionic aqueous solutions and heavy oil form water/oil emulsions, downstream of the combustion front, by the aid of asphaltenes and resins. Upon heating, the nanoparticles are formed, on which asphaltenes are adsorbed and pyrolyzed to provide the fuel for a stable ISC front. NiO nanoparticles were synthesized via the in-situ synthesis process. Ni(NO3)2·6H2O aqueous solution was dispersed in heavy oil model solutions of asphaltenes in toluene-vacuum gasoil. The droplet size, stability, and interface elasticity of the emulsions were monitored by changing the precursor salt concentration, salt solution/oil ratio, and temperature and pressure. Bottle test, micropipette test, microscope imaging, and equilibrium and dynamic IFT measurements were used to characterize the emulsions. The stable emulsions were exposed to high-temperature and high-pressure conditions to deliver nanoparticles. The in-situ prepared coked nanoparticles were characterized by XRD, FTIR, HRTEM, and TGA techniques and compared with ex-situ prepared NiO nanoparticles. Prior and subsequent to the in-situ synthesis, the kinematic viscosity of the model oil, as an upgrading index, was measured. It is found that the emulsions droplet size increases with the precursor salt concentration, at constant salt solution/oil ratios, leading to instability of the emulsions. An optimum value is found for the salt solution/oil ratio, at constant precursor molarities, resulting in stable emulsions. Compared to ex-situ prepared nanoparticles, the in-situ synthesized NiO nanoparticles exhibit around 48% higher coke formation tendency and shift the coke combustion temperature by about 130°C downward. Furthermore, the viscosity of the model oil decreases by 2–8% during the in-situ synthesis procedure, showing an in-situ upgrading potential for the process.

Green Synthesis of Iron Nanoparticles using Aqueous Extract of Musa ornata Flower Sheath against Pathogenic Bacteria

Iron nanoparticles were synthesized using Musa ornata flower sheath extract. The optimum precursor salt concentration, pH of the reaction mixture, ratio between reducing agent and precursor salt and time for the synthesis of iron nanoparticles were found to be 5 mM, 9.0, 3:7 and 0th h respectively. The synthesized iron nanoparticles were characterised by UV/Vis absorption spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy, atomic force microscope and particle size analyser. UV/Vis absorption showed a characteristic absorption peak of iron oxide nanoparticles in the range of 250-350 nm. Fourier transform infrared spectroscopy measurement was carried out to identify the possible molecules like carbonyl, CH and OH band. From the X-ray diffraction method, it was found that the average particle size of magnetite nanoparticles was found to be 43.69 nm. The synthesized iron nanoparticles had antibacterial activity against pathogenic bacteria like Staphylococcus aureus, Streptococcus agalactiae, Escherichia coli and Salmonella enterica by well diffusion method. This biosynthesis approach has been found to be cost effective, eco-friendly and promising for applications in various fields.

Solar photocatalytically active, engineered silver nanoparticle synthesis using aqueous extract of mesocarp of Cocos nucifera (Red Spicata Dwarf)

ABSTRACTSilver nanoparticles synthesised using aqueous extract of Cocos nucifera (CN) mesocarp were evaluated for their photocatalytic activity under solar irradiation. The silver nanoparticles were synthesised by a green method of harnessing bioactive phytocomponents from the mesocarp of Cocos nucifera. Large-scale application of this process necessitates the manoeuvering of the process parameters for increasing the conversion of silver ions to nanoparticles. Process parameters influencing the morphological characteristics of silver nanoparticles such as precursor salt concentration and pH of the synthesis mixture were studied. The crystalline nanoparticles were characterised using UV-vis spectroscopy, XRD, FTIR, SEM and EDX analysis. CN extract and 5 mM silver nitrate solution at a ratio of 1:4 (v/v) in the synthesis mixture was found to be the optimum. Alkaline initial pH of the synthesis mixture was found to favour the synthesis of smaller sized monodispersed silver nanoparticles. Solar energy was harnessed for the photocatalytic degradation of Malachite green dye using silver nanoparticles obtained through the green synthesis method. Overall process aims at utilisation of naturally available resource for the synthesis of silver nanoparticles as well as the degradation of dyes using these nanoparticles, making it useful in the treatment of wastewater.

Utilizing metal tolerance potential of soil fungus for efficient synthesis of gold nanoparticles with superior catalytic activity for degradation of rhodamine B

In recent years, the surging demand of nanomaterials has boosted unprecedented expansion of research for the development of high yielding and sustainable synthesis methods which can deliver nanomaterials with desired characteristics. Unlike the well-established physico-chemical methods which have various limitations, biological methods inspired by mimicking natural biomineralization processes have great potential for nanoparticle synthesis. An eco-friendly and sustainable biological method that deliver particles with well-defined shape, size and compositions can be developed by selecting a proficient organism followed by fine tuning of various process parameter. The present study revealed high metal tolerance ability of a soil fungus Cladosporium oxysporum AJP03 and its potential for extracellular synthesis of gold nanoparticles. The morphology, composition and crystallinity of nanoparticles were confirmed using standard techniques. The synthesized particles were quasi-spherical in shape with fcc packing and an average particle size of 72.32 ± 21.80 nm. A series of experiments were conducted to study the effect of different process parameters on particle size and yield. Biomass: water ratio of 1:5 and 1 mM precursor salt concentration at physiological pH (7.0) favoured the synthesis of well-defined gold nanoparticles with maximum yield. The as-synthesized nanoparticles showed excellent catalytic efficiency towards sodium borohydride mediated reduction of rhodamine B (2.5 × 10−5 M) within 7 min of reaction time under experimental conditions. Presence of proteins as capping material on the nanoparticle surface was found to be responsible for this remarkable catalytic efficiency. The present approach can be extrapolated to develop controlled and up-scalable process for mycosynthesis of nanoparticles for diverse applications.

Influence of zinc oxide morphology in hybrid solar cells of poly(3-octylthiophene)

Hybrid solar cells of semiconductor oxides and conductive polymers have been broadly studied. Poly(3-octylthiophene) (P3OT), is an organic polymer formed by conjugated structures with conductive properties, photoluminescence, a relatively high charge mobility and stability. Zinc oxide (ZnO) has been used as an electron acceptor in this cell type because it offers great electron transport properties, simple manufacturing techniques, non-toxicity, variation and morphologic control. Different ZnO morphologies allow distinct properties in terms of electronic transport in solar cell interfaces. The objective of this paper was to evaluate whether ZnO with its different morphologies can improve the anchorage of P3OT and influence the conductive properties of hybrid solar cells of ZnO/P3OT. ZnO particles were synthetized by co-precipitation with Zn(NO3)2·6H2O in concentrations of 0.05, 0.10 and 0.15 mol L−1. The morphology was evaluated by scanning electron microscopy (SEM), and the suspension was evaluated by thermogravimetric analysis and differential scanning calorimetry and X-ray diffraction. Cells containing the working electrode (ZnO/P3OT) were evaluated by open circuit potential (Voc) and electrochemical impedance spectroscopy (EIS). The SEM images showed three morphologies: spherical ZnO (ZnOE), hexagonal ZnO (ZnOH) and ZnO without defined morphology (ZnOM) due to the variation of the precursor salt concentration. Cells with different morphologies presented medium values of Voc = −0.438 ± 0.027 V. The EIS indicated that ZnOM/P3OT cells have lower values of charge transfer resistance and higher values of capacitance at intermediate frequencies. ZnOM/P3OT solar cells presented the best results in relation to the electron transfer processes.

Influence of precursor molar concentration on the structural, morphological, optical and electrical properties of PbS thin films deposited by spray pyrolysis technique using perfume atomizer

PbS thin films were deposited onto glass substrates at 400°C using lead nitrate and thiourea as sources of Pb and S respectively. The molar concentration of precursor salts (both cationic and anionic) was varied as 0.025, 0.05, 0.075 and 0.1 keeping S/Pb ratio equal to 1. The structural studies reveal that the S:Pb concentration has a strong influence on the microstructural characteristics of the sprayed PbS films. The films were adherent to the substrate and well crystallized according to orthorhombic structure with the preferential orientation making a transition from (004) plane to (413) plane when S:Pb molar concentration increases. All the films have high optical transmittance>70%. The optical band gap values are found to be in the range of 2.44 – 2.55eV. The refractive index dispersion of the films obeys the single oscillator model. Electrical resistivity of all the films was found to be in the order of 102Ωcm. PbS films fabricated by this simplified technique are found to be good in structural, optical and electrical properties which are desirable for window layers in solar cell applications.

Prospects for the use of ultrasonic spray pyrolysis to prepare catalysts for the synthesis of carbon nanofibers

The application of high-frequency ultrasonic spray pyrolysis (USP) of aqueous solutions for the preparation of the NiO-CuO/10%MgO catalyst is discussed. The installation for the catalyst synthesis consists of a household humidifier, a furnace for drying the formed aerosol, and an electric precipitator for collecting the product particles. The secondary structure of the USP catalysts comprises spherical particles (0.2–5 μm), the diameters of which are defined by the concentration of precursor salts in the solution (0.1–5 wt %). It was shown that the use of USP catalysts for the synthesis of feathery carbon nanofibers (CNFs) (C3H8 decomposition at 700°C) allows us to obtain a more uniform product with the maximum yield when compared with similar samples prepared by coprecipitation and mechanochemical activation.

Biosynthesis and characterization of zinc, magnesium and titanium nanoparticles: an eco-friendly approach

In the present study, zinc (Zn), magnesium (Mg) and titanium (Ti) nanoparticles synthesized using fungus by employing various precursor salts of sulfate salts, nitrate salts, chloride salts and oxide salts. To access the nanoparticle production potential, over a hundreds of fungi were isolated from the soil and tested with precursor salts of the Zn, Mg and Ti. Out of which, only 14 fungal isolates were identified, having potential to reduce metal salt into metal nanoparticles. Upon molecular identifica- tion, six were identified as Aspergillus flavus, two each as Aspergillus terreus and Aspergillus tubingensis and one each as Aspergillus niger, Rhizoctonia bataticola, Asper- gillus fumigatus, and Aspergillus oryzae. Factors respon- sible for more production of monodispersed Zn, Mg and Ti nanoparticles were optimized. It was concluded that 0.01 mM precursor salt concentration, 72 h of incubation at pH 5.5 and temperature 28 C resulted smaller nano- particles obtained. The biosynthesized functional Zn and Ti nanoparticles can be stored up to 90 days and Mg nano- particles up to 105 days in its nanoform. Bio-transformed products were analyzed using valid characterization tech- nique i.e. dynamic light scattering, transmission electron microscopy, atomic force microscopy, energy dispersive X-ray spectroscopy to confirm size, shape, surface mor- phology and elemental composition. It was found that the average size of developed nano Zn was 8.2 nm, with sur- face charge of -5.70 mV and 98 % particles were of Zn metal only. Similarly, the average size of Mg nanoparticles was 6.4 nm with surface charge of -6.66 and 97.4 % Mg metal yield, whereas, Ti nanoparticles size were found in the ranges between 1.5 and 30 nm with surface charge of -6.25 mV and 98.6 % Ti metal yield.

Three Dimensional PtRh Alloy Porous Nanostructures: Tuning the Atomic Composition and Controlling the Morphology for the Application of Direct Methanol Fuel Cells

AbstractA strategy for the synthesis of PtRh alloy 3D porous nanostructures by controlled aggregation of nanoparticles in oleylamine is presented. The atomic ratio between the two components (Pt and Rh) is tuned by varying the concentration of precursor salts accommodating the oxidation of methanol. The morphology of PtRh alloy nanostructure is controlled by elevating the temperature of the reaction system to 240 °C. The prepared 3D porous nanostructures provide a high degree of electrochemical activity and good durability toward the methanol oxidation reaction compared to those of the commercial Pt/C (E‐TEK) and PtRh nanoparticles. Therefore, the 3D alloy porous nanostructures provide a good opportunity to explore their catalytic properties for methanol oxidation.

Tailoring structural and electrochemical properties of vertical aligned carbon nanotubes on metal foil using scalable wet-chemical catalyst deposition

A scalable process for the synthesis of vertical aligned carbon nanotubes (VA-CNT) with precise control over structural properties is described. Direct growth on metal foils is achieved using a dip-coating step for the wet-chemical catalyst layer deposition and a subsequent chemical vapor deposition step for CNT growth. Two optimized Fe/Co and Fe/Mo 2-ethylhexanoate/2-propanol solutions are applied as precursors for the catalyst layer deposition and the influence of catalyst film thickness on resulting CNT film properties is investigated. The catalyst layer thickness can be controlled by the precursor salt concentration in the dip coating solution. By using a Fe and Co (2:3 ratio) catalyst, the CNT film homogeneity dramatically drops with lowered catalyst concentration due to a strong Ostwald ripening behavior of the catalyst layer. By using the FeMo (47:3 ratio) catalyst system, homogeneous VA-CNT films are obtained and the average CNT diameter can be adjusted in a range of 5–20nm by the catalyst layer thickness. The electrochemical properties of the CNT electrodes are investigated in a symmetric supercapacitor test cell. The lowest CNT diameters of 5nm results in a specific double layer capacitance up to 60Fg−1, while the density of the films directly correlates with its pore resistance.

Ultradispersed particles in heavy oil: Part I, preparation and stabilization of iron oxide/hydroxide

In this study, ultradispersed colloidal particles of iron oxide/hydroxide were prepared in-situ in heavy oil matrices adopting (w/o) microemulsion approach for nanoparticle preparation detailed in our previous work [1–3]. The effect of composition of heavy oil on the stable concentration of colloidal particles, particle uptake, was investigated. The following trends in particle uptake were common between the (w/o) microemulsions and the heavy oil matrices. An optimum water content was found for which a maximum particle uptake was attained. Particle uptake increased as the content of vacuum residue, VR, and precursor salt concentration increased. Vacuum residue contributes high asphaltene content, which acts as a surface active agent. The iron oxide/hydroxide particles had been recently shown to effectively remove H 2S (g) from oil phase [4]. H 2S (g) is a hazardous by-product of heavy oil recovering and upgrading which should be removed as soon as it forms. Results pertaining to H 2S (g) removal from heavy oil employing ultradispersed particles are communicated in Part II of this study.

Synthesis of ZnO–SnO2 nanocomposites by microemulsion and sensing properties for NO2

Nanocrystalline ZnO–SnO2 composites as NO2 gas sensor materials have been successfully synthesized through a reverse microemulsion method for controlled grain size and morphology. This method was to create a water-in-oil (W/O) microemulsion that contained a minimal amount of surfactant and a maximum amount of water. Pseudo-ternary phase diagrams in the quaternary microemulsion system of cetyltrimethylammonium bromide (CTAB), n-pentanol, n-octane, and water (or aqueous solution of precursor salts) were presented and the effects of the alcohol chain length, the ratio of CTAB to alcohol or water, and the precursor salt concentration on the formation and stability of microemulsions were studied. The performance and structure of the nanocomposites synthesized with the optimal parameters in the phase diagrams of the microemulsions were characterized by Brunauer–Emmett–Teller (BET) specific surface measurement, transmission electron microscopy (TEM), and X-ray diffraction (XRD), and the gas sensing properties were examined. The experimental results showed that these nanocomposites were highly sensitive and selective for the detection of NO2 and CO, and the sensor response depended on the composition of the composites, calcination temperature, operating temperature and gas concentration in air. Their sensing performance was further enhanced through introduction of a small amount of metals or other oxides as dopants or surface coatings. The gas-sensing mechanism of the nanocomposites was discussed by temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopic (XPS) analysis and was attributed to chemical and electronic synergistic effects between the nanocomposites and the gases.

Gold microcrystal synthesis via reduction of HAuCl4 by cellulose in the ionic liquid 1-butyl-3-methyl imidazolium chloride

The formation of gold particles in the ionic liquid 1-butyl-3-methylimidazolium chloride in the presence of cellulose has been studied. In this reaction, cellulose is the reducing agent for the Au(III)–Au(0) reduction. At the same time, cellulose is a (moderately efficient) template for the formation of various gold particles. The gold particle morphologies and sizes mainly depend on the reaction temperature. Morphology and size are less affected by the cellulose or gold precursor salt concentration. The change in the particle shapes can be assigned to the role of the cellulose as a template in conjunction with an effect provided by the ionic liquid. Overall, the approach reported here presents a (partly) sustainable approach towards gold microparticles. It uses a simple metal salt, a reducing agent/template from renewable raw materials, and an ionic liquid, which can (in principle) be retrieved after the reaction. The only side products are oxidized cellulose fragments and oxidation products from the gold salt.

Coulombic Efficiency of Electrodeposited Microspheres of Pt and Pt ∕ Ru Via In Situ Electrochemical Quartz Crystal Microbalance

The electrochemical quartz crystal microbalance technique has been used to obtain coulombic efficiencies for the electro reduction of pure Pt or self-assembled microspheres and the effect of precursor salt concentration and reduction potential. This technique has been demonstrated successfully to simultaneously obtain in situ data for mass change and current-voltage-charge phenomena. The coulombic efficiency for platinum reduction peaked near unity for a potential of vs calomel and tended to lower efficiency at more positive potentials. Similarly, a Pt precursor salt concentration of showed a coulombic efficiency in excess of 90%, while the efficiency decreased as the concentration rose. mixed systems generally gave similar trends, while the efficiency was consistently lower than that of the pure Pt analogs.

Seedless, Surfactantless, High-Yield Synthesis of Branched Gold Nanocrystals in HEPES Buffer Solution

In this work, three-dimensional branched gold nanocrystals were produced at high yield by reacting an aqueous solution of chloroauric acid with a Good's buffer, HEPES, at room temperature. This particular method of preparation was scalable to gram-quantity. The branched nanocrystals containing one to eight tips were stable at room temperature and could be stored as a powder after freeze-drying. They were, however, unstable at higher temperatures and transformed into spherical particles upon boiling. The formation of the branched gold nanocrystals was kinetically controlled, as shown by the dependence of shapes on temperature and precursor salt concentration. The growth of branched gold nanocrystals in the HEPES buffer was monitored by microscopic and spectroscopic techniques, allowing the detection of several key intermediates in the growth process. Piperazine in HEPES molecule was identified as the principal moiety responsible for forming highly branched Au nanocrystals in the HEPES buffer.

Compatibilization of inorganic particles for polymeric nanocomposites. Optimization of the size and the compatibility of ZnO particles

The synthesis of in-situ hydrophobic functionalized ZnO nanoparticles via an emulsion process is systematically investigated. Different parameters are varied, such as precursor salt concentration and ultrasonification, to optimize the size and the size distribution of the ZnO particles. Particles with a size below 25 nm and surrounded by a hydrophobic polymer shell can be easily obtained. The influence of the polymeric shell on the compatibility with different polymeric matrices is described. Due to the small size of the inorganic particles and the excellent hydrophobization, highly transparent inorganic/organic nanocomposites can be obtained by spin-coating and extrusion.

Surfactant-Directed Synthesis and Optical Properties of One-Dimensional Plasmonic Metallic Nanostructures

AbstractOne-dimensional metallic nanostructures such as nanorods and nanowires are of tremendous interest for electronic, sensing, and catalytic applications. Shape anisotropy introduces new optical properties in gold and silver nanoparticles, such as longitudinal plasmon resonance bands in the visible and near-IR portion of the spectrum. Different approaches employed for the shape-controlled synthesis of silver and gold nanocrystals include chemical, electrochemical, and physical methods. The chemical route for the synthesis of nanorods and nanowires, in which metal salts are reduced in an aqueous solution, is one of the most widely used methods. This route commonly employs a surfactant as the directing agent to introduce asymmetry in the nanocrystal shape. Variation in the concentration of precursor salt and the surfactant, the nature of the surfactant, the nature and concentration of reducing agents, the presence of external salts, and the pH of the reaction solution all affect nanocrystal shape, dimension, and yield. The size and shape of the nanocrystals affect the position of the plasmon bands, which in turn has been widely used in surface-enhanced spectroscopies that include both Raman and fluorescence. The aqueous, surfactant-directed route also promises the synthesis of more complex nanostructures with additional desirable properties.