Simple Wet Chemical Process Research Articles

Fabrication of Luminescent Silver Doped PbS Nanowires in Polymer

We report here fabrication of silver (0 to 1.76 mol%) doped PbS nanowires (radius r approximately 1.75 nm) in polymer by a simple wet chemical process. An X-ray photoelectron spectroscopy study clearly confirms the possibility of silver (Ag) doping in PbS nanowires. Both absorption and photoluminescence spectra reveal very strong quantum confinement effect in PbS nanowires as expected for a r/Bohr radius ratio approximately 0.0972 nm. Visible excitonic emission is observed at room temperature in the photoluminescence spectra of undoped and silver doped PbS nanowires in polymer. The excitonic emission is appreciably blue-shifted when doped by silver (1.76 mol%) indicating strong modification of the electronic states by magnetic silver ions. While Ag2+ centers at the substitutional lattice site show an emission band around 525 nm, Ag0 at the interstitial site act as nonradiative recombination centers. Effect of silver doping on the luminescence intensity is also discussed.

Antireflective silicon surface with vertical-aligned silicon nanowires realized by simple wet chemical etching processes

Silicon antireflection is realized with vertical-aligned SiNWs by using improved metal-induced etching technique. The spectral responses of the transmission, reflection, and absorption characteristics for the SiNWs of different lengths are investigated. In order to realize short SiNWs to provide sufficiently low reflection, a post chemical etching process is developed to make the nanowires have a larger length fluctuation and/or tapered structure. The use of short SiNWs can allow a faster process time and avoid the sub-bandgap absorption that frequently occurs in long nanowires. Short SiNWs can also provide more compatible material structure and fabrication procedures than long ones can for applying to make optoelectronic devices. Taking the applications to solar cells as examples, the SiNWs fabricated by the proposed technique can provide 92% of solar weighted absorption with about 720 nm long wires because of the resultant effective graded index and enhanced multiple optical scattering from the random SiNW lengths and tapered wires after KOH etching.

Effect of Fiber Geometry on Macroscale Friction of Ordered Low-Density Polyethylene Nanofiber Arrays

Ordered low-density polyethylene (LDPE) nanofiber arrays are fabricated from silicon nanowire (SiNW) templates synthesized by a simple wet-chemical process based on metal-assisted electroless etching combined with colloidal lithography. The geometrical effect of nanofibrillar structures on their macroscale friction is investigated over a wide range of diameters and lengths under the same fiber density. The optimum geometry for contacting a smooth glass surface is presented with discussions on the compromise between fiber tip-contact area and fiber compliance. A friction design map is developed, which shows that the theoretical optimum design condition agrees well with the LDPE nanofiber geometries exhibiting high measured friction.

Assembled Monolayer Nanorod Heterojunctions

Compositional and interfacial control in heterojunction thin films is critical to the performance of complex devices that separate or combine charges. For high performance, these applications require epitaxially matched interfaces, which are difficult to produce. Here, we present a new architecture for producing low-strain, single-crystalline heterojunctions using self-assembly and in-film cation exchange of colloidal nanorods. A systematic set of experiments demonstrates a cation exchange procedure that lends precise control over compositional depths in a monolayer film of vertically aligned nanorods. Compositional changes are reflected by electrical performance as rectification is induced, quenched, and reversed during cation exchange from CdS to Cu(2)S to PbS. As an additional benefit, we achieve this single-crystal architecture via an inherently simple and low-temperature wet chemical process, which is general to a variety of chemistries. This permits ensemble measurement of transport through a colloidal nanoparticle film with no interparticle charge hopping.

Wet Chemical Synthesis and Self-Assembly of SnS<SUB>2</SUB> Nanoparticles on TiO<SUB>2</SUB> for Quantum Dot-Sensitized Solar Cells

SnS2 nanoparticles were synthesized through a simple wet chemical process at room temperature. The SnS2 nanoparticles were approximately spherical in shape and had diameter about 3-4 nm. SnS2-sensitized TiO2 electrodes were fabricated by the immersion of chemically modified TiO2 to well-dispersed SnS2 solution for 72 h (i.e., self-assembly method.) SnS2-sensitized TiO2 electrodes were applied in quantum dot-sensitized solar cells (QDSSCs). Under AM1.5 irradiation with 100 mW/cm2 light intensity (at 1 sun), the short-circuit current density (J(sc)), the open-circuit voltage (V(oc)), the fill factor (FF), and the energy conversion efficiency (eta) were 0.47 mA/cm2, 0.29 V, 0.58 and 0.081%, respectively.

Green luminescence from triphenylphosphine functionalized single-wall carbon nanotubes

In a simple wet chemical process, purified single-wall carbon nanotubes (SWCNTs) are treated with triphenylphosphine (Ph 3P) at room temperature. The functionalized material is characterized by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy. HRTEM micrograph clearly reveals that triphenylphosphine nanocrystals of nearly uniform size are attached to the surfaces of SWCNTs. The hybrid structure shows remarkable green luminescence with peak emission at around 500 nm, under UV excitation. The photoluminescence may be attributed to charge transfer from the electron-donating phosphorous atoms to the carbon nanotubes.

Degradation of Acid Orange II at neutral pH using Fe 2(MoO 4) 3 as a heterogeneous Fenton-like catalyst

Iron molybdate, Fe 2(MoO 4) 3, has been successfully prepared by a simple wet chemical process. Degradation of Acid Orange II (AOII) was studied in detail using Fe 2(MoO 4) 3 as a heterogeneous Fenton-like catalyst. The results show that this new catalyst is highly effective for the degradation of AOII at neutral pH. For 100 mg l −1 of the initial concentration with an initial pH of 6.7, the degradation efficiency of AOII reaches 94.1% within 60 min. Moreover, the catalytic activity is slightly affected by the solution pH in a wide range of 3.0–9.0. This indicates that the use of Fe 2(MoO 4) 3 overcomes the low efficiency of Fenton-like reaction at neutral and even alkaline pH. Fe 2(MoO 4) 3 exhibits low iron leaching, good structural stability and no loss of performance after five recycle times. A mechanism proposed herein suggests that the high catalytic activity can be attributed to the formation of an acidic microenvironment near the surface of the solid acid Fe 2(MoO 4) 3 particles where catalysis occurs, as well as the synergistic effect of Fe 3+ and MoO 4 2−.

High-Power and High-Energy-Density Flexible Pseudocapacitor Electrodes Made from Porous CuO Nanobelts and Single-Walled Carbon Nanotubes

We report a simple wet-chemical process to prepare porous CuO nanobelts (NBs) with high surface area and small crystal grains. These CuO NBs were mixed with carbon nanotubes in an appropriate ratio to fabricate pseudocapacitor electrodes with stable cycling performances, which showed a series of high energy densities at different power densities, for example, 130.2, 92, 44, 25, and 20.8 W h kg(-1) at power densities of 1.25, 6.25, 25, and 50 k Wh kg(-1), respectively. CuO-on-single-walled carbon nanotube (SWCNT) flexible hybrid electrodes were also fabricated using the SWCNT films as current collectors. These flexible electrodes showed much higher specific capacitance than that of electrodes made of pure SWCNTs and exhibited more stable cycling performance, for example, effective specific capacitances of >62 F g(-1) for the hybrid electrodes after 1000 cycles in 1 M LiPF6/EC:DEC at a current density of 5 A g(-1) and specific capacitance of only 23.6 F g(-1) for pure SWCNT electrodes under the same testing condition.

Layer‐by‐Layer All‐Inorganic Quantum‐Dot‐Based LEDs: A Simple Procedure with Robust Performance

AbstractA novel all‐inorganic electroluminescent device is demonstrated based on highly luminescent CdTe nanocrystals intercalated within a laminar hydrotalcite‐like structure. The laminar scaffold acts to both support and distribute the CdTe nanocrystals. The device is synthesized using simple wet chemical processes at room temperature in ambient conditions. It has high thermal stability, operating continuously up to 90 °C, and a maximum efficiency at J = 0.12 A cm−2. The device is targeted at the automotive industry.

Visible-light Photocatalytic Activity of BiOCl/Bi3O4Cl Nanocomposites

The heterojunction structures of BiOCl/<TEX>$Bi_3O_4Cl$</TEX>, exhibiting considerable visible-light photocatalytic efficiency, were prepared by a simple wet-chemical process at ambient condition. The prepared nanocomposites were characterized by XRD, TEM, and UV-visible diffuse reflectance spectra. Under visible light (<TEX>${\lambda}\geq$</TEX>420 nm) irradiation, BiOCl/<TEX>$Bi_3O_4Cl$</TEX> exhibited an enhanced photocatalytic activity in decomposing 2-propanol (IP) in gas phase and salicylic acid (SA) in aqueous solution, whereas the bare BiOCl and <TEX>$Bi_3O_4Cl$</TEX> showed negligible activities. It is deduced that the remarkable visible-light photocatalytic activity of the BiOCl/<TEX>$Bi_3O_4Cl$</TEX> originates from the hole <TEX>$(h^+)$</TEX> transfer between VB of the <TEX>$Bi_3O_4Cl$</TEX> and BiOCl semiconductors.

Preparation and characterization of electronically conducting polypyrrole-montmorillonite nanocomposite and its potential application as a cathode material for oxygen reduction

Abstract Simple wet chemical processes were deployed to prepare low-cost conducting nanocomposites based on natural clays with 2:1 layered structures such as sodium montmorillonite (MMT). Ce(IV) modified MMT was used for the spontaneous polymerization of pyrrole within clay interlayers. The resulted clay-conducting polypyrrole nanocomposites containing the reduced form of the oxidising agent, have been extensively characterized by X-ray diffraction (XRD) technique for interlayer spacing variations and by Fourier transform infra red (FT-IR) spectroscopy to study the interactions between the clay and polymer functional groups. DC polarization technique with both blocking and non-blocking electrodes was used to distinguish between the ionic and electronic transport numbers and to recognize the type of mobile ionic species. AC impedance analysis further resolved the electrical conduction of these materials. Bulk conductivity analysis implied that the polypyrrole (PPY) formed within Ce(IV) modified MMT posses dominant electronic conductivity. The low-cost, light-weight and stable polymer–clay nanocomposite prepared by Ce(IV) intercalated MMT, [Ce(III)-PPY-MMT], seems to be a promising cathode material for oxygen reduction and hence may find applications in fuel cell industries.

Photoactivation of Ion-exchangeable Trititanate Nanotubes Modified by MS (M = Cd, Zn) Nanoparticles

Ion-exchangable trititanate nanotubes synthesized by the alkali treatment of TiO 2 (anatase) are modified by MS (M = Cd, Zn) nanoparticles via a simple wet chemical process. The obtained samples are characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy. The photocatalytic activities of the samples are evaluated upon the oxidation of methyl orange under UV light illumination. Results show that the photoactivation may be caused by the strong coupling between the nanotube and the nanoparticles, which is a direct consequence of the ion exchange property of the trititanate wall structure during the formation of TiO 2 /MS.

Synthesis and visible-light-induced catalytic activity ofAg2S-coupledTiO2 nanoparticles and nanowires

We present the synthesis and visible-light-induced catalytic activity ofAg2S-coupledTiO2 nanoparticles(NPs) and TiO2 nanowires (NWs). Through a simple wet chemical process from a mixtureof peroxo titanic acid (PTA) solution, thiourea and AgAc, a composite ofAg2S NPsand TiO2 NPs with sizes of less than 7 nm was formed. When the NP composite was further treated with NaOHsolution followed by annealing at ambient conditions, a new nanocomposite material comprisingAg2S NPson TiO2 NWs was created. Due to the coupling with such a low bandgap material asAg2S, theTiO2 nanocomposites could have a visible-light absorption capability much higher than that of pureTiO2. As a result, thesynthesized Ag2S/TiO2 nanocomposites exhibited much higher catalytic efficiency for the decomposition of methyl orange thancommercial TiO2 (Degussa P25, Germany) under visible light.

CO gas sensing of ZnO nanostructures synthesized by an assisted microwave wet chemical route

A simple wet chemical process assisted by microwave has been investigated for the synthesis of ZnO nanostructures for sensing applications. Characterization results have shown that microwave irradiation is able to quickly convert the reaction product zinc hydroxide into single phase crystalline ZnO. Different ZnO nanostructures (spherical-, flower- and star-like) have been prepared by adapting the experimental conditions. These ZnO nanostructures have been tested for CO gas monitoring by depositing them as thick films on an interdigitated alumina substrate and evaluating the surface resistance of the deposited layer as a function of operating temperature and CO concentrations. The gas sensitivity tests have demonstrated that the ZnO nanostructures, especially flower-like morphology, exhibit high sensitivity to CO proving their applicability in gas sensors. The role of the nanostructure on the sensing properties of ZnO is also discussed.

Photo-Fenton-like catalytic activity of nano-lamellar Fe2V4O13 in the degradation of organic pollutants

A new photo-Fenton-like catalyst with high activity, Fe2V4O13, has been found. It can be obtained by a simple wet chemical process. The catalyst has a nano-lamellar structure with a thinness of less than 100 nm, a BET surface of 52.26 m2 g−1, and a band-gap of 1.59 eV favorable to absorption of visible light. Experiments demonstrated that Fe2V4O13 could effectively catalyze degradation of Acid Orange II (AOII) by H2O2 in visible light. The degradation was well fitted by a simple pseudo-first-order reaction with a rate constant of 0.0965 min−1. Moreover, the photo-Fenton-like catalytic activity of Fe2V4O13 was much higher than that of not only α-Fe2O3 and V2O5 but also their mixture (Fe2O3 + 2V2O5) with an identical atomic ratio of Fe and V, and that of both Fe3O4 and γ-FeOOH. The high catalytic activity of Fe2V4O13 possibly involves a special two-way Fenton-like, semiconductor photo-catalytic mechanism and the synergistic activation of Fe(III) and V(V) in Fe2V4O13 towards H2O2.

Nitrogen interaction with hydrogen-terminated silicon surfaces at the atomic scale

Passivation of semiconductor surfaces is conveniently realized by terminating surface dangling bonds with a monovalent atom such as hydrogen using a simple wet chemical process (for example, HF treatment for silicon). However, the real potential of surface chemical passivation lies in the ability to replace surface hydrogen by multivalent atoms to form surfaces with tailored properties. Although some progress has been made to attach organic layers on top of H-terminated surfaces, it has been more challenging to understand and control the incorporation of multivalent atoms, such as oxygen and nitrogen, within the top surface layer of H-terminated surfaces. The difficulty arises partly because such processes are dominated by defect sites. Here, we report mechanistic pathways involved in the nitridation of H-terminated silicon surfaces using ammonia vapour. Surface infrared spectroscopy and first-principles calculations clearly show that the initial interaction is dominated by the details of the surface morphology (defect structure) and that NH and NH(2) are precursors to N insertion into Si-Si bonds. For the dihydride-stepped Si(111) surface, a unique reaction pathway is identified leading to selective silazane step-edge formation at the lowest reaction temperatures.

Characterizations on the structural and electrochemical properties of LiNi 1/3Mn 1/3Co 1/3O 2 prepared by a wet-chemical process

LiNi 1/3Mn 1/3Co 1/3O 2 compounds were prepared at 700 (sample-A) and 900 °C (sample-B) by a simple wet-chemical process. X-ray diffraction showed the sample-A had a larger Li/Ni site exchange (9.9%) than that of the sample-B (4.4%). Raman scattering analysis suggests strong structural disorder within the octahedral [MO 6] units due to different masses and bonding of the M–O bonds, as well as the Li/Ni site exchange in the crystals. The weakening of the E g band was correlated with the Li/Ni site exchange. XPS analysis indicates that a lower annealing temperature than 900 °C leads to the formation of oxygen deficient LiNi 1/3Mn 1/3Co 1/3O 2 − δ . The electrochemical properties of the materials were investigated by charge–discharge experiments and electrochemical impedance spectroscopy. The drastic capacity fading of the sample-A was attributed to its structural properties. The sample-B showed satisfying cycling performance. But the capacity fading in the potential region of 2.5–4.6 V was larger than that in 2.5–4.4 V, which was attributed to the large charge transfer resistance at potentials above 4.4 V.

Oxidation of single-walled carbon nanotubes in dilute aqueous solutions by ozone as affected by ultrasound

A clean and simple wet chemical process using dilute aqueous ozone (O 3) solution with or without ultrasound (US) was used to functionalize single-walled carbon nanotubes (SWCNTs). Both O 3 and O 3/US treatments greatly increased the stability of SWCNTs in water. Results of X-ray photoelectron spectroscopy (XPS) showed that the surface oxygen to carbon atomic ratio increased by more than 600% after 72 h of O 3 treatment. Moreover, the effective particle size of SWCNTs was reduced from the initial 4400 to ∼300 and ∼150 nm, after 24 h of O 3 and O 3/US treatment, respectively. The zeta potential of treated SWCNTs decreased from 3.0 to −35.0 mV (at pH 4) after 2 h of treatment with both O 3 and O 3/US. Based on the XPS results, the oxidation pathway was proposed: at the onset of the oxidation reaction, the C C double bond was first converted to C OH which was then oxidized to C O and O C OH concurrently. Oxidation reactions could be described well with first order expressions. Treatment time controlled the extent of surface oxidation and subsequently the stability and dispersion of SWCNTs in water.

High-Efficiency and Low-Cost Hybrid Nanomaterial as Enhancing Electrocatalyst: Spongelike Au/Pt Core/Shell Nanomaterial with Hollow Cavity

A high-efficiency and low-cost spongelike Au/Pt core/shell electrocatalyst with hollow cavity has been facilely obtained via a simple two-step wet chemical process. Hollow gold nanospheres were first synthesized via a modified galvanic replacement reaction between Co nanoparticles in situ produced and HAuCl4. The as-prepared gold hollow spheres were employed as seeds to further grow spongelike Pt shell. It is found that the surface of this hybrid nanomaterial owns many Pt nanospikes, which form a spongelike nanostructure. All experimental data including scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and UV−vis-near-infrared spectroscopy have been employed to characterize the obtained Au/Pt hybrid nanomaterial. The rapid development of fuel cell has inspired us to investigate the electrocatalytic properties for dioxygen and methanol of this novel hybrid nanomaterial. Spongelike hybrid nanomaterial mentioned here exhibits much higher catalytic activity for ...

Luminescence of Eu 2+ in some fluorides prepared by reactive atmosphere processing

When phosphors are prepared by conventional solid-state route by heating in air, usually unwanted impurities like OH −, O 2 −, etc., get incorporated. Such impurities can be quite harmful to the luminescence processes. Especially, fluorides are highly susceptible to hydrolysis. It is necessary to use highly sophisticated procedures like high vacuum and HF or CF 4 atmosphere for preparation of fluoride based phosphors. It is shown that using a simple wet chemical process and a modified reactive atmosphere processing (RAP) technique, fluorides showing intense Eu 2+ photoluminescence can be prepared.