Formation and mechanism of silicon nanostructures by Ni-assisted etching

Instead of noble metal like Pt, Au and Ag, cheap Ni nanoparticles (Ni NPs) were used to fabricate silicon nanostructures. Ni was found to be etched off during the etching process, while forming silicon nanostructures with very low reflectance of 1.59 % from 400 to 900 nm. The formation mechanism of silicon nanostructures by Ni-assisted etching was presented from the point of view of the low electronegativity of Ni. The Ni NPs were found being etched off during the assisted etching process, which implies that the transfer rate of electrons from Si to Ni is slower than that from Ni to O^? in the case of using Ni as assisted metal. The reason of sparser and deeper silicon nanostructures etched in lower H₂O₂ concentration solution is that the Ni NPs can be lasted for longer time in the etching solution with lower H₂O₂ concentration so that more silicon atoms will be oxidized and then removed for those under Ni NPs due to the hole transfer and those where uncovered by Ni NPs due to the hole diffusion.     

Low doses of TiO2-polyethylene glycol nanoparticles stimulate proliferation of hepatocyte cells

This paper describes the effect of low concentrations of 100 nm polyethylene glycol-modified TiO₂ nanoparticles (TiO₂-PEG NPs) on HepG2 hepatocellular carcinoma cells. Proliferation of HepG2 cells increased significantly when the cells were exposed to low doses (<100 μg ml^–1) of TiO₂-PEG NPs. These results were further confirmed by cell counting experiments and cell cycle assays. Cellular uptake assays were performed to determine why HepG2 cells proliferate with low-dose exposure to TiO₂-PEG NPs. The results showed that exposure to lower doses of NPs led to less cellular uptake, which in turn decreased cytotoxicity. We therefore hypothesized that TiO₂-PEG NPs could affect the activity of hepatocyte growth factor receptors (HGFRs), which bind to hepatocyte growth factor and stimulate cell proliferation. The localization of HGFRs on the surface of the cell membrane was detected via immunofluorescence staining and confocal microscopy. The results showed that HGFRs aggregate after exposure to TiO₂-PEG NPs. In conclusion, our results indicate that TiO₂-PEG NPs have the potential to promote proliferation of HepG2 cells through HGFR aggregation and suggest that NPs not only exhibit cytotoxicity but also affect cellular responses.     

Removal and reuse of Ag nanoparticles by magnetic polyaniline/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanofibers

For the treatment of wastewater containing Ag nanoparticles (NPs), PANI/Fe₃O₄ nanofibers were firstly prepared by a novel self-assemble. And then, the efficiency for the removal of Ag NPs from wastewater was investigated. The magnetic performance of PANI/Fe₃O₄ nanofibers could be optimized by adjusting the pH of the self-assemblied system. Under pH of 3, the as-prepared nanofibers exhibited the highest magnetism and also displayed good efficiency (>?12 mg g^?1) for the removal of Ag NPs. Importantly, the resulted product (PANI/Fe₃O₄/Ag composite) could act as a catalysis for cleaning durable pollutant, 4-nitrophenol. After 10 cycles, only slight decrease in rate constant was found, indicating excellent reusability. Those approaches provide a new way to merge the recovery of Ag NPs as pollutants and reuse of recovered Ag NPs as recyclable material for environmental remediation.     

Nitrogen-doped multiwalled carbon nanotubes decorated with copper(I) oxide nanoparticles with enhanced capacitive properties

We report on the enhanced capacitive properties of a copper(I) oxide nanoparticle (Cu₂O NP)-decorated multiwalled carbon nanotube (MWCNT) forest with nitrogen (N) doping. A careful in situ solid-state dewetting and plasma doping method was developed that ensured homogeneous decoration and contamination-free Cu₂O NPs with N doping on the nanotube sidewalls. The morphology and structure of the hybrid materials were characterised by scanning electron microscopy, transmission electron microscopy, energy-dispersive spectroscopy, Raman spectroscopy and X-ray photoemission spectroscopy. The electrochemical performance of the hybrid materials was investigated by cyclic voltammetry and galvanostatic charge/discharge tests in a 0.1 M Na₂SO₄ electrolyte. The electrochemical tests demonstrated that the Cu₂O NP/N-MWCNT electrode exhibits a specific capacitance up to 132.2 F g^?1 at a current density of 2.5 A g^?1, which is 30% higher than that of the pure MWCNT electrode. Furthermore, the electrode could retain the specific capacitance at 85% stability over 1000 cycles. These observations along with the simple assembly method for the hybrid materials suggest that the Cu₂O NP/N-MWCNT could be a promising electrode for supercapacitor applications.     

Removal of nitrophenols from water using cellulose derived nitrogen doped graphitic carbon material containing titanium dioxide

Nitrophenols (NPs) and their derivatives are highly toxic, mutagenic and bio-refractory pollutants commonly present in natural water resources and industrial wastewater. To remove NPs from water, N-doped graphitic carbon (NGC) and NGC adsorbent containing titanium dioxide (NGC–TiO₂) were synthesized by pyrolysis of microcrystalline cellulose and dopamine mixture, and the mixture along with TiO₂ at 500°C, respectively. NCG-TiO₂ was thoroughly characterized using various analytical techniques. NP adsorption on the NGC–TiO₂ adsorbent surface was studied by varying the pH, initial concentration of NP, and adsorbent dose. The results showed that the most efficient adsorption was achieved at pH 3. After 4?h sonication at pH 3, 80% 4-NP adsorption was achieved using NGC–TiO₂ compared to 74% with NGC adsorbent. The percentage removal of 4-NP was higher than 3-NP which was also higher than 2,4-DNP using NGC–TiO₂. 4-NP adsorption best fitted to the Langmuir isotherm plot with R² value of 0.9981 and adsorption capacity of 52.91?mg?g^?1. The adsorption process of NP was found to follow a pseudo-second-order kinetic model. The rate constant value for the adsorption of 10^?4?M 4-NP at pH 3 using 10?mg of NGC–TiO₂ adsorbent was found to be 3.76?×?10^?5?g.mg^?1.min^?1     

Influence of different sulfur sources on the phase formation of Cu<Subscript>2</Subscript>ZnSnS<Subscript>4</Subscript> (CZTS) nanoparticles (NPs)

Wurtzite (Wz) and kesterite (Ks) phases of Cu₂ZnSnS₄ (CZTS) nanoparticles (NPs) have been selectively synthesized via hot injection method using 1-octadecene (1-ODE) as solvent. The solvents, 1-dodecanethiol (1-DDT) and tert-dodecanethiol (t-DDT) were utilized to control the reactivity of metal precursors and to tune the desirable crystallographic phases. The phase purity of the as synthesized CZTS NPs was confirmed using X-ray diffraction results. TEM images indicate that the developed nanoparticles consist of a mixture of triangular shaped (height 20?±?3 nm, width 17?±?2 nm) and sphere shaped NPs (13.4?±?0.4 nm). These nanoparticles were formed due to the influence of thiols without any additional capping ligands. The band gap of as-synthesized CZTS NPs were calculated as 1.41 eV for wurtzite phase (Wz—1-DDT) and 1.47 eV for kesterite phase (Ks—t-DDT) from UV–Visible absorption results. CZTS thin films were prepared via spin coating and the electrical properties were analysed using Hall Effect measurements. Both the phases of CZTS films exhibit p-type conductivity. Wurtzite phase of CZTS has higher mobility (23.6 cm^?3) and carrier concentration (2.64?×?10¹⁷) compared to kesterite phase of CZTS films.     

High surface area ordered mesoporous carbon for high-level removal of rhodamine B

We report the synthesis of ordered mesoporous carbons (OMCs) with high surface area by the variation of mass ratio of tetraethylorthosilicate (TEOS) to resol, followed by carbonization and removal of silica. The obtained OMCs were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, N₂ adsorption and desorption analysis, Zeta potential and Fourier transform infrared spectroscopy. Results reveal that the OMCs were transformed from ordered to disordered structure at high mass ratio of TEOS/resol. A typical sample of OMCs possesses very high specific surface area of 1906 m² g^?1 and large pore volume of 1.8 cm³ g^?1. The OMCs as adsorbent show an ultrahigh-level adsorption capacity for the removal of toxic dye Rhodamine B (1028 mg g^?1) in the short contact time (60 min). The adsorption follows pseudo second-order kinetics with rate constant 2.5 × 10^?4 g mg^?1 min^?1, showing rapid adsorption properties. The OMCs can be reused; though the adsorption capacity seems to decrease somewhat after each cycle tested over 10 reuse cycles, it might be affected by the chemisorptions. The adsorption mechanism study reveals that the adsorption proceeds with hydrogen bonding between hydrogen atom of carboxylic group at OMCs and electronegative element (nitrogen) of RhB. It is concluded that the surface area and pore volume of the OMCs is tuned by the variation of mass ratio of TEOS to resol which is also demonstrated to have ultrahigh adsorption capacity for the model RhB dye.     

Enhancement on the high-temperature joint reliability and corrosion resistance of Sn–0.3Ag–0.7Cu low-Ag solder contributed by Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Nanoparticles (0.12 wt%)

In this study, the evolution of interfacial microstructures and mechanical properties of the joints soldered with Sn–0.3Ag–0.7Cu (SAC0307) and SAC0307-0.12Al₂O₃ nanoparticles (NPs) aged at 150 °C for different hours (72–840 h) were investigated. It was found the joint soldered with SAC0307-0.12Al₂O₃ displayed a significantly enhanced high-temperature joint reliability, reflected in a higher shear force than that of the original. This enhancement in shear force primarily benefited from the refinement in solder microstructure contributed by Al₂O₃ NPs. As aging time reached 840 h, a controlled growth of interfaical IMC layer resulted from the pinning effect of Al₂O₃ NPs contributed to the increase in shear force. Theoretical analysis showed 0.12 wt% Al₂O₃ NPs effectively lowered the growth constant of total interfacial IMCs (D_T) from 3.19?×?10^?10 to 1.02?×?10^?10 cm² s^?1. Moreover, comparative studies on the corrosion resistances of SAC0307 and SAC0307-0.12Al₂O₃ were also conducted by electrochemical test and analyzed by electrochemical impedance spectroscopy (EIS). The results revealed SAC0307-0.12 Al₂O₃ solder displayed a stronger corrosion resistance (R_t; ~?3.1 kΩ cm² vs?~?7.1 kΩ cm²). This is also related with the tailored microstructure, which provides more grain boundaries for the initial nucleation of passive film.     

Adsorbents made from textile scraps: preparation,characterization and application for removal of reactive dye

Textile scraps from the clothing industry were used to prepare a low-cost adsorbent to remove anionic dye from textile effluents. Adsorbents were prepared through pyrolysis and chemical activation with K₂CO₃. These samples were characterized through thermogravimetric analysis, scanning electron microscopy, N₂ adsorption/desorption isotherms, Fourier transform infrared spectroscopy, point of zero charge, isoelectric point, elemental composition and proximate analysis. Batch kinetic experiments and adsorption isotherm modeling were conducted in different conditions. The surface properties of the adsorbents were significantly influenced by the activation process. The highest BET surface area (S_BET = 358.55 m² g^?1) was attributed to the sample with chemical treatment. The results indicate that activation process raised 700% the adsorption capacity. The adsorption was strongly dependent on the pH. For the activated adsorbent, 6 g L^?1 was sufficient for the complete removal of 40 mg L^?1 Reactive Black 5 (RB5) solution. The monolayer capacity was up to 10.3 mg g^?1 and was higher than a commercial activated carbon commonly used in textile sector, which was 9.7 mg g^?1.     

Toxicological Aspects of Long‐Term Treatment of Keratinocytes with ZnO and TiO2 Nanoparticles

Sunscreens containing ZnO and TiO₂ nanoparticles (NPs) are increasingly applied to skin over long time periods to reduce the risk of skin cancer. However, long‐term toxicological studies of NPs are very sparse. The in vitro toxicity of ZnO and TiO₂ NPs on keratinocytes over short‐ and long‐term applications is reported. The effects studied are intracellular formation of radicals, alterations in cell morphology, mitochondrial activity, and cell‐cycle distribution. Cellular response depends on the type of NP, concentration, and exposure time. ZnO NPs have more pronounced adverse effects on keratinocytes than TiO₂. TiO₂ has no effect on cell viability up to 100 μg mL^?1, whereas ZnO reduces viability above 15 μg mL^?1 after short‐term exposure. Prolonged exposure to ZnO NPs at 10 μg mL^?1 results in decreased mitochondrial activity, loss of normal cell morphology, and disturbances in cell‐cycle distribution. From this point of view TiO₂ has no harmful effect. More nanotubular intercellular structures are observed in keratinocytes exposed to either type of NP than in untreated cells. This observation may indicate cellular transformation from normal to tumor cells due to NP treatment. Transmission electron microscopy images show NPs in vesicles within the cell cytoplasm, particularly in early and late endosomes and amphisomes. Contrary to insoluble TiO₂, partially soluble ZnO stimulates generation of reactive oxygen species to swamp the cell redox defense system thus initiating the death processes, seen also in cell‐cycle distribution and fluorescence imaging. Long‐term exposure to NPs has adverse effects on human keratinocytes in vitro, which indicates a potential health risk.     

Clean technology and response surface approach for the photodegradation of selected antibiotics by catalyst supported on pine activated carbon

This study enthusiastically highlights for the first time, a new nano-photocatalyst (reconstruction of SnO₂/MnO₂/Al₂O₃/TiO₂ on MCM-41 SiO₂@KOH-modified pine bark activated carbon harnessed for the photodegradation of two pharmaceuticals, which are contaminants of emerging concern, namely tetracycline (TCL) and sulfamethoxazole (SMX), using the response surface methodology. The MCM-41 structure-directing agent and a new low-cost/locally synthesized activated carbon were used as support for semiconductor nano-photocatalyst, which in turn enhanced its surface area/pore structure and photoactivity through the decrease in electron–hole pair recombination. The optimal desirability histogram and ramp functions showed each optimal or desirable condition for each dependent variable (factor) and independent variable (response). In overall, after all targets have been achieved, the ramp function plots gave a desirability of 0.689 (68.9%) for the photodegradation of TCL and a desirability of 0.602 (60.2%) for the photodegradation of SMX. The response surface methodology (RSM) technique showed that experimental run 3 gave maximal condition for the photodegradation of TCL with 99.4% of photodegradation of TCL achieved in 30 min, with half-life (time taken for 50% of 20 mg L^?1 of TCL to photodegrade) of 3.04 min and a quantity of 9.94 mg g^?1 of TCL photodegraded. Likewise, experimental run 10 gave maximal condition for the photodegradation of SMX with 94.95% of photodegradation of SMX achieved in 60 min, with half-life (time taken for 50% of 20 mg L^?1 of SMX to photodegrade) of 5.58 min and a quantity of 9.50 mg g^?1 of SMX photodegraded. This lucidly shows that this nano-photocatalyst is more efficient for the photodegradation of low initial concentration of TCL and SMX, when compared to the high initial concentrations of these antibiotics studied.     

Effect of copper nanoparticle addition on the electrical and optical properties of thin films prepared from silver nanoparticles

The fabrication of transparent and conductive silver (Ag) and copper (Cu)-doped Ag films using simple spin-coating method with Ag and Cu nanoparticles (NPs) as starting material is described in this study. The aggregation of Ag NP and the grain formation caused by heat treatment were hindered by the addition of small amount Cu NP, and a continuous film was obtained even though the thickness was in the order of 10 nm. When the total metal concentration of NP solution precursor was 5 wt% with the ratio between Ag and Cu being 95:5, the surface resistivity (ρ _s) of Ag–Cu film was 3.17 Ω/sq; and when the concentration was reduced to 3.5 wt%, the ρ _s was 16.3 Ω/sq. The transmission of latter was more than 60 % with the maximum value 82.1 % at 328 nm in the near-UV region (300–400 nm), however, decreased to about 38 % in the visible region (400–700 nm) and near-IR region. The inhomogeneity of the film increased leading to the decrease of the conductivity with the time extension during the heat treatment.     

Pb/S/1,2-ethanedithiol composite thin films for efficient solid-state quantum-dot sensitized TiO<Subscript>2</Subscript> nanorod array solar cells

The Pb/S/1,2-ethanedithiol composite thin films were successfully deposited on TiO₂ nanorod arrays by spin-coating step-by-step 5 mmol dm^?3 Pb(NO₃)₂, Na₂S and 1% 1,2-ethanedithiol solution and their chemical compositions can be easily adjusted by changing the concentration of Na₂S solution from 5 to 3.5 mmol dm^?3 and 2 mmol dm^?3. The average crystal sizes of Pb/S/1,2-ethanedithiol quantum-dots decreased from 7.9 to 7.1 nm and 6.5 nm with the decrease of the concentration of Na₂S solution and the chemical bonding of Pb²⁺ and S in EDT was chelation of the penta-heterocycle in Pb/S/1,2-ethanedithiol composite thin films. All solid-state Pb/S/1,2-ethanedithiol composite thin film sensitized TiO₂ nanorod array solar cells using 5, 3.5, 2 mmol dm^?3 Na₂S solution exhibited the photoelectric conversion efficiency of 2.68, 3.41 and 4.51% under the illumination of simulated AM 1.5 sunlight (100 mA cm^?2).     

Ultrathin Wall (1 nm) and Superlong Pt Nanotubes with Enhanced Oxygen Reduction Reaction Performance

The synthesis of Pt nanotubes catalysts remains a substantial challenge, especially for those with both sub‐nanometer wall thickness and micrometer‐scale length characteristics. Combining techniques of insulin fibril template with Pd nanowire template, numerous Pt nanotubes with diameter of 5.5 nm, tube‐length of several micrometers, and ultrathin wall thickness of 1 nm are assembled. These tubular catalysts with both open ends deliver electrochemical active surface area (ECSA) of 91.43 m² g_pt^?1 which results from multiple Pt atoms exposed on the inner and outer surfaces that doubled Pt atoms can participate in catalytic reactions, further with enhanced electrocatalytic performance for oxygen reduction reaction (ORR). The ultrafine Pt nanotubes represent a class of hollow nanostructure with increased Pt‐utilization and large ECSA, which is regarded as a type of cost‐effective catalysts for ORR.     

Effect of nitric acid modification on the lead(II) adsorption of mesoporous biochars with different mesopore size distributions

Two mesoporous biochars AC-1 and AC-2 with similar chemical properties but different mesopore size distributions were prepared to study the effect of HNO₃ modification on the lead(II) adsorption. AC-2 possesses higher mesopore volume and broader pore diameter than AC-1, while their surface area and micropore volume are similar. Adsorption experiments showed that AC-2 had far better removal efficiency, indicating the important role of mesopores played in the adsorption. HNO₃ modification enhanced the adsorption capacity of lead AC-1 and AC-2 by 15 and 27 mg g^?1, respectively. In particular, the removal rate of lead for AC-1 was improved from 46 to 99 % by HNO₃ treatment at a low initial lead concentration of 10 mg L^?1. Results of Boehm’s titration demonstrated that the amounts of oxygenic acid groups of AC-1 and AC-2 increased to 2.456 and 2.705 mmol g^?1 after HNO₃ treatment, respectively. Analyses of FTIR spectrum revealed that AC-2 was more likely to graft oxygen-containing acidic functional groups than AC-1, indicating that higher mesoporosity takes advantage of grafting more oxygenic functional groups, thus forming more active adsorption sites. The above results indicate that mesoporous biochars with wider pore width are more favorable to be introduced with oxygenic groups for enhanced lead removal efficiency.     

Preparation of yolk–shell Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@N-doped carbon nanocomposite particles as anode in lithium ion batteries

The yolk–shell-structured Fe₃O₄ nanocomposite particles (Fe₃O₄@Void@C–N NPs) with Fe₃O₄ as the yolk and N-doped carbon as the shell were prepared by using melamine formaldehyde resin as the N and C sources. When used as anode material for lithium ion battery, the yolk–shell structure could not only afford adequate void to accommodate the large volume change during charge/discharge process but also improve structural stability and electrical conductivity. The anode material demonstrated superior long-term and high-rate performance because of the novel structure and the N-doped carbon shell with mesopore. Thus, Fe₃O₄@Void@C–N NPs exhibited a high reversible capacity of 1530 mAh g^?1 after 300 cycles at a current density of 500 mA g^?1, which were approximately 1.5 and 6 times higher than Fe₃O₄@C–N NPs and pure Fe₃O₄ particles, respectively. Even at the higher current density of 2000 mA g^?1, the reversible capacity remained at 651 mAh g^?1 after 500 cycles.     

Direct Synthesis of Ultrathin Pt Nanowire Arrays as Catalysts for Methanol Oxidation

High‐performance electrocatalysts are of critical importance for fuel cells. Morphological modulation of the catalyst materials is a rare but feasible strategy to improve their performance. In this work, Pt nanowire arrays are directly synthesized with a template‐less wet chemical method. The effects of surface functionalization and the reduction kinetics are revealed to be vital to the nanowire growth. The growth mechanism of the Pt nanowires is studied. By adjusting the concentration of the organic ligands, Pt nanowire arrays with tunable surface roughness can be obtained on various substrate surfaces. Such arrays avoid the contact resistance of randomly packed particles and allow open diffusion channels for reactants and products alike, making them excellent electrocatalysts for the methanol oxidation reaction. In particular, Pt nanowire arrays with rough surface have a mass activity of 1.24 A mg_Pt^?1 at 1.12 V (vs Ag/AgCl), 3.18‐fold higher than that of the commercial Pt/C catalysts. It also shows more resistant against poisoning, as indicated by the higher I_f/I_b ratio (2.06), in comparison to the Pt/C catalysts (1.30).     

pH dependent poly[2-(methacryloyloxyethyl)trimetylammonium chloride-co-methacrylic acid]hydrogels for enhanced targeted delivery of 5-fluorouracil in colon cancer cells

Stimuli responsive hydrogels have shown enormous potential as a carrier for targeted drug delivery. In this study we have developed novel pH responsive hydrogels for the delivery of 5-fluorouracil (5-FU) in order to alleviate its antitumor activity while reducing its toxicity. We used 2-(methacryloyloxyethyl) trimetylammonium chloride a positively charged monomer and methacrylic acid for fabricating the pH responsive hydrogels. The released 5-FU from all except hydrogel (GEL-5) remained biologically active against human colon cancer cell lines [HT29 (IC₅₀ = 110–190 μg ml^?1) and HCT116 (IC₅₀ = 210–390 μg ml^?1)] but not human skin fibroblast cells [BJ (CRL2522); IC₅₀ ≥ 1000 μg ml^?1]. This implies that the copolymer hydrogels (1–4) were able to release 5-FU effectively to colon cancer cells but not normal human skin fibroblast cells. This is probably due to the shorter doubling time that results in reduced pH in colon cancer cells when compared to fibroblast cells. These pH sensitive hydrogels showed well defined cell apoptosis in HCT116 cells through series of events such as chromatin condensation, membrane blebbing, and formation of apoptotic bodies. No cell killing was observed in the case of blank hydrogels. The results showed the potential of these stimuli responsive polymer hydrogels as a carrier for colon cancer delivery.     

Influence of oxygen vacancies on the structural,dielectric, and magnetic properties of (Mn,Co) co-doped ZnO nanostructures

We analysed the variation and effect of oxygen vacancies on the structural, dielectric and magnetic properties in case of Mn (4%) and Co (1, 2 and 4%) co-doped ZnO nanoparticles (NPs), synthesized by chemical precipitation route and annealed at 750 °C for 2 h. From the XRD, the calculated average crystallite size increased from15.30?±?0.73 nm to 16.71?±?012 nm, when Co content is increased from 1 to 4%. Enhancement of dopants (Mn, Co) introduced more and more oxygen vacancies to ZnO lattice confirmed from EDX and XPS. The high-temperature annealing leads to reduction of the dielectric properties due to enhancement in grain growth (large grain volume and lesser number of grain boundaries) with the incorporation of Co and Mn ions into the ZnO lattice. The electrical conductivity of the Mn doped and (Mn, Co) co-doped ZnO samples were enhanced due to increase in the volume of conducting grains and charge density (liberation of trapped charge carriers in oxygen vacancies and free charge carriers at higher frequencies). The Mn-doped and (Mn, Co) co-doped ZnO NPs show ferromagnetic (FM) behaviour. The saturation and remnant magnetizations (M_s and M_r) elevates from (0.235 to 1.489)?×?10^?2 and (0.12 to 0.27)?×?10^?2 emu/g while Coercivity (H_c) reduced from 97 to 36 Oe with enhancement in the concentration of dopants in ZnO matrix. Oxygen vacancies were found to be the main reason for room-temperature ferromagnetism (RTFM) in the doped and co-doped ZnO NPs. The results show that the enhanced dielectric and magnetic properties of Mn doped and (Mn, Co) co-doped ZnO is strongly correlated with the concentration of oxygen vacancies. The observed enhanced RTFM, dielectric properties and electrical conductivity makes TM doped ZnO nanoparticles suitable for spintronics, microelectronics and optoelectronics based applications.     

Photochemical deposition of platinum on titanium dioxide–tungsten trioxide nanocomposites: an efficient photocatalyst under visible light irradiation

Highly ordered titanium dioxide–tungsten trioxide nanotubular composites (TiO₂–WO₃) were fabricated on titanium sheets by electrochemical anodizing. Platinum nanoparticles have been successfully deposited onto TiO₂–WO₃ nanotubes by UV light photoreduction method. In this work, X-ray diffraction, field emission scanning electron microscope, ultraviolet–visible spectroscopy and energy dispersive X-ray spectrometer methods were adopted to characterize the samples. The degradation of methylene blue (MB) was used as a model reaction to evaluate the photocatalytic activity of the obtained samples. After irradiated under visible light for 60 min, the degradation rate of MB solution on unmodified TiO₂–WO₃ and Pt/TiO₂–WO₃ reached 77 and 93 %, respectively. Under the same condition, no obvious photodegradation of MB was found for bare TiO₂ (T). Kinetic research showed that photodegradation process followed the first-order reaction; the apparent reaction rate constant of Pt/TiO₂–WO₃-1 was 4.56 × 10^?2 min^?1 which is approximately 1.75 times higher than that on the unmodified TiO₂–WO₃. This work provides an insight into designing and synthesizing new TiO₂–WO₃ nanotubes based hybrid materials for effective visible light-activated photocatalysis.