Fabrication of Neodymium (Nd), Cadmium (Cd) and Nd:Cd doped hybrid copper oxide nanocomposites: Evaluation of their antibacterial activity and cytotoxicity against human L132 cell line

In the present study, Neodymium (Nd), Cadmium (Cd), and the various molar ratios of Nd: Cd doped copper oxide nanocomposites (CuO NCs) were prepared by the co-precipitation method. The as-synthesized Nd, Cd, and Nd:Cd doped CuO NCs [Cu_1-x + yNd_xCd_yO, (x:y = 0.006:0.00, 0.00:0.006, 0.005:0.001, 0.004:0.002, 0.003:0.003, M)] were characterized through various instrumentation techniques such as TGA, UV–Vis–NIR, FTIR, Raman, FL, XRD, ZP, FE-SEM with EDAX elemental mapping, HR-TEM and XPS analyses. Further, the antibacterial activity of doped CuO NCs was tested against Staphylococcus aureus and Escherichia coli. An equal molar ratio of Nd and Cd doped CuO NCs showed excellent antibacterial activity mainly due to the synergistic effect of sufficient Nd³⁺, Cd²⁺, and Cu²⁺ ions releasing ability. Interestingly, the doping effect enhances surface defects and decreases the ability to scavenge free radicals compared to pure CuO nanomaterials. At the same time, the cytotoxicity of NCs was evaluated on the human lung epithelial L132 cell line. Evidently, 75 μg/ml concentration of Nd:Cd doped CuO NCs samples shows 80% viability, which confirms their negligible cytotoxic effect. The Nd:Cd doped CuO NCs (94:3:3) had a high aspect ratio shape, remarkable ion-releasing ability, and biocompatibility while being thermally stable. Because of these qualities, they are well suited for treating bacterial infections in the biomedical area.     

The influence of coating with aminopropyl triethoxysilane and CuO/Cu2O nanoparticles on antimicrobial activity of cotton fabrics under dark conditions

A novel impregnation process for the fabrication of cotton nanocomposite with strong antimicrobial activity against antibiotics-resistant bacteria and yeast was developed. The impregnation process includes the sol–gel treatment of fabric with (3-aminopropyl)triethoxysilane in the first step, and synthesis of the CuO/Cu₂O nanoparticles (NPs) on the fabric surface in the second step. The in situ synthesis of the CuO/Cu₂O NPs was based on the adsorption of Cu²⁺-ions by the introduced amino groups of the sol–gel coating. The adsorbed Cu²⁺-ions are subsequently reduced in the alkaline solution of NaBH₄. X-ray diffraction measurements confirmed the formation of CuO/Cu₂O NPs. Scanning electron microscopy and atomic absorption spectrometry analyses indicate that the particle size, agglomeration, and amounts of synthesized NPs were highly affected by the initial concentration of CuSO₄ solution. The toxicity of nanocomposites to human keratinocytes (HaCaT) and antimicrobial activity against Gram-negative Escherichia coli ATCC 25922, E. coli ATCC BAA 2469, and Klebsiella pneumoniae ATCC BAA 2146, and Gram-positive bacteria Staphylococcus aureus ATCC 25923, S. aureus ATCC 43300 and yeast Candida albicans ATCC 24433 strongly depended on the copper content. In addition to excellent antimicrobial activity, controlled release of Cu²⁺-ions from the fabrics into physiological saline solution was obtained.     

Investigations on electrical characteristics of (PbO)30(CuO)x(As2O3)(70-x) glass ceramics

This study is mainly focused on dielectric properties of lead arsenate glasses crystallized with different concentrations of CuO over continuous ranges of frequency (3 Hz −100 kHz) and temperature (300–633 K). The glasses were prepared by melt quenching technique and were heat treated for prolonged time for ceramization. Prepared samples were characterized by XRD, SEM and DSC techniques. SEM studies indicated that the samples are composed of small crystal grains of the size varying from 0.2 to 1.0 µm cemented with the residual glass phase. XRD studies indicated CuAs₂O₄, Pb₂Cu₇(AsO₄)₆ and Cu₂O are the main crystal phases developed during the crystallization. Optical absorption studies confirmed the presence of copper ions in Cu⁺ valence state in addition to Cu²⁺ state and the fraction of Cu⁺ ions is found to increase with the content of CuO. The optical band gap exhibited increasing trend with CuO content. IR spectral studies indicated an increase of degree of polymerization of the glass network with the CuO content. The observed variations of dielectric parameters with frequency, temperature and CuO content are discussed using different polarization mechanisms. The dielectric relaxation effects exhibited by the loss tangent and the electric moduli are analyzed using graphical method and observed relaxation effects are attributed to the complexes of divalent copper ions with oxygens. The impedance diagrams indicated increase of bulk resistance of the samples with increase of CuO content. The ac conductivity exhibited a decreasing trend with increase of CuO content. The conduction phenomenon is explained using polaron hopping between Cu⁺ and Cu²⁺ ions. The temperature independent part of the conductivity is explained using quantum mechanical tunneling (QMT) model. Finally, it is concluded that the insulating strength of the material increased with CuO content and such materials may be useful as electrical insulators in the low temperature region     

Gas phase hydrogenation of maleic anhydride to γ-butyrolactone by Cu–Zn–Ti catalysts

Cu–Zn–Ti catalysts were prepared by coprecipitation method. The calcined and reduced Cu–Zn–Ti catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), and N₂ adsorption. The calcined Cu–Zn–Ti catalysts were composed of CuO, ZnO, and amorphous TiO₂. There were two kinds of CuO species present in the calcined Cu–Zn–Ti catalyst. At a lower copper content, CuO species interacted with ZnO and TiO₂; at a higher copper content, both the surface-anchored and bulk CuO species were present. After reduction, metallic copper (Cu^o) appeared in all Cu–Zn–Ti catalysts. Cu^o produced by reduction of the surface-anchored CuO favored the deep hydrogenation of maleic anhydride. ZnO and TiO₂ had synergistic effect on the catalytic activity of Cu–Zn–Ti catalysts in hydrogenation of maleic anhydride.     

Influence of seed layer treatment on low temperature grown ZnO nanotubes: Performances in dye sensitized solar cells

Non-aligned and highly densely aligned ZnO nanotube (NTs), synthesized by low temperature solution method were applied as photoanode materials for the fabrication of efficient dye-sensitized solar cells (DSSCs). The crystalline and the morphological analysis revealed that the grown aligned ZnO NTs possessed a typical hexagonal crystal structure of outer and inner diameter ∼250 nm and ∼100 nm, respectively. ZnO seeding on FTO substrates is an essential step to achieve the aligned ZnO NTs. A DSSC fabricated with aligned ZnO NTs photoanode achieved high solar-to-electricity conversion efficiency of ∼2.2% with short circuit current (J_SC) of 5.5 mA/cm², open circuit voltage (V_OC) of 0.65 V and fill factor (FF) of 0.61. Significantly, the aligned ZnO NTs photoanode showed three times improved solar-to-electricity conversion efficiency than DSSC fabricated with non-aligned ZnO NTs. The enhanced performances were credited to the aligned morphology of ZnO NTs which executed the high charge collection and the transfer of electrons at the interfaces of ZnO NTs and electrolyte layer.     

Solar driven photocatalytic properties of Sm3+ doped ZnO nanocrystals

ZnO nanocrystals (NCs) doped with different Sm³⁺ concentrations were prepared by sol gel method. XRD analysis showed that the ZnO:Sm³⁺ NCs crystallized in the hexagonal wurtzite structure with a grain size varying from 61.4 nm to 72.6 nm, with Sm³⁺ concentration. Transmission electron microscopy (TEM) images indicated that ZnO NCs adopted a bimodal size distribution. X-ray photoelectron spectroscopy (XPS) revealed that Sm ions existed in trivalent state and substituted at the Zn²⁺ sites in the ZnO lattice. Raman spectra highlighted the presence of the LO mode, confirming the successful substitution of Zn²⁺ by Sm³⁺. Excitation and emission spectra highlighted the typical 4f-4f transitions of Sm³⁺. A photoluminescence (PL) quenching accompanied by a decrease of PL lifetime was observed for Sm³⁺ concentrations above 1.5%. The processes of excitation and de-excitation of the Sm³⁺ ions in ZnO NCs were discussed based on dipolar interactions between the excited ions. The ZnO:Sm³⁺ (1.5%) photocatalyst induced complete and fast photodegradation of RhB under sunlight irradiation. The photocatalytic mechanism is discussed based on the analysis of PL lifetimes. The role of oxygen vacancies on the reduction of Sm³⁺ ions and its impact on the photocatalytic process is also discussed.     

Effect of Pretreatment Atmosphere on CuO/TiO2 Activities in NO + CO Reaction

Using TiO₂ as carrier, CuO/TiO₂ catalysts with different CuO loading were prepared by the impregnation method. The catalytic activities in NO+CO reaction were examined with a micro-reactor gas chromatography reaction system and the methods of TPR, XPS and NO-TPD. It was found that the catalytic activities were affected by pretreatment atmosphere, i.e. H₂ atmosphere > reduction–reoxidation > 10%CO/He > reaction gas (fresh sample). NO decomposition was better by low-valence Cu species than by high-valence Cu species, i.e. Cu⁰>Cu⁺>Cu²⁺. The XPS results indicated that Cu species on CuO/TiO₂ were Cu⁰, Cu⁺, normal Cu²⁺(Cu²⁺(I)) and chain-structured Cu²⁺(Cu²⁺(II)) as –Cu–O–Ti–O–. The activities of Cu²⁺(II) were much higher than that of Cu²⁺(I), but both species were very unstable in the reaction atmosphere and easily reduced by CO, which accounted for the variable activities of fresh catalysts with increasing reaction temperature. In NO+CO reaction, the redox process was a cycle of Cu⁺–Cu²⁺(I) at low reaction temperature but was a cycle of Cu⁰–Cu⁺ at high reaction temperature. As shown by NO-TPD, high catalytic activities could be attributed to the following factors, e.g. oxygen caves on the catalyst’s surface after pretreatment with H₂ and reduction–reoxidation, formation of Cu⁰ after pretreatment with H₂, and increment of Cu species dispersion and formation of Cu²⁺(II) after pretreatment with reduction–reoxidation.     

Hydrogenation of methyl acetate to ethanol by Cu/ZnO catalyst encapsulated in SBA‐15

The hydrogenation of methyl acetate (MA) is one of the important key processes for synthesis of ethanol from syngas. This work reports a highly efficient Cu‐ZnO/SBA‐15 catalyst prepared by facile solid‐state grinding method. Both copper and zinc species were encapsulated in SBA‐15 in high dispersion with the presence of organic template. The mixed homogeneity and interaction between copper and zinc species was enhanced as well with the help of organic template, resulting in the formation of Cu⁺ species in the reduced catalysts. Moreover, TOF_Cu(0) linearly increased with the Cu⁺/Cu⁰ ratio, indicating that a high proportion of Cu⁺/Cu⁰ induced by ZnO should be a key prerequisite to achieve favorable hydrogenation performance. It seems that the Cu⁺ species originated from Cu‐ZnO_x species are more active than that from Cu‐O‐Si species in the activation of MA. These results may provide an inspiration in rational design of Cu‐ZnO‐based catalysts for esters hydrogenation. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2839–2849, 2017     

Silver-zinc oxide nanocomposite: From synthesis to antimicrobial and anticancer properties

A green method by Verbascum speciosum was used to synthesize zinc oxide nanoparticles (ZnO NPs). ZnO NPs were coated with silver to synthesize Ag–ZnO nanocomposite (NCs). The physicochemical properties of Ag–ZnO NCs were analyzed by Fourier-transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), and zeta potential. The FTIR indicated the peak of Zn–O vibration and some hydroxyl and carboxyl groups. PXRD analyses confirmed the synthesis of ZnO NPs and Ag–ZnO NCs. Due to the size of the crystallite obtained from PXRD, solid-phase sizes (from FESEM and TEM images), and dynamic sizes from DLS, agglomeration was observed. The Ag–ZnO NCs showed a negative charge surface (?49.3 mV). Ag–ZnO NCs had a high antibacterial activity towards two most important infectious bacteria (i.e., Escherichia coli and Staphylococcus aureus) and anticancer activity against human liver-carcinoma cells (HepG2). Later, it depended on time and concentration of Ag–ZnO NCs. The cytotoxicity properties of Ag–ZnO NCs were also studied against NIH-3T3 as a normal cell, where the results verified the lower cell toxicities of nanocomposite than the HepG2.     

Comparative Study of the Physico-Chemical Properties of Nanocrystalline CuO–ZnO–Al2O3 Prepared from Different Precursors: Hydrogen Production by Vaporeforming of Bioethanol

The physico-chemical and catalytic properties of CuO–ZnO–Al₂O₃, synthesised by sol–gel process (SG), impregnation method (IMP) and a combination of both preparative procedures (ISG), were comparatively studied. Samples were characterised with thermogravimetric-differential thermal analysis (TG–DTA), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) techniques and oxygen chemisorption. XPS study was not consistent with the bulk findings and revealed the presence of Cu²⁺, Cu⁺ and/or Cu⁰ species at the catalysts surface. Surface analysis revealed also that copper enrichment occurred mainly at the surface of SG and IMP solids. The reducibility of the mixed oxides catalysts was always modified with respect to that of pure copper oxides phases and the reduction of CuO was markedly affected by the presence of ZnO–Al₂O₃. Temperature programmed reduction (H₂-TPR) analysis showed that the temperature corresponding to maximum reduction rate of copper oxide was ca. 256 °C for IMP sample and ca. 296 °C for both SG and ISG solids. These latter showing a high resistance to reduction suggest a strong interaction of copper species with ZnO–Al₂O₃, limiting thus copper particles sintering. CuO particle size was found to be ca. 20 nm for both SG and ISG solids and ca. 40 nm for IMP catalysts. Besides, at 300 °C SG and ISG samples showed superior amount of reversible O₂ uptake with respect to IMP solids. Catalytic activity of CuO–ZnO–Al₂O₃ was measured with bio-ethanol steam reforming reaction. SG catalysts exhibited both high selectivity to hydrogen and high stability with time on stream than IMP and ISG catalysts. This was attributed both to the particles size of copper species, their amount on the catalytic surface and to their strong interaction with ZnO–Al₂O₃.     

Effect of silver (Ag) ions irradiation on the structural,optical and photovoltaic properties of Mn doped TiO2 thin films based dye sensitized solar cells

Dye sensitized solar cell (DSSC) is an emerging energy harvesting tool which converts direct sunlight into electrical energy. These cells have much better properties in contrast with silicon based solar cells because of their flexible nature, light weight, low cost, environment friendly nature, and involvement of a simple manufacturing process. Since, a photoanode is the backbone of DSSC, we synthesized a pure and 1% manganese (Mn) doped titanium dioxide (TiO₂) films by sol-gel method which are irradiated with silver (Ag) ions at two different concentrations (2 × 10¹⁴ and 4 × 10¹⁴) ions-cm^?2. X-ray diffraction revealed that Mn doping followed by Ag irradiation transformed TiO₂ from pure anatase to rutile phase. Ultraviolet–visible spectroscopy exposed the reduction in band gap of TiO₂ film during this doping and irradiation process. Therefore, absorption is enhanced with red shift in UV-range. When these films are used as a photoanode in DSSC, 1% Mn doped TiO₂ film exposed with Ag at the concentration of (2 × 10¹⁴) ions-cm^?2 exhibited maximum efficiency of 2.40%.     

Acute Toxicity of Cu-MOF Nanoparticles (nanoHKUST-1) towards Embryos and Adult Zebrafish

Metal-organic frameworks (MOFs) demonstrate unique properties, which are prospective for drug delivery, catalysis, and gas separation, but their biomedical applications might be limited due to their obscure interactions with the environment and humans. It is important to understand their toxic effect on nature before their wide practical application. In this study, HKUST-1 nanoparticles (Cu-nanoMOF, Cu₃(btc)₂, btc = benzene-1,3,5-tricarboxylate) were synthesized by the microwave (MW)-assisted ionothermal method and characterized by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) techniques. The embryotoxicity and acute toxicity of HKUST-1 towards embryos and adult zebrafish were investigated. To gain a better understanding of the effects of Cu-MOF particles towards Danio rerio (D. rerio) embryos were exposed to HKUST-1 nanoparticles (NPs) and Cu²⁺ ions (CuSO₄). Cu²⁺ ions showed a higher toxic effect towards fish compared with Cu-MOF NPs for D. rerio. Both forms of fish were sensitive to the presence of HKUST-1 NPs. Estimated LC₅₀ values were 2.132 mg/L and 1.500 mg/L for zebrafish embryos and adults, respectively. During 96 h of exposure, the release of copper ions in a stock solution and accumulation of copper after 96 h were measured in the internal organs of adult fishes. Uptake examination of the major internal organs did not show any concentration dependency. An increase in the number of copper ions in the test medium was found on the first day of exposure. Toxicity was largely restricted to copper release from HKUST-1 nanomaterials structure into solution.     

Selective preparation of Ag species on photoluminescence of Sm3+ in borosilicate glass via Ag+-Na+ ion exchange

Photoluminescence (PL) of rare earth ion-doped glasses could be enhanced by diverse Ag species such as Ag⁺ ions, Ag⁺-Ag⁺ pairs, Ag nano-clusters (NCs), and Ag nanoparticles (NPs). Selective preparation of silver species in rare earth ion-doped glasses is a crucial step to obtain the luminescence enhancement of rare earth ions caused by the different silver species. In this work, Ag⁺ ions and Ag NCs were selectively prepared in the Sm³⁺-doped borosilicate glass via the Ag⁺-Na⁺ ion exchange. The influence of AgNO₃/NaNO₃ ratio in the molten salt on the Ag existing states was investigated. The results demonstrate that the isolated Ag⁺ ions exist in the Sm³⁺-doped borosilicate glass when the ratio of AgNO₃/NaNO₃ is 1/1000. The Ag NCs are formed in the Sm³⁺-doped borosilicate glass when the AgNO₃/NaNO₃ ratio is 1/10. The influence of Ag⁺ ions or Ag NCs on the PL of Sm³⁺ was systematically investigated. The results show that the PL of Sm³⁺ was enhanced by the energy transfer from Ag⁺ ions or Ag NCs to Sm³⁺.     

Chitosan reinforced with modified CaCO<Subscript>3</Subscript> nanoparticles to enhance thermal,hydrophobicity properties and removal of cu(II) and cd(II) ions

The role of nanoparticles (NPs) in the enhancement of thermal, wettability and adsorption properties of chitosan (CS) was inspired by loading of CaCO₃ modified with diacid (DA) based on L- phenyl aniline (2–8 wt%) within the CS by ultrasound agitation. The diameter of CaCO₃-DA into the CS extended from 40 to 70 nm. A thermal test on the CS/CaCO₃-DA nanocomposite (NC) 2 wt% revealed that T ₅ (temperature with 5% weight loss) was increased up to 312 °C, which is twice the value of the pure polymer. The wettability property of the CS/CaCO₃-DA NCs was transformed from hydrophilicity to hydrophobicity as the CaCO₃-DA NPs concentration was increased. It is due to decrease of the accessibility of the CS polar groups to water. The CS/CaCO₃-DA NC 5 wt% was selected as the adsorbent for uptake of metal ions from the wastewater. It showed maximum adsorption capacity of 21.74 and 29.41 mg.g^?1 for Cu(II) and Cd(II), respectively. These are attributed to strong complexation reaction between the metal ions and functional groups in the obtained NC.     

Copper incorporation in Mn2+-doped Sn2S3 nanocrystals and the resultant structural,optical, and electrochemical characteristics

Sn₂S₃ nanocrystals (NCs) with both Mn²⁺ doping and Cu²⁺ incorporation were synthesized using a chemical bath deposition method. The Cu²⁺ ions formed an anorthic Mn²⁺-doped Cu₂SnS₃ structure with E_g =?1.44?eV, which altered the material's optical and photo/electrochemical properties. After coating the bare Nb₂O₅ electrode with Mn²⁺-doped Sn₂S₃ or Mn²⁺-doped Cu₂SnS₃ NCs, the photoluminescence spectrum was blue-shifted to 411.13?nm from 411.69?nm. Compared to the sample without Cu²⁺, the Cu²⁺-incorporated sample showed a slightly stronger emission at the same position, possibly due to disorder in the crystalline structure based on variations at the interface of Mn²⁺-doped Cu₂SnS₃ NCs. Electrochemical analysis showed a lower charge transfer resistance in the Mn²⁺-doped Cu₂SnS₃, which is related to its larger electroactive surface area. The larger electroactive surface area is attributed to the Faradaic redox processes at the electrode surface, which suppresses the carrier recombination. The coexistence of Cu²⁺ and Mn²⁺ ions shortened the electron transport pathway at the interface and improved the carrier diffusion coefficient and diffusion length, leading to a higher specific capacitance that implies higher energy storage performance. Finally, the I-V characteristics of the Mn²⁺-doped Cu₂SnS₃-coated Nb₂O₅ electrode under various light illumination conditions indicated its better efficiency in photoresponse, electron generation, and charge collection, owing to a superior charge transport mechanism. Detailed results were obtained about the charge dynamics in the as-prepared photo/electrochemical devices with Cu²⁺ incorporation in the Mn²⁺-doped SnS₃ electrode.     

Synthesis of polypyrrole/Ni-doped TiO2 nanocomposites (NCs) as a protective pigment in organic coating

This study reports the synthesis of polypyrrole/Ni-doped TiO₂ nanocomposites (NCs) as a protective pigment in organic coatings. Polypyrrole/Ni-doped TiO₂ NCs were prepared by in situ chemical oxidative polymerization of pyrrole monomer in the presence of Ni-doped TiO₂ nanoparticles (NPs) with ammonium persulfate (APS) as oxidant. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) result show a core–shell structure of the pigments. The XRD results indicate that the average crystalline size of Ni-doped TiO₂ NPs is larger than TiO₂ NPs while the sizes of polypyrrole/TiO₂ NCs and polypyrrole/Ni-doped TiO₂ NCs were 93.46 ± 0.06 and 26.16 ± 0.06 nm respectively. Hence the thickness of the shell in the core–shell incorporating the Ni-doped/TiO₂ NPs was very thin and the area of synthesized PPy is increased. The electrochemical impedance spectroscopy (EIS) results show that increasing the area of synthesized polypyrrole in the presence of Ni-doped-TiO₂ NPs can increase its ability to interact with the ions liberated during the corrosion reaction of steel in the presence of NaCl.     

Synthesis,structural, magnetic and NO2 gas sensing property of CuO nanoparticles

Cupric oxide (CuO) nanoparticles are synthesized by the oxidation of Cu/Cu₂O, which is obtained by the chemical reduction of Cu²⁺ ions with ascorbic acid. XRD pattern confirmed the formation of CuO, and FE-SEM image shows the clusters consisting of 25–30 nm sized particles. The band gap energy (3.7 eV) from optical absorption spectra is blue shifted to that of bulk values. The Néel temperature, T_N ≈ 230 K for paramagnetic to antiferromagnetic transition was clearly seen. The magnetic hysteresis loops at 5 K showed weak ferromagnetic behavior. Based on the dc electrical conductivity (300–500 K), the apparent activation energy was 0.36 eV. The NO₂ gas sensing property of CuO was reasonably good in the temperature range of 200–300 °C, and the sensitivity increased with an increase in gas concentration but the effect of temperature is marginal.     

Effective methodology for the production of novel nanocomposite films based on poly(vinyl chloride) and zinc oxide nanoparticles modified with green poly(vinyl alcohol)

Ultrasonic irradiation and solution dispersion methods were used to organize transparent worthwhile poly(vinyl chloride) (PVC) nanocomposite (NC) films which contain different amounts of modified zinc oxide nanoparticles (NP)s. First, modification of ZnO NPs was accomplished by biocompatible poly(vinyl alcohol) (PVA) to increase NCs compatibility and dispersity in the PVC matrix. The investigation followed by the fabrication and characterization of PVC/ZnO‐PVA NCs which obtained via fast and facile ultrasonication irradiation. The measurements of X‐ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, and field emission scanning electron microscopy were used for the characterization of properties, structure and morphology of the obtained NPs and their NCs. Furthermore, thermal and optical properties of the resulting NCs were also carried out by thermogravimetric analysis, ultraviolet‐visible transmission, and absorption spectra. Morphology results demonstrate well‐dispersed characteristics of ZnO‐PVA NPs incorporated in the PVC matrix which resulted from modification. Also, modified ZnO NPs enhanced mechanical properties of prepared NC films. Prepared NCs could be categorized as self‐extinguishing materials on the basis of the limiting oxygen index values. POLYM. COMPOS., 38:1800–1809, 2017. © 2015 Society of Plastics Engineers     

Solvothermal synthesis and optical limiting properties of carbon nanotube-based hybrids containing ternary chalcogenides

Two or three types of semiconductor nanoparticles (NPs) have been deposited on the sidewalls of multi-wall carbon nanotubes (MWCNTs) by a solvothermal treatment of a mixture containing poly(sodium 4-styrenesulfonate) (PSS) wrapped MWCNTs, metal chloride (CuCl₂ and SnCl₂), and thiourea. Changing the ratio of Cu²⁺ to Sn²⁺ alters the composition of the resultant MWCNT–PSS–NP hybrids. Under Cu/Sn ratios of 3:1 and 2:1, MWCNTs can be simultaneously decorated with Cu₂S and Cu₃SnS₄ NPs. When the ratio is reduced to 1:1, Cu₃SnS₄, Cu₂S and SnO₂ NPs would be formed at the same time. Further decreasing the ratio results in the formation of Cu₂SnS₃ and SnO₂ instead of Cu₃SnS₄ and Cu₂S. Open-aperture z-scan measurements have been carried out on three typical MWCNT–PSS–NP samples to study their optical limiting (OL) properties. The addition of semiconductor NPs can improve the OL performance of MWCNTs, and the composition of the NPs has a significant effect on the OL behavior of the hybrids.     

Cuprous delafossites,Cu3(MFeSb)O6 (M = Na,Li) with honeycomb arrays,realized by topochemical ion-exchange reactions

The current work describes the synthesis, structure, magnetic and optical properties of Cu¹⁺ based delafossite oxides, Cu₃(MFeSb)O₆ (M = Na, Li) synthesized by the topotactic ion-exchange reactions (around 400 °C) of CuCl with Na₄FeSbO₆ and Na₃LiFeSbO₆ in an inert argon atmosphere. The synthetic procedure is significant as the oxides could not be synthesized by the solid state methods. Chemical analysis coupled with energy dispersive spectral analysis confirmed the extent of replacement of Na⁺ ions by Cu⁺ ions. A complete exchange of alkali metal ion, Na⁺ by Cu¹⁺ in the interlayers of these honeycomb oxides has been achieved using a ratio of 1:3 between Na₄FeSbO₆ and CuCl. An additional exchange of approximately 70 % Na⁺ ions from the honeycomb arrays is possible by varying the ratio to 1:4. Rietveld refinements (space group C2/c) of the powder X-ray diffraction data have been carried out to ascertain the phase purity and to verify the structure formed by edge shared honeycomb arrays separated by Cu¹⁺ in dumbbell configuration (O–Cu¹⁺-O). X-ray photoelectron spectroscopy analysis confirmed the oxidation states of the constituent ions, specifically copper as Cu¹⁺. A similar method is adopted to synthesize Cu₃(LiFeSb)O₆ by reacting Na₃(LiFeSb)O₆ and CuCl in the ratio 1:3 at 400 °C. These new delafossite oxides, Cu₃(MFeSb)O₆ (M = Na, Li) and Cu₃((Cu_0.7Na_0.3)FeSb)O_6, exhibit interesting magnetic properties which are significantly different from the rock salt based parent sodium analogs. Dominant antiferromagnetic interactions with a specific ordering temperature have been observed for these samples containing Fe³⁺ (d⁵) ions in the honeycomb. UV–visible diffuse reflectance measurements indicated the decrease in the band gap of Cu¹⁺ based oxides. This study highlights the importance of low temperature ion-exchange reactions as an effective route to stabilize multifunctional materials of potential importance for various applications.