Suresh S. Umare

Mineralization of malachite green dye over visible light responsive bismuth doped TiO2–ZrO2 ferromagnetic nanocomposites

We report enhanced visible light photocatalytic activity for ferromagnetic Bi doped (1% by atomic weight) TiO2–ZrO2 nanocomposites for the degradation of malachite green in aqueous solution. X-ray diffraction, Raman and High resolution Transmission electron microscopy (HRTEM) analysis indicate the presence of monoclinic ZrO2 and anatase TiO2 in the composite sample. The particle size of the nanocomposite is ∼20 nm. A significant absorption of visible light is observed for the doped TiO2 composite as compared to P25 and undoped TiO2–ZrO2. The photocatalytic activity of different concentrations of the TiO2–ZrO2 nanocomposite for the degradation of malachite green follows the order: 98% TiO2–2% ZrO2 < 80% TiO2–20% ZrO2 < 90% TiO2–10% ZrO2. The Bi doped TiO2–ZrO2 (90% TiO2–10% ZrO2) composite shows a still higher activity as compared to the undoped composite and commercial P25. TOC analysis exhibited 88% mineralization of malachite green over Bi doped TiO2–ZrO2 (90% TiO2–10% ZrO2). The enhanced photocatalytic activity of the doped TiO2–ZrO2 composite is attributed to improved visible light absorption and efficient separation of photogenerated charge carriers. The composite samples are found to be photo-stable and the photocatalytic activity remains almost the same for four cycles of degradation experiments. Testing with different quenchers suggest that hydroxyl radicals, holes and superoxide radicals play a considerable role in the photodegradation of malachite green. It is noteworthy that the Bi doped TiO2–ZrO2 nanocomposite exhibits defect induced room temperature ferromagnetism.

Influence of Copolymer Composition on the Structure of Conducting Poly(aniline-co-o-phenylenediamine)

Abstract This study covers the synthesis of polymers of aniline, o-phenylenediamine, and their copolymers by chemical oxidation in HCl medium. The composition of the copolymers was changed by varying the monomer feed ratio. For examining the effect of composition on copolymer structure and properties, the copolymers were characterized by elemental analysis, FTIR, UV-visible spectra, and thermal analysis. The electrical conductivity of the compressed pellets was measured by the two-probe method. Magnetic studies shows that the polyaniline is paramagnetic in nature, which shows the presence of three unpaired electrons per chain unit, while the poly(o-phenylenediamine) and copolymers are diamagnetic and are found to contain no unpaired electrons. The copolymer exhibits excellent solubility in DMF. It was interesting to find that 20% o-phenylenediamine-containing copolymer exhibits good solubility by retaining a conductivity similar to polyaniline. The spectroscopic analysis, solubility test, and electrical conductivity suggest that aniline and o-phenylenediamine units are distributed along the copolymer chain and the properties of copolymers can be modified by varying the monomer composition in copolymerization reactions. TG thermogram shows three-stage decomposition of the copolymer. Rapid decomposition starts after 400°C. The observed weight loss of samples was less than 17% at 225°C, showing good thermal stability of copolymers.

Photocatalytic mineralization of anionic dyes using bismuth doped CdS–Ta2O5 composite

A stable and efficient bismuth doped CdS–Ta2O5 heterostructured system is synthesized for the photocatalytic degradation of anionic dyes like acid violet 7, indigo carmine and methyl orange. This composite is found to be effective not only for the degradation but also for the mineralization of these dyes under sunlight type irradiation. Bi doping improves the optical absorption property and enhances the visible light absorption. In this composite, CdS exists as the hexagonal wurtzite structure and Ta2O5 has an orthorhombic structure. Increased fluorescence lifetime is observed for the charge carriers in the composite sample compared to CdS due to the efficient charge separation occurring in this system. The enhanced photocatalytic activity of the composite system arises due to the improved optical absorption properties and increased life time of the photogenerated charge carriers. This heterostructured catalyst is found to be photostable and reusable. Photocatalytic degradation experiments with different quenchers suggest that hydroxyl radicals (OH˙), superoxide anion radicals (O2˙−) and photogenerated holes (h+) play significant roles in the mineralization process.

Ethylene glycol mediated synthesis of SnS quantum dots and their application towards degradation of eosin yellow and brilliant green dyes under solar irradiation

SnS (tin sulfide) quantum dots (QDs) were synthesized by a chemical coprecipitation method using ethylene glycol as a solvent and capping agent and thiourea as a sulfur source at a temperature of 160 °C, 4 h. The as synthesized SnS QDs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-Vis-NIR spectroscopy and FT-Raman spectroscopy. XRD patterns show the formation of single phase SnS QDs with rhombohedral structure. Ethylene glycol mediated synthesis resulted 2.5–3 nm SnS QDs. The UV-Vis-NIR optical absorption spectra of the SnS QDs displayed that the SnS QDs possess an absorption profile across the whole visible-light and near-infrared region. The direct band gap and indirect band gap energy for SnS QDs are found to be 1.17 eV and 1.11 eV, respectively. FT-Raman spectra of SnS QDs demonstrate vibrational modes at 73, 97, 162, 188, 222 cm−1. The Brunauer–Emmett–Teller (BET) surface area of SnS QDs was found to be 5.63 m2 g−1. SnS QDs showed powerful photodegradation activity towards degradation of eosin yellow and brilliant green dyes under sunlight. The enhanced photocatalytic activity of SnS QDs is attributed to improved visible light absorption and efficient separation of photogenerated charge carriers. In addition, the quenching effects of different quenchers suggest that superoxide radicals play a major role in the photodegradation process.

Microwave assisted in situ decoration of a g-C3N4 surface with CdCO3 nanoparticles for visible light driven photocatalysis

Graphitic carbon nitride (g-C3N4) supported cadmium carbonate (CdCO3) as an organic–inorganic hybrid nanophotocatalyst was realised by an in situ microwave heating method. The hybrid composite retains the structure of each component, which was verified by p-XRD, FT-IR and solid state 13C-NMR analysis. The as-prepared hybrid g-C3N4/CdCO3 composites were evaluated as a photocatalyst towards the degradation of indigo carmine (IC) dye and inactivation of the Gram negative E. coli pathogen. In this composite, the wide band gap CdCO3 acts as an electron accepting platform from g-C3N4 and facilitates the subsequent photocatalytic reaction. The optimized hybrid g-C3N4/CdCO3-90 photocatalyst exhibits four-fold increase in the degradation of IC dye compared to pristine g-C3N4 and almost a complete mineralization of the dye occurs after 180 min of irradiation. Besides, this photocatalyst completely inhibits the growth of E. coli bacteria within 45 min of visible light irradiation. The enrichment in the photoactivity of CdCO3 decorated g-C3N4 is ascribed to the combined effects of improved visible light absorption, enhanced dye adsorption and facile separation of electron–hole pairs as evidenced by electrochemical impedance spectroscopy (EIS) measurements. The present work may provide valuable information and insights into the microwave assisted synthesis of g-C3N4 hybrid composites and may permit a better comprehension of future advancements in high performance materials for environmental remediation applications.

Mineralization of anionic dyes over visible light responsive Cd(x)Zn(y)S–Nb2O5 heterostructured photocatalysts

A novel, CdxZnyS–Nb2O5 heterostructured photocatalyst is found to have enhanced photocatalytic activity for the degradation and mineralization of a variety of anionic dyes such as acid violet 7, methyl orange and indigo carmine compared to its single phase constituents. This composite catalyst exhibits adsorption enhanced photocatalytic activity and it is found to degrade relatively high concentrations of AV 7 solution (120 ppm) in nearly 45 min using a fluorescent lamp as a source of light (UV < 3%), which has not been reported so far. In this composite system, CdxZnyS exists as a solid solution and both phases, CdxZnyS and Nb2O5 exist in a dispersed state. The composite system exhibits improved visible light absorption compared to pure CdS. Photoluminescence and time resolved fluorescence studies indicate an increased lifetime for the photogenerated charge carriers in the composite compared to CdS and Nb2O5. The improved activity of the composite is attributed to increased lifetime of the charge carriers as well as to the increased adsorption of the dyes on the composite catalysts. A slight, gradual decrease in the photocatalytic activity is observed during repeated cycles of degradation experiment but the catalyst regains its activity after heat treatment. Based on the experiments with different quenchers, it is concluded that the photogenerated holes play a significant role in the degradation reaction.

Synthesis, Characterization, and Biodegradation Studies of Poly(1,4-cyclohexanedimethylene-adipate-carbonate)s

Aliphatic/alicyclic poly(1,4-cyclohexanedimethylene-adipate-carbonate)s (PCACs) were synthesized by a transesterification from 1,4-cyclohexamethylendimethanol (1,4-CHDM), adipic acid (AA), diethyl carbonate (DEC), and titanium butoxide Ti(OBu)4 as a transesterification catalyst. The synthesized PCACs were characterized by the Fourier transform infrared (FTIR), X-ray diffraction analysis (XRD), solubility, solution viscosity, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscope (SEM) for their structural, physical, thermal, and morphological investigation. The structure of synthesized PCACs was confirmed by FTIR. All TGA curves of PCACs shows 10% weight loss above 270°C, and they reveal good thermal stability. Biodegradability of PCACs was investigated by hydrolytic degradation at (pH 7.2 and 11.5), enzymatic degradation using Rhizopus delemar lips at 37°C in phosphate buffer solution (PBS), and soil burial degradation at 30°C. The hydrolytic degradation shows the greater rate of weight loss in PBS at pH-11.5 than pH-7.2. The hydrolytic and soil burial degradation shows faster rate of weight loss as compared to enzymatic degradation. Biodegradation rate of PCACs follows the order: PCAC-20 > PCAC-40 > PCAC-60. SEM images show that degradation occurred all over the film surface, creating holes and cracks. These biodegradable PCACs may be able to replace conventional polymer in the fabrication of packaging film in near future.

Effects of NCO:OH ratio and HEMA on the physicochemical properties of photocurable poly(ester-urethane)methacrylates

A series of UV-curable isophorone diisocyanate-based poly(ester-urethane)methacrylate (IPEUMA) oligomers were synthesized by a two-step polymerization process. The amount of isophorone diisocyanate was varied during the synthesis. The effects of NCO:OH ratio and HEMA on the structural and physicochemical properties of UV-cured IPEUMAs were investigated. As the NCO:OH ratio increased, the tensile strength and thermal stability increased, whereas the elongation and hydrolytic degradation of the film decreased. The higher strength and thermal stability for higher NCO:OH ratio may be due to the increase in intermolecular hydrogen bonding in the UV-cured film. UV-cured IPEUMA films also show excellent chemical and solvent resistance.

Synthesis and characterization of electroactive novel poly-2-cynoaniline

Uniform needle-like structures of poly-2-cynoaniline are formed without the use of any template by electrochemical oxidative polymerization method on copper electrode in acidic medium. The structural characterizations are performed by FT-IR, UV-Visible spectroscopy and X-ray diffraction studies. The morphology of the polymer is demonstrated by scanning electron microscopy (SEM). The framework of the needle-like structure, which is seen at low and high magnifications appeared as nanorods of 50–80 nm diameter and of length up to a few micrometres to form a scaffold of interconnected nanorods. Thermogravimetic analysis (TGA) indicates that poly-2-cynoaniline is thermally more stable than polyaniline. The conductivity of pressed pellet of the as-synthesized polymer measured at room temperature of 25 °C by four-probe measurement method was found to be 9.1824 × 10−5 S/cm. The polymer is easily dispersed in some organic solvents and shows high solubility.