Biswajoy Bagchi

Synthesis and characterization of Cu/Ag nanoparticle loaded mullite nanocomposite system: A potential candidate for antimicrobial and therapeutic applications.

BACKGROUND Microbial resistance to antibiotics has triggered the development of nanoscale materials as an alternative strategy. To stabilize these particles an inert support is needed. METHOD Porous nanomullite developed by sol-gel route is loaded with copper and silver nanoparticle by simple adsorption method. These nanocomposites are characterized using XRD, FTIR, TEM, SEM, EDAX and UV-visible spectrophotometer. Antibacterial activity of these nanocomposites against Gram positive and Gram negative bacteria are performed by bactericidal kinetics, flow cytometry and MTT assay. The underlying mechanisms behind the antimicrobial property and cell death are also investigated by EPR spectroscopy, intracellular ROS measurement and β-galactosidase assay. The cytocompatibility of the nanocomposites is investigated by cell viability (MTT), proliferation (Alamar blue) and wound healing assay of mammalian fibroblast cell line. RESULTS Nanocomposites show a fairly uniform distribution of metal nanoparticle within mullite matrix. They show excellent antibacterial activity. Metal ions/nanoparticle is found to be released from the materials (CM and SM). Treated cells manifested high intracellular oxidative stress and β-galactosidase activity in the growth medium. The effect of nanocomposites on mammalian cell line depends on exposure time and concentration. The scratch assay shows normal cell migration with respect to control. CONCLUSION The fabricated nanoparticles possess diverse antimicrobial mechanism and exhibit good cytocompatibility along with wound healing characteristics in mouse fibroblast cell line (L929). GENERAL SIGNIFICANCE The newly synthesized materials are promising candidates for the development of antimicrobial ceramic coatings for biomedical devices and therapeutic applications.

Sol–gel synthesis of transition-metal ion conjugated alumina-rich mullite nanocomposites with potential mechanical, dielectric and photoluminescence properties

Nanocrystalline mullite have been synthesized from non-stoichiometric alkoxide precursors via sol–gel route with Co2+, Ni2+ and Cu2+ as dopant metal ions. Transition-metal aluminate spinel phases, formed from the reaction between dopant metal ions and dissolved alumina species, introduced prominent colors to the composites after sintering. Interesting colors combined with suitable densification lead these composites to have potential use as ceramic pigments. A comparative Vickers and Knoop hardness have been evaluated in terms of dislocation movement along grain boundaries with highest hardness and Young’s modulus values of ∼8.7 GPa and ∼207 GPa for copper and cobalt incorporated mullite, respectively. Greater porosity of pure mullite results in an unconventionally high dielectric constant of ∼91 whereas larger interfacial polarization is responsible for the varying dielectric response of transition-metal incorporated mullite composites. Formation of oxygen like defects in the composites cause prominent PL bands with highest PL intensity for dopant cobalt ions in mullite matrix.

In situ synthesis of environmentally benign montmorillonite supported composites of Au/Ag nanoparticles and their catalytic activity in the reduction of p -nitrophenol

In the present work, composites of montmorillonite clay supported silver and gold nanoparticles were synthesized by in situ chemical reduction method and characterized by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), UV-vis spectroscopy and Transmission Electron Microscopy (TEM). The clay–nanoparticle composites were synthesized at two different temperatures (25 °C and 75 °C) where nanoparticle size was found to depend on synthesis temperature. The distribution of the catalytic nanoparticles was uniform in the clay matrix with sizes in the range of 20–45 nm (at 25 °C) and 5–15 nm (at 75 °C), respectively. Catalytic activity of the clay–nanoparticle composites were monitored by UV-visible spectroscopy using p-nitrophenol and NaBH4 as model reactants. The best catalytic efficiency was observed in the case of silver–clay nanocomposites with a rate constant of 5.6 × 10−3 s−1.

Copper Ion Doped Mullite Composite in Poly (vinylidene Fluoride) Matrix: Effect on Microstructure, Phase Behavior and Electrical Properties

Highly crystallized copper ion doped mullite composites have been synthesized at 1100°C and 1400°C via sol-gel technique with five different strengths of copper ion and was incorporated in poly-vinylidene fluoride (PVDF) to make doped mullite composite/polymer films. We have studied the effects of this dopant on microstructure, phase transformation, and electrical properties of the polymer films over a wide range of frequency from 1.0 KHz to 2.0 MHz. Characterizations were done by various analytical tools at room temperature. Prominent mullite phases were observed from XRD, FTIR spectroscopy and FESEM characterization of composite polymer. The concentration of the dopant and the sintering temperature were found to be the two basic factors which affect the phase transition of the polymer. The composite film showed maximum dielectric constant of 19.96 at 1 KHz for 1.2M concentration of copper ion doped mullite sintered at 1400°C, compared to 3.09 for the pure polymer. Furthermore, both dielectric constant and electrical conductivity of the composite were found to be highly frequency and temperature dependent. After doping, the A.C. conductivity of the composite was found to increase with increasing temperature following Jonscher’s power law and the electrical resistivity reduced too. Moreover, the results revealed that the phase behaviors and micro structural changes of the copper ion doped mullite composite/polymer film affected its electrical properties with possible impact on its applications.

Effect of vanadic anhydride and copper oxide on the development of hard porcelain composite and its antibacterial activity

Abstract A mullite-reinforced porcelain composite with antibacterial properties has been developed using transition metal oxides by solid state sintering. The composite has been characterized in terms of mullite content, hardness, color and antibacterial properties. The physico-chemical properties of the porcelain were substantially increased in the presence of V2O5 and CuO. Well-crystallized needle shaped mullite of average length ∼ 3 μm was observed in the porcelain body at 1300 °C and 1500 °C after the addition of V2O5 and CuO. Vickers hardness of the composite increased 4.2 times for 2% V2O5 at 1500 °C. The porcelain composites showed satisfactory antibacterial activity on gram negative bacteria Escherichia coli with mortality rates of 45% and 22% for V2O5 and CuO doped porcelain respectively.