Dipankar Halder

Anti-biofilm activity and food packaging application of room temperature solution process based polyethylene glycol capped Ag-ZnO-graphene nanocomposite

Present work reports on synthesis and anti-biofilm activity as well as food packaging application of Ag-ZnO-reduce graphene oxide (rGO)-polyethylene glycol (PEG) (AZGP) nanocomposites via adopting room temperature solution process by varying silver nitrate content (up to 0.1 M) with fixed content of graphene oxide and PEG used in the precursors. Presence of Ag and ZnO nanoparticles (NPs) distributed uniformly over rGO nanosheets has been confirmed by X-ray diffraction and transmission electron microscopic analyses whereas FTIR, Raman, UV-Visible and X-ray photoelectron spectral studies have been performed to confirm the existence of chemical interaction/complexation that happened between the available oxygen functionalities of rGO and PEG with the inorganic moieties (Ag-ZnO/Zn2+) of AZGP samples. A formation mechanism of AZGP nanocomposite is proposed based on the experimental results. Anti-biofilm activity has been studied on Staphylococcus aureus and Pseudomonas aeruginosa bacteria to confirm the efficiency of the nanocomposites for killing the bacterial cells. It is found that 0.05 M silver nitrate based AZGP nanocomposite at 31.25 μg/mL sample dosage shows about 95% inhibition activity towards the biofilm formation as well as eradication of preformed biofilm. Also, agar based AZGP film has been fabricated and characterized by X-ray diffraction study for the purpose of food packaging application. Textural analysis of agar based film shows an enhanced film tensile strength. The film also shows an excellent antimicrobial activity even after keeping it for a prolong period of about 90 days. This cost effective simple synthesis strategy can make an avenue for development of Ag incorporated other biocompatible metal oxide based rGO-PEG nanocomposites for potential food packaging application.

Fruit extract capped colloidal silver nanoparticles and their application in reduction of methylene blue dye

Abstract Green synthesis of silver nanoparticles (AgNPs) has become a promising environmentally benign synthetic route in nanoscience and nanotechnology during recent years. In the present work, we have developed an environment-friendly and low-cost method for synthesis of silver nanoparticles from silver nitrate using aqueous fruit extract of Dillenia indica. The as-synthesized nanoparticles were characterized by UV-Vis spectrophotometer, transmission electron microscopy (TEM) and X-ray diffraction (XRD). FTIR study was performed to know the interaction of bio-molecules present in the fruit extract with AgNPs. The catalytic application of the as-synthesized AgNPs was demonstrated against degradation of methylene blue (MB) in aqueous system. The absorption spectra of colloidal suspension of AgNPs showed characteristic surface plasmon resonance (SPR) band centred at a wavelength of 416 nm. TEM image showed that the AgNPs were almost spherical in shape having an average diameter of 10.78 ± .48 nm. XRD pattern and selected area electron diffraction (SAED) pattern with bright spots signify the crystalline nature of nanoparticles. The fruit extract-capped AgNPs was highly stable and have showed the effective catalytic activity in reduction of MB dye.

Catalytic and antibacterial activity of copper nanoparticle-starch composite

We report the successful synthesis of copper nanoparticle (CuNP)-starch composite employing low cost green protocol without inert gas protection. UV-Vis spectroscopy, X-Ray diffraction (XRD) and Transmission electron microscopy (TEM) were used to characterize the CuNP-starch composite. Mono-disperse almost spherical CuNP having average diameter 4.02 ± 0.076 nm was obtained. The catalytic activity of the as-synthesized CuNP-starch composite during reduction of pollutants, like, 4-nitrophenol (4-NP) and dyes, Eosine Blue (EB), Eriochrome Black T (EBT) and Brilliant Cresyl Blue (BCB by NaBH4 has been investigated. High catalytic efficiency of the composite was demonstrated by rapid decrease of the intensity of the UV-Vis absorption peaks at respective λmax of the pollutants with time when reaction mixture contained NaBH4 and small quantity of CuNP-starch composite. The rate constant of each processes was calculated by considering that the reactions follow pseudo-first-order kinetics with respect to substrate. The obtained rate constants for 4-NP, EB, EBT and BCB are 0.021S -1 , 0.011S -1 , 0.036S -1 and 0.032S -1 respectively. The other application, antibacterial activity was tested against Gm positive and Gm negative bacteria. Plate count and minimum inhibitory concentration (MIC) studies show higher susceptibility of Gm positive bacteria towards CuNP-starch composite. The as-synthesized CuNP-starch composite may find potential application in the field of environmental remedies and antibacterial formulations. Copyright©2018 VBRI Press.

Study of the antibacterial and catalytic activity of silver colloids synthesized using the fruit of Sapindus mukorossi

Green synthesis of silver nanoparticles has been demonstrated using an aqueous extract of the pericarp of Sapindus mukorossi fruit as a reducing agent as well as a stabilizer. The reducing power of the extract has been evaluated by Cyclic Voltammetry (CV) experiments. The as-synthesized colloid is highly stable and the particles remain dispersed even after one year of storage. The existence of metallic silver nanoparticles was confirmed by UV-Vis spectroscopy and selected area electron diffraction (SAED) patterns obtained from high resolution transmission electron microscopic (HRTEM) analysis. TEM study shows that the particles are almost spherical with an average diameter of 3.32 ± 0.58 nm. The as-synthesized silver colloid (Ag-colloid) exhibits antibacterial activity against Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. The catalytic efficiency of the Ag-colloid has also been evaluated and reported in terms of the catalytic activity parameter (κ) and turn over frequency (TOF) against the degradation of the common environmental pollutants 4-nitro phenol and Eosin blue.