S. V. N. Pammi

Green synthesis, characterization and antimicrobial activity of silver nanoparticles using methanolic root extracts of Diospyros sylvatica

The current research study focuses to formulate the biosynthesized silver nanoparticles for the first time from silver acetate using methanolic root extracts of Diospyros sylvatica, a member of family Ebenaceae. TEM analysis revealed the average diameter of Ag NPs around 8nm which is in good agreement with the average crystallite size (10nm) calculated from X-ray Diffraction (XRD) analysis. Further the study has been extended to the antimicrobial activity against test pathogenic Gram (+) ve, Gram (-) ve bacterial and fungal strains. The bioinspired Ag-NP showed promising activity against all the tested bacterial strains and the activity was enhanced with increased dosage levels.

Low-Temperature Nanocluster Deposition (NCD) for Improvement of the Structural, Electrical, and Optical Properties of ITO Thin Films

Indium tin oxide (ITO) thin films were grown using nanocluster deposition (NCD) on glass substrates in low temperature range from 170 to 250°C. X-ray diffraction pattern revealed that ITO thin films deposited above 200°C were preferentially oriented along (1 1 1) direction. A dramatic change in electrical properties of ITO thin films deposited from 200 to 170°C was attributed to the change in microstructure and chemical bonding states. The ITO thin films deposited at 170°C exhibited semiconducting properties with high optical transmittance of 95% at 550-nm wavelength. Films of approximately 140 ± 5 nm thicknesses exhibited both the lowest resistivity of 7 × 10^-4 Ω·cm and the figure-of-merit value of 1.3 × 10^-2 Ω^-1. The NCD technique is possible for deposition of ITO films crystallized at low temperatures below 200°C on glass or flexible polymer substrates.

Self-catalytic growth of indium oxide flower-like nanostructures by nano-cluster deposition (NCD) at low temperature

Flower-shaped indium oxide nanostructures were grown at a low temperature (250 °C) on Si (100) substrates by NCD technique without using metal catalyst. Bud shaped leaf like structures are obtained with lengths and diameters in the range of 150–250 nm and 75–125 nm, respectively, which are compacted into a flower-shaped structure. Transmission electron microscopy and selected area electron diffraction patterns taken on the leaf-like structure show crystalline cubic phase, with preferential orientation along (222) and (400) directions. The composition of indium and oxygen was confirmed from XPS analysis. The room temperature photoluminescence (PL) spectrum of flower-like In2O3 nanostructure shows a blue emission centered around 428 nm under the 383 nm UV excitation, which is mainly attributed to the oxygen vacancy in the In2O3 nano/microstructures. A growth model for the formation mechanism of the self-catalytic growth of flower shaped structure is proposed.

Enhanced thermoelectric properties of flexible Cu2−xSe (x ≥ 0.25) NW/polyvinylidene fluoride composite films fabricated via simple mechanical pressing

We report the fabrication of Cu2−xSe NW-polyvinylidene fluoride (PVDF) composite flexible thin films using various approaches such as simple drop casting (DC), vacuum filtration (VF), and vacuum filtration followed by mechanical pressing (VFMP). The highest power factor of Cu2−xSe NW-PVDF composite films reached 105.32 μW m−1 K−2 when mechanical pressing was performed following vacuum filtration at 303 K, and this was further enhanced to 253.49 μW m−1 K−2 at 393 K. Cu2−xSe NW-PVDF composite films fabricated via vacuum filtration without mechanical pressing showed a reasonable power factor (<40 μW m−1 K−2 at room temperature), whereas films fabricated via the drop casting method showed a poor power factor (<10μW m−1 K−2 at room temperature). VFMP-treated Cu2−xSe NW-PVDF thermoelectric films showed good mechanical durability until 1000 bending cycles without significant performance degradation. When all these results are considered, the fabricated composite films could be a feasible option for p-type thermoelectric materials in thermoelectric power generators.

Ultra Small, mono dispersed green synthesized silver nanoparticles using aqueous extract of Sida cordifolia plant and investigation of antibacterial activity

The present study is focused on the synthesis of silver nano particles (Ag NPs) using an aqueous extract of the whole plant of Sida cordifolia as a potential bio-reducing agent and assessment of their antibacterial activity. UV-Vis spectroscopy of composed silver colloidal solution displayed surface Plasmon resonance peak at 420 nm. XRD and TEM analysis revealed the morphology as ultra-small, monodispersed spherical nanoparticles with face-centered cubic structure and mean particle size of 3-6 nm. This ultra-small nano size might owe to the slow reaction time and phytochemicals existing in the S. cordifolia extract. The Ag NPs are trailed for antibacterial activity against 5 fish (Aeromonas hydrophila, Pseudomonas fluorescence, Flavobacterium branchiophilum, Edwardsiella tarda and Yersinia rukeri) and 4 human (Escherichia coli, Klebsiella pneumonia, Bacillus subtilis and Staphyloccocus aureus) bacterial pathogens. In all the cases, Ag NPs from Sida cordifolia plant extract manifested noteworthy antibacterial effects on par with positive control i.e.; Gentamicin.

Self-powered pressure and light sensitive bimodal sensors based on long-term stable piezo-photoelectric MAPbI3 thin films

Chemical vapor deposited CH3NH3PbI3 (MAPbI3) thin films showed a long-term stability of approximately one month after exposure to air at room temperature. Self-powered sensors using 500 nm-thick MAPbI3 films were demonstrated for pressure and light sensitive bimodal sensor applications. The generated output voltage was attributed to an intrinsic piezoelectric property of the MAPbI3 films and their sensitivities for sensors were approximately 8.34 mV kPa−1 and 0.02 nA kPa−1. The output current generated in the release mode showed a strong dependence on the light power irrespective of the applied pressure, revealing the light-sensitive effect of the MAPbI3 films. The response time of bimodal sensors for applied pressure and light power was approximately 0.066 and 0.320 s at an applied pressure of 30 kPa, respectively. The CVD-MAPbI3 films have attracted attention for simultaneous realization of both pressure and light sensitive bimodal sensor applications.

Enhanced wound healing activity of Ag-ZnO composite nanoparticles in Wistar Albino rats

In the present study, silver (Ag) and Ag-zinc oxide (ZnO) composite nanoparticles (NPs) were synthesised and studied their wound-healing efficacy on rat model. Ultraviolet-visible spectroscopy of AgNPs displayed an intense surface plasmon (SP) resonance absorption at 450 nm. After the addition of aqueous Zn acetate solution, SP resonance band has shown at 413.2 nm indicating a distinct blue shift of about 37 nm. X-ray diffraction analysis Ag-ZnO composite NPs displayed existence of two mixed sets of diffraction peaks, i.e. both Ag and ZnO, whereas AgNPs exhibited face-centred cubic structures of metallic Ag. Scanning electron microscope (EM) and transmission EM analyses of Ag-ZnO composite NPs revealed the morphology to be monodispersed hexagonal and quasi-hexagonal NPs with distribution of particle size of 20-40 nm. Furthermore, the authors investigated the wound-healing properties of Ag-ZnO composite NPs in an animal model and found that rapid healing within 10 days when compared with pure AgNPs and standard drug dermazin.

Giant figure of merit (ZT) of Ge 2 Sb 2 Te 5 thin films through the control of crystal structure

300nm-thick Ge2Sb2Te5 Thin Films were prepared using RF sputtering with different deposition temperatures. Thermoelectric properties of GST thin films were measured at room temperature including the Seebeck coefficient, the electrical conductivity and thermal conductivity. The highest power factor (1.1 × 10-3 W/K2m) was shown in the GST film deposited at 250°C, which has the mixture phases of FCC and HCP structure. And the moderate degree of electrical conductivity and the Seebeck coefficient in the GST film deposited at 250°C lead to the highest ZT value of nearly 2.0. In order to explain giant ZT value, the crystal structure, the electrical parameters and the chemical composition were investigated.