Biosynthesis and characterization of Gynocardia odorata R. Br. mediated silver nanoparticles and evaluation of its antimicrobial activity

The present study was designed to synthesize Silver Nanoparticles (Ag-NPs) in aqueous medium using leaf extract of Gynocardia odorata R. Br. (Achariaceae). The synthesized Ag-NPs were characterized using different technique such as UV-Visible Spectroscopy, X-Ray Diffraction (XRD) Spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR) and Transmission Electron Microscopy (TEM). The reduction of Ag ions to initiate nucleation and subsequent Ostwald Ripening to form nanoparticles was made possible by the presence of various antioxidants in the leaves of Gynocardia odorata. These antioxidants served both as reducing and capping agents. The synthesized Ag-NPs were found to be polydispersed in nature and spherical in shape. With the Surface Plasmon Resonance (SPR) optical absorption band peak at ~440 nm was observed using UV-Vis spectrophotometer. FTIR confirmed the presence of methoxy and allyl groups in the synthesized Ag-NPs and nearly 15-45 nm diameter spherical shaped NPs was validated using TEM. The synthesized Ag-NPs were stable for a long period (more than six months) and showed good antibacterial activity against both gram positive and gram negative bacterial strains and the effect was higher as compared to the normal aqueous extract.

Preparation, Structural, Electrochemical and Photocatalytic Studies of Cadmium Sulfide Quantum Dots

We report the preparation, structural, electrochemical and photocatalytic studies of monodispersed cadmium sulphide quantum dots from didecylaminyl dithiocarbamate and 4-chloro-3-(trifluoromethyl) anilinyl dithiocarbamate cadmium(II) complexes. Powder X-ray diffraction pattern confirms hexagonal crystalline phases for the as-preapred CdS quantum dots irrespective of the precursor used with particle size of 3.39-5.51 nm. Optical absorption band edges of 515 nm were observed for the cadmium sulfide quantum dots with energy band gaps estimated from the Tauc plots of 1.97 eV for OLM-CdS1 prepared from Cd(II) didecylaminyl dithiocarbamate and 1.92 eV for OLM-CdS2 prepared from Cd(II) 4-chloro-3-(trifluoromethyl) anilinyl dithiocarbamate. These energy band gaps are blue shifted with respect to the bulk cadmium sulphide. The calculated electrochemical band gap of 2.34 V and 3.30 V are higher than band gap energy. The as-prepared CdS quantum dots were used as photocatalysts for the photocatalytic decomposition of methylene blue (MB) with efficiency of 61 % and 55 %.

A Comparative Study of Different Synthetic Methods of Copper Metal-Organic Frameworks (Cu-MOF)

The metal-organic framework of copper (Cu-MOF) was prepared using the reflux method and microwave method. The results of the two techniques were compared with each other to determine the best method to prepare Cu-MOF. Preparation of Cu-MOF using different techniques has shown that it influences the morphology of the MOF. The results showed that there was a correlation between the two methods. The obtained products were characterized by scanning electron microscopy (SEM), X-ray diffractometry (XRD), Fourier transform infrared (FTIR), thermogravimetric analysis (TGA) and ultraviolet-visible (UV-Vis) spectroscopy. The SEM images showed that the microwave method synthesized particles were cubic while the reflux method produced amorphous material. The XRD spectra showed intense diffraction peaks at 2θ values of 17.61º, 20.47º, 25.34º, 29.59º, 43.01º and their miller indices were (511), (442), (731), (751) and (662), respectively. FTIR results revealed that the materials had functional groups such as (C=O, C-O, O-C=O and Cu-O), UV-visible results showed optical absorption band of Cu-MOF was at 274.18 nm for the microwav and 274.41 nm for the reflux methods. This band could be allocated to the charged transfer from the oxygen in carboxylate to Cu2+ ions.

Spin transition properties of metal (Zn, Mn) diluted Fe(phen)2(NCS)2 spin-crossover thin films

We report here the effect of metal (Zn and Mn) dilution on the spin transition of Fe(phen)2(NCS)2 thin film spin-crossover (SCO) complex. The SCO complexes are deposited on glass and indium-tin-oxide (ITO) coated glass by dip-coating technique. The growth of the films is clearly confirmed by the appearance of the sharp optical absorption band at 521–540 nm corresponding to 1A1g to 1T1g ligand field absorption of the SCO complex. Although the microstructure of the films remains unaffected by metal dilution, substitution of Fe(II) by either Zn(II) (diamagnetic) or Mn(II) (paramagnetic) results in subtle changes in the bonding environment of the host metal as inferred form X-ray diffraction and Raman studies. The high spin to low spin (or vice versa) transition can be triggered either by electric field or magnetic field as revealed in the measured current (I)–voltage (V) profile or magnetization data of the films. The data further shows the effect of metal dilution on the spin transition temperatures(T1/2), produced hysteresis loop width and loop area, which are the crucial parameter for fabricating spin-based room temperature switching devices.

Synthesing and Studying the Structure of Nanoscale Copper (II) Oxide Stabilized by Polyethylene Glycol

We developed a method for synthesising polyethylene glycol-stabilized copper oxide nanoparticles via a sol-gel process, obtained samples and investigated their structure, morphology and properties. We used photon correlation spectroscopy to establish that the copper oxide nanoparticles feature a monomodal size distribution with the average hydrodynamic radius of a particle being approximately 50 nm irrespective of the stabiliser molar mass. We detected an optical absorption band at 290 nm in all samples. We established that copper oxide samples consist of aggregates formed out of spherical nanoparticles whose diameters lie in the range of 10 to 30 nm. Phase composition analysis of the copper oxide samples revealed that the samples consist of particles featuring a monoclinic structure. We simulated the process of polyethylene glycol interacting with the copper oxide. We show that the most energetically favourable interaction model includes bond formation between the neighbouring intramolecular etheric oxygen atoms and the copper atom

MICROWAVE ASSISTED GREEN SYNTHESIS OF SILVER NANOPARTICLES USING COLEUS AMBOINICUS LEAF EXTRACT

Objective: Current study is aimed at the formulation of silver nanoparticles loaded with the extract of Coleus amboinicus leaf extract by microwave irradiation. A facile and green synthesis of silver nanoparticles by using a biological agent such as plant extracts with the aid of microwave irradiation is proposed as an economical and environmentally friendly approach alternative to chemical and physical methods. Methods: In order to fabricate silver nanoparticles by microwave irradiation, aqueous extract of leaves Coleus amboinicus (CA) were treated with aqueous silver nitrate solution and mixture was placed in the microwave oven for exposure to microwave. Optimizations of the process were carried out by varying the quantity of extract, silver nitrate concentration and duration of microwave irradiation. Formations of nanoparticles were confirmed by UV-visible spectroscopy observing for the presence of surface plasmon resonance (SPR) peak. Nanoparticles were characterized by scanning electron microscopy, transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy. Results: Silver nanoparticle showed the SPR optical absorption band peak at 434 nm by UV-Visible spectrophotometer. Reaction mixture containing 2 mmol silver nitrate and 9 ml of extract subjected to microwave irradiation of 60 sec at a temperature of 60 °C was found to be optimised condition, which produced nanoparticles that were spherical in shape and had an average diameter of 15.685 nm. Conclusion: This research study opens an innovative design to progress our understanding of how silver nanoparticles behave can be optimized to improve their surface morphology, which is beneficial to improve its therapeutic effect.

Quantum scale biomimicry of low dimensional growth: An unusual complex amorphous precursor route to TiO2 band confinement by shape adaptive biopolymer-like flexibility for energy applications

Crystallization via an amorphous pathway is often preferred by biologically driven processes enabling living species to better regulate activation energies to crystal formation that are intrinsically linked to shape and size of dynamically evolving morphologies. Templated ordering of 3-dimensional space around amorphous embedded non-equilibrium phases at heterogeneous polymer─metal interfaces signify important routes for the genesis of low-dimensional materials under stress-induced polymer confinement. We report the surface induced catalytic loss of P=O ligands to bond activated aromatization of C−C C=C and Ti=N resulting in confinement of porphyrin-TiO2 within polymer nanocages via particle attachment. Restricted growth nucleation of TiO2 to the quantum scale (≤2 nm) is synthetically assisted by nitrogen, phosphine and hydrocarbon polymer chemistry via self-assembly. Here, the amorphous arrest phase of TiO2 is reminiscent of biogenic amorphous crystal growth patterns and polymer coordination has both a chemical and biomimetic significance arising from quantum scale confinement which is atomically challenging. The relative ease in adaptability of non-equilibrium phases renders host structures more shape compliant to congruent guests increasing the possibility of geometrical confinement. Here, we provide evidence for synthetic biomimicry akin to bio-polymerization mechanisms to steer disorder-to-order transitions via solvent plasticization-like behaviour. This challenges the rationale of quantum driven confinement processes by conventional processes. Further, we show the change in optoelectronic properties under quantum confinement is intrinsically related to size that affects their optical absorption band energy range in DSSC.

Optical Study of the Electronic Structure and Lattice Dynamics of NdBaMn2O6 Single Crystals

We investigated the electronic structure and lattice dynamics of double perovskite NdBaMn2O6 single crystals through spectroscopic ellipsometry and Raman scattering spectroscopy. The optical absorption band centered at approximately 0.88 eV was assigned to on-site d–d transitions in Mn, whereas the optical feature at approximately 4.10 eV was assigned to charge-transfer transitions between the 2p state of O and 3d state of Mn. Analysis of the temperature dependence of the d-d transition indicated anomalies at 290 and 235 K. The activated phonon mode, which appeared at approximately 440 cm−1 alongside with the enhancement of the 270 cm−1 phonon mode, coupled strongly to the metal–insulator transition at 290 K, which was associated with a charge/orbital ordering. Moreover, the MnO6 octahedral breathing mode at 610 cm−1 exhibited softening at a temperature lower than 235 K (temperature of the antiferromagnetic phase transition), which revealed the strong coupling between the lattice and magnetic degrees of freedom. The spin–phonon coupling constant obtained was λ = 2.5 cm−1. These findings highlight the importance of charge–orbital–spin interactions in establishing NdBaMn2O6 phases with novel properties.