Tuneable luminescence properties of EDTA-assisted ZnS:Mn nanocrystals from a yellow-orange to a red emission band.

Luminescence technology has been improved with the help of semiconductor nanoparticles that possess novel optical and electrical properties compared with their bulk counterpart. The aim of this study was to design semiconductor nanocrystals in their pure (ZnS) or doped form (ZnS:Mn) with different concentrations of Mn2+ ions by a wet chemical route stabilized by ethylenediamine tetra-acetic acid (EDTA) and to evaluate their luminescence properties. The nanocrystals were characterized by physicochemical techniques such as X-ray diffraction (XRD), High-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SEAD), EDS, and ultraviolet (UV)-visible light and photoluminescence (PL) studies. These results showed the presence of cubic phase and spherically shaped nanocrystals. A blue shift with respect to their bulk counterpart was observed. PL emission spectra were observed with a fixed blue peak and the yellow-orange bands were red shifted towards the red region under the same excitation wavelength. The orange-red bands were attributed to the radiation transition of electrons in 3d5 unfilled shells of Mn2+ ions [4 T1 (4 G)-6 A1 (6 S)]; the ZnS matrix varied with Mn2+ concentration. Shift and increase in the intensity of the PL and absorption bands were observed with increase in Mn content. The study showed that Mn2+ -doped ZnS nanocrystal emission bands can be tuned from the yellow-orange to the red regions under a controlled synthesis process and could be used as promising luminescent emitters in the biology field upon functionalization with suitable materials. Further studies on construction with various other materials will be useful for practical applications.

Synthesis of Carbon Nanospheres Through Carbonization of Areca nut.

We demonstrate a bio-inspired one-pot synthesis of carbon nanospheres with micro-porosity achieved from a promising carbon-rich source (Areca nut) using direct pyrolysis in nitrogen atmosphere at 550 °C in a tube-furnace without adding any catalysts. The resultant carbon spheres are highly monodispersed, uniformly shaped and possess good absorption behaviour (10.5 mg · g−1) for methylene blue (MB).

Biosynthesis of silver nanoparticles using pre-hydrolysis liquor of Eucalyptus wood and its effective antimicrobial activity.

Herein, we described for the first time, biosynthesis of silver nanoparticles (AgNPs) using pre-hydrolyzed liquor of Eucalyptus wood under ambient conditions. The pre-hydrolyzed liquor containing a high amount of metabolites such as polyphenols, hemicelluloses and its derivatives are mainly assisted for the reduction and stabilization process of Ag+ ions to AgNPs. The formation of AgNPs is monitored by recording the UV-vis spectrophotometer for surface plasmon resonance (SPR) peak observed at ∼415nm. The intensity of SPR increased linearly with increasing the reaction time at ambient condition. X-ray diffraction (XRD) pattern of AgNPs reveals the formation of face-centered cubic structure. Field emission electron microscopy (FESEM) and transmission electron microscopy (TEM) images show the spherical shaped particles and narrow size distribution with an average diameter of 25-30nm. The elemental analysis by energy dispersive X-ray (EDAX) analysis confirms the presence of Ag as the major amount and is found to be 82%. Analysis of the fourier transform infrared (FT-IR) spectra of the NPs revealed the presence of phytoconstituents from pre-hydrolyzed liquor adsorbed on the surface of AgNPs. Moreover, in vitro, antimicrobial activity is found to be effective for as-synthesized AgNPs on tested bacteria (viz., P. aeruginosa, S. aureus and E. coli) followed by fungus (C. oxysporum, P. chrysogenum, C. albicans and A.niger). Thus, these results suggest the use of biosynthesized AgNPs as effective growth inhibitors for various biomedical applications.

A facile and green strategy for the synthesis of Au, Ag and Au-Ag alloy nanoparticles using aerial parts of R. hypocrateriformis extract and their biological evaluation.

A facile and green strategy is reported here to synthesize gold (Au), silver (Ag) and gold-silver (Au-Ag) alloy nanoparticles (NPs) through bio-reduction reactions of aqueous corresponding metal precursors mediated by extracts of aerial parts of R. hypocrateriformis, which act as both reducing and stabilizing agents, under microwave irradiation. UV-vis spectrophotometer, XRD, FT-IR, FESEM/TEM, TGA and EDAX analysis were used to characterize the obtained NPs. The formation of NPs is evident from their surface plasmon resonance peak observed at λmax=∼550, 450 and 500nm for Au, Ag and Au-Ag alloy NPs respectively. XRD pattern revealed that fcc structure, while FT-IR spectra signify the presence of phytochemicals adsorbed on NPs. Such a biofunctionalized NPs were characterized by their weight loss, 30% due to thermal degradation of plant phytochemicals observed in TG analysis. The spherical shape of Au, Ag and Au-Ag alloy NPs (∼10-50nm) is observed by FE-SEM/TEM images. EDAX analysis confirms the expected elemental composition. Moreover, these NPs showed enhanced antimicrobial, antioxidant, and anticancer activities, though it is more pronounced for Au-Ag alloy NPs, which is due to the combining effect of phytochemicals, Au and Ag metals. Thus, the biosynthesized NPs could be applied as effective growth inhibitors for various biomedical applications.

Development and validation of reverse phase high performance liquid chromatography for citral analysis from essential oils.

Citral is a widely used monoterpene aldehyde in aromatherapy, food and pesticide industries. A new validated reverse phase high performance liquid chromatography (RP - HPLC) procedure for the detection and quantification of cis-trans isomers of citral was developed. The RP-HPLC analysis was carried out using Enable C - 18G column (250×4.6mm, 5µ), with acetonitrile and water (70: 30) mobile phase in isocratic mode at 1mL/min flow. A photodiode array (PDA) detector was set at 233nm for the detection of citral. The method showed linearity, selectivity and accuracy for citral in the range of 3-100µg/mL. In order to compare the new RP-HPLC method with the available methods, one of the commercially available essential oil from Cymbopogon flexuosus was analyzed using new RP-HPLC method and the same was analyzed using GC-MS for the comparison of the method for the detection of citral. The GC-MS analysis was done using mass selective detector (MSD) showed citral content to be of 72.76%; wherein the new method showed to contain that same at 74.98%. To prove the application of the new method, essential oils were extracted from lemongrass, lemon leaves and mosambi peels by steam distillation. The citral content present in the essential and also in the condensate was analyzed. The method was found to be suitable for the analysis of citral in essential oils and water based citral formulations with a very good resolution of its components geranial and neral.

Phytochemically Functionalized Cu and Ag Nanoparticles Embedded in MWCNTs for Enhanced Antimicrobial and Anticancer Properties.

Nanomedicine is an emerging field concerned with the use of precision engineered nanomaterials, which leads to the development of novel remedial and diagnostic modalities for human use. In this study, Cu(NO3)2 and AgNO3 precursors were reduced to copper nanoparticles (CuNPs) and silver nanoparticles (AgNPs) using Terminalia arjuna bark extracts under microwave irradiation in the presence of well-dispersed multi-walled carbon nanotubes (MWCNTs) in aqueous medium. The formation of CuNPs or AgNPs and their functionalization with MWCNTs via bioactive molecules of plant extract were evidenced from UV-Vis spectra, XRD, FTIR, FESEM, EDX, and TEM images. The phytochemically functionalized Cu-MWCNTs and Ag-MWCNTs nanomaterials showed enhanced biocide activity, and the inhibitory activity for bacteria was higher than that of fungus. Furthermore, these biohybrid nanomaterials are non-toxic to normal epithelial cells (Vero), whereas they are highly toxic for tested human cancer cells of MDA-MB-231, HeLa, SiHa, and Hep-G2. The cell viability was found to decrease with the increasing dose from 10 to 50 µg mL-1, as well as incubation time from 24 to 72 h. For instance, the cell viability was found to be ~91 % for normal Vero cells and ~76 % for cancer cells for lower dose of 10 µg mL-1.

Phytosynthesis of gold nanoparticles using Mappia foetida leaves extract and their conjugation with folic acid for delivery of doxorubicin to cancer cells.

Mappia foetida leaves extract is used as bioreductant for the synthesis of gold nanoparticles and their application in the efficient delivery of doxorubicin to human cancer cells is reported here. The formation of gold nanoparticles is evident from their characteristic optical absorption at ~560 nm. X-ray diffraction pattern of gold nanoparticles confirmed their fcc structure. Fourier transform infrared spectroscopy shows the bioactive molecules from plant extract capped on the surface of gold nanoparticles and conjugation of doxorubicin along with activated folic acid as navigational molecules for targeted drug delivery. Such a conjugation of gold nanoparticles is characterized by their weight loss, ~35-40 %, due to thermal degradation of plant biomass and conjugated drug along with receptor, as observed in thermogravimetric analysis. The spherical shaped gold nanoparticles (Φ 10-20 nm) are observed by field emission scanning electron microscopy and transmission electron microscopy images and the expected elemental composition by energy dispersive X-ray spectroscopy. Gold nanoparticles conjugated with activated folic acid and doxorubicin complex is found to be toxic for human cancer cells viz., MDA-MB-231, HeLa, SiHa and Hep-G2. Furthermore, the amount of drug released was maximum at pH 5.3 (an ambient condition for intravenous cancer drugs) followed by pH 7.2 and pH 6.8.

Phytosynthesis of stable Au, Ag and Au-Ag alloy nanoparticles using J. sambac leaves extract, and their enhanced antimicrobial activity in presence of organic antimicrobials.

A green chemistry approach for the synthesis of Au, Ag and Au-Ag alloy nanoparticles (NPs) using the corresponding metal precursors and Jasminum sambac leaves extract as both reducing and capping media, under microwave irradiation, is reported. During the formation, as expected, the reaction mixture shows marginal decrease in pH and an increase in solution potential. The formation of NPs is evident from their surface plasmon resonance (SPR) peak observed at ∼555 nm for Au, ∼435 nm for Ag and ∼510 nm for Au-Ag alloy. The XRD pattern shows fcc structure while the FTIR spectra indicate the presence of plant residues adsorbed on these NPs. Such a bio-capping of NPs is characterized by their weight loss, ∼35% due to thermal degradation of biomass, as observed in TG analysis. The colloidal dispersion of NPs is stable for about 6 weeks. The near spherical shape of NPs (ϕ20-50 nm) is observed by FE-SEM/TEM images and EDAX gives the expected elemental composition. Furthermore, these NPs showed enhanced antimicrobial activity (∼1-4-fold increase in zone of inhibition) in combination with antimicrobials against test strains. Thus, the phytosynthesized NPs could be used as effective growth inhibitors for various microorganisms.

Microwave assisted rapid synthesis and biological evaluation of stable copper nanoparticles using T. arjuna bark extract.

Terminalia arjuna (T. arjuna) bark extract is used to reduce Cu(2+)→Cu(0) under microwave irradiation. The formation of copper nanoparticles (CuNPs) is monitored by recording the UV-Vis absorption spectra for surface plasmon resonance (SPR) peak, ~535 nm. The intensity of SPR increased linearly with increasing temperature of the reaction mixture. The formation mechanism of CuNPs is supported by the observed marginal decrease in pH and an increase in solution potential (E) of the reaction mixture. X-ray diffraction (XRD) pattern of the CuNPs agrees with the reported data for Cu metal and the crystallite size is ~23 nm. Fourier transform infrared spectroscopy (FT-IR) and solid-state (13)C NMR shows the presence of plant residues on the CuNPs, i.e., in situ bio-capping is possible by this method. Thermo gravimetric (TG) analysis shows the thermal degradation of plant residue and the conversion of Cu to CuO. Field emission electron microscopic (FESEM) image shows uniform spherical particles obtained here. Elemental analysis by energy dispersive X-ray (EDX) analysis confirms the presence of Cu alone, as expected. The in vitro antimicrobial activity is found to be effective for CuNPs dried at RT when compared to CuNPs dried at 70 °C. In addition, CuNPs shows very good antioxidant property.