Study on luminescence properties of Ce3+ and Eu3+ ions in a nanocrystalline hexagonal Zn4Al22O37 novel system

The present communication is strongly focused on the investigation of synthesis, structural and luminescence properties of cerium (Ce³⁺)- and europium (Eu³⁺)-activated Zn₄Al₂₂O₃₇ phosphors. Ce³⁺- and Eu³⁺-doped Zn₄Al₂₂O₃₇ novel phosphors were prepared using a solution combustion synthesis route. Structural properties were studied using powder X-ray diffraction and high-resolution transverse electron microscopy. The optical properties were studied using ultraviolet–visible light spectroscopy and Fourier transform infrared spectroscopy; luminescence properties were studied using a photoluminescence (PL) technique. The crystal structure of the prepared Zn₄Al₂₂O₃₇ host and Ce³⁺- and Eu³⁺-activated Zn₄Al₂₂O₃₇ phosphors was investigated and was found to have a hexagonal structure. The measured PL emission spectrum of the Ce³⁺-doped Zn₄Al₂₂O₃₇ phosphor showed an intense and broad emission band centred at 421 nm under a 298 nm excitation wavelength. By contrast, the Eu³⁺-doped Zn₄Al₂₂O₃₇ phosphor exhibited two strong and intense emission bands at approximately 594 nm (orange) and 614 nm (red), which were monitored under 395 nm excitation. The Commission Internationale de l’Eclairage (CIE) colour coordinates of the Ce³⁺-doped Zn₄Al₂₂O₃₇ were investigated and found to be x = 0.1567, y = 0.0637 (blue) at 421 nm and for Eu³⁺-doped Zn₄Al₂₂O₃₇ were x = 0.6018, y = 0.3976 (orange) at 594 nm and x = 0.6779, y = 0.3219 (red) at 614 nm emission. The luminescence behaviour of the synthesized phosphors suggested that these phosphors may be used in lighting applications.     

Bio-reduction of hexachloroplatinic acid to platinum nanoparticles employing Acinetobacter calcoaceticus

Acinetobacter calcoaceticus PUCM 1011 efficiently synthesized platinum nanoparticles (PtNP) of size 2–3 nm intracellularly when challenged with hexachloroplatinic acid. Salt concentration (1 mM), temperature (30 °C), pH (7) and incubation period (72 h) influenced the efficiency of monodisperse cuboidal PtNP synthesis. Resolution of ordered lattice fringes with “d” value of 0.23 nm corresponding to (1 1 1) plane and EDAX confirmed presence of metallic platinum. AFM, TEM and HR-TEM confirmed synthesis of PtNP and its effect on cell viability. Total cell protein profile for 120 h with an interval of 24 h after PtNP synthesis revealed prominent four protein bands (97, 66, 43 and 29 kDa) when compared to control. Combinations of three proteins initiated PtNP synthesis within 4 h in range of 1–4 nm and few in picometers under HR-TEM. This is the first report of PtNP synthesis employing whole cell and total cell protein of A. calcoaceticus.     

Structural characterization,antioxidant and anticancer properties of gold nanoparticles synthesized from leaf extract (decoction) of Antigonon leptopus Hook. & Arn.

Tea is an aromatic beverage prepared by pouring boiling water over alleviated leaves of the tea plant. Tea prepared from the aerial parts of Antigonon leptopus has been traditionally used as remedy for cold, diabetes and pain in many countries. The gold nanoparticles (Au NPs) synthesized from powdered leaf extract (decoction) of A. leptopus were characterized by UV–visible spectroscopy (UV–vis), X-ray diffraction (XRD), Fourier transform-infrared (FT-IR), high resolution transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED) pattern and energy dispersive X-ray (EDX) analyses to define the formation of Au NPs. Further, the synthesized Au NPs were well characterized based on their strong surface plasmon resonance (SPR), crystalline nature, functional groups, size and dispersed shapes, purity and Bragg's reflections of face centered cubic (fcc) structure of metallic gold. The Au NPs showed higher free radical scavenging property when compared to the effect of leaf extract. Cytotoxicity study of synthesized Au NPs exhibited the growth inhibitory property at the concentration (GI₅₀) of 257.8 μg/mL in human adenocarcinoma breast cancer (MCF-7) cells after 48 h. Thus, the Au NPs synthesized from the Mexican creeper, A. leptopus revealed the important biological properties: as a free radical as well as anticancer agent. We conclude that the A. leptopus derived biological materials have promising potential as a source for the development of anticancer drug in future.     

Synthesis of copper nanoclusters from Bacopa monnieri leaves for fluorescence sensing of dichlorvos

In this work, a facile one-step green synthesis was developed for the fabrication of blue fluorescent copper nanocluster (Brahmi-CuNCs) from the extract of Bacopa monnieri (common name is Brahmi) via a microwave method. The as-prepared Brahmi-CuNCs emitted blue fluorescence at 452 nm when excited at 352 nm and showed a quantum yield of 31.32%. Brahmi-derived blue fluorescent CuNCs acted as a probe for fluorescence sensing of dichlorvos. Upon the addition of dichlorvos, the blue emission for Brahmi-CuNCs was gradually turned off, favouring establishment of a calibration graph in the range 0.5–100 μM with a detection limit of 0.23 μM. The as-synthesized Brahmi-CuNCs exhibited marked sensitivity and selectivity towards dichlorvos, favourable for assaying dichlorvos in various samples (cabbage, apple juice, and rice).     

Microwave-assisted synthesis of blue fluorescent molybdenum nanoclusters with maltose-cysteine Schiff base for detection of myoglobin and γ-aminobutyric acid in biofluids

The fabrication of stable fluorescent MoNCs (molybdenum nanoclusters) in aqueous media is quite challenging as it is not much explored yet. Herein, we report a facile and efficient strategy for fabricating MoNCs using 2,3 dialdehyde maltose-cysteine Schiff base (DAM-cysteine) as a ligand for detecting myoglobin and γ-aminobutyric acid (GABA) in biofluids with high selectivity and sensitivity. The DAM-cysteine-MoNCs displayed fluorescence of bright blue color under a UV light at 365 nm with an emission peak at 444 nm after excitation at 370 nm. The synthesized DAM-cysteine-MoNCs were homogeneously distributed with a mean size of 2.01 ± 0.98 nm as confirmed by the high-resolution transmission electron microscopy (HR-TEM). Further, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) techniques were utilized to confirm the elemental oxidation states and surface functional groups of the DAM-cysteine-MoNCs. After the addition of myoglobin and GABA, the emission peak of DAM-cysteine-MoNCs at 444 nm was significantly quenched. This resulted in the development of a quantitative assay for the detection of myoglobin (0.1–0.5 μM) and GABA (0.125–2.5 μM) with the lower limit of detection as 56.48 and 112.75 nM for myoglobin and GABA, respectively.