Nanoparticles are increasingly being recognized for their potential utility in biological applications including nanomedicine. Here, we have synthesized zinc oxide (ZnO) nanorods using zinc acetate and hexamethylenetetramine as precursors followed by characterizing using X-ray diffraction, fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. The growth of synthesized zinc oxide nanorods was found to be very close to its hexagonal nature, which is confirmed by X-ray diffraction. The nanorod was grown perpendicular to the long-axis and grew along the [001] direction, which is the nature of ZnO growth. The morphology of synthesized ZnO nanorods from the individual crystalline nucleus was confirmed by scanning and transmission electron microscopy. The length of the nanorod was estimated to be around 21 nm in diameter and 50 nm in length. Our toxicology studies showed that synthesized ZnO nanorods exposure on hela cells has no significant induction of oxidative stress or cell death even in higher concentration (10 μg/ml). The results suggest that ZnO nanorods might be a safer nanomaterial for biological applications.Keywords: Zinc oxide [ZnO]; Nanorods; XRD; SEM & TEM; Cytotoxicity Citation: R. Gopikrishnan, K. Zhang, P. Ravichandran, S. Baluchamy, V. Ramesh, S. Biradar, P. Ramesh, J. Pradhan, J. C. Hall, A. K. Pradhan and G. T. Ramesh, "Synthesis, characterization and biocompatibility studies of zinc oxide (ZnO) nanorods for biomedical application", Nano-Micro Lett. 2, 31-36 (2010). doi: 10.5101/nml.v2i1.p31-36 Nanotechnology has extraordinary potential to change our lives by improving existing products and enabling new ones. It facilitates the development of new materials in the 1a100 nm range, comparable to the size range of biological molecules and structures [1]. Nanomaterials are very attractive materials for the manipulation, sensing and detection of biological structures and systems [2]. The principal factors which make nanomaterials different from their bulk counterparts include an increase in their relative surface area and quantum effects, which affect their physical and chemical properties [2]. This is due to the large surface area-to-volume ratio of nanoparticles, which increases surface free energy to a point that is comparable to their lattice energy. For example, a particle of 30 nm size has 5% of its atoms on its surface compared to 50% of the atoms on the surface of a 3 nm particle [3]. The altered properties of nanomaterials, and their size similarity to naturally occurring cell structures, will allow them to interact readily with bio molecules and potentially affect the cellular responses in a dynamic and selective manner. Materials that exploit these characteristics are becoming increasingly attractive for use in novel biomedical applications.Nano structured materials exhibit unique properties related to their size, and are used in an array of applications such as optoelectronics, nano/microelectronics, sensors, transducers, cosmetics as w...

Photoluminescence of halide perovskite nanocrystals (NCs) quenches rapidly due to ambient instability, inherent trap states, and imperfect ligand–NC passivation. We report a novel synthetic strategy to enhance the stability and eliminate trap states of CsPbBr3 NCs simultaneously by in situ introduction of a tripodal tertiary ammonium bromide ion pair ligand [tris­(2-aminoethyl)­ammonium bromide (TREN·4HBr)]. Tetrabromide ions saturate the PbBr6 octahedra of CsPbBr3 NCs to eliminate the anion vacancies, while TREN with three NH3 + branches enhances efficient encapsulation. TREN·4HBr binds strongly to prevent proton transfer that leads to a facile ligand loss from the NCs surfaces. Ultrafast femtosecond transient absorption kinetics reveals the removal of shallow trap states in the CsPbBr3 NCs leading to a faster carrier recombination to enhance the photoluminescence quantum yield (PLQY). We validate the enhancement in the PLQY by designing light-emitting diodes with an external quantum efficiency of 3.4%. Our work unveils a mechanism for rational improvements of stability and PLQY of CsPbBr3 NCs simultaneously.

Two-dimensional (2D) materials with downscaled thicknesses are the quest of the electronics industry because of their immense potential in modern microelectronics. Despite the discovery of several novel 2D materials, the flexible design of highperformance free-standing ultrathin 2D dielectric nanocrystals (NCs) with a large planar morphology remains the most challenging task. We develop a method for synthesizing high-quality free-standing ultrathin 2D NCs of PbS with a well-defined large rectangular morphology with a thickness of ∼2 nm. The lateral size can be tuned up to a few hundred nanometers by changing only the reaction annealing time. Microscopic and spectroscopic analyses at different stages of the reaction reveal formation of 2D NCs by a continuous growth mechanism. The 2D NCs exhibit a nearly temperature and frequency independent high dielectric constant (>13.4) with a small dielectric loss (0.0006 at 20 K and <0.06 at 350 K for 100 kHz) over broad temperature and frequency ranges. Low-frequency dispersion from 125 Hz to 1 MHz, frequency stability with a small dielectric loss (<0.03 at 100 kHz), and a stable temperature coefficient of the dielectric constant outline the merits of 2D NCs as a potential dielectric material. Complex impedance analyses demonstrate dominant intrinsic effects contributed by polarons in covalent NCs. Equal activation energies for the conduction and relaxation processes offer uniform energy barriers for the charges in NCs leading to high-performance dielectric behavior. This work opens up promising features of non-oxide binary semiconductors as dielectric alternatives for miniaturized electronics using flexible solution processing routes.

Direct conversion of preprocessed binary semiconductor NCs as template holds the key toward the shape control of hybrid perovskites. Here we report on an innovative route for realizing shape-controlled hybrid organohalide perovskite NCs from two-dimensional PbS NCs on solid substrates. Rectangular PbI 2 NCs are first synthesized by iodination of PbS NCs. Resultant PbI 2 NCs are subsequently transformed into the well-defined rectangular hybrid perovskite NCs upon controlled CH 3 NH 3 Br exposure. Structural analyses using X-ray absorption fine structure reveal transition of cubic lattice of PbS to hybrid perovskites with a mixture of cubic and tetragonal phases exhibiting a bimodal distribution of shorter Pb−Br and longer Pb−I bonds around an immediate neighboring lead absorber within the first coordination shell. This direct all anion exchange reaction route opens up new strategies for the fabrication of shape-controlled perovskite NCs on flexible substrates from suitable existing binary NCs as template for optoelectronic applications.

Self-trapping of excitons (STE) and concomitant useful broadband emission in the low-dimensional metal halides occur due to strong electron-phonon coupling, which exhibit potential applications in optoelectronics and solid-state lighting. Lattice...