A simple strategy for quantum dot assisted selective detection of cadmium ions

Here we report a simple strategy for selective detection of cadmium ions by manipulating the electron transfer pathways of surface-engineered quantum dots.     

Spectroscopic and structural signature of the CH-O hydrogen bond

It has been observed that the vibrational stretching frequency of a C-H covalent bond commonly shifts to the blue and suffers intensity loss, when the CH engages in a hydrogen bond. However, the shift does not always occur in this direction, and there are cases when a CH blue shift may be present even in the absence of a CH...O interaction. Ab initio quantum calculations are used to analyze the structure, and vibrational and NMR spectra of small model systems containing both conventional and CH...O H-bonds, and thereby identify patterns that unambiguously signal the presence of a CH...O interaction.     

Impact of Zn-doping on the composition,stability, luminescence properties of silica coated all-inorganic cesium lead bromide nanocrystals and their biocompatibility

Cesium lead halide (CsPbX₃: X = I, Br, Cl) nanocrystals (NCs) are believed to be potential candidates for bioimaging applications. However, their low structural stability against polar solvents remains as a major limitation. To improve the NCs stability and maintain high emission intensity, we synthesized silica coated Zn-doped core@shell perovskite NCs via modified ligand assisted reprecipitation (LARP) synthetic method under relatively high humid condition. We systemically varied the composition inside the perovskite structure and then studied their photophysical properties and stability. Interestingly, the Zn-doping amount controls the ratio of CsPbBr₃ to Cs₄PbBr₆ perovskites inside the core and also facilitates the growth of (OA)₂PbBr₄ shell, enables overall increase in NCs emission intensity and stability. We observed green color emission from these NCs in the spectral range of 494-506 nm with a maximum photoluminescence quantum yield (PLQY) up to 88%. The optimized Zn-doped NCs exhibited nearly four times better water stability compared to the bare NCs and retain emission properties for several months even in highly polar solvents. Finally, we performed biocompatibility test of the NCs generated on biological samples and hydroponics test in a gardenia leaf for their potential bioimaging applications.     

Molecular dynamics simulation of the formation of twin boundaries during agglomeration of nanoparticles

The processes controlling early stages of agglomeration of nanoparticles have been investigated by the molecular dynamics method. It has been established that the formation of boundaries with twin misorientation is the main mechanism of structural relaxation during primary agglomeration of nanoparticles. It has been shown that an increase in the temperature leads to an increase in the number of twin boundaries and that their mutual arrangement depends on the misorientation of the nanoparticles. In the case where twin boundaries are noncoplanar, structure relaxation results in the formation of pentagonal twin boundaries. The role of twinning in the formation of interfaces upon compaction of nanoparticles has been discussed.     

Cluster based copper(II)-azide polymer: Synthesis,structure and magnetic study

The reaction of ethylene diamine with Cu(NO₃)₂·3H₂O and an excess of NaN₃ (1:2:4 molar ratio) lead to the formation of copper-azido based polymer [Cu₄(N₃)₈(en)₂]_n (1), which has been successfully characterized by elemental analyses, IR spectroscopy, single-crystal X-ray diffraction and variable temperature magnetic study. X-ray crystal structure determination of 1 reveals that the structure consists of 1D chains of a centrosymmetric tetranuclear copper(II)-azido cluster, connected through double azido end-to-end bridges. Variable-temperature magnetic studies (between 2 and 300 K) suggest dominant antiferromagnetic interactions in this complex, although ferromagnetic interactions have been observed in all other copper-azido based polymers produced with ethylene diamine reported so far.     

Physical properties of ion beam treated electrospun poly(vinyl alcohol) nanofibers

We show that the mechanical properties of nano-sized electrospun poly(vinyl alcohol) fibers can be modified using broad-energy ion beam implantation. The elastic moduli were determined using atomic force microscopy multi-point mechanical bending tests on individual fibers before and after treatment. With a dose of 8.0 × 10¹⁵ ions/cm² of nitrogen ion we observed 30% increases in fiber elastic modulus with a simultaneous fiber diameter reduction. Two additional doses of nitrogen ion as well as a 8.0 × 10¹⁵ ions/cm² of helium ion treatment showed that this stiffness improvement effect was dependent on ion dosage and ion species. The surface morphological features of the fiber mat were shown to be unaltered due to the ion beam treatment. Key chemical modifications via nitrogen ion treatment were the introduction of the functional groups amine and amide. These groups are important in promoting cell compatibility on polymer surfaces.