IR study on the effect of chloride ion on porous silicon

Infrared (IR) studies have been carried out on porous silicon samples to infer on the changes in the surface bonding in the porous silicon (PS) layer due to chloride (Cl⁻) and subsequent fluoride (F⁻) ion exposures with respect to time. It is observed that silicon hydride linkages decreases and silicon oxide linkages increases with time of exposure to HCl, suggesting a possible oxidation of the porous layer. IR study revealed the formation of SiO (silanones) bonds. A possible mechanism for the formation of silanones from SiOH species has been proposed to explain the observation. We also observed a saturation of silicon oxide groups with complete disappearance of silicon hydride peaks indicating the complete conversion of silicon hydride to oxides. Furthermore on exposure to F⁻, the IR spectrum showed a rapid destruction of silicon oxygen linkages.     

Ratiometric and Near‐Infrared Molecular Probes for the Detection and Imaging of Zinc Ions

The detection and imaging of Zn²⁺ in biological samples are of paramount interest owing to the role of this cation in physiological functions. This is possible only with molecular probes that specifically bind to Zn²⁺ and result in changes in emission properties. A “turn‐on” emission or shift in the emission color upon binding to Zn²⁺ should be ideal for in vivo imaging. In this context, ratiometric and near‐IR probes are of particular interest. Therefore, in the area of chemosensors or molecular probes, the design of fluorophores that allow ratiometric sensing or imaging in the near‐IR region is attracting the attention of chemists. The purpose of this Focus Review is to highlight recent developments in this area and stress the importance of further research for future applications.     

Development of a new experimental setup for studying collisions of keV-electrons with thick and thin targets

Development of a new lectron-recoil ion/photon coincidence setup for investigating some of the electron induced collision processes, such as electron bremsstrahlung, electron backscattering, innershell excitation and multiple ionization of target atoms/molecules in bombardment of electrons having energies from 2.0 keV to 30.0 keV with solid and gaseous targets is described. The new features include the use of a compact multipurpose scattering chamber, a time-of-flight spectrometer for detection of multiply charged target ions, a 45°-parallel plate electrostatic analyzer for measuring energy and angle of the ejected electrons, a room temperature high resolution Si-PIN photo diode X-ray detector for counting the collisionally induced photons, a coincidence data acquisition system consisting of a 200 MHz Pentium based 8K-multichannel analyzer and a standard network of a fast/slow coincidence electronics. In particular, the details of design, fabrication and assembly of indigenous components employed in the setup are presented. Selected experiments planned with the setup are mentioned and briefly discussed. A report on performance, optimization, efficiency, time resolution etc. of the time-of-flight (TOF) spectrometer and that of the 45°-parallel plate electrostatic analyzer (PPEA) is presented. Test spectra of electron-recoil ion coincidences, energy distribution of ejected electrons and characteristic plus non-characteristic X-ray spectrum are illustrated to exhibit the satisfactory performance of the developed setup.     

Particle-rotor-model calculations in 125I

Recent experimental data on ¹²⁵I has revealed several interesting structural features. These include the observation of a three quasiparticle band, prolate and oblate deformed bands, signature inversion in the yrast positive-parity band and identification of the unfavoured πh _11/2 band showing very large signature splitting. In the present work, particle-rotor-model calculations have been performed for the πh _11/2 band, using an axially symmetric deformed Nilsson potential. The calculations reproduce the experimental results well and predict a moderate prolate quadrupole deformation of about 0.2 for the band.     

Effect of Mg doping on morphology,photocatalytic activity and related biological properties of Zn1−xMgxO nanoparticles

The objective of this study is to synthesize ZnO and Mg doped ZnO (Zn_1−xMg_xO) nanoparticles via the sol-gel method, and characterize their structures and to investigate their biological properties such as antibacterial activity and hemolytic potential.Nanoparticles (NPs) were synthesized by the sol-gel method using zinc acetate dihydrate (Zn(CH₃COO)₂.2H₂O) and magnesium acetate tetrahydrate (Mg(CH₃COO)₂.4H₂O) as precursors. Methanol and monoethanolamine were used as solvent and sol stabilizer, respectively. Structural and morphological characterizations of Zn_1−xMg_xO nanoparticles were studied by using XRD and SEM-EDX, respectively. Photocatalytic activities of ZnO and selected Mg-doped ZnO (Zn_1−xMg_xO) nanoparticles were investigated by degradation of methylene blue (MeB). Results indicated that Mg doping (both 10% and 30%) to the ZnO nanoparticles enhanced the photocatalytic activity and a little amount of Zn0.90 Mg0.10 O photocatalyst (1.0 mg/mL) degraded MeB with 99% efficiency after 24 h of irradiation under ambient visible light. Antibacterial activity of nanoparticles versus Escherichia coli ( E. coli ) was determined by the standard plate count method. Hemolytic activities of the NPs were studied by hemolysis tests using human erythrocytes. XRD data proved that the average particle size of nanoparticles was around 30 nm. Moreover, the XRD results indicatedthat the patterns of Mg doped ZnO nanoparticles related to ZnO hexagonal wurtzite structure had no secondary phase for x ≤ 0.2 concentration. For 0 ≤ x ≤ 0.02, NPs showed a concentration dependent antibacterial activity against E. coli . While Zn_0.90Mg_0.10 O totally inhibited the growth of E. coli , upper and lower dopant concentrations did not show antibacterial activity.     

A Three‐Photon Active Organic Fluorophore for Deep Tissue Ratiometric Imaging of Intracellular Divalent Zinc

Deep tissue bioimaging with three‐photon (3P) excitation using near‐infrared (NIR) light in the second IR window (1.0–1.4 μm) could provide high resolution images with an improved signal‐to‐noise ratio. Herein, we report a photostable and nontoxic 3P excitable donor‐π‐acceptor system (GMP) having 3P cross‐section (σ₃) of 1.78×10^?80 cm⁶ s² photon^?2 and action cross‐section (σ₃η₃) of 2.31×10^?81 cm⁶ s² photon^?2, which provides ratiometric fluorescence response with divalent zinc ions in aqueous conditions. The probe signals the Zn²⁺ binding at 530 and 600 nm, respectively, upon 1150 nm excitation with enhanced σ₃ of 1.85×10^?80 cm⁶ s² photon^?2 and σ₃η₃ of 3.33×10^?81 cm⁶ s² photon^?2. The application of this probe is demonstrated for ratiometric 3P imaging of Zn²⁺ in vitro using HuH‐7 cell lines. Furthermore, the Zn²⁺ concentration in rat hippocampal slices was imaged at 1150 nm excitation after incubation with GMP, illustrating its potential as a 3P ratiometric probe for deep tissue Zn²⁺ ion imaging.