Shashi B. Rana

Structural, optical, magnetic and antibacterial study of pure and cobalt doped ZnO nanoparticles

In this research paper, pure and Co-doped ZnO nanoparticles were synthesized by using the wet precipitation method. The structural, morphological, optical and magnetic properties of the pure and Co doped ZnO nanoparticles were investigated. X-ray diffraction (XRD) spectra of Co doped ZnO NPs shows the shifting of characteristic XRD peak toward the higher angle which revealed that dopant Co is successfully incorporated into the lattice structure of ZnO nanoparticles. Structural morphology of pure and Co-doped ZnO nanoparticles samples was ascertained by using the scanning electron microscopy which confirms the formation of fine and clear spherical nanocrystallites with clear and distinctive boundaries. Energy-dispersive X-ray spectroscopy spectra show the elemental composition of Co2+ ions effectively in lattice site of Zn2+ ions. Photoluminescence and Raman spectra indicate the presence of oxygen vacancies and donor defects in the doped samples. UV–visible absorption spectroscopy showed the blue shifting of absorption edge as compared to pure ZnO nanoparticles sample. Pure and Co-doped ZnO nanoparticles revealed considerable changes in the M–H loop, particularly the diamagnetic behavior changed into ferromagnetic for Co-doped samples in vibrating sample magnetometer investigation. In this study, the antibacterial properties of the cobalt doped zinc oxide were further studied against three Gram-negative pathogens via using agar well diffusion technique. Co doped nanoparticles samples were then investigated as antibacterial agent to control the bacterial growth. It is further confirmed from our study that Co-doped ZnO NPs and their exposure to sunlight enhanced the antibacterial activity against three bacterial pathogens under study.

Synthesis and optical characterization of ZnO nanoparticles capped with 2-aminothiols

ZnO nanoparticles were synthesized by precipitation method. To reduce the agglomeration among small ZnO nanoparticles, an efficient surface modification method was proposed using 2-aminothiols as a capping agent. The effect of capping reagent is investigated on optoelectronics properties of ZnO. The capping of ZnO with 2-aminothiol leads to the shift in fluorescence intensity and also effected the UV–vis spectra of ZnO. The strategy exposed new dimensions to fine tune the fluorescence signatures of the ZnO.

Influence of surface modification by 2-aminothiophenol on optoelectronics properties of ZnO nanoparticles

In this study, a precipitation method was used to synthesise ZnO nanoparticles using suitable precursors. An efficient surface modification method was proposed in order to reduce the agglomeration among synthesised small sized ZnO nanoparticles using 2-aminothiophenol as a capping agent. This article briefly investigated the effects of capping agent like 2-aminothiophenol on the optoelectronic properties of ZnO nanoparticles. The modified effectivity of 2-aminothiophenol has been examined on the nanosized ZnO nanoparticle for fluorescence and UV–visible (UV–vis) studies. The mechanism was studied for ZnO nanoparticles light emitting capability under different conditions. By facilitating the capping of ZnO with 2-aminothiophenol, fluorescence emission of the surface defects vanishes and ultraviolet (UV) emission increases. Surface capping by 2-aminothiophenol effectively covers most of the surface defects of ZnO and results in quenching of the visible region. The UV–vis absorption spectra of modified ZnO nanoparticles has been influenced by modified ZnO nanoparticles as a result of surface modification; where marked blue shift in absorption edge results. By surface modification of ZnO nanoparticles, change in optoelectronics properties has opened the new scope and possibilities to explore and fine tune the optical character of the modified ZnO for various optoelectronics applications such as UV laser.

Influence of CTAB assisted capping on the structural and optical properties of ZnO nanoparticles

In this research work structural and optoelectronics properties of ZnO nanoparticles capped with functionalized group Cetyl trimethylammonium bromide (CTAB) were highlighted and investigated. The molecules of this capping agent CTAB were attached to the surface of the ZnO nanoparticles by using the wet chemical precipitation method choosing suitable precursors. Synthesized capped ZnO nanoparticles were then further investigated and characterized by using different techniques like XRD, SEM, and FTIR spectroscopy. Thereafter, the optical investigation of these capped ZnO nanoparticles were investigated by using photoluminescence (PL) and UV–visible absorption spectroscopy. The mechanism of the phenomenon like photoluminescence and UV–visible absorption was studied comprehensively. The process of capping results in enhancement of the near-band-edge UV emission and led to reduction the defect-related emission in the PL spectra. The increase in UV emission from these capped ZnO nanoparticles suggests that surface defects such as oxygen vacancies were efficiently passivated. This enhancement in optical properties is advantageous for practical applications such as UV LEDs, UV lasers and various optoelectronics devices.

Performance analysis of ZnO and HfO2 micro-pillars based capacitive antennas

Abstract In this research paper, performance analysis of two different material-based micropillars capacitive antennas is proposed. The method involves formation of self-organized mask, micropillar formation by using process of etching and metal deposition (Au/Cr) on the top and bottom of micropillars. For fabrication of these capacitive antennas, we considered 2-inch p-type silicon (Si) wafers as a substrates material while upper and lower plates of capacitive antenna were fabricated by using gold as plating material on top and bottom. Both capacitive antennas were fabricated by taking the two different materials (ZnO and HfO2) micropillars which acts a dielectric material between two upper and lower gold plates. For realization of both antennas firstly we have simulated both the antenna using CST Microwave studio software and thereafter fabricated by using appropriate microfabrication technique. Both the metamaterial-based capacitive antennas were designed by taking dimension of 35 × 26 mm on the 2″ Si substrate. The thickness (h) and dielectric constant (εr) of silicon substrate were taken as 0.270 mm and 11.7, respectively. The proposed antenna was designed to operate at frequency range of 1–10 GHz, which signifies that return loss (S11) parameter must be less than −10 dB and voltage standing wave ratio must be less than 2. To validate the design, various parameters of RF antenna such as the return loss, gain, surface current distribution, and radiation patterns were obtained and compared for the fabricated antennas. The simulated and experimental results were found to show good agreement.

Design of Star Shaped Slotted Rectangular Microstrip Patch Antenna for Multiband Applications

In today’s world of wireless communication there is need of antennas having multiband characteristics. This paper presents the design of star shaped slotted rectangular microstrip patch antenna for multiband applications. The star slots are introduced in the geometry of rectangular patch antenna to increase the operating frequency bands to make it a multiband antenna. Proposed antenna is designed on FR4 epoxy substrate having relative permittivity 4.4 and 1.6mm thickness. The resonant frequency used for designing the proposed antenna is 3.2GHz. The proposed antenna works on seven frequency bands such as 3.08GHz, 4.68GHz, 5.67GHz, 5.93GHz, 8.14GHz, 8.46GHz and 9.93GHz. HFSS 13 software is used for designing, simulating and analyzing the different parameters of proposed antenna. The antenna is fabricated and tested. The experimental results are compared with simulated results which are in good agreement with each other Keywords—Multiband; Wireless Communications, Star Slots