Phani Kiran Vabbina

Bio: Phani Kiran Vabbina is an academic researcher from Florida International University. The author has contributed to research in topics: Graphene & Terahertz radiation. The author has an hindex of 11, co-authored 24 publications receiving 575 citations. Previous affiliations of Phani Kiran Vabbina include University of Miami & International University, Cambodia.

Highly Sensitive Wide Bandwidth Photodetector Based on Internal Photoemission in CVD Grown p-Type MoS2/Graphene Schottky Junction

Abstract: Two dimensional (2D) Molybdenum disulfide (MoS2) has evolved as a promising material for next generation optoelectronic devices owing to its unique electrical and optical properties, such as band gap modulation, high optical absorption, and increased luminescence quantum yield. The 2D MoS2 photodetectors reported in the literature have presented low responsivity compared to silicon based photodetectors. In this study, we assembled atomically thin p-type MoS2 with graphene to form a MoS2/graphene Schottky photodetector where photo generated holes travel from graphene to MoS2 over the Schottky barrier under illumination. We found that the p-type MoS2 forms a Schottky junction with graphene with a barrier height of 139 meV, which results in high photocurrent and wide spectral range of detection with wavelength selectivity. The fabricated photodetector showed excellent photosensitivity with a maximum photo responsivity of 1.26 AW–1 and a noise equivalent power of 7.8 × 10–12 W/√Hz at 1440 nm.

Hot electron generation by aluminum oligomers in plasmonic ultraviolet photodetectors.

Abstract: We report on an integrated plasmonic ultraviolet (UV) photodetector composed of aluminum Fano-resonant heptamer nanoantennas deposited on a Gallium Nitride (GaN) active layer which is grown on a sapphire substrate to generate significant photocurrent via formation of hot electrons by nanoclusters upon the decay of nonequilibrium plasmons. Using the plasmon hybridization theory and finite-difference time-domain (FDTD) method, it is shown that the generation of hot carriers by metallic clusters illuminated by UV beam leads to a large photocurrent. The induced Fano resonance (FR) minimum across the UV spectrum allows for noticeable enhancement in the absorption of optical power yielding a plasmonic UV photodetector with a high responsivity. It is also shown that varying the thickness of the oxide layer (Al2O3) around the nanodisks (tox) in a heptamer assembly adjusted the generated photocurrent and responsivity. The proposed plasmonic structure opens new horizons for designing and fabricating efficient opto-electronics devices with high gain and responsivity.

A label-free electrochemical immunosensor for beta-amyloid detection

Abstract: A label-free detection of beta-amyloid (βA) protein using an electrochemical immunosensor fabricated via immobilizing specific anti-beta-amyloid antibodies (An-βA-Abs) onto an interdigitated electrode of gold (IDE-Au) modified using a self-assembled monolayer (SAM) of dithiobis(succinimidyl propionate) [DTSP] is presented here. The βA has been investigated as a potential biomarker for monitoring Alzheimer's disease (AD), permanent irreversible and progressive brain damage. Thus βA detection at the pM level is of high significance for AD diagnostics. The IDE-Au modification and covalent immobilization of An-βA-Abs onto electrodes were characterized by differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) as a function of electrical response variation in each step involved in sensor fabrication. The EIS studies confirmed that the developed βA immunosensor is selective and exhibits a detection limit of 10 pM, its detection range varies from 10 pM to 100 nM, and it has a high sensitivity of 11 kΩ M−1 with a regression coefficient of 0.99. Thus, the developed sensitive and selective immunosensor with the features of the IDE-Au can be integrated with a miniaturized potentiostat (M-P) to develop a sensing system to detect βA for point-of-care (POC) applications for the assessment and management of AD. The bio-informatics gathered from such a system could be useful to make timely therapeutic decisions.

Nanoparticle-Based Immunochemical Biosensors and Assays: Recent Advances and Challenges

Abstract: We review the progress achieved during the recent five years in immunochemical biosensors (immunosensors) combined with nanoparticles for enhanced sensitivity. The initial part introduces antibodies as classic recognition elements. The optical sensing part describes fluorescent, luminescent, and surface plasmon resonance systems. Amperometry, voltammetry, and impedance spectroscopy represent electrochemical transducer methods; electrochemiluminescence with photoelectric conversion constitutes a widely utilized combined method. The transducing options function together with suitable nanoparticles: metallic and metal oxides, including magnetic ones, carbon-based nanotubes, graphene variants, luminescent carbon dots, nanocrystals as quantum dots, and photon up-converting particles. These sources merged together provide extreme variability of existing nanoimmunosensing options. Finally, applications in clinical analysis (markers, tumor cells, and pharmaceuticals) and in the detection of pathogenic microorganisms, toxic agents, and pesticides in the environmental field and food products are summarized.

Electrically-Transduced Chemical Sensors Based on Two-Dimensional Nanomaterials

Abstract: Electrically–transduced sensors, with their simplicity and compatibility with standard electronic technologies, produce signals that can be efficiently acquired, processed, stored, and analyzed. Two dimensional (2D) nanomaterials, including graphene, phosphorene (BP), transition metal dichalcogenides (TMDCs), and others, have proven to be attractive for the fabrication of high–performance electrically-transduced chemical sensors due to their remarkable electronic and physical properties originating from their 2D structure. This review highlights the advances in electrically-transduced chemical sensing that rely on 2D materials. The structural components of such sensors are described, and the underlying operating principles for different types of architectures are discussed. The structural features, electronic properties, and surface chemistry of 2D nanostructures that dictate their sensing performance are reviewed. Key advances in the application of 2D materials, from both a historical and analytical pers...

Advanced Oxidation Processes for the Removal of Antibiotics from Water. An Overview

Abstract: In this work, the application of advanced oxidation processes (AOPs) for the removal of antibiotics from water has been reviewed. The present concern about water has been exposed, and the main problems derived from the presence of emerging pollutants have been analyzed. Photolysis processes, ozone-based AOPs including ozonation, O3/UV, O3/H2O2, and O3/H2O2/UV, hydrogen peroxide-based methods (i.e., H2O2/UV, Fenton, Fenton-like, hetero-Fenton, and photo-Fenton), heterogeneous photocatalysis (TiO2/UV and TiO2/H2O2/UV systems), and sonochemical and electrooxidative AOPs have been reviewed. The main challenges and prospects of AOPs, as well as some recommendations for the improvement of AOPs aimed at the removal of antibiotics from wastewaters, are pointed out.