Current Measurement and Noise Modeling in Solid State Nanopores
Abstract: Selective and label free sensing of ions, bio-molecules and organic compounds are the major advantages of current monitoring along the solid state nanopores. This paper reviews the promising field of nanopore technology- noise modeling of current recording through solid state nanopores. Current across the nanopore is measured by resistive pulse sensing technique. In resistive pulse sensing (RPS) technique, a molecule is allowed to pass through the nanopores and the molecule will then partially displace the conducting fluid inside the pore, resulting in the loss of current across the nanopore. Ionic current through the solid state nanopore is prone to wide varieties of noise.
The paper will focus on the low frequency Johnson’s noise and high frequency noise modeling of the measured current by RPS technique and the method for reducing this noise. Label free detection is only possible by reducing thee noise and optimizing the signal to noise ratio. Standard models are applied to understand low and high frequency noise in solid state nanopores. Additionally, PDMS coated nanopores are discussed being advantageous towards noise reduction.
Figure (1): Current (A) measurement through a nanopore. V is the biasing potential.
Figure (2): (a) A 2 nm solid state nanopores in silicon nitride substrate. (b) Movement of double stranded DNA (dsDNA) within the nanopores. (c) Current measured during the dsDNA translocation within the nanopores, with 100 mM KCl with V = 1.0V as applied bias potential across the nanopore .
 Dimitrov, V.; Mirasaidov, W.; Wang, D. Nanopores in solid-state membranes engineered for single molecule detection, Nanotechnology 21, 065502-23 (2010).
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Applications of Frequency-Resolved Optical Spectroscopy in Nanoscience
Abstract: Advancement of technology and development of high resolution optical elements, today optical spectroscopy has stood as the major analytical tool applied in every branch of science. This paper deals with two major applications of frequency resolved optical spectroscopy in the field of nanoscience- resonance Raman spectroscopy of single walled carbon nanotubes (SWCNTs) and photoluminescence (PL) spectroscopy of quantum dots (QDs).
CNTs have grown much attraction these days, being a novel and versatile material with very high tensile strength and electronically both semiconducting as well as metallic. SWCNTs can be generated by rolling a sheet of graphene (single atomic layer of graphite) at certain vector. Analysis of resonance Raman spectroscopy of SWCNT elucidates various features specific to both fullerene (C60) family and sp2 hybridized organic molecules. For example, SWCNT exhibits longitudinal and transverse optical phononic vibration mode (G band), radial breathing mode (RBM), G’ band and D band. G band is common to all sp2 hybridized organic molecules while RBM and G’ band are present only in nanotubes.
QD are zero dimensional physical systems forming bridge between bulk and the atomic system. For example, presence of separate valence and conduction band similar to bulk system and discrete energy levels within the bands featuring atomic systems. Hence, spectroscopic behavior is similar to those of bulk as well as atomic system. PL spectroscopy of empty and charged quantum dots is discussed under different biasing condition. Biasing is necessary to lift the fermi level of dots to quantize the number of electrons inside the dot. Carrier confinement is proved observing the PL spectra of the quantum dots. Furthermore, growth dependent PL spectra of self assembled InGaAs QD is discussed. PL count is found to be narrow with high intensity peak for slowly deposited dots.
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Short Presentation on Spectroscopy of the Quantum Dots
Single molecule rectifier
Abstract: The objective of the project is to realize a unimolecular rectifier, capable of working under ambient condition. This rectifier will have very high rectification ratio for storing logical information. This device will have a size of only few nm, ideal for the nano-processor and nano-architect design. Both electrical characteristics and conduction behaviour of different supramolecule molecules will be studied. Profound research on the different substrates and electrode materials will be carried out, for the development of real life novel nano-device. Novel fabrication techniques will be developed to place a single molecular nano-device on the substrate.
Figure (1): A molecular rectifier for C60NPy oligomer, where gold and Platinum/Iridium are the corresponding contact terminals for electrical connection .
 Bing Wang, Yunshen Zhou, Xunlei Ding, Kedong Wang, Xiapoing Wang, Jinlong Yang, J. G. Hou, ‘Conduction mechanism of Aviram-Ratner Rectifier with single pyridine-σ-C 60 Oligomers’, J. Phy. Chem. B, 110, 24505-24512 (2006).
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Presentation on Realization of a Unimolecular Rectifier
Quantum Entanglement and its Aspects
Over the past few years, quantum mechanics has developed as interdisciplinary branch of physics which exploits one of the prominent physical and quantum mechanical phenomena, quantum entanglement. Quantum entanglement is such quantum phenomena that happen at the heart of quantum communication and quantum computation.
Man has always sought of new discoveries and inventions that make our life easier and simpler. People devised the communication system for easy transmission of information and electronics as the medium of storage and computation. Embarking on the era nanotechnology is the outcome of the demerits which we’re facing today, which includes huge power consumption and greater chip area.
Hence, device fabricated in nano sizes demands quantum information rather than classical information as the mode of communication. Quantum entanglement is that mode of quantum communication utilized by the nano-sized devices that leads to lots of advantages which isn’t possible in classical information system. Quantum entanglement will lead us to that era of quantum communication in nano-world which deals with every necessity for essential communication system and development of communication mechanism.
Electron spin is the quantum information which are stored as the spin of the single electron. This spin are quantum mechanica information represented as qubits. Spin qubit when entangled, there exists either clockwise or anti-clock wise spin, and it forms the basic platform of quantum information storage. Similarly, photon are also entangled and exist in two states wither vertical or horizontal states. These are termed as maximally entangled states where one state is clockwise or anti-clockwise spin pair and the other is horizontal and vertical polarization pair. Advantages of quantum entanglement include quantum teleportation for long distance communication through available medium, quantum cryptography for the secured communication and development of quantum computer for high speed quantum computation. Additionally, quantum teleportation results in very high speed communication in the available classical channel.
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