Detection Schemes for High Sensitivity Electronic Biomolecular Detection

2007 ◽  
Author(s):  
Tasreen Charania ◽  
Ash M. Parameswaran
Keyword(s):  
High Sensitivity ◽  
Biomolecular Detection ◽  
Detection Schemes

scholarly journals Biosynthesis of silver nanoparticles and exopolysaccharide using novel Thermophilic strain (Ts-1) of Bacillus amyloliquefaciens

2020 ◽  
Author(s):  
Sharath Chandra Thota ◽  
Bathini Sreelatha
Keyword(s):  
Silver Nanoparticles ◽  
Bacillus Amyloliquefaciens ◽  
High Sensitivity ◽  
Visual Observation ◽  
Purification And Characterization ◽  
Chemical Methods ◽  
Biomolecular Detection ◽  
Exopolysaccharide Biosynthesis ◽  
Uv Visible

AbstractIn the developing world, Nanotechnology became an efficient method in therapeutics, antimicrobials, diagnostics, catalysis, microelectronics, and high sensitivity biomolecular detection. As well as on the other hand, Exopolysaccharides are biopolymers which are also widely used in food formulation, bio- flocculants, bio-absorbents, drug delivery agents. As the chemical methods of synthesizing nanoparticles and polymers are environmentally risky, costly, and toxic. In the present study, we focused on production, purification, and characterization of silver nanoparticles (AgNPs) and exopolysaccharide (EPS) by eco-friendly, extracellular biosynthetic methods using novel thermophilic Bacillus amyloliquefaciens strain Ts-1. This strain was isolated from soil samples by employing pour and spread plate techniques. After obtaining pure culture, the bacterium was used for the synthesis of AgNPs and EPS. Nanoparticles were synthesized from AgNO3 by using reducing agents secreted by bacteria, and Exopolysaccharide biosynthesis is carried out in three steps by the organism in the presence of a carbon source. Synthesis of colloidal AgNPs and EPS was monitored by UV-Visible spectroscopy and Visual observation, respectively. SEM, Edax and FTIR were performed for the characterization of the AgNPs and EPS such as their size, morphology and composition and we also showed the catalytic activity of AgNps in degradation of methylene blue.

scholarly journals Liquid crystal-amplified optofluidic biosensor for ultra-highly sensitive and stable protein assay

PhotoniX ◽  
2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Ziyihui Wang ◽  
Yize Liu ◽  
Chaoyang Gong ◽  
Zhiyi Yuan ◽  
Liang Shen ◽  
...  
Keyword(s):  
Internal Surface ◽  
High Sensitivity ◽  
Optical Microscope ◽  
Wavelength Shift ◽  
Biomolecular Detection ◽  
Alignment Layer ◽  
Protein Assay ◽  
Sensing Platform ◽  
Protein Molecules ◽  
Protein Assays

AbstractProtein assays show great importance in medical research and disease diagnoses. Liquid crystals (LCs), as a branch of sensitive materials, offer promising applicability in the field of biosensing. Herein, we developed an ultrasensitive biosensor for the detection of low-concentration protein molecules, employing LC-amplified optofluidic resonators. In this design, the orientation of LCs was disturbed by immobilized protein molecules through the reduction of the vertical anchoring force from the alignment layer. A biosensing platform based on the whispering-gallery mode (WGM) from the LC-amplified optofluidic resonator was developed and explored, in which the spectral wavelength shift was monitored as the sensing parameter. The microbubble structure provided a stable and reliable WGM resonator with a high Q factor for LCs. It is demonstrated that the wall thickness of the microbubble played a key role in enhancing the sensitivity of the LC-amplified WGM microcavity. It is also found that protein molecules coated on the internal surface of microbubble led to their interactions with laser beams and the orientation transition of LCs. Both effects amplified the target information and triggered a sensitive wavelength shift in WGM spectra. A detection limit of 1 fM for bovine serum albumin (BSA) was achieved to demonstrate the high-sensitivity of our sensing platform in protein assays. Compared to the detection using a conventional polarized optical microscope (POM), the sensitivity was improved by seven orders of magnitude. Furthermore, multiple types of proteins and specific biosensing were also investigated to verify the potential of LC-amplified optofluidic resonators in the biomolecular detection. Our studies indicate that LC-amplified optofluidic resonators offer a new solution for the ultrasensitive real-time biosensing and the characterization of biomolecular interactions.

LABEL-FREE BIOMOLECULAR DETECTION USING CARBON NANOTUBE FIELD EFFECT TRANSISTORS

NANO ◽  
2008 ◽  
Vol 03 (06) ◽  
pp. 415-431 ◽  
Author(s):  
HYE RYUNG BYON ◽  
SUPHIL KIM ◽  
HEE CHEUL CHOI
Keyword(s):  
Carbon Nanotube ◽  
Field Effect ◽  
Surface Passivation ◽  
Field Effect Transistors ◽  
High Sensitivity ◽  
Detection Methods ◽  
Label Free ◽  
Biomolecular Detection ◽  
Great Opportunity ◽  
High Level

Carbon nanotube field effect transistor (FET) type biosensors have been widely investigated as one of the promising platforms for highly sensitive personalized disease-monitoring electronic devices. Combined with high level cutting edge information technology (IT) infra systems, carbon nanotube transistor biosensors afford a great opportunity to contribute to human disease care by providing early diagnostic capability. Several key prerequisites that should be clarified for the real application include sensitivity, reliability, reproducibility, and expandability to multiplex detection systems. In this brief review, we introduce the types, fabrication, and detection methods of single-walled carbon nanotube FET (SWNT-FET) devices. As surface functionalization of the devices by which nonspecific bindings (NSBs) are efficiently prohibited is also another important issue regarding reliable biosensors, we discuss several key strategies about surface passivation along with examples of various biomolecules such as proteins, DNA, small molecules, aptamers, viruses, and cancer and neurodegenerative disease markers which have been successfully sensed by SWNT-FET devices. Finally, we discuss proposed detection mechanisms, according to which strategies for fabricating sensor devices having high sensitivity are determined. Two main mechanisms — charge transfer (or electrostatic gate effect) and Schottky barrier effect, depending on the place where biomolecules are adsorbed — will be covered.

Radio Measurements of Coronal Magnetic Fields

1994 ◽  
Vol 144 ◽  
pp. 21-28 ◽  
Author(s):  
G. B. Gelfreikh
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Active Regions ◽  
High Sensitivity ◽  
Coronal Magnetic Field ◽  
Transverse Magnetic ◽  
Radio Sources ◽  
Radio Waves ◽  
Solar Active Regions

AbstractA review of methods of measuring magnetic fields in the solar corona using spectral-polarization observations at microwaves with high spatial resolution is presented. The methods are based on the theory of thermal bremsstrahlung, thermal cyclotron emission, propagation of radio waves in quasi-transverse magnetic field and Faraday rotation of the plane of polarization. The most explicit program of measurements of magnetic fields in the atmosphere of solar active regions has been carried out using radio observations performed on the large reflector radio telescope of the Russian Academy of Sciences — RATAN-600. This proved possible due to good wavelength coverage, multichannel spectrographs observations and high sensitivity to polarization of the instrument. Besides direct measurements of the strength of the magnetic fields in some cases the peculiar parameters of radio sources, such as very steep spectra and high brightness temperatures provide some information on a very complicated local structure of the coronal magnetic field. Of special interest are the results found from combined RATAN-600 and large antennas of aperture synthesis (VLA and WSRT), the latter giving more detailed information on twodimensional structure of radio sources. The bulk of the data obtained allows us to investigate themagnetospheresof the solar active regions as the space in the solar corona where the structures and physical processes are controlled both by the photospheric/underphotospheric currents and surrounding “quiet” corona.

Backscattered Electron Imaging of GaAs/AlGaAs Super Lattice Structures with an Ultra-High- Resolution SEM

1988 ◽  
Vol 46 ◽  
pp. 204-205
Author(s):  
Kazumichi Ogura ◽  
Michael M. Kersker
Keyword(s):  
High Resolution ◽  
Layer Structure ◽  
High Sensitivity ◽  
Beam Current ◽  
Electron Beam Current ◽  
Lattice Structures ◽  
Super Lattice ◽  
Different Types ◽  
Backscattered Electron ◽  
Electron Imaging

Backscattered electron (BE) images of GaAs/AlGaAs super lattice structures were observed with an ultra high resolution (UHR) SEM JSM-890 with an ultra high sensitivity BE detector. Three different types of super lattice structures of GaAs/AlGaAs were examined. Each GaAs/AlGaAs wafer was cleaved by a razor after it was heated for approximately 1 minute and its crosssectional plane was observed.First, a multi-layer structure of GaAs (100nm)/AlGaAs (lOOnm) where A1 content was successively changed from 0.4 to 0.03 was observed. Figures 1 (a) and (b) are BE images taken at an accelerating voltage of 15kV with an electron beam current of 20pA. Figure 1 (c) is a sketch of this multi-layer structure corresponding to the BE images. The various layers are clearly observed. The differences in A1 content between A1 0.35 Ga 0.65 As, A1 0.4 Ga 0.6 As, and A1 0.31 Ga 0.69 As were clearly observed in the contrast of the BE image.

An x-ray microprobe based upon a close-coupled focal-spot / glass capillary arrangement

1992 ◽  
Vol 50 (2) ◽  
pp. 1758-1759
Author(s):  
D. A. Carpenter ◽  
M. A. Taylor
Keyword(s):  
Imaging Techniques ◽  
Fluorescence Analysis ◽  
High Sensitivity ◽  
Specimen Preparation ◽  
X Rays ◽  
Glass Capillary ◽  
Close Coupling ◽  
X Ray ◽  
Point To Point ◽  
Beam Damage

The development of intense sources of x rays has led to renewed interest in the use of microbeams of x rays in x-ray fluorescence analysis. Sparks pointed out that the use of x rays as a probe offered the advantages of high sensitivity, low detection limits, low beam damage, and large penetration depths with minimal specimen preparation or perturbation. In addition, the option of air operation provided special advantages for examination of hydrated systems or for nondestructive microanalysis of large specimens.The disadvantages of synchrotron sources prompted the development of laboratory-based instrumentation with various schemes to maximize the beam flux while maintaining small point-to-point resolution. Nichols and Ryon developed a microprobe using a rotating anode source and a modified microdiffractometer. Cross and Wherry showed that by close-coupling the x-ray source, specimen, and detector, good intensities could be obtained for beam sizes between 30 and 100μm. More importantly, both groups combined specimen scanning with modern imaging techniques for rapid element mapping.

Ultrastructural identification of three types of sensory setae on copepod antennae

1995 ◽  
Vol 53 ◽  
pp. 956-957
Author(s):  
T. M. Weatherby ◽  
P.H. Lenz
Keyword(s):  
Phase Locking ◽  
Membrane Surface ◽  
Reaction Times ◽  
High Sensitivity ◽  
Structural Features ◽  
Calanoid Copepods ◽  
Marine Food Webs ◽  
Dendritic Membrane ◽  
Ultrastructural Characterization

Crustaceans, as well as other arthropods, are covered with sensory setae and hairs, including mechanoand chemosensory sensillae with a ciliary origin. Calanoid copepods are small planktonic crustaceans forming a major link in marine food webs. In conjunction with behavioral and physiological studies of the antennae of calanoids, we undertook the ultrastructural characterization of sensory setae on the antennae of Pleuromamma xiphias.Distal mechanoreceptive setae exhibit exceptional behavioral and physiological performance characteristics: high sensitivity (<10 nm displacements), fast reaction times (<1 msec latency) and phase locking to high frequencies (1-2 kHz). Unusual structural features of the mechanoreceptors are likely to be related to their physiological sensitivity. These features include a large number (up to 3000) of microtubules in each sensory cell dendrite, arising from or anchored to electron dense rods associated with the ciliary basal body microtubule doublets. The microtubules are arranged in a regular array, with bridges between and within rows. These bundles of microtubules extend far into each mechanoreceptive seta and terminate in a staggered fashion along the dendritic membrane, contacting a large membrane surface area and providing a large potential site of mechanotransduction.

Slow-Scan CCD Observation of Backscattering Patterns in SEM

1992 ◽  
Vol 50 (2) ◽  
pp. 1308-1309
Author(s):  
F. Ouyang ◽  
D. A. Ray ◽  
O. L. Krivanek
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Dynamic Range ◽  
High Sensitivity ◽  
Lens System ◽  
Wide Dynamic Range ◽  
Peltier Cooler ◽  
Diffraction Patterns ◽  
Scanning Electron

Electron backscattering Kikuchi diffraction patterns (BKDP) reveal useful information about the structure and orientation of crystals under study. With the well focused electron beam in a scanning electron microscope (SEM), one can use BKDP as a microanalysis tool. BKDPs have been recorded in SEMs using a phosphor screen coupled to an intensified TV camera through a lens system, and by photographic negatives. With the development of fiber-optically coupled slow scan CCD (SSC) cameras for electron beam imaging, one can take advantage of their high sensitivity and wide dynamic range for observing BKDP in SEM.We have used the Gatan 690 SSC camera to observe backscattering patterns in a JEOL JSM-840A SEM. The CCD sensor has an active area of 13.25 mm × 8.83 mm and 576 × 384 pixels. The camera head, which consists of a single crystal YAG scintillator fiber optically coupled to the CCD chip, is located inside the SEM specimen chamber. The whole camera head is cooled to about -30°C by a Peltier cooler, which permits long integration times (up to 100 seconds).

Exit-surface wave reconstruction using a focal series

1992 ◽  
Vol 50 (2) ◽  
pp. 988-989
Author(s):  
W.J. de Ruijter ◽  
M.R. McCartney ◽  
David J. Smith ◽  
J.K. Weiss
Keyword(s):  
Surface Wave ◽  
Spherical Aberration ◽  
Data Extraction ◽  
High Sensitivity ◽  
Geometric Distortion ◽  
Variation Method ◽  
Objective Lens ◽  
Immediate Reconstruction ◽  
Exit Surface ◽  
Electron Microscopes

Further advances in resolution enhancement of transmission electron microscopes can be expected from digital processing of image data recorded with slow-scan CCD cameras. Image recording with these new cameras is essential because of their high sensitivity, extreme linearity and negligible geometric distortion. Furthermore, digital image acquisition allows for on-line processing which yields virtually immediate reconstruction results. At present, the most promising techniques for exit-surface wave reconstruction are electron holography and the recently proposed focal variation method. The latter method is based on image processing applied to a series of images recorded at equally spaced defocus.Exit-surface wave reconstruction using the focal variation method as proposed by Van Dyck and Op de Beeck proceeds in two stages. First, the complex image wave is retrieved by data extraction from a parabola situated in three-dimensional Fourier space. Then the objective lens spherical aberration, astigmatism and defocus are corrected by simply dividing the image wave by the wave aberration function calculated with the appropriate objective lens aberration coefficients which yields the exit-surface wave.

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