8 research outputs found
Graphene Nanogrids FET Immunosensor: Signal to Noise Ratio Enhancement
Recently, a reproducible and scalable chemical method for fabrication of smooth graphene nanogrids has been reported which addresses the challenges of graphene nanoribbons (GNR). These nanogrids have been found to be capable of attomolar detection of biomolecules in field effect transistor (FET) mode. However, for detection of sub-femtomolar concentrations of target molecule in complex mixtures with reasonable accuracy, it is not sufficient to only explore the steady state sensitivities, but is also necessary to investigate the flicker noise which dominates at frequencies below 100 kHz. This low frequency noise is dependent on the exposure time of the graphene layer in the buffer solution and concentration of charged impurities at the surface. In this paper, the functionalization strategy of graphene nanogrids has been optimized with respect to concentration and incubation time of the cross linker for an enhancement in signal to noise ratio (SNR). It has been interestingly observed that as the sensitivity and noise power change at different rates with the functionalization parameters, SNR does not vary monotonically but is maximum corresponding to a particular parameter. The optimized parameter has improved the SNR by 50% which has enabled a detection of 0.05 fM Hep-B virus molecules with a sensitivity of around 30% and a standard deviation within 3%. Further, the SNR enhancement has resulted in improvement of quantification accuracy by five times and selectivity by two orders of magnitude
Modeling the Effective Conductance Drop Due to a Particle in a Solid State Nanopore Towards Optimized Design
Noise Spectroscopy Analysis for Estimation of a Specific Biomolecule in a Complex Mixture Using Solid-State Nanopore
Palladium–Silver-Activated ZnO Surface: Highly Selective Methane Sensor at Reasonably Low Operating Temperature
Metal
oxide semiconductors (MOS) are well known as reducing gas
sensors. However, their selectivity and operating temperature have
major limitations. Most of them show cross sensitivity and the operating
temperatures are also relatively higher than the value reported here.
To resolve these problems, here, we report the use of palladium–silver
(70–30%) activated ZnO thin films as a highly selective methane
sensor at low operating temperature (∼100 °C). Porous
ZnO thin films were deposited on fluorine-doped tin oxide (FTO)-coated
glass substrates by galvanic technique. X-ray diffraction showed polycrystalline
nature of the films, whereas the morphological analyses (field emission
scanning electron microscopy) showed flake like growth of the grains
mainly on xy plane with high surface roughness (107 nm). Pd–Ag
(70–30%) alloy was deposited on such ZnO films by e-beam evaporation
technique with three different patterns, namely, random dots, ultrathin
(∼1 nm) layer and thin (∼5 nm) layer as the activation
layer. ZnO films with Pd–Ag dotted pattern were found show
high selectivity towards methane (with respect to H<sub>2</sub>S and
CO) and sensitivity (∼80%) at a comparatively low operating
temperature of about 100°C. This type of sensor was found to
have higher methane selectivity in comparison to other commercially
available reducing gas sensor
Molecularly Imprinted Polymer Interface on Screen-Printed ZnO Nanorod Field Effect Transistors for Serotonin Detection in Clinical Samples
Ultrasensitive detection of serotonin is crucial for
the early
diagnosis of several diseases like Parkinson’s and Alzheimer’s.
Most of the existing detection strategies are still not suitable for
sensitive point-of-care applications. This study presents direct molecular
imprinting of serotonin on the surface of three-dimensional zinc oxide
(ZnO) nanorod devices connected in a field effect transistor (FET)
configuration to achieve ultrasensitive, real-time, and rapid detection
with a convenient and affordable approach, which has significant potential
for translation to clinical settings. This strategy has enabled pushing
the detection limit to 0.1 fM in a physiological analyte in real time
with screen-printed electrodes, thereby resulting in the convenient
batch fabrication of sensors for clinical validation. The response
of the sensor with the clinical sample has been correlated with that
of the gold standard and has been observed to be statistically similar
Palladium–Silver-Activated ZnO Surface: Highly Selective Methane Sensor at Reasonably Low Operating Temperature
A review on amperometric-type immunosensors based on screen-printed electrodes
In this brief review, we summarize the recent research activities involved in the development of amperometric-type immunosensors based on screen-printed electrodes (SPEs). We focus on the underlying principle involved in these types of sensors, their fabrication and electrode surface modification. We also discuss the various factors involved in the designing of such immunosensors and how they affect their performances. Finally we provide an insight into the rawbacks associated with these SPEs