The quality by design approach for optimization of slayer exciter based low power portable atmospheric plasma jet on bactericidal efficacy of Pseudomonas aeruginosa.

A simple, portable, economical low-temperature atmospheric plasma (LTAP) for bactericidal efficacy of Gram-negative bacteria (Pseudomonas aeruginosa) with different carrier gases (argon, helium, and nitrogen) using the quality by design (QbD) approach, design of experiments (DoE), and response surface graphs (RSG) is presented. Box-Behnken design was used as the DoE to narrow down and further optimize the experimental factors of LTAP. Plasma exposure time, input DC voltage, and carrier gas flow rate were varied to examine the bactericidal efficacy using the zone of inhibition (ZOI). A higher bactericidal efficacy was achieved under the optimal bactericidal factors having ZOI of 50.837 ± 2.418 mm2 with the plasma power density of 132 mW/cm3 for LTAP-Ar at 61.19 s, 14.8747 V, and 219.379 sccm than LTAP-He and LTAP-N2 . The LTAP-Ar was further evaluated at different frequencies and probe lengths to achieve a ZOI of 58.237 ± 4.01 mm2 .

Influence of laser and alkali treatment on an Ag/TiO2nanotube based dopamine sensor.

Herein, TiO2nanotubes (T-NTs) arrays were subjected to two types of treatment followed by a simple metal deposition technique to significantly enhance the performances of T-NTs based electrochemical sensing of dopamine. The first type of treatment was done by soaking T-NTs in sodium hydroxide solution for an optimal time to enhance the conductivity and charge carrier density. The second type of treatment employed was laser irradiation, which induces crystallinity disorder and forms rutile TiO2, promoting active analyte adsorption sites. Afterward, silver (Ag) was electro-deposited on the T-NTs as a dopamine sensing catalyst to form T-NTs/Ag nanohybrids. The dual-treated T-NTs based sensor showed 3-fold enhancement in sensitivity (from 8.2µA mM-1cm-2to 32µA mM-1cm-2), reduced charge transfer resistance (from 38 × 10-6Ω to 0.7 × 10-6Ω), above 2 order higher donor charge density (from 3.58 × 1018cm-3to 1.41 × 1021cm-3), and reduced limit of detection (from 32.3µM to 2.8µM) in comparison to plain T-NTs based sensor. In addition, the sensitivity reported here is significantly higher than most of the previously reported TiO2based dopamine sensors. Perspective-wise, the dual treatment approach is a promising technique and is highly desirable for enhancing the performances of T-NTs and other nanomaterial based electrochemical sensors.

A label-free aptasensor FET based on Au nanoparticle decorated Co3O4 nanorods and a SWCNT layer for detection of cardiac troponin T protein.

Acute myocardial infarction (AMI) is a serious health problem that must be identified in its early stages. Considerable progress has been made in understanding the condition of AMI through ascertaining the role of biomarkers, such as myoglobin, cardiac troponin proteins (T and I), creatine kinase-MB, and fatty acid-binding protein (FABP). A field-effect transistor (FET) is an effective platform; however, innovations are required in all layers of the FET for it to become robust and highly sensitive. For the first time, we made use of the synergistic combination of noble metal nanoparticles (AuNPs) with Co3O4 for the detection of cardiac troponin T (cTnT) in a FET platform. We determined the morphology of Au-decorated Co3O4 NRs and their electronic properties by characterizing the channel layer using electron microscopies and transient measurements. Subsequently, we performed the detection of cardiac troponin T by immobilizing its complementary biotinylated DNA aptamer on the channel surface using a drop-casting method. To understand the changes in drain current caused by this interaction, we probed our SWCNT-Co3O4 NR transistor with limited gate and drain bias (≤1 V), achieving a sensitivity of 0.5 µA µg-1 mL-1 for the Au-decorated NRs. A 250% increase in the sensitivity and a limit of detection (LOD) of 0.1 µg mL-1 were achieved by using this device. Finally, selectivity studies proved that this synergistic combination works well in the FET configuration for the successful detection of cTnT.

A Comparative Study of Interdigitated Electrode and Quartz Crystal Microbalance Transduction Techniques for Metal⁻Organic Framework-Based Acetone Sensors.

We present a comparative study of two types of sensor with different transduction techniques but coated with the same sensing material to determine the effect of the transduction mechanism on the sensing performance of sensing a target analyte. For this purpose, interdigitated electrode (IDE)-based capacitors and quartz crystal microbalance (QCM)-based resonators were coated with a zeolitic⁻imidazolate framework (ZIF-8) metal⁻organic framework thin films as the sensing material and applied to the sensing of the volatile organic compound acetone. Cyclic immersion in methanolic precursor solutions technique was used for depositing the ZIF-8 thin films. The sensors were exposed to various acetone concentrations ranging from 5.3 to 26.5 vol % in N2 and characterized/compared for their sensitivity, hysteresis, long-term and short-term stability, selectivity, detection limit, and effect of temperature. Furthermore, the IDE substrates were used for resistive transduction and compared using capacitive transduction.

Tunable nanoelectromechanical resonator for logic computations.

There has been remarkable interest in nanomechanical computing elements that can potentially lead to a new era in computation due to their re-configurability, high integration density, and high switching speed. Here we present a nanomechanical device capable of dynamically performing logic operations (NOR, NOT, XNOR, XOR, and AND). The concept is based on the active tuning of the resonance frequency of a doubly-clamped nanoelectromechanical beam resonator through electro-thermal actuation. The performance of this re-configurable logic device is examined at elevated temperatures, ranging from 25 °C to 85 °C, demonstrating its resilience for most of the logic operations. The proposed device can potentially achieve switching rate in µs, switching energy in nJ, and an integration density up to 106 per cm2. The practical realization of this re-configurable device paves the way for nano-element-based mechanical computing.

In-Plane MEMS Shallow Arch Beam for Mechanical Memory.

We demonstrate a memory device based on the nonlinear dynamics of an in-plane microelectromechanical systems (MEMS) clamped⁻clamped beam resonator, which is deliberately fabricated as a shallow arch. The arch beam is made of silicon, and is electrostatically actuated. The concept relies on the inherent quadratic nonlinearity originating from the arch curvature, which results in a softening behavior that creates hysteresis and co-existing states of motion. Since it is independent of the electrostatic force, this nonlinearity gives more flexibility in the operating conditions and allows for lower actuation voltages. Experimental results are generated through electrical characterization setup. Results are shown demonstrating the switching between the two vibrational states with the change of the direct current (DC) bias voltage, thereby proving the memory concept.

Site-specific and patterned growth of TiO2 nanotube arrays from e-beam evaporated thin titanium film on Si wafer.

Growth of TiO(2) nanotubes on thin Ti film deposited on Si wafers with site-specific and patterned growth using a photolithography technique is demonstrated for the first time. Ti films were deposited via e-beam evaporation to a thickness of 350-1000 nm. The use of a fluorinated organic electrolyte at room temperature produced the growth of nanotubes with varying applied voltages of 10-60 V (DC) which remained stable after annealing at 500 °C. It was found that variation of the thickness of the deposited Ti film could be used to control the length of the nanotubes regardless of longer anodization time/voltage. Growth of the nanotubes on a SiO(2) barrier layer over a Si wafer, along with site-specific and patterned growth, enables potential application of TiO(2) nanotubes in NEMS/MEMS-type devices.

Growth and characterization of TiO2 nanotubes from sputtered Ti film on Si substrate.

In this paper, we present the synthesis of self-organized TiO2 nanotube arrays formed by anodization of thin Ti film deposited on Si wafers by direct current (D.C.) sputtering. Organic electrolyte was used to demonstrate the growth of stable nanotubes at room temperature with voltages varying from 10 to 60 V (D.C.). The tubes were about 1.4 times longer than the thickness of the sputtered Ti film, showing little undesired dissolution of the metal in the electrolyte during anodization. By varying the thickness of the deposited Ti film, the length of the nanotubes could be controlled precisely irrespective of longer anodization time and/or anodization voltage. Scanning electron microscopy, atomic force microscopy, diffuse-reflectance UV-vis spectroscopy, and X-ray diffraction were used to characterize the thin film nanotubes. The tubes exhibited good adhesion to the wafer and did not peel off after annealing in air at 350 °C to form anatase TiO2. With TiO2 nanotubes on planar/stable Si substrates, one can envision their integration with the current micro-fabrication technique large-scale fabrication of TiO2 nanotube-based devices.