ABSTRACT
Semiconducting single-walled carbon nanotubes (SWCNTs) with tailored corona phases (CPs), or surface-adsorbed molecules, have emerged as a promising interface for sensing applications. The adsorption of an analyte can be specifically transduced as a modulation of their band-gap near-infrared (nIR) photoluminescence (PL). One such CP ideal for this purpose is single-stranded DNA (ssDNA), where subsequent sequence-dependent hybridization can result in PL emission wavelength shifts. Due to ssDNA adsorption to the SWCNT surface, the resultant noncanonical hybridization and its effect on SWCNT photophysical properties are not well understood. In this work, we study 20- and 21-mer DNA and RNA hybridization on the complementary ssDNA-SWCNT CP in the context of nucleic acid sensing for SARS-CoV-2 sequences as model analytes. We found that the van't Hoff transition enthalpy of hybridization on SWCNT CP was −11.9 kJ mol-1, much lower than that of hybridization in solution (−707 kJ mol-1). We used SWCNT solvatochromism to calculate the solvent-exposed surface area to indicate successful hybridization. We found that having a 30-mer anchor region in addition to the complementary region significantly improved PL response sensitivity and selectivity, with a (GT)15 anchor preferred for RNA targets. Coincubation of ssDNA-SWCNTs with an analyte at 37 °C resulted in faster hybridization kinetics without sacrificing specificity. Other methods aimed to improve CP rearrangement kinetics such as bath sonication and surfactant additions were ineffective. We also determined that the target sequence choice is important as secondary structure formation in the target is negatively correlated with hybridization. Best-performing CPs showed detection limits of 11 and 13 nM for DNA and RNA targets, respectively. Finally, we simulated sensing conditions using the saliva environment, showing sensor compatibility in biofluids. In total, this work elucidates key design features and processing to enable sequence-specific hybridization on ssDNA-SWCNT CPs. © 2022 American Chemical Society.
ABSTRACT
COVID-19, which was first spread in China in 2019 and consequently spread worldwide, is caused by the SARS-CoV-2. Today, various carbon-based nanomaterials such as graphene, graphene oxide, carbon dots, and carbon nanotubes have been explored for the specific detection and targeted inhibition/inactivation of SARS-CoV-2 due to their great surface chemical structures, easy to-functionalization, biocompatibility, and low toxicity. According to exclusive inherent properties, carbon-based nanomaterials are promising candidates for targeted antiviral drug delivery and the inhibitory effects against pathogenic viruses based on photothermal effects or reactive oxygen species (ROS) formation. These high-stability nanomaterials exhibited unique physicochemical properties, providing efficient nanoplatforms for optical and electrochemical sensing and diagnostic applications with high sensitivity and selectivity. Up to now, these materials have been used for the fabrication of diagnostic kits, different types of personal protective equipment (PPE) such as anti-viral masks, vaccines, self-cleaning surfaces, and other subjects. This review article explores the most recent developments in carbon-based nanomaterials' diagnostic and therapeutic potential towards SARS-CoV-2 detection and inhibition, different mechanisms, challenges and benefits of the carbon-based nanomaterials.
ABSTRACT
This paper develops a multilayered triboelectric energy harvester and demonstrates its application as a smart floor mat. Triboelectrification is the process in which contact and separation between two triboelectric electrode surfaces result in the generation of opposite charges on them. Due to the tendency of conductive materials to attain charge equilibrium, the electrons flow from the ground to the conductor or vice versa to make it neutral. As a result, an alternating current (AC) flows in the external circuit as the materials contact and separate. In this work, we fabricated an array of triboelectric nanogenerators (TENG) by connecting eight zigzag-shaped multilayered TENGs (each containing three units) in series to realize a smart floor mat. The TENG array was sandwiched between two wooden slabs and was placed in front of the library entrance to control the occupancy by tracking the number of people entering/leaving. This smart floor mat generated a maximum output power of 119.7 μW, which lit up to 40 light-emitting diodes (2mA current with 10μF capacitance) when the mat was compressed and released periodically. The device will have potential applications in tracking the number of people entering/leaving a facility. In this Covid-19 era, the control of occupancy rate becomes more crucial in an indoor setting such as in libraries, shopping malls, etc. This study provides a simple, straightforward, and low-cost solution to achieving the control measure. In addition, the traditional occupancy tracking systems based on cameras, processors, and sensors are expensive compared to our low-cost and energy-efficient smart floor mat. Hence, our design has the potential to provide a promising alternative to the existing solutions. © 2022 IEEE.
ABSTRACT
Ionization spectra of substances are extensively used in their label free detection. Here we demonstrate the possibility of using plasma ionization to detect airborne and saliva SARS-COV-2 viruses through their emission spectra. It consists of an ionization chamber monitored by a fiber-optic UV-VIS spectrometer. The technique is completely label-free and can be programmed in real-time to detect different viral particles through their ionization emission spectra. Its average sensitivity for detecting deoxyribonucleic acid (DNA) bases in water is 20%/g in 1 mL of water. Its selectivity for DNA bases is through their relative emission peaks for adenine at 439.5 nm, cytosine at 440, thymine at 440.5, and guanine at 421.5 nm. The emission spectra of different electrode materials were also obtained to account for their contributions to the emission spectra of analytes. Gold electrodes were used owing to their resistance to corrosion and very low reaction with ionized species. The technique has the potential to be used in the point-of-care diagnostic and testing applications. IEEE