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Coronavirus 2019 (COVID-19) spreads an extremely infectious disease where there is no specific treatment. COVID-19 virus had a rapid and unexpected spread rate which resulted in critical difficulties for public health and unprecedented daily life disruption. Thus, accurate, rapid, and early diagnosis of COVID-19 virus is critical to maintain public health safety. A graphite oxide-based field-effect transistor (GO-FET) was fabricated and functionalized with COVID-19 antibody for the purpose of real-time detection of COVID-19 spike protein antigen. Thermal evaporation process was used to deposit the gold electrodes on the surface of the sensor substrate. Graphite oxide channel was placed between the gold electrodes. Bimetallic nanoparticles of platinum and palladium were generated via an ultra-high vacuum (UHV) compatible system by sputtering and inert-gas condensation technique. The biosensor graphite oxide channel was immobilized with specific antibodies against the COVID-19 spike protein to achieve selectivity and specificity. This technique uses the attractive semiconductor characteristics of the graphite oxide-based materials resulting in highly specific and sensitive detection of COVID-19 spike protein. The GO-FET biosensor was decorated with bimetallic nanoparticles of platinum and palladium to investigate the improvement in the sensor sensitivity. The in-house developed biosensor limit of detection (LOD) is 1 fg/mL of COVID-19 spike antigen in phosphate-buffered saline (PBS). Moreover, magnetic labelled SARS-CoV-2 spike antibody were studied to investigate any enhancement in the sensor performance. The results indicate the successful fabrication of a promising field effect transistor biosensor for COVID-19 diagnosis.

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Biomolecular detection methods have evolved from simple chemical processes to laboratory sensors capable of acquiring accurate measurements of various biological components. Recently, silicon nanowire field-effect transistors (SiNW-FETs) have been drawing enormous interest due to their potential in the biomolecular sensing field. SiNW-FETs exhibit capabilities such as providing real-time, label-free, highly selective, and sensitive detection. It is highly critical to diagnose infectious diseases accurately to reduce the illness and death spread rate. In this work, a novel SiNW-FET sensor is designed using a semiempirical approach, and the electronic transport properties are studied to detect the COVID-19 spike protein. Various electronic transport properties such as transmission spectrum, conductance, and electronic current are investigated by a semiempirical modeling that is combined with a nonequilibrium Green’s function. Moreover, the developed sensor selectivity is tested by studying the electronic transport properties for other viruses including influenza, rotavirus, and HIV. The results indicate that SiNW-FET can be utilized for accurate COVID-19 identification with high sensitivity and selectivity.

DNA detection has revolutionized medical and biological research fields. It provides a wealth of medical information for each individual, which can be used in a personalized medicinal procedure in the future. Genome sequence helps to enhance our perception of inheritance, disease, and individuality. This work aims to improve DNA sequencing accuracy and the overall current signal using a novel nano pore based sensor that is developed to detect and identify the DNA bases. Herein, a novel z-shaped field effect transistor with a nano pore for the aim of DNA detection is studied, where a gate terminal is added below the center of the z-shaped graphene nano ribbon. First-principle transport calculations are used to identify the DNA bases and electronic signature. An efficient density functional theory approach combined with non-equilibrium Green's function formalism (DFT + NEGF) are utilized to detect the transmission spectrum and current for DNA nucleo bases: Adenine, Thymine, Guanine, and Cytosine. Using transmission current, a distinctive electronic signature is generated for each DNA base to detect each DNA sequence. Various orientations and lateral position for each DNA base are considered. Moreover, the effect of decorating the developed DNA sensor with gold and silver nanoparticles on the sensor's electrical current and transmission spectra is studied and analyzed. The results suggest that the z-shaped sensor could achieve DNA sequencing with high accuracy. The practical implementation of this work represents the capability to anticipate and cure diseases from the genetic makeup perspective.

Graphene field effect transistor (FET) biosensors have attracted huge attention in the point-of-care and accurate detection. With the recent spread of the new emerging severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the need for rapid, and accurate detection & screening tools is arising. Employing these easy-to-handle sensors can offer cheap, rapid, and accurate detection. Herein, we propose the design of a reduced graphene oxide (rGO) FET biosensor for the detection of SARS-CoV-2. The main objective of this work is to detect the SARS-CoV-2 spike protein antigen on spot selectively and rapidly. The sensor consists of rGO channel, a pair of golden electrodes, and a gate underneath the channel. The channel is functionalized with COVID-19 spike protein antibodies to achieve selectivity, and with metal nanoparticles (MNPs) such as copper and silver to enhance the bio-sensing performance. The designed sensor successfully detects the SARS-CoV-2 spike protein and shows singular electrical behavior for detection. The semi-empirical modeling approach combined with none-equilibrium Green’s function were used to study the electronic transport properties of the rGO-FET biosensor before and after the addition of the target molecules. The sensor’s selectivity is also tested against other viruses. This study provides a promising guide for future practical fabrication.

The photo-isomerization of azobenzene (AZB) provides the essential stimulation for the controlled regulation of spin-crossover in the iron­(III)­porphyrin complex. We have performed theoretical simulations to predict the strategic design of a modular material via attachment of azobenzene to the iron­(III) center. The light-induced isomerization of azobenzene triggers a cascade of electronic changes resulting from a low to a high-spin transition in the electronic configurations of Fe­(III) ions. In principle, the successive conformational changes in AZB exert considerable distortion on the iron coordination sphere, subsequently changing the crystal field splitting pattern. The light-induced rotatory motion of AZB is the necessary driving force to manipulate the spin state of the Fe­(III) ion. The density functional theory-based calculations on the 2D extended porphyrin array and its coupling to AZB molecules affirm considerable changes in the electronic properties of the system. The consequence of light-induced isomerization in azobenzene effectively modulates the electronic transport behavior of the system in the two different spin states. This was checked through the calculations of transmission, conductance, and IV characteristics. The comprehensive spectral simulations manifest a reasonable correlation to the predicted spin crossover in the system, with clear evidence provided by the transport properties.