The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a single-stranded RNA virus closely related to bat-derived SARS-like coronaviruses that first emerged in Wuhan, China, in December 2019 [1][2]. On March 11, 2020, the WHO declared COVID-19 a global pandemic [3]. Since then, the virus has rapidly spread around the globe, infecting millions of people. SARS-CoV-2 is the causative agent of COVID-19. Common causes or symptoms of COVID-19 are fever, dry cough, and for some patients, with difficulty breathing, muscle or joint pain, headache or dizziness, a decreased sense of taste and smell, diarrhea, and nausea. Some of the patients will develop acute respiratory distress syndrome, characterized by difficult breathing and low blood oxygen levels, which may directly result in respiratory failure. The attack of the virus and the vast release of cytokines (cytokine storm) can result in inducing multi-organ damage, which may lead to organ failure. Secondary infection and symptoms of sepsis cause death in 28% of fatal Covid-19 patients [4][5].
Figure 1 shows that favipiravir, also known as T-705 (6-fluoro-3-hydroxy-2-pyrazinecarboxamide: C5H4FN3O2), has broad-spectrum antiviral activity against several pathogenic viruses discussed in [6][7]. It was developed by Fujifilm Toyama Chemical Company in Japan. It particularly inhibits RNA-dependent RNA polymerase (RdRP) [8][9]. FVP is marketed in China (Favilavir) and Japan (Avigan) as a second-line treatment of novel coronaviruses or re-emerging influenza outbreaks [10]. This one may have antiviral action on SARS-CoV-2, which is an RNA virus. Favipiravir effectively inhibits the SARS-CoV-2 infection by blocking its RNA syntheses, and FVP, approved for influenza treatment, can effectively inhibit RNA-dependent RNA viruses such as influenza, Ebola, chikungunya, yellow fever, norovirus, and enterovirus, and recent research reported its activity against Covid-19 [11][12]. It was emphasized as a lethal Ebola virus treatment during the pandemic in the West Africa in 2014 [13]. Clinical trials were initiated early in the pandemic to assess the efficacy of HCQ and favipiravir in treating COVID-19 patients. The antimalarial drug hydroxychloroquine, the influenza drug oseltamivir, and the antiretrovirals lopinavir/ritonavir, darunavir/ritonavir, remdesivir, and favipiravir are some potential drugs listed globally in various combinations for the treatment of COVID-19 [2][14].
In the literature, several analytical techniques have been stated for the detection of FVP in pharmaceutical and
biological samples, in addition to high-performance liquid chromatography (HPLC) and ultraviolet spectra (UV) [15], colorimetric analysis method (CAM) [16], thin layer chromatography (TLC) [17], and liquid chromatography-tandem mass spectrometry (LC-MS) [18]. Among the most extensively used instrumental methods, the electrochemical technique offers a suitable method with good physicochemical properties such as being inexpensive, having high catalytic activity, high sensitivity, and selectivity [19][20].Thus, electrochemical sensors are broadly used to determine trace amounts of drugs and other analytes in pharmaceutical, biological, and environmental samples [21]. Electrochemical sensors have to be enhanced with good materials to improve their analytical performance. If we use a simple bare electrode, it has more drawbacks. Here, we used nanomaterials as conducting materials for electrochemical sensors. Thus, carbon nanomaterials are profitable because they increase interfacial adsorption properties [22].
Graphene is a carbon allotrope that is widely used in material science, chemistry, physics, and nanotechnology. It has a unique nanostructure that consists of a flat monolayer with sp2 bonding nature between the carbon atoms and a tightly arranged two-dimensional honeycomb lattice[23][24][25]. It has great applications, such as nanoelectronic devises applied to the DNA sensor, etc.[26]
In2O3 is a low-cost, ecofriendly, n-type semiconductor with redox activity in nature. Recently, In2O3 has taken much attention because of its wide bandgap range (Eg∼3.65 eV), high optical transmittance, high electrical conductivity, good luminescence, and potential applications in gas sensing. It also has various morphologies, such as nanocones, nanobouquets, and nanotowers, [27][28][29], hollow microspheres [30], hollow nanofibers [31], urchin-like In2O3, etc. [32]. In2O3 nanostructures, in particular, with improved sensing properties, were used to detect C2H5OH, HCHO, and NH3 [33]. In2O3 is used due to its low toxicity, electronic structure, and structural stability [34]. superior theoretical abilities [35]. used as electrodes, luminophore, catalyst, solar cells, etc. [36]. Among the nanomaterials used as surface modifiers in electrochemical sensors, G/In2O3 has taken much heed due to its greater sensitivity, low toxicity, and low recovery time against hydrogen gas sensing [37]. NO2 gas sensor monitors, health, and the environment can all benefit from In2O3 cubes/rGO [38]. Bastakoti et al. reported that an In2O3/Carbon composite modified electrode showed outstanding rate capability or cycle performance, which will enhance the electrochemical energy storage capability of the compound. Chen et al. recorded through In2O3 nanowires/carbon nanotubes a prototype of flexible, transparent super capacitors with a specific surface area [39][40]. The distinctive features of G/In2O3 enhance the conducting surface area of the sensor and enhance the active sites for the combination and immobilization of G@In2O3 nanoparticles, which trigger good catalytic activity towards the electrochemical oxidation of FVP.
In this existing work, G/In2O3 nanomateriale were blended by an easy and simple precipitation process to construct the electrochemical sensor. G/In2O3 approves that particularly advanced performance to detect trace amounts of FVP in a real sample with urine and tablets also has acceptable ease and cost effectiveness. Its detection and synthesis techniques are methodically shown in Scheme 1.