A review of the role of graphene-based nanomaterials in tackling challenges posed by the COVID-19 pandemic

In 2020, the World Health Organization (WHO) declared a pandemic due to the emergence of the coronavirus disease (COVID-19) which had resulted by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). At present, the emergence of many new variants and mutants were found to be more harmful compared to the previous strains. As a result, research scientists around the world had devoted significant efforts to understand the mechanism, causes and transmission due to COVID-19 along with the treatment to cure these diseases. However, despite achieving several findings, much more was unknown and yet to be explored. Hence, along with these developments, it is also extremely essential to design effective systems by incorporating smart materials to battle the COVID-19. Therefore, several approaches have been implemented to combat against COVID-19. Recently, the graphene-based materials have been explored for the current COVID-19 and future pandemics due to its superior physicochemical properties, providing efficient nanoplatforms for optical and electrochemical sensing and diagnostic applications with high sensitivity and selectivity. Moreover, based on the photothermal effects or reactive oxygen species formation, the carbon-based nanomaterials have shown its potentiality for targeted antiviral drug delivery and the inhibitory effects against pathogenic viruses. Therefore, this review article sheds light on the recent progress and the most promising strategies related to graphene and related materials and its applications for detection, decontamination, diagnosis, and protection against COVID-19. In addition, the key challenges and future directives are discussed in detail for fundamental design and development of technologies based on graphene-based materials along with the demand aspects of graphene-based products and lastly, our personal opinions on the appropriate approaches to improve these technologies respectively.

Past-expiration-date liquid disinfectants to deactivate biological and chemical toxins on building material surfaces

In this study, we evaluated the deactivating efficacy of strong basicity-based (T4-102) and hydrogen peroxide-based (DF-200) disinfectants that were past their expiration date when used to deactivate biological and chemical toxins on building material surfaces. The decontamination efficacies of DF-200 and T4-102 disinfectants against dimethyl methylphosphonate (DMMP) and 2-chloroethyl ethylsulfide (2-CEES) were studied using GC-MS analysis. The bactericidal efficacies of disinfectants against Gram-negative E. coli and P. aeruginosa, and Gram-positive B. subtilis and S. aureus, were assessed in terms of the zone of inhibition, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC). The results indicated that the deactivation efficacy varied significantly according to the disinfectant amount, contact time, and building material. Higher efficacy of up to 99-100% was observed for biological toxins, despite passing their expiration dates. Approximately 70-78% of deactivation efficacies were observed for disinfectants against DMMP on the tile coupon at 100 μL and 24 h contact time. Moreover, the deactivation efficacy of DF-200 was better than that of T4-102. The data presented here demonstrate that the responders may use past-expiration-date disinfectants for efficacious disinfectaion in large-scale contamination incidents.

Functionalized graphene oxide-based lamellar membranes for organic solvent nanofiltration applications

In this study, two-dimensional graphene oxide-based novel membranes were fabricated by modifying the surface of graphene oxide nanosheets with six-armed poly(ethylene glycol) (PEG) at room conditions. The as-modified PEGylated graphene oxide (PGO) membranes with unique layered structures and large interlayer spacing (∼1.12 nm) were utilized for organic solvent nanofiltration applications. The as-prepared 350 nm-thick PGO membrane offers a superior separation (>99%) against evans blue, methylene blue and rhodamine B dyes along with high methanol permeance ∼ 155 ± 10 L m^-2 h^-1, which is 10-100 times high compared to pristine GO membranes. Additionally, these membranes are stable for up to 20 days in organic solvent. Hence the results suggested that the as-synthesized PGO membranes with superior separation efficiency for dye molecules in organic solvent can be used in future for organic solvent nanofiltration application.

Recent progress on fabrication methods of graphene-based membranes for water purification, gas separation, and energy sustainability

Graphene-based layered materials have got significant interest in membrane technology for water desalination, gas separation, organic nanofiltration, pervaporation, proton exchange applications, etc. and show remarkable results. Up to date, various methods have been developed for fabrication of high performance membrane. Most of them are only suitable for research purposes, but not appropriate for mass transport barrier and membrane applications that require large-area synthesis. In this comprehensive review, we summarized the current synthesis and fabrication methods of graphene-based membranes. Emphasis will be given on fabrication of both graphene-based nanoporous and lamellar membranes. Finally, we discuss the current engineering hurdles and future research directions yet to be explored for fabrication of such membranes.

Review elucidating graphene derivatives (GO/rGO) supported metal sulfides based hybrid nanocomposites for efficient photocatalytic dye degradation

Photocatalysis by utilizing semiconductors for the removal of toxic pollutants has gained tremendous interest for remediation purposes. The organic pollutants usually include; pesticides, dyes and other phenolic compounds. An imperative restraint associated with the photocatalytic effectiveness of the catalyst is the rapid recombination of the light generated electrons and holes. The particle agglomeration and electron-hole recombination hinders the rate of pollutant removal. For decades, researchers have used metal-sulfides efficiently for photocatalytic dye degradation. The recent use of hybrid nanomaterials with the combination of graphene derivatives such as graphene oxide and reduced graphene oxide (GO/rGO)-metal sulfide has gained interest. These composites have displayed an impressive upsurge in the photocatalytic activity of materials. The current review describes the various researches on dye photodegradation by employing (GO/rGO)-metal sulfide, exhibiting a boosted potential for photocatalytic dye degradation. A comprehensive study on (CuS, ZnS and CdS)–GO/rGO hybrid composites have been discussed in detail for effective photocatalytic dye degradation in this review. Astonishingly improved dye degradation rates were observed in all these studies employing such hybrid composites. The several studies described in the review highlighted the varying degradation rates based on diverse research parameters and efficacy of graphene derivatives for enhancement of photocatalytic activity.