O2 adsorption on defective Penta-Graphene lattices: A DFT study

Adsorption of singlet and triplet oxygen on B-doped graphene: adsorption and electronic characteristics

The density functional calculations of electronic and structural properties of the adsorption of dioxygen on boron-doped graphene surfaces are conducted using spin-polarized density functional theory methods, including van der Waals correction. The results show significant differences in the adsorption characteristics of singlet and triplet oxygen on boron-doped graphene surfaces. Both triplet and singlet show only weak attraction to intrinsic and singly doped graphene. The singlet oxygen adsorption on doped graphene shows fascinating features involving chemisorption with dioxetane ring formation with appreciable charge transfer. In contrast, the triplet oxygen is only weakly physisorbed on the boron-doped surfaces. Chemisorption of singlet oxygen occurs with noticeable charge transfer and leads to almost featureless band structures, while the triplet oxygen physisorption proceeds with a well-defined band structure. Chemisorption of the singlet oxygen is attributed to the enormous mixing of π* of dioxygen and the p-orbitals of dopant and carbon. Because of the difference in adsorption characteristics, chemically modified graphene can find use in detecting and trapping singlet oxygen, which has potential applications in photodynamic therapy.

First-Principles Insight into a B4C3 Monolayer as a Promising Biosensor for Exhaled Breath Analysis

Nanomaterial-based room temperature gas sensors are used as a screening tool for diagnosing various diseases through breath analysis. The stable planar structure of boron carbide (B₄C₃) is utilized as a base material for adsorption of human breath exhaled VOCs, namely formaldehyde, methanol, acetone, toluene along, with interfering gases of carbon dioxide and water. The adsorption energy, charge density, density of states, energy band gap variation, recovery time, sensitivity, and work function of adsorbed molecules on pristine B₄C₃ are analyzed by density functional theory. The computed adsorption energies of VOC are in the range of - 0.176 to - 0.238 eV, and a larger interaction distance validate the physisorption behavior of these VOCs biomarkers on pristine boron carbide monolayer. Minute changes are determined from the electronic band structure of all adsorbed systems conserving the semiconducting nature of the B₄C₃ monolayer. The band gap variation upon adsorption of VOCs and interfering gases is examined between 0.05 and 0.52%. The 13.63 × 10^-9 s recovery time of methanol is slower among VOCs, and 0.556 × 10^-9 s of carbon dioxide (CO₂) is faster for desorption. The results reveal that boron carbide can be utilized as a biosensor at room temperature for the analysis of exhaled VOCs from human breath.

Emerging properties of carbon based 2D material beyond graphene

Graphene turns out to be the pioneering material for setting up boulevard to a new zoo of recently proposed carbon based novel two dimensional (2D) analogues. It is evident that their electronic, optical and other related properties are utterly different from that of graphene because of the distinct intriguing morphology. For instance, the revolutionary emergence of Dirac cones in graphene is particularly hard to find in most of the other 2D materials. As a consequence the crystal symmetries indeed act as a major role for predicting electronic band structure. Since tight binding calculations have become an indispensable tool in electronic band structure calculation, we indicate the implication of such method in graphene's allotropes beyond hexagonal symmetry. It is to be noted that some of these graphene allotropes successfully overcome the inherent drawback of the zero band gap nature of graphene. As a result, these 2D nanomaterials exhibit great potential in a broad spectrum of applications, viz nanoelectronics, nanooptics, gas sensors, gas storages, catalysis, and other specific applications. The miniaturization of high performance graphene allotrope based gas sensors to microscopic or even nanosized range has also been critically discussed. In addition, various optical properties like the dielectric functions, optical conductivity, electron energy loss spectra reveal that these systems can be used in opto-electronic devices. Nonetheless, the honeycomb lattice of graphene is not superconducting. However, it is proposed that the tetragonal form of graphene can be intruded to form new hybrid 2D materials to achieve novel superconducting device at attainable conditions. These dynamic experimental prospects demand further functionalization of these systems to enhance the efficiency and the field of multifunctionality. This topical review aims to highlight the latest advances in carbon based 2D materials beyond graphene from the basic theoretical as well as future application perspectives.