Transition Metal (Cu, Pd, and Ag)-Modified Nb2S2C Monolayer for Highly Efficient Catechol Sensing: A First-Principles Investigation.

Motivated by recent advancements and the escalating application of two-dimensional (2D) gas or molecule sensors, this study explores the potential of the 2D Nb2S2C monolayer for detecting biomolecule catechol (Cc), whose excess concentration is highly dangerous to living beings. We use first-principles density functional theory (DFT) calculations to assess the Cc sensing performance of pure and transition metal (TM = Cu, Pd, Ag)-modified Nb2S2C monolayers. The Nb2S2C monolayer belonging to the new class of synthesized 2D materials, TM carbo-chalcogenides (TMCC), combines distinctive properties from both TM dichalcogenides and TM carbides and exhibits physisorption (-0.66 eV) toward the Cc molecule. Notably, the surface modifications with these TMs significantly enhanced the adsorption energy of Cc. The chemisorption of the Cc molecule on the Pd to Cu-modified monolayer is demonstrated with adsorption energies ranging from -1.09 to -1.3 eV and is due to the robust charge transfer and orbital interactions between the valence orbitals of TMs and Cc. In addition, the modification of the surface by TM leads to an increased work function sensitivity toward the Cc molecule. The study establishes the thermal stability at 300 K and dynamic stability of TM-Nb2S2C through ab initio molecular dynamics (AIMD) simulations and Phonon calculations, respectively. The theoretical estimation of achievable recovery time at 400 and 450 K for Pd and Ag and at 500 K for the Cu-modified Nb2S2C monolayer, respectively, confirms the potential practical application of the sensor for Cc detection. These compelling characteristics position the Nb2S2C monolayer as a promising nanomaterial for detecting Cc molecules in the environment.

Defect engineered N-S codoped TiO2 nanoparticles for photocatalytic and optical limiting applications: Experimental and DFT insights.

N-S codoped TiO2 nanoparticles (NPs) were synthesized using a sol-gel cum hydrothermal approach, with ammonium sulfate as the nitrogen and sulfur source compound. The calcination temperature was varied from 500 to 700 °C. The pristine samples exhibited a mixed phase of anatase and brookite, while the doped samples exhibited only the anatase phase, as confirmed by X-ray diffraction (XRD) analysis. Fourier-transform infrared spectroscopy (FTIR) confirmed the presence of N-H vibrations and S-O bidentate complexation with Ti4+ ions. Electron paramagnetic resonance (EPR) revealed the presence of Ti3+ signals, confirming the creation of oxygen defects in the doped samples. The absorption and emission properties of the samples were investigated using ultraviolet-visible (UV-Vis) and photoluminescence (PL) spectroscopy. Vibrating sample magnetometry (VSM) analysis confirms the room-temperature ferromagnetic behavior of the N-S doped TiO2, which was attributed to the presence of oxygen vacancies, as evidenced by the EPR and PL results. The N-S doped TiO2 samples demonstrated superior photocatalytic degradation of Rhodamine B (RhB), Methylene Blue (MB), and Congo Red (CR) dyes under visible light illumination compared to the pristine TiO2. This enhanced performance was attributed to the presence of N and S dopants in TiO2, which create new energy levels within the band structure of TiO2, allowing for efficient absorption of visible light and subsequent generation of reactive species for dye degradation. N-S doping modifies the electronic structure of TiO2, enhancing two-photon absorption (TPA). This increased TPA efficiency suggests promising applications in optical devices, such as laser protection systems and optical limiters. Density Functional Theory (DFT) investigation also confirms that the presence of oxygen vacancies generates energy states below the conduction band. This, in turn, benefits the absorption of more visible light during photocatalytic activities and leads to a notable nonlinear absorption in optical limiting. Overall, the N-S doping strategy significantly improves the photocatalytic and optical limiting performance of TiO2 NPs, making them promising candidates for a wide range of applications.

Catechol Sensing Performance of Pd-Functionalized Two-Dimensional Polyaramid: A DFT Investigation.

Catechol (Cc) molecule adsorption on a pristine and transition metal (TMs = Sc, Pd, and Cu)-functionalized two-dimensional polyaramid (2DPA) monolayer is systematically studied by the first-principles density functional theory method. The weak physisorption (-0.29 eV) and charge transfer of the Cc molecule with p-2DPA result in a very quick recovery time (150 µs), hindering the Cc sensing capability of p-2DPA. Although TM functionalization greatly improved the adsorption ability, the Pd-functionalized 2DPA was shown to be the best choice for Cc adsorption due to the reasonable adsorption energy of -1.39 eV and expedited charge transfer between the Cc and Pd atom. The change of band gap and, hence, the conductivity of the Pd-2DPA system in response to the adsorption of the Cc molecule demonstrate its higher sensitivity than that of p-2DPA. The work function sensitivity of Pd-2DPA upon the Cc adsorption is also investigated. In addition to the change in the electronic properties, the change in the optical properties of Pd-2DPA after Cc adsorption is also analyzed. The structural stability of Pd-2DPA is validated by performing ab initio molecular dynamics simulations at 300 K. The complete desorption of the Cc molecule from Pd-2DPA is attained by annealing the material at 550 K under visible light (τ = 5.4 s) and at 450 K under UV light (τ = 3.7 s). Moreover, the higher diffusion energy barrier of +1.35 eV confirmed that the functionalized Pd atoms did not diffuse through the crystal to form clusters. This study could lay a theoretical foundation for developing possibly new-generation sensors for detecting Cc molecules.

Influence of vacancy defects on 2D BeN4monolayer for NH3adsorption: a density functional theory investigation.

Two-dimensional materials have attracted a great deal of interest in developing nanodevices for gas-sensing applications over the years. The 2D BeN4monolayer, a recently synthesized single-layered Dirac semimetal, has the potential to function as a gas sensor. This study analyzes the NH3sensing capacity of the pristine and vacancy-induced BeN4monolayers using first-principles density functional theory (DFT) calculations. As per the results, the NH3molecule is physisorbed on the pristine BeN4via weak Van der Waals interaction with a poor adsorption energy of -0.41 eV and negligible charge transfer. Introducing Be vacancy in BeN4increased the NH3adsorption energy to -0.83 eV due to the improved charge transfer (0.044 e) from the defective monolayer to the NH3molecule. The structural stability, sufficient recovery time (74 s) at room temperature, and superior work function sensitivity promise the potential application of defective BeN4as an NH3sensor. This research will be a theoretical groundwork for creating innovative BeN4-based NH3gas sensors.

Metal-decorated γ-graphyne as a drug transporting agent for the mercaptopurine chemotherapy drug: a DFT study.

In recent years, carbon-based two-dimensional (2D) materials have gained popularity as the carriers of various anticancer therapy drugs, which could reduce the crucial side effects by directly applying the drugs to the intended tumor cells. In this study, through first-principles density functional theory simulations, we have investigated the adsorption properties of a famous cancer chemotherapy drug called mercaptopurine (MC) on a 2D γ-graphyne (GYN) monolayer. Analyzing the geometric and electronic properties, we can summarize that the MC interaction with the pristine GYN is weak, with a small adsorption energy of -0.15 eV, which is too low for potential applications. Therefore, we have decorated the GYN monolayer with biocompatible metals such as Al, Ag, and Cu to trigger the adsorption capacity. The Al- and Cu-decorated GYN offered improved adsorption towards MC compared to the pristine case. The drug release from these metal-decorated systems was examined by creating an acidic environment. In addition, the desorption temperature of the drug from the system was also evaluated using ab initio molecular dynamics simulations. The calculations demonstrated that the Al-decorated GYN is a potential vehicle for MC drug delivery because of the favourable adsorption energy of -0.63 eV, charge transfer of 0.17e and desorption temperature above 270 K. The current research will stimulate the investigation of other low-dimensional carbon materials for drug-delivery applications.

Recent Developments and Future Perspective on Electrochemical Glucose Sensors Based on 2D Materials.

Diabetes is a health disorder that necessitates constant blood glucose monitoring. The industry is always interested in creating novel glucose sensor devices because of the great demand for low-cost, quick, and precise means of monitoring blood glucose levels. Electrochemical glucose sensors, among others, have been developed and are now frequently used in clinical research. Nonetheless, despite the substantial obstacles, these electrochemical glucose sensors face numerous challenges. Because of their excellent stability, vast surface area, and low cost, various types of 2D materials have been employed to produce enzymatic and nonenzymatic glucose sensing applications. This review article looks at both enzymatic and nonenzymatic glucose sensors made from 2D materials. On the other hand, we concentrated on discussing the complexities of many significant papers addressing the construction of sensors and the usage of prepared sensors so that readers might grasp the concepts underlying such devices and related detection strategies. We also discuss several tuning approaches for improving electrochemical glucose sensor performance, as well as current breakthroughs and future plans in wearable and flexible electrochemical glucose sensors based on 2D materials as well as photoelectrochemical sensors.

Catechol sensor based on pristine and transition metal embedded holey graphyne: a first-principles density functional theory study.

To develop a highly sensitive and selective biosensor for detecting noxious biomolecules from the environment, we examined catechol (Cc) adsorption in pristine and transition metal (TM = Sc, Cu, and Pd) embedded 2D holey graphyne (hGY) monolayers using the first-principles density functional theory method. The interaction between Cc and the pristine hGY is purely weak, and hence the response of the sensing device will be difficult to detect. Therefore, the TM doping strategy is adopted to improve the sensitivity. According to our findings, Sc binds strongly to the hGY monolayer, with a binding energy of -4.09 eV and a charge transfer of 1.89e from the valence orbitals of Sc to the C 2p orbitals. Later on, the Cc adsorption on the TM-embedded hGY was investigated. The interaction of Cc with the transition metal involves charge transfer from Cc to the metal d orbital. A large binding energy of -3.22 eV and a significant charge transfer of about 0.9e from the O 2p orbitals of Cc to the valence orbital of Sc suggest that the Sc embedded hGY monolayer is a good choice for the efficient sensing of Cc molecules. Furthermore, ab initio MD simulations confirmed the structural stability of the Sc + hGY system at room temperature. We strongly believe that this theoretical work will aid the experimentalists in designing and developing 2D semiconducting nanolayer-based biosensors for commercial purposes.