Abstract: In this study, we conducted a systematic density functional theory (DFT) investigation of the interaction between Ti3C2-MXene monolayer and biological molecules dopamine (DA) and serine (Ser) as neurotransmitter and amino acid, respectively. Our calculations show good agreement with previous literature findings for the optimized Ti3C2 monolayer. We found that DA and Ser molecules bind to the Ti3C2 surface with adsorption energies of -2.244 eV and -3.960 eV, respectively. The adsorption of Ser resulted in the dissociation of one H atom. Electronic density of states analyses revealed little changes in the electronic properties of the Ti3C2-MXene monolayer upon adsorption of the biomolecules. We further investigated the interaction of DA and Ser with Ti3C2 monolayers featuring surface -termination with OH functional group, and Ti -vacancy. Our calculations indicate that the adsorption energies significantly decrease in the presence of surface termination, with adsorption energies of -0.097 eV and -0.330 eV for DA and Ser, respectively. Adsorption energies on the Ti -vacancy surface, on the other hand, are calculated to be -3.584 eV and -3.856 eV for DA and Ser, respectively. Our results provide insights into the adsorption behavior of biological molecules on Ti3C2-MXene, demonstrating the potential of this material for biosensing and other biomedical applications. These findings highlight the importance of surface modifications in the development of functional materials and devices based on Ti3C2-MXene, and pave the way for future investigations into the use of 2D materials for biomedical applications.

Abstract: Nitrogen-doped diamond (N-D) is one of the most important carbon-based electronic and optical materials. Here we study the terahertz (THz) magneto-optical (MO) properties of N-D grown by microwave plasma-enhanced chemical vapor deposition. The optical microscope, SEM, XRD, Raman spectrum, FTIR spectroscopy and XPS are used for the characterization of N-D samples. Applying THz time-domain spectroscopy (TDS), in combination with the polarization test and the presence of magnetic field in Faraday geometry, THz MO transmissions through N-D are measured from 0 to 8 T at 80 K. The complex right- and left-handed circular transmission coefficients and MO conductivities for N-D are obtained accordingly. Through fitting the experimental results with theoretical formulas of the dielectric constant and MO conductivities for an electron gas, we are able to determine magneto-optically the key electronic parameters of N-D, such as the static dielectric constant epsilon b, the electron density ne, the electronic relaxation time tau, the electronic localization factor alpha and, particularly, the effective electron mass m* obtained under non-resonant condition. The dependence of these parameters upon magnetic field is examined and analyzed. We find that the MO conductivities of N-D can be described rightly by the MO Drude-Smith formulas developed by us previously. It is shown that N-doping and the presence of the magnetic field can lead towards the larger epsilon b and heavier m* in diamond, while ne/tau/alpha in N-D decreases/increases/decreases with increasing magnetic field. The results obtained from this work are benefit to us in gaining an in-depth understanding of the electronic and optoelectronic properties of N-D.