Three distinct conductance states in polycyclic aromatic hydrocarbon derivatives.

Tight-binding model (TBM) and density functional theory (DFT) calculations were employed. Both simulations have demonstrated that the electrical conductance for eight polycyclic aromatic hydrocarbons (PAHs) can be modulated by varying the number of aromatic rings (NAR) within the aromatic derivatives. TBM simulations reveal three distinct conductance states: low, medium and high for the studied PAH derivatives. The three distinct conductance states suggested by TBM are supported by DFT transmission curves, where the low conductance evidenced by T(E) = 0, for benzene, naphthalene, pyrene and anthracene. While azulene and anthanthrene exhibit a medium conductance as T(E) = 1, and tetracene and dibenzocoronene possess a high conductance with T(E) = 2. Low, medium and high values were elucidated according to the energy gap E g and E g gaps are strongly dependent on the NAR in the PAH derivatives. This study also suggests that any PAH molecules are a conductor if E g < 0.20 eV. A linear relationship between the conductance and NAR (G ∝ NAR) was found and conductance follows the order G (benzene, 1 NAR) < G (anthanthrene, 4 NAR) < G (dibenzocoronene, 9 NAR). The proposed study suggests a relevant step towards the practical application of molecular electronics and future device application.

Mg/S@g-C3N4 nanosheets: A promising fluorescence sensor for selective Cu2+ detection in water.

This work describes the development of a novel fluorescence sensor based on magnesium/S@g-C3N4 nanosheets for selective detection of copper (Cu2+) ions in water. Mg/S@g-C3N4 nanosheets were prepared by the polycondensation technique and investigated by X-ray diffraction (XRD), ATR-FTIR spectroscopy, scanning electron microscopy (SEM), surface area (BET), and UV-Vis optical absorption measurements. XRD and ATR-FTIR analysis showed the characteristic peaks for S@g-C3N4. The broad full width at half maximum (0.056 radians) implies a smaller crystallite size, representing smaller Mg/S@g-C3N4 sheets. SEM micrograph showed non-exfoliated nanosheets with flake-like structures. The EDS mapping confirmed the presence of magnesium, carbon, nitrogen, and sulfur throughout the nanosheets. The Mg/S@g-C3N4 nanosheets possess a high surface area of 40 m2/g and mesopores within the nanosheets, with a size of 1.57 nm. The band gap of the Mg/S@g-C3N4 nanosheet was estimated to be 3.0 eV. The sensor exhibits a strong quenching response towards Cu2+ ions, with a decrease in fluorescence intensity as the concentration of Cu2+ increased from 1 µM to 20 µM. The Stern-Volmer quenching constant (KSV) showed a relatively high value of 185053 M-1. The estimated value of LOD by the Mg/S@g-C3N4 sensor for Cu2+ was 16.2 nM. The sensor offered high sensitivity and selectivity for Cu2+ detection over other heavy metals.