No abstract

No abstract

Detecting low dose rates of X-rays is critical for making safer radiology instruments, but is limited by the absorber materials available. Here, we develop bismuth oxyiodide (BiOI) single crystals into effective X-ray detectors. BiOI features complex lattice dynamics, owing to the ionic character of the lattice and weak van der Waals interactions between layers. Through use of ultrafast spectroscopy, first-principles computations and detailed optical and structural characterisation, we show that photoexcited charge-carriers in BiOI couple to intralayer breathing phonon modes, forming large polarons, thus enabling longer drift lengths for the photoexcited carriers than would be expected if self-trapping occurred. This, combined with the low and stable dark currents and high linear X-ray attenuation coefficients, leads to strong detector performance. High sensitivities reaching 1.1  × 103 μC Gyair−1 cm−2 are achieved, and the lowest dose rate directly measured by the detectors was 22 nGyair s−1. The photophysical principles discussed herein offer new design avenues for novel materials with heavy elements and low-dimensional electronic structures for (opto)electronic applications.

In this work synthesis of water-dispersible reduced graphene oxide (rGO), decorated with gold nanoparticles (AuNPs), was carried out in the presence of poly(diallyldimethylammonium chloride) solution (PDDA). The as-prepared hybrid nanocomposite (Au/PDDA/rGO) was characterized using various surface, structural, and electrochemical analysis techniques, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and voltammetry. The electrochemical performance of Au/PDDA/rGO-modified glassy carbon electrode (GCE) was investigated by studying the voltammetric behavior with different concentrations of levofloxacin (LV). Under optimized experimental conditions, at the Au/PDDA/rGO/GCE it was found that the response is linearly proportional to the concentration of LV in the ranges of 1.0 × 10 −5 -2.0 × 10 −4 and 2.0 × 10 −4 -8.0 × 10 −4 mol L −1 , with detection limit estimated to be 3.9 × 10 −6 mol L −1 . The fabricated sensor was successfully applied for determination of LV in pharmaceutical tablets. Additionally, investigation of the interaction between LV and RNA molecules has also been carried out.