3D printed optical sensor for highly sensitive detection of picric acid using perovskite nanocrystals and mechanism of photo-electron transfer

Hand-held, compact and portable sensors for on-site detection of environmental contaminants are in high demand for industry 4.0. Here, we have developed a sensor based on luminescent organic-inorganic metal halide hybrid perovskites nanocrystals (CH₃NH₃PbBr₃) with p-xylylenediamine as an additional capping agent for highly sensitive and selective detection of picric acid (PA), with a good linear range of 1.8 μM-14.3 μM achieving detection of limit (LOD) of 0.3 μM. The electrostatic interaction between PA and the capping ligand of perovskite nanocrystals resulted in significant fluorescence quenching, as revealed by the steady-state and time-resolved spectroscopy. The applicability of the developed sensor for PA detection was validated with a 3D printed device integrating surface mounting device (SMD) and paper microfluidics. This prototype device was successfully applied as a fluorescence turn-off sensor to detect PA, showing great potential for on-site detection. This 3D-printed paper-based microfluidic optical sensor proved very efficient for naked-eye detection of PA with an inbuilt excitation source, avoiding the requirement of expensive and complex instrumentation.

Recent Development of Halide Perovskite Materials and Devices for Ionizing Radiation Detection

Ionizing radiation such as X-rays and γ-rays has been extensively studied and used in various fields such as medical imaging, radiographic nondestructive testing, nuclear defense, homeland security, and scientific research. Therefore, the detection of such high-energy radiation with high-sensitivity and low-cost-based materials and devices is highly important and desirable. Halide perovskites have emerged as promising candidates for radiation detection due to the large light absorption coefficient, large resistivity, low leakage current, high mobility, and simplicity in synthesis and processing as compared with commercial silicon (Si) and amorphous selenium (a-Se). In this review, we provide an extensive overview of current progress in terms of materials development and corresponding device architectures for radiation detection. We discuss the properties of a plethora of reported compounds involving organic-inorganic hybrid, all-inorganic, all-organic perovskite and antiperovskite structures, as well as the continuous breakthroughs in device architectures, performance, and environmental stability. We focus on the critical advancements of the field in the past few years and we provide valuable insight for the development of next-generation materials and devices for radiation detection and imaging applications.

Efficient charge transfer from organometal lead halide perovskite nanocrystals to free base meso-tetraphenylporphyrins

The efficient charge transfer from methylammonium lead halide, MAPbX3 (X = Br, I), perovskite nanocrystals (PNCs) to 5,10,15,20-tetraphenylporphyrin (TPP) molecules has been investigated in detail. The hydrophobically-capped MAPbX3 PNCs exhibited bright fluorescence in the solution state. However, in the presence of TPP, the fluorescence intensity was quenched, which is ascribed to the electron transfer from the PNCs to TPP. Photoluminescence (PL) spectroscopy and absolute quantum yield measurements were used to evaluate the fluorescence quenching. This efficient fluorescence quenching leads to an increase in the quenching efficiency value. The quenching of fluorescence intensity is not attributed to the change in lifetime, as evidenced by time-correlated single-photon counting (TCSPC) measurements, suggesting a static electron transfer from the PNCs to TPP molecules. Such a static fluorescence quenching corresponds to the adsorption of TPP onto the surface of hydrophobic PNCs, and has been examined via transmission electron microscopy (TEM). Cyclic voltammetry (CV) studies were used to compare the PNCs and PNCs@TPP nanocomposites, revealing that the electron transfer process takes place from the PNCs to the organic acceptor TPP molecules.