Detection of nitroaromatic explosives with high sensitivity and selectivity is extremely important for civilian and military safety. Here, we report the synthesis and multimodal sensing applications of an emissive alanine based dansyl tagged copolymer P(MMA-co-Dansyl-Ala-HEMA) ( DCP ), synthesized by RAFT copolymerization. The fluorescent co-polymer exhibited high sensitivity and selectivity towards conventional nitroaromatic explosives such as DNT, TNT and TNP in solution at lower range of µM level and also with saturated vapor of NACs. The quantum yield of the co-polymer was measured to be very high (Φ f = 77%) which make it an ideal candidate for sensing in solution as well as in vapor phase. The fluorescence signal from DCP copolymer gets significantly quenched upon addition of aliquots of DNT, TNT, and TNP. The Stern-Volmer constant was calculated to be very high. The quenching mechanism was further established by fluorescence up-conversion, time-resolved fluorescence and steady state absorption spectroscopy. The energetics of sensing process was calculated by Density Functional Theory (DFT) studies. We also fabricate a thin film polymer sensor which was able to detect nitroaromatic vapors with high selectivity. This opens up the possibility of building a low-cost and light-weight nitroaromatic explosives sensor for field use.

Quasi-two-dimensional (2D) Ruddlesden–Popper (RP) perovskites are currently considered as the material of choice for the next-generation light-emitting diodes (LEDs) due to their superior optoelectronic properties. Despite their spectacular external quantum efficiency, the excessive surface defect states generated due to the reduced crystal size and phase impurity limit their radiative recombination efficiency. In the present work, we have shown the order of magnitude enhancement of radiative emission in butylamine (BA)-based quasi-2D perovskite (BA)2(MA) n−1Pb n Br3n+1 after passivating with two different Lewis basesa small organic molecule triphenylphosphine oxide (TPPO) and an insulating polymer polymethyl methacrylate (PMMA). The reduction in crystal grain size was observed after passivation, attributed to the complexation of the passivating molecules (PM) on the surface and nanocrystal pinning (A-NCP) phenomena. Both the steady-state and time-resolved photoluminescence study confirmed significant enhancement in fluorescence intensity and improved average lifetime (τavg. = 19.4 ns) after surface passivation. The interaction mechanism between the layered perovskite and PMs was probed with FTIR spectroscopy, XPS, and KPFM study. All these studies confirmed that the CO group in PMMA and PO group in TPPO deactivate the acceptor-type defects (uncoordinated Pb2+ and Br vacancies) in these RP perovskites. Furthermore, the stability of the passivated film enhanced significantly, as confirmed by contact angle measurement. Our study establishes that uncoordinated Pb2+ passivation by a Lewis base provides a viable strategy for photoluminescence (PL) lifetime, intensity, and stability enhancement in quasi-2D perovskite films.

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