Ruddlesden–Popper (RP) phase metal halide organo perovskites are being extensively studied due to their quasi-two dimensional (2D) nature which makes them an excellent material for several optoelectronic device applications such as solar cells, photo-detectors, light emitting diodes (LEDs), lasers etc. While most of reports show use of linear carbon chain based organic moiety, such as n-Butylamine, as organic spacer in RP perovskite crystal structure, here we report a new series of quasi 2D perovskites with a ring type cyclic carbon group as organic spacer forming RP perovskite of type (CH)2(MA)n−1PbnI3n+1; CH = 2-(1-Cyclohexenyl)ethylamine; MA = Methylamine). This work highlights the synthesis, structural, thermal, optical and optoelectronic characterizations for the new RP perovskite series n = 1–4. The demonstrated RP perovskite of type for n = 1–4 have shown formation of highly crystalline thin films with alternate stacking of organic and inorganic layers, where the order of PbI6 octahedron layering are controlled by n-value, and shown uniform direct bandgap tunable from 2.51 eV (n = 1) to 1.92 eV (n = 4). The PL lifetime measurements supported the fact that lifetime of charge carriers increase with n-value of RP perovskites [154 ps (n = 1) to 336 ps (n = 4)]. Thermogravimetric analysis (TGA) showed highly stable nature of reported RP perovskites with linear increase in phase transition temperatures from 257 °C (n = 1) to 270 °C (n = 4). Scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) are used to investigate the surface morphology and elemental compositions of thin films. In addition, the photodetectors fabricated for the series using (CH)2(MA)n−1PbnI3n+1 RP perovskite as active absorbing layer and without any charge transport layers, shown sharp photocurrent response from 17 nA/cm2 for n = 1 to 70 nA/cm2 for n = 4, under zero bias and low power illumination conditions (470 nm LED, 1.5 mW/cm2). Furthermore, for lowest bandgap RP perovskite n = 4, (CH)2MA3Pb4I13 the photodetector showed maximum photocurrent density of ~ 508 nA/cm2 at 3 V under similar illumination condition, thus giving fairly large responsivity (46.65 mA/W). Our investigations show that 2-(1-Cyclohexenyl)ethylamine based RP perovskites can be potential solution processed semiconducting materials for optoelectronic applications such as photo-detectors, solar cells, LEDs, photobatteries etc.
In this paper, we present a surface decontamination system that substitutes traditional chemicals and scrubbing agents, which will be useful for the general public during a pandemic. The technique is based on a hybrid process in which UV-C light and its photons interact with metal oxide nano-catalysts to generate hydroxyl radicals, which can enhance the deactivation process, and the system can work even in the shadow regions via a dry process. The optimum number of UV light sources in combination with TiO2 nanoparticles catalysts on aluminum plates have been used synergistically in the system. The UV dose in the disinfection chamber has been optimized, which is between 60 and 500 mJ/cm2 throughout the disinfection chamber. The concentration of hydroxyl radicals is reported more than 25 000 ions/cm3 within the disinfection chamber. These ions are circulated throughout the disinfection volume. The disinfection efficiency has been tested on bacteria and spores, and the obtained results are correlated. Around 8 log reductions in the counts of the test bacteria of Escherichia coli and Klebsiella pneumoniae have been achieved in just 2 min of exposure in the continuous operation of the system. Tests have also been performed on Geobacillus stearothermophilus spores, and the method described here is the result of multiple tests, a review of the scientific literature, and the incorporation of current laboratory practice. The deactivation tested in the system is larger than that of known bacteria and viruses in terms of UV-doses, signifying its utility during the pandemic.
We report the hydrogen-sensing response on low-cost-solution-derived ZnO nanorods (NRs) on a glass substrate, integrated with aluminum as interdigitated electrodes (IDEs). The hydrothermally grown ZnO NRs on ZnO seed-layer-glass substrates are vertically aligned and highly textured along the c -axis (002 plane) with texture coefficient ∼2.3. An optimal hydrogen-sensing response of about 21.46% is observed for 150 ppm at 150 °C, which is higher than the responses at 100 and 50 °C, which are ∼12.98 and ∼10.36%, respectively. This can be attributed to the large surface area of ∼14.51 m 2 /g and pore volume of ∼0.013 cm 3 /g, associated with NRs and related defects, especially oxygen vacancies in pristine ZnO nanorods. The selective nature is investigated with different oxidizing and reducing gases like NO 2 , CO, H 2 S, and NH 3 , showing relatively much lower ∼4.28, 3.42, 6.43, and 3.51% responses, respectively, at 50 °C for 50 ppm gas concentration. The impedance measurements also substantiate the same as the observed surface resistance is initially more than bulk, which reduces after introducing the hydrogen gas during sensing measurements. The humidity does not show any significant change in the hydrogen response, which is ∼20.5 ± 1.5% for a large humidity range (from 10 to 65%). More interestingly, the devices are robust against sensing response, showing no significant change after 10 months or even more.
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