Novel pyrene- and anthracene-based Schiff base derivatives P1 and A1 were synthesized via a one-pot reaction and utilized as fluorescence turn-on sensors towards Cu²⁺ and Fe³⁺ ions, respectively, and for aggregation induced emissions (AIEs). P1 in CH₃CN and A1 in THF illustrated the fluorescence turn-on sensing towards Cu²⁺ and Fe³⁺ ions, respectively, via chelation enhanced fluorescence (CHEF) through excimer (P1–P1* and A1–A1*) formation. The 2 : 1 stoichiometry of the sensor complexes (P1 + Cu²⁺ and A1 + Fe³⁺) were calculated from Job plots based on UV-Vis absorption titrations. In addition, the binding sites of sensor complexes (P1 + Cu²⁺ and A1 + Fe³⁺) were well established from the ¹H NMR titrations and supported by the fluorescence reversibility by adding metal ions and PMDTA sequentially. The detection limits (LODs) and the association constant (K_a) values of P1 + Cu²⁺ and A1 + Fe³⁺ sensor responses were calculated by standard deviations, linear fittings and from their fluorescence binding isotherms. More importantly, P1 + Cu²⁺ and A1 + Fe³⁺ sensors were found to be active in wide ranges of pHs (1–14 and 2–14, respectively). Moreover, the time effect along with the enhancements of quantum yield (Φ) and time resolved photoluminescence (TRPL) decay constant (τ) towards sensor responses were investigated. Similarly, P1 in CH₃CN and A1 in THF showed AIEs by increasing the aqueous media concentration from 0% to 90%, with altered fluorescence peak shifts (red and blue shifts, respectively). As well as τ value enhancements, the Φ values of 0.506 and 0.567 (with 630- and 101-fold enhancements) were acquired for P1 in CH₃CN : H₂O (20 : 80) and A1 in THF : H₂O (40 : 60), respectively.

The structural and photophysical characteristics of MAPbBr₃ single crystals prepared using the inverse temperature crystallization method are evaluated using temperature-dependent X-ray diffraction (XRD) and optical spectroscopy. Contrary to previous research reports on perovskite materials, we study phase transitions in crystal lattice structures accompanied with changes in optical properties expand throughout a wide temperature range of 300–1.5 K. The XRD studies reveal several phase transitions occurred at ~210 K, ~145 K, and ~80 K, respectively. The coexistence of two different crystallographic phases was observed at a temperature below 145 K. The emission peaks in the PL spectra are all asymmetric in line shape with weak and broad shoulders near the absorption edges, which are attributed to the Br atom vacancy on the surface of the crystals. The time-resolved PL measurements reveal the effect of the desorption/adsorption of gas molecules on the crystal surface on the PL lifetimes. Raman spectroscopy results indicate the strong interplays between cations and different halide atoms. Lastly, no diamagnetic shift or split in emission peaks can be observed in the magneto-PL spectra even at an applied magnetic field up to 5 T and at a temperature as low as 1.5 K.

Recently, perovskite-based nanomaterials are utilized in diverse sustainable applications. Their unique structural characteristics allow researchers to explore functionalities towards diverse directions, such as solar cells, light emitting devices, transistors, sensors, etc. Many perovskite nanomaterial-based devices have been demonstrated with extraordinary sensing performance to various chemical and biological species in both solid and solution states. In particular, perovskite nanomaterials are capable of detecting small molecules such as O₂, NO₂, CO₂, etc. This review elaborates the sensing applications of those perovskite materials with diverse cations, dopants and composites. Moreover, the underlying mechanisms and electron transport properties, which are important for understanding those sensor performances, will be discussed. Their synthetic tactics, structural information, modifications and real time sensing applications are provided to promote such perovskite nanomaterials-based molecular designs. Lastly, we summarize the perspectives and provide feasible guidelines for future developing of novel perovskite nanostructure-based chemo- and biosensors with real time demonstration.

Simple pyridyl-salicylimine derivatives (F1, F2 and F3) are reported for the first time as fluorescence “turn-on” sensors for distinct detections of Zn²⁺, Al³⁺ and OH⁻ ions in mixed-aqueous media CH₃CN/H₂O with volume ratios of 6/4 and 3/7 (at pH = 7 and 25 °C) via internal charge transfer (ICT), chelation enhanced fluorescence (CHEF), and deprotonation mechanisms. F1 and F2 show diverse turn-on sensing applications to Zn²⁺, Al³⁺ and OH⁻ ions, but F3 exhibited the fluorescence turn-on sensing to Al³⁺ and OH⁻ ions in CH₃CN/H₂O (6/4; vol/vol). F1+Zn²⁺ and F2+Zn²⁺ complexes revealed the reversibilities and ratiometric displacements of Zn²⁺ with ethylene diamine tetra acetic acid (EDTA) and Al³⁺ ions, respectively, in CH₃CN/H₂O (6/4; vol/vol). On the other hand, F1, F2 and F3 in CH₃CN/H₂O (3/7; vol/vol) showed sensitivities only to Al³⁺ ions but negligible selectivities to OH⁻ ions. Stoichiometry of all sensor complexes were calculated as 1 : 1 by job's plots based on UV/Vis and PL titrations. The complex formation and binding sites of all sensor materials were well characterized by ¹H, ¹³C NMR, and mass (FAB) spectral analysis. Detection limits were calculated from standard deviations and linear fitting calculations. The association constant (log K_a) values of sensor complexes were evaluated from the fluorescence binding isotherms. The fluorescence decay constant (τ) values were estimated from time resolved fluorescence studies. Time, temperature, pH and solvent concentration effects towards sensor responses were fully investigated in this report.