Temperature-dependent excited states for detecting reversible phase transitions in 2D lead(II) iodide perovskites.

Significant interest exists in water-tolerant 2D lead iodide perovskites owing to their stability and proven potential in photovoltaic and photonic applications. These materials have solid-state phase transitions that are accessible below 100 °C. Here, the study witnesses the multiple phase transitions of the last members of a series of organic-inorganic hybrid materials, [(CnH2n+1NH3)2PbI4], with even n as n = 14, 16, and 18, once again. By employing temperature-dependent steady-state photoluminescence (PL) and temperature-dependent time-resolved photoluminescence (TRPL) spectroscopy in the temperature range of -18 to +90 °C and at -196 °C, we explore the thermal responses of these materials. The investigation reveals reversible phase transitions occurring between room temperature (RT) and elevated temperatures, impacting the optical properties and emitting colors of the perovskite compounds. The longer the alkyl chain, the higher the phase transition temperature, attributed to increased conformational disorder and enhanced perovskite symmetry. The decay constants for all compounds are very close in value, which confirms the underlying excited-state dynamics, pointing to contributions primarily from inorganic components across different phases. We anticipate that our results on the detection of phase transitions in 2D perovskites will not only motivate the use of these techniques for detecting phase transitions but also would help to understand their excited states in more details to selectively use them for solar cell and next-generation display technologies.

Copper(I) Iodide Thin Films: Deposition Methods and Hole-Transporting Performance.

The pursuit of p-type semiconductors has garnered considerable attention in academia and industry. Among the potential candidates, copper iodide (CuI) stands out as a highly promising p-type material due to its conductivity, cost-effectiveness, and low environmental impact. CuI can be employed to create thin films with >80% transparency within the visible range (400-750 nm) and utilizing various low-temperature, scalable deposition techniques. This review summarizes the deposition techniques for CuI as a hole-transport material and their performance in perovskite solar cells, thin-film transistors, and light-emitting diodes using diverse processing methods. The preparation methods of making thin films are divided into two categories: wet and neat methods. The advancements in CuI as a hole-transporting material and interface engineering techniques hold promising implications for the continued development of such devices.

Photoluminescent copper(I) iodide alkylpyridine thin films as sensors for volatile halogenated compounds.

The paper presents the fabrication and characterization of [CuI(L)]n thin films, where L represents various alkylpyridine ligands including 4-methylpyridine, 3-methylpyridine, 2-methylpyridine, 4-tbutylpyridine, 3,4-dimethylpyridine, and 3,5-dimethylpyridine. The thin films were synthesized by exposing the corresponding ligands to CuI thin films through vapor deposition. The coordination reactions occurring on the films were investigated using PXRD and time-dependent photoluminescence spectroscopy, and a comparison was made between the structures of the thin films and the corresponding powder phases. The films showed primarly blue emission (λem = 457-515 nm) and polymeric structures with excited state lifetimes ranging from 0.6 to 5.5 µs. Significantly, the studied compounds exhibited fast reversible luminescence quenching when exposed to vapors of dichloromethane and dibromomethane (15 and 30 min respectively), and the luminescence was restored upon re-exposure to the alkylpyridine ligand (after 20 min). These findings indicate that these thin films hold promise for applications as sensors (with sensitive and reversible detection capability) for volatile halogen-based compounds (VHC).

Determination of Human Papillomavirus Type 18 Lineage of E6: A Population Study from Iran.

The epidemiological studies in Iran on HPV18 nucleotide changes are rare. This type of virus is prevalent in the Iranian population. Therefore, in the present study, we aimed to identify the genetic variability in HPV18 in the E6 region to evaluate the prevalence of lineage distribution and sublineages in a sample population in Iran. Overall, 60 HPV18 confirmed cases were investigated between 2019 and 2021. The specimens were collected, and molecular genotyping was done using the Linear Array HPV Genotyping Test. DNA extraction was performed by a viral DNA/RNA kit. The HPV E6 gene was amplified by using type-specific primers designed according to the HPV18 genome prototype sequence. The sequencing of the E6 region was successfully done on 43 samples which were then compared to the reference sequence. The most frequent sublineage of HPV18 in this study was A4 (69.7%), followed by A1 (18.6%) and A3 (11.6%). Neither A2 nor A5 sublineage was not detected in this study. The related nucleotide acid changes according to the main references were as follows: A3: T104C/T232G/T485C/C549A, A4: T104C/T485C/C549A. The predominance of A lineage with the high frequency of A4 sublineage was found in the present research. The importance of sublineages in susceptibility to a progressive form of infection requires to be more investigated among the different population.

Influence of the Diphosphine Coordination Mode on the Structural and Optical Properties of Cyclometalated Platinum(II) Complexes: An Experimental and Theoretical Study on Intramolecular Pt···Pt and π···π Interactions.

The reaction of [Pt(C^N)(CF3CO2)(SMe2)] (1), in which C^N is either benzo[ h]quinolinate (bhq), 1a, or 2-phenylpyridinate (ppy), 1b, with 1 equiv of bis(diphenylphosphino)methane (dppm) gave the bischelate complexes [Pt(C^N)dppm]CF3CO2 (2). The binuclear complexes [Pt2(C^N)2(CF3CO2)2(µ-dppm)] (3) were prepared, using an unusual reaction pathway, by the addition of equimolar amount of complexes 1 and 2, through the ring opening of the chelating dppm ligand and coordination of the CF3CO2 anion to the platinum center. The proposed reaction pathway and effect of the solvent polarity were investigated by density functional theory (DFT) calculations. The crystal structure of 3a shows considerable intramolecular Pt···Pt and π···π interactions. The crystal structure and formation pathway toward 3 were compared with the similar analogue [Pt2(bhq)2(Cl)2(µ-dppm)] (5). All complexes were fully characterized using multinuclear NMR spectroscopy and elemental analysis. Furthermore, the crystal structures of some complexes including 1b, 2a, 2b, 3a, and 5 were confirmed by X-ray crystallography. The effect of dimerization via a change in the coordination mode of dppm, from a chelate mode in complex 2 to a bridge mode in complexes 3 and 5, upon the excited states of the studied compounds was investigated in their distinguished absorption and emission profiles. The appearance of a remarkably low energy band in the absorption spectra of 3, which was assigned to a metal-metal to ligand charge transfer [MMLCT; dσ*(Pt2) → π*(C^N)] transition showing negative solvatochromism, is important evidence for the Pt···Pt intramolecular interaction. The vibronically resolved and long-lifetime emission of 2a in poly(methyl methacrylate) media and powder states at 77 and 300 K, along with time-dependent DFT calculations, suggested that the triplet ligand-centered (3LC) emission was mixed with some 3MLCT character. Unstructured and short-lifetime emission in 3 refers to the phosphorescence 3MMLCT [dσ*(Pt2) → π*(C^N)] transition. Although complex 5 is a binuclear compound, the long distance of the Pt···Pt interaction caused the occurrence of the 3MMLCT transition to fade and act as a mononuclear unit, and the emission originated mostly from the 3MLCT transition. As a result, more metal participation leads to more red-shifted absorption and emission spectra of the studied complexes upon going from LC to MLCT to MMLCT transitions (λabs and λem: 3a > 3b > 5 > 2a > 2b).

Phosphorescent heterobimetallic complexes involving platinum(iv) and rhenium(vii) centers connected by an unsupported µ-oxido bridge.

Heterobimetallic compounds [(C^N)LMe2Pt(µ-O)ReO3] (C^N = ppy, L = PPh3, 2a; C^N = ppy, L = PMePh2, 2b; C^N = bhq, L = PPh3, 2c; C^N = bhq, L = PMePh2, 2d) containing a discrete unsupported Pt(iv)-O-Re(vii) bridge have been synthesized through a targeted synthesis route. The compounds have been prepared by a single-pot synthesis in which the Pt(iv) precursor [PtMe2I(C^N)L] complexes are allowed to react easily with AgReO4 in which the iodide ligand of the starting Pt(iv) complex is replaced by an ReO4- anion. In these Pt-O-Re complexes, the Pt(iv) centers have an octahedral geometry, completed by a cyclometalated bidentate ligand (C^N), two methyl groups and a phosphine ligand, while the Re(vii) centers have a tetrahedral geometry. Elemental analysis, single crystal X-ray diffraction analysis and multinuclear NMR spectroscopy are used to establish their identities. The new complexes exhibit phosphorescence emission in the solid and solution states at 298 and 77 K, which is an uncommon property of platinum complexes with an oxidation state of +4. According to DFT calculations, we found that this emission behavior in the new complexes originates from ligand centered 3LC (C^N) character with a slight amount of metal to ligand charge transfer (3MLCT). The solid-state emission data of the corresponding cycloplatinated(iv) precursor complexes [PtMe2I(C^N)L], 1a-1d, pointed out that the replacement of I- by an ReO4- anion helps enhancing the emission efficiency besides shifting the emission wavelengths.

The influence of thiolate ligands on the luminescence properties of cycloplatinated(ii) complexes.

Complexes [Pt(C^N)(PPh3)Cl] (C^N = bzq (7,8-benzoquinolinyl, A) and ppy (2-phenylpyridinyl, B)) were reacted with various thiolate ligands to afford complexes [Pt(C^N)(PPh3)(κ1-S-SR)], C^N = bzq, R = SPh (thiophenolate, 1a); C^N = ppy, R = SPh (1b); C^N = bzq, R = Spy (pyridine-2-thiolate, 2a); C^N = ppy, R = Spy (2b); C^N = bzq, R = SpyN (pyrimidine-2-thiolate, 3a); C^N = ppy, R = SpyN (3b). Complexes 1-3 were characterized by NMR spectroscopy, and the solid-state structures of 1a and 2a were determined by X-ray diffraction methods. Replacing a chloride ligand with electron-rich thiolates changes the lowest energy singlet and triplet excited states to the ones that feature charge transfer from the thiolate (mixed with some metal character) to the C^N ligand, which was supported by TD-DFT calculations. All complexes are emissive at 298 K in the solid state except 2b and 3b, which are emissive only at 77 K having a less rigid structure compared to others. The emission of 1a and 1b originates from a low-energy excited state of dPt/πSR → π*C^N while 3a exhibits a 3LC/3MLCT transition. For 1a and 1b, the radiative rate and the quantum efficiency are higher in a rigid environment such as a solid compared to a polymer and solution. Decreasing the rigidity of the environment leads to a flexibility of rotation of the -SR around the axis of the Pt-S bond. So the geometry can be easily changed after radiation and the lowest lying triplet excited state would have the effective contribution of the dd* transition, which opens a nonradiative pathway at room temperature.