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While the development of red and green phosphorescent organic light-emitting diodes (OLEDs) has seen rapid progress, that of efficient blue phosphorescent OLEDs remains a challenge. In the present report, the introduction of a bulky substituent on the pyridyl rings of a cycloplatinated 1,3-bis(pyridine-2-yl)-4,6-difluoro-benzene appears as a facile strategy to hinder strong Pt⋯Pt interactions, allowing the fabrication of efficient blue OLEDs. Thus, the preparation and characterization of a chlorido platinum(II) complex bearing a well-designed new N^C^N-cyclometalating ligand, namely 1,3-bis(4-mesityl-pyridin-2-yl)-4,6-difluoro-benzene, are reported. Its structure, along with that of the related pro-ligand, is determined by X-ray diffraction studies on a single crystal. The shortest Pt⋯Pt distance is much longer (8.59 Å) than that observed for other N^C^N-platinum(II) chlorido complexes including one with the bulky mesityl group on the cyclometalated benzene ring (4.4 Å). This new complex exhibits intense blue phosphorescence (470–471 nm) in dichloromethane solution (Φlum = 0.97) and in the PMMA film (1 wt% complex, Φlum = 0.95) whereas red phosphorescence (672 nm) is observed in a neat film (Φlum = 0.72). Even in the solid state, the novel complex is highly luminescent suggesting that the introduction of mesityl groups on the pyridine rings is a way to inhibit self-quenching both in the PMMA matrix and in neat films. It represents a useful tool for the fabrication of efficient blue OLEDs (8% wt complex) with CIE coordinates (0.13, 0.29) approaching true blue. The molecular geometry, ground state, electronic structure, and excited electronic states of the complex, both as a monomer and dimer aggregate in solution, are calculated using density functional theory (DFT) and time-dependent (TD) DFT approaches, giving insight into the electronic origin of the absorption spectra. [ABSTRACT FROM AUTHOR]

Significant work has recently focused on developing novel materials suitable for solar technologies with better conversion efficiencies, while maintaining low costs. BaF2 has been investigated as a fluoride host for doping with luminescent ions for energy conversion processes in photovoltaic cells. This work employed a metal–organic chemical vapor deposition technique to prepare nanostructured europium-doped BaF2 thin films on silicon and quartz substrates. Samples have been fabricated by varying the deposition temperature from 300 to 600 °C in order to examine how temperature affects the structure, morphology, and luminescence of Eu-doped BaF2 thin films. A multicomponent combination of fluorinated β-diketonate metal–organic precursors of barium and europium, Ba(hfa)2·tetraglyme and Eu(hfa)3·diglyme, in an appropriate molar ratio, is employed to fabricate BaF2 based thin films. These precursors serve as a single molten source by delivering all the elements required (Ba, Eu, and F) for forming the Eu-doped BaF2 phase due to the similar nature of the ligands. On silicon substrates, preliminary deposition tests have been carried out to confirm the purity, homogeneity, and appropriate stoichiometry of films. The obtained results pave the way for the production of BaF2 thin films doped with lanthanide ions, particularly interesting for their up-conversion (UC), down-conversion (DC), and down-shifting (DS) properties. [ABSTRACT FROM AUTHOR]

Methylammonium lead iodide perovskite (MAPbI3) is today considered the most promising component for highly efficient third generation solar cells. However, the lifetime of the solar devices is strongly affected by the stability of the MAPbI3 films toward humidity, UV irradiation, and temperature. The search for efficient protective additives to be used for building up composite perovskite films with enhanced stability is a topic of great interest in the scientific community. In the present paper, a layered zirconium phosphate‐phosphonate based on N,N‐phosphonomethylglycine, exfoliated in thin nanosheets (NS), as additive for the stabilization of MAPbI3 crystalline films toward humidity, UV‐irradiation, and temperature changes is applied. Notably, the additive is extremely efficient in preventing degradation of the perovskite film, preserving the optical and structural properties, and avoiding the phase transitions normally observed due to temperature increase. [ABSTRACT FROM AUTHOR]

Recently, room-temperature phosphorescence (RTP) in 2D hybrid perovskites has proved due to energy transfer from inorganic sheets to conjugated organic cations harnessing the triplet states. Thus far, only the sensitization of triplet states by inorganic excitons has been demonstrated. Herein, we report a novel (110)-oriented lead bromide perovskite, (C3H8N6)PbBr4 [abbreviated (H2mela)PbBr4], where within the inorganic sheets the self-trapped excitons generate broad-band emission and the Br−⋯π+ interactions harness the triplet excitons of organic components, via intersystem crossing (ISC), leading to dual fluorescence emission and RTP. To the best of our knowledge, based on the strategy of heavy-atom-participated anion–π+ interactions, the first RTP-active 2D-perovskite was successfully stabilized. The solid-state photoluminescence studies showed that the color rendering index (CRI) and chromaticity coordinates (x,y) as well as the correlated color temperature (CCT) of the white-light emission can be tuned via excitation energy variation. The emission of light varies from "cold" white light to "warm" white light by decreasing the excitation energy. When excited at 365 nm and 375 nm, our perovskite yielded "cold" white-light emission with the highest CRI of 97 and 99. [ABSTRACT FROM AUTHOR]

Molecularly imprinted polymers (MIPs) are synthetic receptors made by template-assisted synthesis. MIPs might be ideal receptors for sensing devices, given the possibility to custom-design selectivity and affinity toward a targeted analyte and their robustness and ability to withstand harsh conditions. However, the synthesis of MIP is an inherently random process that produces a statistical distribution of binding sites, characterized by a variety of affinities. This is verified both for bulk MIP materials and for MIP's thin layers. In the present work, we aimed at assessing the effects of inhomogeneous versus homogeneous imprinted binding sites on electrochemical sensing measurements, and the possible implications on the sensor's performance. In the example of an Electrochemical Impedance Spectroscopy (EIS) sensor for the 17β-estradiol (E2) hormone, the scenario of inhomogeneous binding sites was studied by modifying electrodes with an E2-MIP polyaniline (PANI) thin layer, called the "Imprinted PANI layer". In contrast, the condition of discrete and uniform binding sites was epitomized by electrodes modified with a thin PANI layer purposedly doped with E2-MIP nanoparticles (nanoMIPs), which were referred to as "nanoMIP-doped PANI". The behaviors of the two EIS sensors were compared. Interestingly, the sensitivity of the nanoMIP-doped PANI was almost twice with respect to that of the imprinted PANI layer, strongly suggesting that the homogeneity of the binding sites has a fundamental role in the sensor's development. The nanoMIP-doped PANI sensor, which showed a response for E2 in the range 36.7 pM-36.7 nM and had a limit of detection of 2.86 pg/mL, was used to determine E2 in wastewater.

We employ a fine-tuned theoretical framework, combining ab initio molecular dynamics (AIMD), density functional theory (DFT), and time-dependent (TD) DFT methods, to investigate the interactions and optical properties of the iodoplumbates within the low coordinative γ-butyrolactone (GBL) solvent environment, widely employed in the perovskite synthesis. We uncover the extent of GBL coordination to PbI 2 investigating its relation to the solvated PbI 2 optical properties. The employed approach has been further validated by comparison with the experimental UV-vis absorption spectrum of PbI 2 in GBL solvent. A comparison with other solvents, commonly employed in the perovskite synthesis, such as N , N -dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) is also reported. The methodology developed in this work can be reasonably extended to the investigation of similar systems.

We have developed a colloidal synthesis of nearly monodisperse nanocrystals of pure Cs 4 PbX 6 (X = Cl, Br, I) and their mixed halide compositions with sizes ranging from 9 to 37 nm. The optical absorption spectra of these nanocrystals display a sharp, high energy peak due to transitions between states localized in individual PbX 6 4- octahedra. These spectral features are insensitive to the size of the particles and in agreement with the features of the corresponding bulk materials. Samples with mixed halide composition exhibit absorption bands that are intermediate in spectral position between those of the pure halide compounds. Furthermore, the absorption bands of intermediate compositions broaden due to the different possible combinations of halide coordination around the Pb 2+ ions. Both observations are supportive of the fact that the [PbX 6 ] 4- octahedra are electronically decoupled in these systems. Because of the large band gap of Cs 4 PbX 6 (>3.2 eV), no excitonic emission in the visible range was observed. The Cs 4 PbBr 6 nanocrystals can be converted into green fluorescent CsPbBr 3 nanocrystals by their reaction with an excess of PbBr 2 with preservation of size and size distributions. The insertion of PbX 2 into Cs 4 PbX 6 provides a means of accessing CsPbX 3 nanocrystals in a wide variety of sizes, shapes, and compositions, an important aspect for the development of precisely tuned perovskite nanocrystal inks.