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Photochromism and photomagnetism are two important features for the generation of smart materials that are of utility for optical switches and memory devices. Very few materials that exhibit both the features at room temperature are known to date, the reported ones mostly contain metal-ions to assist the electron transfer with photo stimuli. Herein, we report a new class of organic materials that show photochromism and photomagnetism at room temperature due to the generation of free radicals in the solid-state. 1,4-bis(4,5-diphenyl-1H-imidazol-2-yl)benzene (BDPI) was found to acts as organic photomagnet without use of any traditional photochromic couplers or radical containing moieties. Solvent molecules (eg. water and DMSO) form hydrogen bonds with the imidazole rings which act as binding glue in stacking of 1,4-bis(imidazolyl)benzene moieties via π···π interactions. These interactions found to play a significant role in promoting strong spin-spin interaction in the solid-state which can be inferred from the appearance of broad EPR signal, whereas a sharp signal appeared only after irradiation. The sharp signal indicates formation of paramagnetic free radicals which influence antiferromagnetic exchange interactions with weakening of the magnetic susceptibility significantly. This work provides a new direction in the ongoing research of photochromic and photomagnetic materials, where a simple 1,4- bis(imidazolyl)benzene system changes its color, radical activity and magnetic behavior with photoirradiation.

Although the piezoelectric property of a BaTiO3 nanoparticle is routinely used in energy harvesting application, it can also be exploited for wireless cell stimulation and cell therapy. However, such biomedical application is rare due to limited availability of colloidal BaTiO3 nanoparticles of

Piezocatalysis is a promising alternative of photocatalysis where the strained state of a piezoelectric material is exploited for electrochemical surface reactions under dark conditions. Among vari...

In recent years, rare-earth-doped nanophosphors have attracted great attention in the field of luminescent materials for advanced solid-state lighting and high-resolution display applications. However, the low efficiency of concurrent red phosphors creates a major bottleneck for easy commercialization of these devices. In this work, intense red-light-emitting K+-codoped BaAl2O4:Eu3+ nanophosphors having an average crystallite size of 54 nm were synthesized via a modified sol–gel method. The derived nanophosphors exhibit strong red emission produced by the 5D0 → 7FJ (J = 0, 1, 2, 3, 4) transitions of Eu3+ upon UV and low-voltage electron beam excitation. Comparative photoluminescence (PL) analysis is executed for Eu3+-activated and K+-coactivated BaAl2O4:Eu3+ nanophosphors, demonstrating remarkable enhancement in PL intensity as well as thermal stability due to K+ codoping. The origin of this PL enhancement is also analyzed from first-principles calculations using density functional theory. Achievement of ...

A Raman scattering investigation of a single α-CuPc nanorod is demonstrated here within the temperature range 300–770 K. From the typical thermal dispersion of Raman shift and phonon line width of in-plane B1g mode at 1526 cm–1, the metastable α polymorph is observed to undergo unambiguous phase transition to thermally stable β phase. The phase transition temperature (456 K) is observed to be significantly lower than that reported for bulk samples. Extensive computation of normal modes associated with both α- and β-CuPc reveal that the “fingerprint” domain across 1300–1600 cm–1 is particularly sensitive to this polymorphic transition where a silent B2g mode appears at 1303 cm–1 in the spectral vicinity of molecular edge vibration sensitive Ag–Bg Davydov doublet.

Modification of orbital interactions by suitable “orbital alloying” is a necessity to obtain direct gap group IIIA delafossite with shallow acceptor states, which unfortunately have never been realized. This Letter promotes an optimistic trend regarding the oxide delafossite family to obtain significant hole delocalization in the vicinity of the (Cu 3d + O 2p) valence band with an unprecedented direct gap by chalcogen (Ch = S, Se) doping-induced polytype formation (R3m → P3m1). Polytypism and a modulated valence band in prototype CuAlO2 are “observed” upon sulfur incorporation at the O site. From the exhibition of better transport properties, weak local σ symmetry between Cu 3dz2 and O 2pz states are reflected in the doped material. Dispersion of Cu 3d character by incorporating shallower acceptor (Ch 3p) states is concluded upon analyzing the photoemission spectra of the valence band.

Photoluminescence (PL) and absorption features of high-quality nanocrystalline Sn1-xMgxO2 series (0 ≤ x ≤ 0.03) were investigated at room temperature. Although particle sizes of as-synthesized samples are larger than Bohr radius (aB), Fermi edge absorption is observed both in undoped and doped samples. Incorporation of Mg 2p states near valence band maxima (VBM) widens the band gap (Eg) consistently and stable, high-yield room temperature free exciton (RTFE) emission (3.81 eV) results. Deconvolution of each UV emission reveals band tail emission (3.54 eV) along with excitonic recombination. A feeble green emission (2.34 eV) is also observed and its intensity strongly depends on tensile strain (η) and formation energy (Ef) of oxygen vacancy (VO) and hydrogen at VO (HO). H2 annealing at 300 °C introduces interesting doping dependent modulation in UV emission intensity. Elemental projective density of states (DOS) exhibit Sn 5s–H 1s hybridization in undoped passivated supercell and Mg 2p–H 1s hybridization i...