Hysteretic Piezochromism in a Lead Iodide-Based Two-Dimensional Inorganic-Organic Hybrid Perovskite.

Two-dimensional inorganic-organic hybrid perovskites are in the limelight due to their potential applications in photonics and optoelectronics. They are environmentally stable, and their various chemical compositions offer a wide range of bandgap energies. Alternatively, crystal deformation enables in situ control over their optical properties.

Syntheses, structural, photophysical and theoretical studies of heteroleptic cycloplatinated guanidinate(1-) complexes bearing acetylacetonate and picolinate ancillary ligands.

Cycloplatination of symmetrical ,',''-triarylguanidines, (ArNH)C[double bond, length as m-dash]NAr with -[Pt(TFA)(S(O)Me)] in toluene afforded -[Pt(TAG)(TFA)(S(O)Me)] (TAG = triarylguanidinate(1-)-κ,κ; TFA = OC(O)CF; 6-9) in 75-82% yields. The reactions of 6-9 and the previously known -[Pt(TAG)X(S(O)Me)] (X = Cl (1) and TFA (2-5)) with acetylacetone (acacH) or 2-picolinic acid (picH) in the presence of a base afforded [Pt(TAG)(acac)] (acac = acetylacetonate-κ,'; 10-18) and [Pt(TAG)(pic)] (pic = 2-picolinate-κ,κ; 19) in high yields. The new complexes were characterised by analytical, IR and multinuclear NMR spectroscopies.

Spectrally resolved nonlinearities within a laser pulse in a single-scan and spectrometer-based nonlinear optical probing.

The intricate spectrally resolved optical nonlinearities resulting from a spectrally broad femtosecond Gaussian laser pulse have been unraveled using a single-scan and spectrometer-based nonlinear optical probing technique. The interaction of the broad femtosecond laser pulse with a strongly absorbing organic dye has unveiled a remarkably distinct nonlinear absorption behavior across the broad spectral window. The nonlinear absorption behavior unveils an unusual transition from the reverse saturation absorption (RSA) to the saturation absorption (SA) as we sweep the wavelength on both sides of the central wavelength of the excitation laser pulse.

Ultrafast Dynamics, Optical Nonlinearities, and Chemical Sensing Application of Free-Standing Porous Silicon-Based Optical Microcavities.

The present work demonstrates the ultrafast carrier dynamics and third-order nonlinear optical properties of electrochemically fabricated free-standing porous silicon (FS-PSi)-based optical microcavities via femtosecond transient absorption spectroscopy (TAS) and single-beam Z-scan techniques, respectively. The TAS (pump: 400 nm, probe: 430-780 nm, ∼70 fs, 1 kHz) decay dynamics are dominated by the photoinduced absorption (PIA, lifetime range: 4.7-156 ps) as well as photoinduced bleaching (PIB, 4.

Structural Investigation and Optical Properties of Dysprosium (Dy) Ions Doped Oxyfluoro Antimony Borate Glasses for Photonics Applications.

Dysprosium oxide-doped glasses with a composition of 60BO-10SbO-10AlO-10NaF-(10-x) LiF-xDyO (x = 0.1,0.5, 1.

Enhanced Femtosecond Nonlinearities and Multiphoton Absorptions in Discrete Bands of Porphyrins.

Optical nonlinearities of discrete absorption energy levels of one of the typical heterocyclic aromatic molecules, free-base porphyrins, have been probed over a broad spectral region (400-1600 nm) utilizing intense femtosecond pulses. A wide range of strong one- and multiphoton-induced nonlinear absorptions of both the blue-end Soret (B) band (a → b) and red-end orbital mixing split quasi-allowed Q-bands (Q(0,0; 0,1), Q(0,0; 0,1), a → e) are critically probed and reported. During the resonant excitation within B- (400 nm) and Q-bands (600-750 nm), the nonlinear absorption has become predominant by the saturation of absorption (SA) of the one-photon absorption (1PA) process due to ground-state bleaching.

Germylenes Exhibiting Solid-State Emissions that Extend to NIR.

Low-valent main group compounds that fluoresce in the solid-state were previously unknown. To address this, we investigated room-temperature photoluminescence from a series of crystals of germylenes 3-8 in this article; they exhibited emissions nearly reaching the NIR. Germylene carboxylates (3-8) were synthesized by reacting dipyrromethene stabilized germylene pyrrolide (2) with carboxylic acids such as acetic acid, trifluoroacetic acid, benzoic acid, p-cyanobenzoic acid, p-nitrobenzoic acid, and acetylsalicylic acid.

Unsymmetrically β-Functionalized π-Extended Porphyrins: Synthesis, Spectral, Electrochemical Redox Properties, and Their Utilization as Efficient Two-Photon Absorbers.

Two new series of unsymmetrically -functionalized porphyrins, MTPP(NO)MA (), (MA = methyl acrylate) and MTPP(NO)MB () (MB = mono-benzo) (where M = 2H, Co(II), Ni(II), Cu(II) and Zn(II)), were synthesized and characterized by various spectroscopic techniques. The saddle shape conformation of ZnTPP(NO)MAPy and ZnTPP(NO)MB was confirmed by single-crystal X-ray analysis. Density functional theory (DFT) calculation revealed that NiTPP(NO)MB has a severe nonplanar geometry possessing a high magnitude of ΔC = ±0.

Synthesis and the spectral, electrochemical, and nonlinear optical properties of β-dicyanovinyl-appended 'push-pull' porphyrins.

A series of "push-pull" porphyrins, MTPP(MN)(TPA) (M = 2H, Cu, Ni, and Zn), having triphenylamine (TPA) and dicyanovinyl (DCN) groups at antipodal positions were synthesized and characterised by UV-Vis, fluorescence and NMR spectroscopic techniques, MALDI-TOF mass spectrometry, cyclic voltammetry, DFT, and elemental analysis, which were then further utilized for third-order nonlinear optical measurements under mild conditions using femtosecond laser pulses. Remarkably, MTPP(MN)(TPA) (M = 2H, Cu, Ni, and Zn) exhibited 21-48 nm and 38-80 nm bathochromic shifts in B and Q(0,0) bands as compared to the corresponding MTPPs (M = 2H, Cu, Ni, and Zn); the results are consistent with the effect of enhanced resonance due to TPA and -I effect of DCN moieties. In cyclic voltammetry, the push-pull porphyrins exhibited a cathodic shift (0.

Strong two-photon absorption and ultrafast dynamics of meso-functionalized "push-pull"trans-ABC porphyrins.

A new series of "push-pull"meso-substituted trans-ABC porphyrins, where A = mesityl, B = phenothiazine (push) and C = o/p-nitrophenyl moiety (pull) and M = 2H, Ni(ii), Cu(ii), and Zn(ii), were synthesized. These trans-ABC porphyrins were characterized by various techniques viz. UV-Vis, fluorescence and NMR spectroscopy, matrix assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry, cyclic voltammetry, single-crystal X-ray diffraction analysis and density functional theory (DFT) studies.

Strong structural phase sensitive rare-earth photoluminescence color flips in KLaF:RE (RE = Eu, Er/Yb) nanocrystals.

Systematic and strong rare-earth photoluminescence (PL) color flips that are highly sensitive to structural phase transformation in KLaF:RE (RE = Eu, Er/Yb) nanocrystals are demonstrated. Room-temperature wet chemical synthesis at various reaction times involves a systematic conversion from cubic (α, space group Fm3[combining macron]m) to hexagonal (β, space group P6[combining macron]2m) polymorph nanocrystals of 4 to 8 nm sizes. The unusual down-conversion photoluminescence (DC-PL) asymmetric ratio of the hypersensitive transition (D→F, Red) to that of nearly invariant transition (D→F, Orange) (R/O from 1.

Linear and nonlinear optical probing of various excitons in 2D inorganic-organic hybrid structures.

Nonlinear optical properties, such as two-(or multi-) photon absorption (2PA), are of special interest for technologically important applications in fast optical switching, in vivo imaging and so on. Highly intense infrared ultrashort pulses probe deep into samples and reveal several underlying structural perturbations (inter-layer distortions, intra-layer crumpling) and also provide information about new excited states and their relaxation. Naturally self-assembled inorganic-organic multiple quantum wells (IO-MQWs) show utility from room-temperature exciton emission features (binding energies ~200-250 meV).

Unusual Red-Shift and Enhanced Photoluminescence of BaMgAlO:Eu Phosphor Under Ultraviolet A Excitation for Modern Lighting Systems.

An unconventional red-shift but enhanced photoluminescence (PL) under ultraviolet A (UV-A) irradiation of Eu doped Barium Magnesium Aluminate (BAM) phosphor prepared in both bulk and nanoforms useful for modern lighting applications has been presented. The solid-state reaction and solution combustion approaches were used for the preparation of phosphors with post-annealing step in reduced atmosphere. A significant broad blue-green (˜500 nm) PL associated with the transition of Eu from 4 5d excited state to the 4 ground state has been observed.

Color-Tunable Upconversion in Er/Yb-Codoped KLaF Nanophosphors by Incorporation of Tm Ions for Biological Applications.

Heavily doped nanocrystals of host KLaF with rare earth (RE = Er, Tm, and Yb) ions prepared by a simple one-step template-free wet-chemical route have been reported. Prepared KLaF nanocrystals reveal phase-pure cubic structures (lattice constant = 5.931Å) with space group 3.

Pseudocapacitance of Mesoporous Spinel-Type MCoO (M = Co, Zn, and Ni) Rods Fabricated by a Facile Solvothermal Route.

We present the structural properties and electrochemical capacitance of mesoporous MCoO (M = Co, Zn, and Ni) rods synthesized by a facile solvothermal route without necessity to use templates. The Brunauer-Emmett-Teller specific surface areas of these mesoporous rods are found to be about 24, 54, and 62 m g with major pore diameters of about 31, 15, and 9 nm for MCoO, M = Co, Zn, and Ni, respectively. X-ray photoelectron spectroscopy and X-ray diffraction studies reveal the phase purity of the samples with a predominant spinel-type crystal structure.

Laser-induced microstructuring of two-dimensional layered inorganic-organic perovskites.

Non-contact bi-directional micropatterning of two-dimensional (2D) layered inorganic-organic (IO) perovskite [(R-NH3)2PbI4, R = organic moiety] thin films by direct laser writing (DLW) has been reported. These 2D materials are in the form of natural multiple quantum well (MQW) structures and show excitonic luminescence at room temperature because of quantum and dielectric confinement effects. Systematic optical and structural analyses of these laser processed hybrid systems provide an insight into laser-matter interaction and a pathway to develop technology to define complex 2D material based devices with new functionalities.

In situ intercalation dynamics in inorganic-organic layered perovskite thin films.

The properties of layered inorganic semiconductors can be manipulated by the insertion of foreign molecular species via a process known as intercalation. In the present study, we investigate the phenomenon of organic moiety (R-NH3I) intercalation in layered metal-halide (PbI2)-based inorganic semiconductors, leading to the formation of inorganic-organic (IO) perovskites [(R-NH3)2PbI4]. During this intercalation strong resonant exciton optical transitions are created, enabling study of the dynamics of this process.

Optical studies of Sm³⁺ ions doped zinc alumino bismuth borate glasses.

Zinc Alumino Bismuth Borate (ZnAlBiB) glasses doped with different concentrations of samarium (Sm(3+)) ions were prepared by using melt quenching technique and characterized for their lasing potentialities in visible region by using the techniques such as optical absorption, emission and emission decay measurements. Radiative properties for various fluorescent levels of Sm(3+) ions were estimated from absorption spectral information using Judd-Ofelt (JO) analysis. The emission spectra and con-focal photoluminescence images obtained by 410 nm laser excitation demonstrates very distinct and intense orange-red emission for all the doped glasses.

Phase stabilization by rapid thermal annealing in amorphous hydrogenated silicon nitride film.

We have studied the effect of rapid thermal annealing (RTA) in the context of phase evolution and stabilization in hydrogenated amorphous silicon nitride (a-SiN(x):H) thin films having different stoichiometries, deposited by an Hg-sensitized photo-CVD (chemical vapor deposition) technique. RTA-treated films showed substantial densification and increase in refractive index. Our studies indicate that a mere increase in flow of silicon (Si)-containing gas would not result in silicon-rich a-SiN(x):H films.

Tunable resonant optical microcavities by self-assembled templating.

Micrometer-scale optical cavities are produced by a combination of template sphere self-assembly and electrochemical growth. Transmission measurements of the tunable microcavities show sharp resonant modes with Q factors of >300 and 25-fold local enhancement of light intensity. The presence of transverse optical modes confirms the lateral confinement of photons.