[en] Infrared, Raman, electron absorption, excitation and emission spectra were measured for RbCr_xAl_1-x(MoO₄)₂ and CsCr_xAl_1-x(MoO₄)₂ crystals (x=0-2%) at the temperatures ranging from 7 to 300 K. A very rich vibronic structure of the emission band was explained and assigned to the respective vibrational modes. One Cr³⁺ center characterized by 2.35 ms lifetimes for rubidium derivative and 1.3 ms for cesium one at 7 K for the ²E→⁴A₂ transition was identified for both crystals. The local structure of the Cr³⁺ surrounding is discussed in terms of the spectroscopic results and the crystal field parameters are derived for both materials

[en] Highlights: • Four novel heterometallic formate frameworks have been synthesized. • These compounds are weak ferromagnets. • The largest average canting angle of 4.8 degrees has been found for Cr(III)-Co(II) analogue. • Cr(III)-Mn(II) compound exhibits efficient Cr(III)-based emission. - Abstract: Four novel compounds, [NH₃CH₂CH₂OH][M^IIIM^II(HCOO)₆] with M^III = Fe and M^II = Mn (HEAFeMn), M^III = Fe and M^II = Ni (HEAFeNi), M^III = Cr and M^II = Mn (HEACrMn) and M^III = Cr and M^II = Co (HEACrCo), have been synthesized. They crystallize in the trigonal niccolite-type structure (space group P $\overline{3}$ 1c). Magnetic studies revealed that HEAFeNi, HEAFeMn and HEACrCo are weak ferromagnets with the ordering temperature of 43, 27 and 11 K, respectively, whereas HEACrMn does not order magnetically at least down to 2 K. A source of the ferromagnetic component is most likely a canting of the antiferromagnetically ordered moments by a small angle resulting from antisymmetric exchange or single-ion anisotropy. Raman and IR data confirm that all obtained samples are isostructural. Optical studies of HEACrMn show that local crystal field around Cr³⁺ ion is of intermediate strength with the Dq/B value of 2.57. Luminescence studies indicate that HEACrMn exhibits efficient Cr³⁺-based emission. Below 200 K, the ²E-⁴A₂ phosphorescence observed as two bands at 686 and 696 nm becomes predominate.

[en] We have incorporated Cr(III) into [(CH_3)_2NH_2][Mn(HCOO)_3] (DMMn) multiferroic metal organic framework (MOF). The highest concentration of Cr(III) in the synthesized samples reached 15.9 mol%. The obtained samples were characterized by powder and single-crystal X-ray diffraction, DSC, magnetic susceptibility, dielectric, EPR, Raman and IR methods. These methods and the performed chemical analysis revealed that electrical charge neutrality after substitution of Cr(III) for Mn(II) is maintained by partial replacement of dimethylammonium (DMA"+) cations by neutral HCOOH molecules. These changes in the chemical composition are responsible for weakening of the hydrogen bonds and decreased flexibility of the framework. This in turn leads to lowering of the ferroelectric phase transition temperature, observed around 185 K for undoped DMMn and around 155 K for the sample containing 3.1 mol% of Cr(III), and lack of macroscopic phase transition for the samples with Cr(III) content of 8.2 and 15.9 mol %. Another interesting effect observed for the studied samples is pronounced strengthening of the weak ferromagnetism of in Cr(III)-doped samples, associated with slight decrease of the ferromagnetic ordering temperature from 8.5 K for DMMn to 7.0 K for the sample with 15.9 mol % Cr(III) content. - Graphical abstract: Incorporation of Cr(III) into [(CH3)2NH2[Mn(HCOO)3] framework increases the magnetization. - Highlights: • Chromium(III) substitutes for Mn(II) in the studied MOF. • Charge neutrality is maintained by replacing DMA"+ cations by neutral HCOOH molecules. • Compounds with 8.2 and 15.9% of Cr(III) show no phase transition above 100 K. • Doping with Cr(III) increases magnetization.

[en] Thin films of silica functionalized with NH₂ groups were prepared by the sol-gel technique from tetraethoxysilane (TEOS) and (3-aminopropyl)-triethoxysilane (APTES) precursors. Selected proteins labeled with isothiocyanate fuorescein (FTIC) were covalently attached to their surfaces via the NH2 groups. The presence of the functional groups was confirmed by infrared absorption and Raman spectra measurements. The obtained films were immersed in a buffer and polarized emission spectra were measured. Next, the samples were incubated with selected bacterial endotoxin and the emission spectra were collected again. The influence of the endotoxin binding on the luminescence depolarization has been proven. The system based on this effect is suggested as an optical biosensor for the endotoxin recognition

[en] Nonlinear optical (NLO) crystals CoTeMoO_6 have been grown from high temperature solution by means of spontaneous crystallization. These crystals have been characterized by temperature-dependent X-ray diffraction, infrared and electron absorption methods. Moreover, polarized Raman spectra have been measured at room temperature. These studies showed that the Mo"6"+ and Te"4"+ ions are in asymmetric coordination environment, and CoTeMoO_6 has the largest flexibility index among MTeMoO_6 family of telluro-molybdates (M=Zn, Mg, Cd, Mn, Co), making this compound attractive NLO material. Raman and IR studies allowed assigning the observed modes to respective motions of atoms in the unit cell. They have also showed evidence for spin–phonon coupling at low temperatures and suggested that CoTeMoO_6 is prospective material for solid-state Raman laser-frequency converters. Analysis of electron absorption data has shown that Co"2"+ ions are located in sites of weak crystal field with the crystal field parameters Dq and B equal to 548 cm"−"1 and 882 cm"−"1, respectively. - Graphical abstract: View of CoTeMoO_6 crystal structure along the b-axis. - Highlights: • Single crystals of nonlinear optical telluromolybdate CoTeMoO_6 were grown. • Crystal structure was solved by means of single crystal X-ray diffraction. • Raman and IR spectra were measured and analyzed. • Crystal field strength acting on Co"2"+ ions was established from analysis of electron absorption spectra

[en] Amorphous silica materials have been successfully prepared by the controlled hydrolysis of tetraethoxysilane and glycidyloxypropyltrimethoxysilane. The rhodamine B has been introduced into the hydrolized silicate solutions. Thin films have been obtained by spin-coating of the obtained hydrolizates on quartz glass substrates. The morphology of the resulting thin-film samples have been characterized by optical and atomic force microscopies. The spectroscopic properties of samples have been characterized by FT IR and UV-VIS-NIR absorption measurements. The photoluminescence spectra have been recorded at room temperature. The emission of the hybrid materials doped with the dye exposed to UV radiation as a function of laser pulses has been measured. Basic physicochemical properties of the modified silica materials have also been determined