Absorption Spectra Of Crystals Research Articles

Sm3+ as effective deactivator for enhanced ∼3 μm laser emission in Er,Sm:SrLaAlO4 crystal

A promising mid-infrared (MIR) laser crystal with Er, Sm co-doped SrLaAlO4 (Er,Sm:SLA) crystal was successfully grown using the Czochralski (CZ) method. It was the first time that co-doped Sm3+ ion as deactivator for Er3+ activated ∼ 3.0 μm laser. The crystal structure, absorption spectra, emission spectra, and energy level lifetime were discussed in detail. The band structure and density of states were calculated by the density functional theory. The spectral parameters were calculated using Judd-Ofelt (J-O) theory and the deactivate effect of Sm3+ was systematically studied. The introduction of Sm3+ ions enhance the 2.7 µm mid infrared emission intensity by three times, and decrease the lifetime of 4I13/2 energy level of Er3+ ion from 4.35 ms to 0.98 ms. The lifetime ratio of upper and lower levels for 2.7 µm emission was calculated to be 0.63, which is 2.6 times of Er:SLA crystal and comparable to some commercial crystals. All the results indicate that the Sm3+ ion is an effective deactivator for ∼3 μm laser emission. The long upper level lifetime, as well as the large lifetime ratio, the broadening spectra characteristics and the appropriate emission cross-section show the Er,Sm:SLA crystal a good gain material for ultrafast and tunable lasers at ∼3.0 μm.

The Wannier-Mott Exciton, Bound Exciton, and Optical Phonon Replicas of Single-Crystal GaSe

We report the absorption and photoluminescence spectra of GaSe single crystals in the near-edge region. The temperatures explored the range from 17 to 300 K. Specifically, at a temperature of 17 K, the photoluminescence spectrum reveals an interesting phenomenon: the Wannier-Mott exciton separates into two states. These states are a triplet state with an energy of 2.103 eV and a singlet state with an energy of 2.109 eV. The energy difference between these two states is 6 meV. Furthermore, the bound exciton (BX) can be localized at an energy of 2.093 eV. It is worth noting that its phonon replicas (BX-nLO) can be clearly distinguished up to the fourth order. Interestingly, the energy gaps between these replicas exhibit a consistent spacing of 7 ± 0.5 meV. This intriguing finding suggests a high-quality crystalline structure as well as a strong coupling between the phonon and BX-nLO. Additionally, at low temperatures, both the ground state (n = 1) at 2.11 eV and the excited state (n = 2) at 2.127 eV of free excitons can be observed.

Growth, optical and thermal properties of YbxHo1-xCa4O(BO3)3 crystals

YbxHo1-xCa4O(BO3)3 (Yb:HoCOB, x = 0, 0.1, 0.2, 0.3) crystals were grown by the Bridgman method for the first time. The crystal structure, rocking curve, transmission spectra, absorption spectra, band structure and thermal properties of Yb:HoCOB were characterized in detail. The maximum half peak width (FMHW) of Yb0.1Ho0.9COB and Yb0.2Ho0.8COB is 26.7″ and 23.8″, respectively, and the effective segregation coefficient is greater than 0.9. In addition, the transmittance of Yb:HoCOB is 88 %. New absorption peaks are introduced by doping Yb3+ at 850–1000 nm. The UV absorption cut-off edge of Yb:HoCOB is red-shifted with increasing Yb3+ doping. The thermal diffusivity and thermal conductivity of Yb:HoCOB decrease with increasing temperature. The specific heat increases with the increasing temperature and finally approaches a constant value. The specific heat of Yb:HoCOB crystal are above 0.670 J/gK at room temperature. Yb:HoCOB with good crystallization quality, high transmittance and high specific heat has the application potential in laser frequency and QPCPA. This work provides a useful exploration for the study of nonlinear optical materials in solid state lasers.

2,3-Dichloroanthracene crystal, a new rigid matrix for single molecule optical investigations.

Absorption and emission spectra of single crystals of 2,3-dichloroathracene (23DCA) and 23DCA dispersed in n-nonane matrix were studied at 5 K. Singlet and triplet excitonic bands in the crystal were estimated to be at about 415 nm and at wavelengths shorter than 700 nm, respectively. Thus, from the spectroscopic point of view, these crystals satisfy all criteria for a transparent and rigid matrix for low temperature optical studies of single molecules of dibenzoterrylene, which have their purely electronic S0→S1 transition at around 785 nm. Quantum-chemistry calculations were used to analyze the spectra.

Cu-MOF attached with pyrene-cored probes as a highly sensitive indicator for carbon monoxide in coal mine gas: Synthesis and performance

As a toxic component in coal mine gas, CO has both acute and long-term damages to human health. Suitable CO probes satisfying the requirement for long-distance real-time monitoring in confined space are still underdeveloped. In this work, a series of fluorescent probes derived from pyrene were synthesized and coordinated onto [Cu3(BTC)2(H2O)3]n (H3BTC meant 1,3,5-benzenetricarboxylic acid) via a coordination bond with Cu2+. These probes were carefully analyzed, including their single crystal structure, absorption spectra, excitation spectra, and emission spectra. Their emission response towards CO gas was analyzed, with a sensing mechanism of probe release which was triggered by a dynamic wagging between the trans- and cis- configuration of –C = N–N = C– moiety upon photoexcitation. These probes were attached onto a classic MOF (metal-organic framework) [Cu3(BTC)2(H2O)3]n, which was confirmed by SEM, fluorescence microscopy, XRD, N2 adsorption/desorption, and TGA. The resulting composite samples (denoted as Pm@CuBTC) showed emission recovery upon trace amount CO (LOD = 0.005 % vs N2, 50 ppm), with a short response time of 31 s at room temperature. High sensing selectivity over competing species of alkane was observed, with stable signal for 5 days.

Size Quantization of the Electron Energy Spectrum in a Microscopic Semiconductor Crystal

The interband absorption spectrum of microscopic CdS crystals ranging in size from ~30 to 800 Å and dispersed in a transparent insulating matrix has been studied. There is a significant (~0.8-eV) shift of the fundamental absorption edge in the short-wavelength direction, and there are oscillations in the interband absorption spectrum caused by quantum size effect.

Quantum Size Effect in Three-Dimensional Microscopic Semiconductor Crystals

The exciton absorption spectrum of microscopic CuCl crystals grown in a transparent dielectric matrix has been studied. The size of the microscopic crystals was varied in a controlled manner from several tens of angstroms to hundreds of angstroms. There is a short-wave shift (of up to 0.1 eV) of the exciton absorption lines, caused by a quantum size effect.

Effect of doping on the optical properties of lanthanum-gallium tantalate

Nominally pure lanthanum-gallium tantalate La3Ga5.5Ta0.5O14 crystals doped with aluminum, silicon and gallium oxide to above stoichiometric content have been grown by the Czochralski technique in iridium crucibles in argon and in agron with addition of oxygen atmospheres. The transmittance spectra of the crystals have been measured on a Cary-5000 UV-Vis-NIR spectrophotometer in the 200–800 nm range. Absorption spectra α(λ) have been plotted on the basis of the experimental data. The absorption spectra of the undoped crystals grown in an oxygen-free atmosphere have one weak absorption band at λ ~ 290 nm. The absorption spectra of the crystals grown in an agron with addition of oxygen have absorption bands at λ ~ 290, 360 and 480 nm. We show that for the crystals grown in an oxygen-free atmosphere, gallium doping to above stoichiometric content reduces the intensity of its only λ ~ 290 nm absorption band. Aluminum doping of the La3Ga5.5Ta0.5O14 crystals grown in an oxygen-free atmosphere significantly reduces the intensity of the λ ~ 290 nm absorption band and increases the intensity of the λ ~ 360 and 480 nm bands. Aluminum doping of the La3Ga5.5Ta0.5O14 crystals grown in an oxygen-containing atmosphere reduces the intensity of the λ ~ 360 and 480 nm bands and increases the intensity of the λ ~ 290 nm absorption band. Silicon doping of these crystals significantly reduces the intensity of the λ ~ 480 nm band and also reduces the intensity of the λ ~ 290 and 360 nm bands.

Synthesis, characterization, and anticancer activity of some mononuclear ruthenium(II) compounds

Mononuclear Ru-based compounds cis-RuII(dppm)2Cl2 (1) and trans-RuII(dppe)2Cl2 (4) were synthesized by treatment of RuIICl2(DMSO)4 with dppm or dppe, respectively (dppm = bis(diphenylphosphino) methane, dppe = 1,2-bis(diphenylphosphino) ethane, DMSO = dimethyl sulfoxide). Mononuclear Ru-based compounds trans-RuII(dppm)2Cl2 (2) and cis-RuII(dppe)2Cl2 (3) were obtained by reaction of RuIICl2(PPh3)3 with dppm or dppe, separately. These two pair of cis–trans isomers, cis/trans-RuII(dppm)2Cl2 and cis/trans-RuII(dppe)2Cl2, were characterized by electronic absorption spectra, infrared, elemental analysis, 1H NMR, 13C NMR, 31P NMR, and single-crystal X-ray diffraction analysis. Both the crystal structure data and electronic absorption spectra indicate that the cis-isomer is a more thermodynamically stable structure and has lower energy than the trans-isomer. The luminescence spectroscopic study and relative cell viability of 1–4 on HeLa cancer cells has been investigated.

Effect of doping on the optical properties of lanthanum-gallium tantalate

Nominally pure lanthanum-gallium tantalate La3Ga5.5Ta0.5O14 crystals doped with aluminum, silicon and gallium oxide to above stoichiometric content have been grown by the Czochralski technique in iridium crucibles in argon and in agron with addition of oxygen atmospheres. The transmittance spectra of the crystals have been measured on a Cary-5000 UV-Vis-NIR spectrophotometer in the 200–800 nm range. Absorption spectra α(λ) have been plotted on the basis of the experimental data. The absorption spectra of the undoped crystals grown in an oxygen-free atmosphere have one weak absorption band at λ ~ 290 nm. The absorption spectra of the crystals grown in an agron with addition of oxygen have absorption bands at λ ~ 290, 360 and 480 nm. We show that for the crystals grown in an oxygen-free atmosphere, gallium doping to above stoichiometric content reduces the intensity of its only λ ~ 290 nm absorption band. Aluminum doping of the La3Ga5.5Ta0.5O14 crystals grown in an oxygen-free atmosphere significantly reduces the intensity of the λ ~ 290 nm absorption band and increases the intensity of the λ ~ 360 and 480 nm bands. Aluminum doping of the La3Ga5.5Ta0.5O14 crystals grown in an oxygen-containing atmosphere reduces the intensity of the λ ~ 360 and 480 nm bands and increases the intensity of the λ ~ 290 nm absorption band. Silicon doping of these crystals significantly reduces the intensity of the λ ~ 480 nm band and also reduces the intensity of the λ ~ 290 and 360 nm bands.

Optical Characteristics of MgAl2O4 Single Crystals Irradiated by 220 MeV Xe Ions.

In In this study, the optical properties of magnesium-aluminate spinel were examined after being irradiated with 220 MeV Xe ions. The research aimed to simulate the impact of nuclear fuel fission fragments on the material. The following measurements were taken during the experiments: transmission spectra in the IR region (190-7000) nm, optical absorption spectra in the range (1.2-6.5) eV, and Raman spectra were measured along the depth of ion penetration from the surface to 30 µm. A peak with a broad shape at approximately 5.3 eV can be observed in the optical absorption spectrum of irradiated spinel crystals. This band is linked to the electronic color centers of F+ and F. Meanwhile, the band with a maximum at ~(3-4) eV is attributed to hole color centers. Apart from the typical Raman modes of an unirradiated crystal, additional modes, A1g* (720 cm-1), and Eg* (385 cm-1), manifested mainly as an asymmetric shoulder of the main Eg mode, are also observed. In addition, the Raman spectroscopy method showed that the greatest disordering of crystallinity occurs in the near-surface layer up to 4 μm thick. At the same time, Raman scattering spectroscopy is sensitive to structural changes almost up to the simulated value of the modified layer, which is an excellent express method for certifying the structural properties of crystals modified by swift heavy ions.

High-Resolution Spectroscopy of the ErCrO3 Crystal: A New Phase Transition?

Infrared absorption spectra of the ErCrO3 crystal in the region of f{-} f transitions in the Er3+ ion are recorded for the first time. An analysis of high-resolution temperature-dependent spectra reveals a step at T{kern 1pt} ' = 47 K on the temperature dependences of the characteristics of spectral lines, in addition to the features at temperatures of magnetic ordering TN = 133 K and spin-reorientation transition {{T}_{{{text{SR}}}}} = 9.3{kern 1pt} K. This feature can be associated with either a previously unknown phase transition or with local changes in the crystal structure. The shape of the lines at liquid helium temperatures indicates the presence of additional positions for Er3+ ions in the ErCrO3 crystal. Presumably, these are positions near uncontrolled impurities that enter the crystal during its growth by the solution–melt method and form regions with a distorted structure responsible for the occurrence of polarization.

Growth and spectroscopic properties of a novel Tm3+-doped YSr3(PO4)3 disordered crystal

A novel Tm3+-doped YSr3(PO4)3 (Tm:YSP) crystal with a disordered crystal structure was grown by using the Czochralski pulling method. The single crystal growth, structure, absorption and emission spectra were systematically analyzed. The absorption bandwidth at ∼792 nm was found to be 21 nm, showing that the Tm:YSP crystal was very suitable for commercial laser diodes pumping of AlGaAs. Furthermore, the maximum emission cross section centering at 1835 nm was determined to be 0.86 × 10−20 cm2 with an emission bandwidth of 202 nm, which indicates the promising applications in the fields of ultrafast and tunable lasers. In addition, Spectroscopic parameters, containing Judd – Ofelt intensity, line strengths, radiative transition probabilities, fluorescence branching ratio and radiative lifetime, were analyzed by using the Judd – Ofelt theory. All above results showed that the Tm:YSP crystal with a disordered structure was a potential laser medium in the ⁓ 2 μm region.

Modification of calcium orthovanadate single crystal due to cobalt doping

Activation of calcium orthovanadate crystals by cobalt ions was carried out by introducing cobalt oxide into the melt during Czochralski growth process or during high-temperature annealing of nominally pure Ca3(VO4)2 single-crystal using Co3O4 powder as a solid-phase diffusant. The maximum concentration of the Co ions in the matrix is achieved in the case of the diffusion doping process. For the concentration series of Ca3(VO4)2:nCo crystals, the local structure was investigated and the crystal chemical composition was determined. Polarized absorption spectra of doped crystals are obtained. The influence of the atmosphere and the annealing temperature on the redistribution of the intensities of the characteristic absorption bands in the visible and near-IR spectral regions is shown. Luminescence parameters of the doped crystals were studied.

A New Look at the Explanation of Differences in Properties between La3+ and Lu3+ Titanate Hosts Occupied by Eu3+

In order to improve the quality of WLEDs, considerable efforts have been devoted to investigate red phosphor. In this study, two double perovskites La2MgTiO6 and La2ZnTiO6 and two novel pyrochlores Lu2MgTiO6 and Lu2ZnTiO6 doped with 1%Eu3+ were synthesized by the co-precipitation method. The crystal structure, absorption, excitation, and emission spectra of all samples were investigated in detail. Dissimilar luminescent behaviors of the studied samples were observed. Due to the different site symmetry of Eu3+, each compound exhibits a different emission spectrum. The emission of the magnetic dipole transition is dominant in all the spectra of the Lu-based hosts, while the forced electric dipole transition is the strongest one in the spectra of the others. Besides, the ones crystallized in double perovskite structures possess larger bandgaps and show a more intense emission from the 5D1 level of Eu3+ as compared to the pyrochlore compounds. Furthermore, the distinct mechanism of the cross-relaxation of four titanate compounds was investigated. The above findings contribute to the understanding of the two novel pyrochlore hosts.

Radiation and Emission Phenomena in Combination

Radiation and Emission Phenomena in Combination

Determination of Nicotine in Human Saliva Using Electrochemical Sensor Modified with Green Synthesized Silver Nanoparticles Using Phyllanthus reticulatus Fruit Extract

In this study, for the first time, Phyllanthus Reticulatus fruit extract was utilized as a reducing agent in the synthesis of silver nanoparticles (Ag-NPs). For sample analysis, a number of approaches were employed. The synthesized Ag-NPs have a spherical shape and a homogeneous in size. The well-known crystal structure and optical energy absorption spectrum of Ag-NPs were respectively revealed by the XRD and UV-VIS analysis. This new method is simple and eco-friendly for producing silver and other noble metals in large quantities. The Ag-NPs modified glassy carbon electrode was prepared for nicotine oxidation which indicated that Ag NPs had the ability to enhance the electron transfer rate of the oxidation process. In 0.1 M phosphate buffer (pH of 7.4), a significant increase in the oxidation peak current of nicotine was observed at the modified electrode. Cyclic voltammetry, amperometry, and electrochemical impedance spectroscopy characterizations showed that Ag-NPs had better electrocatalytic performance toward nicotine (NIC) oxidation with good stability, and selectivity. This sensor showed a linear response with the concentration of NIC in the range of 2.5 to 105 μM. The limit of detection (LOD) was estimated to be 0.135 μM. The interference analysis was carried out on the Ag-NPs/GCE with various molecules like acetic acid, ascorbic acid, calcium chloride, glucose, magnesium chloride, urea, and uric acid. Hence, these molecules did not interfere with NIC detection, indicating a perfect selectivity of Ag-NPs/GCE. Moreover, the Ag-NPs/GCE sensor was effectively applied to detect NIC in a real-world sample (saliva) of a tobacco chewer. Furthermore, the Ag-NPs/GCE sensor exhibited very good stability and repeatability in human saliva samples. Finally, Ag-NPs/GCE was also successfully applied to detect spiked nicotine in saliva samples with high recovery value, indicating its high accuracy and effectiveness in NIC analysis.

Observation of electronic spectra modulation in a CH3NH3PbBr3 crystal by utilizing transient absorption microscopy

Organic–inorganic lead halide perovskite materials have attractive properties not only for solar cells but also for LED because of their high performance and wavelength tunability. Such an efficient light-emitting and lasing nature are indispensable for their applications, and the essential needs are miniaturization and low lasing threshold. One material that satisfies these requirements is lead halide perovskite. To understand the time evolution of the interaction between light and matter in a perovskite crystal system, it is necessary to reveal the carrier dynamics in each crystal. In this study, the transient absorption spectra of CH3NH3PbBr3 crystals were measured using a femtosecond transient absorption microscopy. Surprisingly, strong spectra modulation has been observed and these results indicate the charge separation on the surface of the crystal. Amplified spontaneous emission dynamics were also observed in the transient absorption spectra.

Crystal Structure, Raman, FTIR, UV-Vis Absorption, Photoluminescence Spectroscopy, TG-DSC and Dielectric Properties of New Semiorganic Crystals of 2-Methylbenzimidazolium Perchlorate.

Single crystals of 2-methylbenzimidazolium perchlorate were prepared for the first time with a slow evaporation method from an aqueous solution of a mixture of 2-methylbenzimidazole (MBI) crystals and perchloric acid HClO4. The crystal structure was determined by single crystal X-ray diffraction (XRD) and confirmed by XRD of powder. Angle-resolved polarized Raman and Fourier-transform infrared (FTIR) absorption spectra of crystals consist of lines caused by molecular vibrations in MBI molecule and ClO4- tetrahedron in the region ν = 200-3500 cm-1 and lattice vibrations in the region of 0-200 cm-1. Both XRD and Raman spectroscopy show a protonation of MBI molecule in the crystal. An analysis of ultraviolet-visible (UV-Vis) absorption spectra gives an estimation of an optical gap Eg~3.9 eV in the crystals studied. Photoluminescence spectra of MBI-perchlorate crystals consist of a number of overlapping bands with the main maximum at Ephoton ≅ 2.0 eV. Thermogravimetry-differential scanning calorimetry (TG-DSC) revealed the presence of two first-order phase transitions with different temperature hysteresis at temperatures above room temperature. The higher temperature transition corresponds to the melting temperature. Both phase transitions are accompanied by a strong increase in the permittivity and conductivity, especially during melting, which is similar to the effect of an ionic liquid.

Influence of Neutron Irradiation Conditions on Maximal Frequency of IR Absorption Spectra of LiF:OH Single Crystal

For many solids operating under irradiation conditions, the study of their behavior at the neutron irradiation is of importance. Herein, the influence of neutron irradiation conditions on the infrared (IR) absorption spectra of LiF crystals containing different amounts of hydroxyl and metallic impurities is considered. The investigations are carried out for discovering new peculiarities under the extreme irradiation conditions of LiF—being a very important material for practical applications. In the crystals with OH− impurity after the action of neutron irradiation, quite clear bands are appeared in the region of 1900–2200 cm−1. The delivered doses vary from 1014 to 3 × 1017nnvt. LiF crystals are investigated by differing both in qualitative and quantitative contents of OH− ions. With the increase in irradiation dose, the maximum IR absorption of all investigated groups of crystals shifts to the region of low energies. The appearance of a new band in the IR spectrum and its shift as a function of dose is associated with the radiolysis of OH− molecule.