Ultraviolet Absorption Edge Research Articles

Enhanced UV Nonlinear Optical Properties in Layered Germanous Phosphites through Functional Group Sequential Construction

AbstractThis study pioneers a novel strategy for synthesizing solar‐blind ultraviolet (UV) nonlinear optical (NLO) crystals through functional groups sequential construction, effectively addressing the inherent trade‐offs among broad transmittance, enhanced second‐harmonic generation (SHG), and optimal birefringence. We have developed two innovative van der Waals layered germanous phosphites: GeHPO3, the first Ge(II)‐based oxide NLO crystal which exhibits a black phosphorus‐like structure, and K(GeHPO3)2Br, distinguished by its exceptional birefringence and graphene‐like structure. Significantly, GeHPO3 exhibits a remarkable array of NLO properties, including the highest SHG coefficient recorded among all NLO crystals for phase‐matching and generating 266 nm coherent light via quadruple frequency conversion. It delivers a potent SHG intensity, surpassing KH2PO4 (KDP) by 10.3 times at 1064 nm and β‐BaB2O4 by 1.3 times at 532 nm, complemented by a distinct UV absorption edge at 211 nm and moderate birefringence of 0.062 at 546 nm. Comprehensive theoretical analysis links these exceptional characteristics to the unique NLO‐active GeO34− units and the distinctive, highly ordered layered structures. Our findings deliver essential experimental insights into the development of Ge(II)‐based optoelectronic materials and present a strategic blueprint for engineering structure‐driven functional materials with customized properties.

Enhanced UV Nonlinear Optical Properties in Layered Germanous Phosphites through Functional Group Sequential Construction.

This study pioneers a novel strategy for synthesizing solar-blind ultraviolet (UV) nonlinear optical (NLO) crystals through functional groups sequential construction, effectively addressing the inherent trade-offs among broad transmittance, enhanced second-harmonic generation (SHG), and optimal birefringence. We have developed two innovative van der Waals layered germanous phosphites: GeHPO3, the first Ge(II)-based oxide NLO crystal which exhibits a black phosphorus-like structure, and K(GeHPO3)2Br, distinguished by its exceptional birefringence and graphene-like structure. Significantly, GeHPO3 exhibits a remarkable array of NLO properties, including the highest SHG coefficient recorded among all NLO crystals for phase-matching and generating 266 nm coherent light via quadruple frequency conversion. It delivers a potent SHG intensity, surpassing KH2PO4 (KDP) by 10.3 times at 1064 nm and β-BaB2O4 by 1.3 times at 532 nm, complemented by a distinct UV absorption edge at 211 nm and moderate birefringence of 0.062 at 546 nm. Comprehensive theoretical analysis links these exceptional characteristics to the unique NLO-active GeO3 4- units and the distinctive, highly ordered layered structures. Our findings deliver essential experimental insights into the development of Ge(II)-based optoelectronic materials and present a strategic blueprint for engineering structure-driven functional materials with customized properties.

Optimization of Functional Building Blocks Generates a Substantial Improvement in Birefringence from Sn2OSO4 to Sn3O2(OH)(HSO4).

In this work, two tin(II)-based sulfates, Sn2OSO4 and Sn3O2(OH)(HSO4), were synthesized via the mild hydrothermal method. Both compounds employ the Sn2+ cation with stereochemically active lone pair (SCALP) electrons and non-π-conjugated tetrahedral anionic groups SO4 as the functional structural blocks. Interestingly, the experimental birefringence of Sn3O2(OH)(HSO4) is 0.169@546 nm, approximately 42 times larger than that of Sn2OSO4, which is 0.004@546 nm. Detailed structural analysis and theoretical calculations suggest that this significant birefringence difference arises from the optimization of functional building blocks in coordination environments and spatial arrangements. Furthermore, both compounds exhibit ultraviolet absorption edges at 308 and 307 nm, respectively. This indicates that Sn3O2(OH)(HSO4) has the potential to be a candidate for an ultraviolet (UV) birefringent crystal. This study offers inspiration for further exploration of tin(II)-based compounds with excellent comprehensive properties.

A Rare-Earth-Based Borate Optical Crystal with Enlarged Dihedral Angles of Distinct [BO3] Groups Exhibiting a Wide UV Transparent Range.

Borates, as advanced optical materials, have garnered wide interest due to their diverse structural configurations and great potential for applications in the ultraviolet (UV) regions. Herein, we synthesized a new rare-earth borate crystal, namely, K2NaYB2O6, which is classified as one of the ABReB2O6 compounds, where A and B represent alkali metal and Re denotes rare-earth metal. K2NaYB2O6 adopts in the monoclinic space group P21/c (No. 14), showcasing a three-dimensional (3D) framework composed of a planar triangular configuration of [BO3] units and distortive [YO7] polyhedra. Notably, both dihedral angles between distinct [BO3] units reach 79.6°, which represents an unprecedented structural feature in monoclinic ABReB2O6-type crystals. Moreover, the compound has a short UV absorption edge at around 204 nm, corresponding to a wide band gap of approximately 5.67 eV. Additionally, it possesses a moderate birefringence of 0.028 at 1064 nm. Further analysis utilizing theoretical calculations suggests that the optical behaviors of K2NaYB2O6 are mainly governed by its basic structural unit [BO3] triangles and distorted [YO7] polyhedra. These findings enrich the structure chemistry of rare-earth borates and offer valuable insights for the design of optical crystals in the UV wavelength range.

Na3K6(CO3)3(NO3)2X·6H2O (X = NO3, Cl, Br): Exploring High-Performance UV Birefringent Crystals Induced by Coplanar π-Conjugated CO3 and NO3 Groups.

Planar π-conjugated groups, like CO3, NO3, and BO3 triangles, are ideal functional units for designing birefringent materials due to their large optical anisotropy and wide band gap. The key point for designing birefringent crystals is to select appropriate functional building blocks (FBBs) and the proper arrangement mode. It is well known that the substitution strategy has proven to be a promising and accessible approach. In this work, alkali metals were chosen to regulate and control two different π-conjugated groups, CO3 and NO3, to build new compounds with large birefringence. Subsequently, three new compounds, Na3K6(CO3)3(NO3)2X·6H2O (X = NO3, Cl, Br), were successfully synthesized using the hydrothermal method. The aliovalent substitution between the [NO3]- anionic group and halogen anions [Cl]-/[Br]- has been achieved in these compounds. Na3K6(CO3)3(NO3)2X·6H2O feature the well-coplanar CO3 and NO3 groups in their crystal structure. This coplanar arrangement mode may effectively enhance the anisotropic polarizability of Na3K6(CO3)3(NO3)2X·6H2O. And their experimental birefringence can reach 0.094-0.131 at 546 nm. Diffuse reflectance spectra demonstrate that these compounds exhibit short ultraviolet (UV) absorption edges of ∼235 nm. Meanwhile, Na3K6(CO3)3(NO3)2X·6H2O also have an easily grown capacity under facile conditions. This work not only reports three new potential UV birefringent crystals but also provides a strategy to make the π-conjugated MO3 group coplanar.

Assembling Ag@CuO/UiO-66-NH2 nanocomposites for efficient photocatalytic degradation of xylene.

Achieving efficient and stable photocatalytic degradation of xylene hinges on the advancement of photocatalytic materials with outstanding visible light activity. This low-carbon strategy serves as a promising solution to combat air pollution effectively. In this study, we synthesized a Z-scheme heterojunction Ag@CuO/UiO-66-NH2 nanocomposite by hydrothermal method to investigate its photodegradation properties for xylene gas under visible light conditions. XRD, XPS, SEM, FTIR, and UV-vis analyses were employed to confirm the presence of the Z-scheme heterojunction. The CuO/UiO-66-NH2 (CuU-2) composite has high photocatalytic activity, which is 2.37 times that of the original UiO-66-NH2. The incorporation of Z-scheme heterojunction facilitates efficient charge transfer and separation, leading to a substantial enhancement in photocatalytic activity. The Ag@CuO/UiO-66-NH2 (Ag-1@CuU) composite has the highest photocatalytic activity with a degradation efficiency of 84.12%, which is 3.36 times and 1.41 times that of UiO-66-NH2 and CuO/UiO-66-NH2, respectively. The silver cocatalyst improves the absorption capacity of the composite material to visible light, makes the ultraviolet visible absorption edge redshift, and significantly improves the photocatalytic performance. This study introduces a novel approach for xylene gas degradation and offers a versatile strategy for designing and synthesizing metal-organic framework (MOF)-based photocatalysts with exceptional performance.

A new potential choice for scintillation fiber

In order to enrich the application demands of neutron detection field, this study prepared a series of Ce3+/Gd3+ co-doped borosilicate scintillating glass materials. The ultraviolet (UV) absorption edges were all below 400 nm. The optical band gap was shortened from 3.48 eV to 3.24 eV as well as the optical basicity increased from 0.4941 to 0.5063 with the added concentration of Gd3+ ions. When the samples were excited by a 330 nm light source, the central wavelength of the emission spectra was 375 nm. The fluorescence lifetime of the sample was 30.99 ns. The emission intensity of the G2 sample increases linearly with the increase of X-ray excitation current, and has a stable optical response at 374 nm. The G2 glass fiber with the highest fluorescence intensity had a prominent emission peak at 375 nm and the fluorescence lifetime of 2.22 ns.

The study of optical-electrical properties of ZnO(AZO)/Si heterojunction

In this paper, zinc oxide (ZnO) thin films and Al-doped zinc oxide (AZO) films are prepared. The XRD results show that the addition of Al ions at the middle stage of AZO film (ms-AZO) preparation can increase the grain size and change the preferential growth orientation from (100) crystal plane to (002) crystal plane. The results of UV-VIS spectra show that the addition of Al ions at the ms-AZO preparation can greatly increase the absorption intensity in the visible light region, and the addition of Al ions at the early stage of AZO film (es-AZO) preparation can make the blue shift of the ultraviolet absorption edge. The patterns of I–V curves show that the addition of Al ions can increase the forward current of AZO/Si heterojunction, comparing to that of ZnO/Si heterojunction. Furthermore, the leakage current mechanism may dominate the carrier transport.

Two UV organic-inorganic hybrid antimony-based materials with superior optical performance derived from cation-anion synergetic interactions

Finding suitable strategies to effectively enhance the optical properties of materials are the goal being pursued by researchers. Herein, cation-anion synergetic interactions strategy was proposed to develop two novel organic-inorganic hybrid antimony-based optical materials, (C3H5N2)SbF2SO4 (I) and (C5H6N)SbF2SO4 (II), which were obtained by introducing Sb3+cation containing stereochemically active lone-pair (SCALP) and organic π-conjugated cations into sulphate system. The synergistic interactions of the organic π-conjugated cations, the inorganic [SbO2F2]3− seesaw anions and the [SO4]2− distorted tetrahedra anions make their ultraviolet (UV) absorption edges approach 297 and 283 nm, respectively, and raise their birefringence up to 0.193@546 nm and 0.179@546 nm, respectively. Interestingly, although the two compounds have the same stoichiometric ratio and similar one-dimensional (1D) chain structure, they show opposite macroscopic symmetry, where the NCS compound (II) exhibits a large second-harmonic generation (SHG) response (1.6 times that of KH2PO4). The two reported compounds are found to be promising UV optical materials in the experimental tests.

Sr(NH2SO3)(NO3)·H2O: An Ultraviolet Nonlinear Optical Material Exhibiting Strong Second-Harmonic Generation Response and Sufficient Birefringence.

Second-harmonic generation (SHG) response and birefringence stand as fundamental optical properties for nonlinear optical (NLO) materials. Up to now, engineering a strong SHG response and substantial birefringence in the sulfamate system has proven to be exceedingly challenging. A novel noncentrosymmetric compound, Sr(NH2SO3)(NO3)·H2O, has been meticulously designed by introducing the (NO3)- group characterized by significant polarizability anisotropy and hyperpolarizability into the polar non-π-conjugated (NH2SO3)- system. This compound exhibits a robust SHG response (5.2 × KDP), ample birefringence (0.077 at 546.1 nm), and a short ultraviolet (UV) absorption edge (290 nm). The linear and nonlinear optical properties can be attributed to the (NO3)- group and the (NH2SO3)- group. This study presents an effective approach that contributes to the design of more composite anionic UV NLO materials with excellent and balanced optical properties.

Regulation of optical, thermal, and electrical properties of GaNbO4 crystal by Mg2+ doping

In this paper, GaNbO4 crystal properties were regulated by Mg2+ doping. The refractive indexes, optical properties, and thermal properties were characterized, the influence of Mg2+ doping and air annealing on the conductivity and photoluminescence properties of GaNbO4 was systematically studied. The Mg2+ doping causes the ultraviolet absorption edge of GaNbO4 crystal blue shift, and the band gap of Mg: GaNbO4 crystal is 3.463 eV. The thermal expansion coefficient in b-direction was presented, which is -0.977 × 10−6 K−1; the high-temperature resistivity of the Mg: GaNbO4 crystal decreases from 1.7 × 109 to 3.0 × 106 W·cm in the temperature range of 500 to 800 °C, decreasing by about an order of magnitude after air annealing. The photoluminescence spectrum shows an enhanced blue emission in Mg: GaNbO4 crystals, and x-ray photoelectron spectroscopy was measured, the element's chemical states and oxygen vacancies in the crystal were analyzed. The regulation mechanism of the crystal properties was discussed in detail.

Li2RbSO4Cl with a Short Ultraviolet Absorption Edge and an Acentric Structure through Assembling Heteroleptic [LiO3Cl] Tetrahedra.

Currently, short-wavelength nonlinear optical materials are urgently needed. Through substituting homoleptic [LiO4] in centrosymmetric LiRbSO4 with heteroleptic [LiO3Cl] tetrahedra, an acentric sulfate chloride, Li2RbSO4Cl, was designed and synthesized by the high-temperature melting method. Li2RbSO4Cl shows a relatively short ultraviolet absorption edge (<200 nm) among newly reported sulfate chlorides. Millimeter-sized crystals were grown due to the congruent melting behavior and high thermal stability of the compound.

ASb(SO4)2 (A = Rb, Cs): Two short-wave UV antimony sulfates exhibiting large birefringence

Herein, two antimony sulfates, named RbSb(SO4)2 (1) and CsSb(SO4)2 (2), have been successfully synthesized with the introduction of Sb3+ cation with stereochemically active lone pairs (SCALP) into sulfates by the conventional hydrothermal method. Both two compounds endow short UV absorption edges (281 nm and 278 nm, respectively) and large birefringence ([email protected] nm and [email protected] nm, respectively), which means that they are promising short-wave ultraviolet (UV) optical materials. Interestingly, though both of the two compounds exhibit similar 1D chained structures, and possess the same functional moieties including SbO4 seesaws and SO4 tetrahedral groups, they exhibit significantly opposite macroscopic symmetries, i.e., compound 1 crystallizes in a centrosymmetric (CS) manner (P21/n) and compound 2 in a noncentrosymmetric (NCS) manner (P212121), due to the size of cations [r(Rb+) = 1.56 Å, r(Cs+) = 1.67 Å] affects the orientation of SCALP of the adjacent Sb3+.

First-principles study on electronic and optical properties of sn-doped topological insulator Bi2Se3

Electronic structures and optical properties of pure and sn-doped Bi2Se3 were investigated by first-principles calculations based on density functional theory (DFT). For Bi2-xSnxSe3 (x = 0, 0.083, 0.167, 0.25), the introduction of Sn induced impurity bands near the Fermi level. Sn@(0,3) configuration with longer sn-Sn distance was more stable for the smallest formation energy. From the charge density result, sn-doped Bi2Se3 was the material with covalent and ionic characteristic. There was obvious blue shifting in the dielectric function and ultraviolet absorption edges for sn-doped Bi2Se3. The results had implications for the fabrication of sn-doped Bi2Se3 optical devices that can be blue-shifted in ultraviolet (UV) region.

Giant dielectric constant and ac electrical conductivity: Cu and Cu/W incorporated perovskite BaTiO3

Gigantic relative permittivity and ac electrical conductivity characteristics were realized in BaTiO3 through incorporation of Cu2+ and Cu2+/W4+ ions. The XRD results evidenced that pure BaTiO3 powder has a single phase with tetragonal structure. In Cu doped and (Cu, W) codoped samples, α-Ba2TiO4 phase with ratio of 17–25% was formed into BaTiO3 powder. The crystal analysis proved that the formed α-Ba2TiO4 phase naturally decay with time or heating at high temperature. The SEM micrographs illustrated the formation of elongated connected network particles in Cu doped and (Cu, 1%W) codoped BaTiO3 while cauliflower-like grains were seen for (Cu, 3% W) codoped BaTiO3 sample. Pure BaTiO3 powder reveals an ultraviolet (UV) absorption edge, corresponding to band gap energy of 3.25 eV. Owing to Cu2+ doping and (Cu2+, W4+) codoping, the absorption edge of BaTiO3 structure was powerfully red shifted and displayed oblique lines, matching to band gap energies within 3.06–2.68 eV. Pure BaTiO3 reveals a relative permittivity value of 811 (42 Hz) which transferred to gigantic values of (7.01572 × 105), (9.54016 × 105) and (3.00234 × 105) after insertion of Cu2+ and (Cu2+, W4+) ions. For Cu doped and (Cu, 1% W) codoped BaTiO3, the giant relative permittivity was considerably increased with temperature up to 125 °C and until 150 °C for (Cu, 3% W) codoped BaTiO3 sample. After decomposition of α-Ba2TiO4 phase (α-Ba2TiO4 → BaTiO3 + BaO), the dielectric constant still reveals stable colossal values equal to (7.5300 × 104), (3.66431 × 105) and (1.2277 × 104) at frequency of 42 Hz for Cu doped, (Cu, 1% W) and (Cu, 3% W) codoped BaTiO3, respectively.

Optical dispersion and bandgap of ultralow expansion glass

The thermal-optical property of an ultralow expansion (ULE®) 7973 glass wafer was assessed using spectrophotometers and variable angle spectroscopic ellipsometers. By modeling both the spectral transmission and the ellipsometric data, we derived optical dispersion of the glass over a broad spectral region from 180 nm up to 12 μm. Our results indicate that the transparency region of the glass is terminated by two fundamental absorption edges in the ultraviolet (UV) and the infrared (IR). The UV and IR absorption edges are dominated by the titania and silica constituents, respectively. The exponential absorption tail, the Urbach energy, in the UV increases linearly with the temperature ranging from room temperature to 650°C, whereas the optical bandgap decreases linearly over the same temperature range. The temperature-dependent coefficient is 18 μeV / ° C for the Urbach energy and −0.7 meV / ° C for the optical bandgap.

Ultraviolet photodetector based on RbCu2I3 microwire

Copper-based halide perovskites have shown great potential in lighting and photodetection due to their excellent photoelectric properties, good stability and lead-free nature. However, as an important piece of copper-based perovskites, the synthesis and application of RbCu2I3 have never been reported. Here, we demonstrate the synthesis of high-quality RbCu2I3 microwires (MWs) by a fast-cooling hot saturated solution method. The prepared MWs exhibit an orthorhombic structure with a smooth surface. Optical measurements show the RbCu2I3 MWs have a sharp ultraviolet absorption edge with 3.63 eV optical band gap and ultra-large stokes shift (300 nm) in photoluminescence. The subsequent photodetector based on a single RbCu2I3 MW shows excellent ultraviolet detection performance. Under the 340 nm illumination, the device shows a specific detectivity of 5.0 × 109 Jones and a responsivity of 380 mA·W−1. The synthesis method and physical properties of RbCu2I3 could be a guide to the future optoelectronic application of the new material.

Phosphites: A Nonlinear Optical Materials System with a Wide Band Gap and Moderate Second-Harmonic Generation Effect

Ultraviolet (UV) nonlinear optical (NLO) materials have crucial practical applications in modern laser science and technology. Phosphates are promising candidates for searching UV NLO materials. However, small optical anisotropy of high-symmetrized (PO4)3- tetrahedron hinders phase matching (PM) in the UV wavelength range. Herein, a low-symmetrized phosphite anionic group (HPO3)2- is proposed as a new NLO-active group that exhibits a larger optical anisotropy and second-harmonic generation (SHG) coefficients than (PO4)3-. Accordingly, two phosphites, (C(NH2)3)2Zn(HPO3)2 and [Al2(HPO3)3(H2O)3]·H2O, that contain (HPO3)2- groups are screened out and synthesized. The UV absorption edges of the two compounds are 6.18 and 6.23 eV, respectively. (C(NH2)3)2Zn(HPO3)2 exhibited an SHG intensity of 1 times that of KDP at 1064 nm. This work proposes a new NLO-active fundamental building unit (FBU) and a new materials system for searching NLO materials.

Isoreticular Design of KTiOPO4-Like Deep-Ultraviolet Transparent Materials Exhibiting Strong Second-Harmonic Generation.

Second-harmonic generation (SHG) is of great technological importance for applications in nonlinear optics, but it remains challenging to engineer large SHG responses in the short-wavelength ultraviolet (UV) region owing to competing microstructure requirements. Herein, we report the first examples of d0 transition-metal-based (TM-based) deep-UV-transparent nonlinear optical (NLO) crystals MOF4H2 (M = Zr (ZOF), Hf (HOF)), which exhibit unprecedented short UV absorption edges (below 190 nm). Evolving from the KTiOPO4 (KTP) structure by an isoreticular node substitution strategy, the three-dimensional frameworks of ZOF and HOF consist of corner-sharing [MO2F6] moieties that are new functional units in deep-UV NLO material design, conferring wide UV transparency and strong phase-matchable SHG response (2.2 × KH2PO4 (ZOF) and 1.8 × KH2PO4 (HOF) at 1064 nm). Such d0-TM-based [MO2F6] polyhedra preclude deleterious d-d electronic transitions, resulting in significantly blue-shifted UV absorption edges of ZOF and HOF (<190 nm). The d0-TM-based [MO2F6] polyhedra introduced in this work offer a new perspective in the construction of deep-UV transparent NLO materials, demonstrating the feasibility of an isoreticular design strategy in developing functional NLO materials.

Using UV-Vis-NIR absorption spectroscopy as a tool for the detection of iron and cobalt in glass: A case-study on HLLA material from the Low Countries

The early modern period is mainly characterised by High Lime-Low Alkali (HLLA) glass, a lime-rich glass made from plant or tree ashes, originating from 14th-century Germany and later used all over Europe. Attempts to link HLLA chemical subgroups to a particular point in time have failed so far. Driven by a request from the archaeological community, our research group has been exploring the feasibility of UV–Vis-NIR absorption spectroscopy as a non-destructive and in-situ applicable analysis technique for more than a decade. The main goal of this research is to provide a better understanding of the subgroups of HLLA glass and their respective dating via non-destructive means. A second topic relates to the role of cobalt as a potential indicator for either the type of applied ashes or for glass recycling.In this paper, we present the UV–Vis-NIR and LA-ICP-MS results of a total of 45 HLLA colourless glass objects or fragments, supplemented with three blue glasses from the 15th to the 17th centuries. First, we observed a correlation between iron and cobalt contents and that these two elements show more elevated concentrations starting from the middle of the 16th century. Different types of sources can be responsible, such as the type of raw materials, the tools employed, and recycling. We hypothesised that both elements were introduced through the wood or plant ashes used as fluxing agent. Then, we noted that the presence of low amounts of cobalt in colourless glass, can be observed through the analysis of the Co2+ absorption bands in the optical spectra down to 18 ppm. Next, we describe an approach to quantify iron and cobalt from the optical spectra and to date HLLA material by means of absorption spectroscopy, a valid, rapid, and non-destructive alternative for laboratory measurements. Finally, we show that the optical parameters (the Ultra-violet Absorption Edge (UVAE), the calculated Fe2+ and total iron contents, and the Co2+ absorption bands characteristics) allow discerning two glass groups: one dating to the end of the 15th-middle of the 16th centuries, and the other to the second half 16th-17th centuries. These results gain valuable information to further resolve the study on recycling, on the influence of the glassmaking tool on the glass batch composition and/or on the selection or treatment of the raw materials in HLLA glass.