Facile Synthesis Method for the Preparation of Large‐scale Ultra‐small GdPO4:Tb and GdPO4:Tb@LaPO4 Nanowires

A simple and efficient method is presented for the large‐scale synthesis of ultra‐small, wired‐shaped GdPO₄:Tb nanostructured phosphor material with an average diameter of 2–5 nm and typical average length of 100 nm. X‐ray diffraction (X RD), transmission electron microscopy (TEM), energy dispersive X‐ray (EDX) analysis, as well as FTIR, UV–vis, emission, and excitation spectral techniques were employed to examine the crystal phase, purity, morphology, surface chemistry, and optical and photoluminescence properties of the as‐prepared nanoproducts. The TEM image clearly revealed the single‐phase, highly crystalline, narrow‐size‐distributed, ultra‐small, wire‐shaped nanostructures, which was confirmed from the XRD pattern. Optical absorption spectra in the ultraviolet region show high absorbance because of the high solubility and colloidal stability in aqueous solvents. Surface coating of an undoped LaPO₄ shell remarkably enhanced the crystallinity and photoluminescence properties of the nanowires (NWs). Core/shell NWs represent high emission and excitation intensity regardless of the core NWs because of a decrease in multiphoton relaxation pathways. It could be a highly suitable nanomaterial for optical bioprobes, biodetectors, and so on.     

Preparation and Luminescence Properties of Color-tunable Single-phased LaPO4: Eu3+/Tb3+ Phosphors

A novel series of color-tunable single-phased phosphors La_1-x-yPO₄:xEu³⁺/yTb³⁺(x=0, 0.01, 0.02, 0.03, 0.04, 0.05; y=0, 0.05, 0.10, 0.15, 0.20) was synthesized via microwave-assisted co-precipitation method with diammonium hydrogen phosphate as precipitant. The morphology, crystal structure and photoluminescence properties of the as-prepared samples were characterized by means of X-ray diffraction(XRD), scanning electron microscopy(SEM) and fluorescence spectrophotometer. The results reveal that the as-synthesized samples calcined at 1100℃ display spherical morphology with uniform distribution. Upon excitation with 350 nm ultraviolet radiation, the LaPO₄:Eu³⁺/Tb³⁺ phosphors showed a green light peaking at 543 nm assigned to the characteristic ⁵D₄-⁷F₅ emission of Tb³⁺ and a red light peaking at 591 nm corresponding to the characteristic ⁵D₀-⁷F₁ emission of Eu³⁺ simultaneously. For the Eu³⁺/Tb³⁺ co-activated phosphors, Tb³⁺ acts as an efficient sensitizer to enhance the emission intensity of Eu³⁺ ions. The energy transfer mechanism and the emission color tunability of LaPO₄:Eu³⁺/Tb³⁺ have been studied. The results indicate that a color-tunable luminescence(from green to white to red) can be achieved by adjusting the Eu³⁺/Tb³⁺ doping ratio in the LaPO₄ host matrix.     

Designing of luminescent GdPO4:Eu@LaPO4@SiO2 core/shell nanorods: Synthesis,structural and luminescence properties

GdPO₄:Eu³⁺ (core) and GdPO₄:Eu@LaPO₄ (core/shell) nanorods (NRs) were successfully prepared by urea based co-precipitation process at ambient conditions which was followed by coating with amorphous silica shell via the sol-gel chemical route. The role of surface coating on the crystal structure, crystallinity, morphology, solubility, surface chemistry and luminescence properties were well investigated by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis, Fourier Transform Infrared (FTIR), UV-Vis, and photoluminescence spectroscopy. XRD pattern revealed highly purified, well-crystalline, single phase-hexagonal-rhabdophane structure of GdPO₄ crystal. The TEM micrographs exhibited highly crystalline and narrow size distributed rod-shaped GdPO₄:Eu³⁺ nanostructures with average width 14–16 nm and typical length 190–220 nm. FTIR spectra revealed characteristic infrared absorption bands of amorphous silica. High absorbance in a visible region of silica modified core/shell/Si NRs in aqueous environment suggests the high solubility along with colloidal stability. The photoluminescence properties were remarkably enhanced after growth of undoped LaPO₄ layers due to the reduction of nonradiative transition rate. The advantages of presented high emission intensity and high solubility of core/shell and core/shell/Si NRs indicated the potential applications in monitoring biological events.     

Synthesis, crystal structure and vibrational spectra characterization of MLa(PO3)4 (M=Na, Ag)

The single crystals of lanthanum metaphosphate MLa(PO₃)₄ (M=Na, Ag) have been synthesized and studied by a combination of X-ray crystal diffraction and vibrational spectroscopy. The sodium and silver compounds crystallize in the same monoclinic P2₁/n space group ( factor group) with the following respective unit cell dimensions: a=7.255(2), b=13.186(3), , β=90.40(2)°, , Z=4 and a=7.300(5), b=13.211(9), , β=90.47(4)°, , Z=4. This three-dimensional framework is built of twisted zig-zag chains running along a direction and made up of PO₄ tetrahedra sharing two corners, connected to the LaO₈ and NaO₇ or AgO₇ polyhedra by common oxygen atoms to the chains. The infrared and Raman vibrational spectra have been investigated. A group factor analysis leads to the determination of internal modes of (PO₃)⁻ anion in the phosphate chain.     

Comparative Structural,Optical, and Photoluminescence Studies of YF3:Pr,YF3:Pr@LaF3, and YF3:Pr@LaF3@SiO2 Core–Shell Nanocrystals

Praseodymium (Pr³⁺)‐doped YF₃ (core) and LaF₃ ‐covered YF₃ :Pr (core–shell) nanocrystals (NCs ) were prepared successfully by an ecofriendly, polyol‐based, co‐precipitation process, which were then coated with a silica shell by using a sol–gel‐based Stober method. X‐ray diffraction (XRD), transmission electron microscopy (TEM ), thermal analysis, Fourier transform infrared (FTIR) , UV /vis, energy bandgap, and photoluminescence studies were used to analyze the crystal structure, morphology, and optical properties of the nanomaterial. XRD and TEM results show that the grain size increases after sequential growth of crystalline LaF₃ and the silica shell. The silica surface modification enhances the solubility and colloidal stability of the core–shell‐SiO₂ NCs . The results indicate that the surface coating affects the optical properties because of the alteration in crystalline size of the materials. The emission intensity of silica‐modified NCs was significantly enhanced compared to that of core and core–shell NCs . These results are attributed to the formation of chemical bonds between core–shell and noncrystalline SiO₂ shell via La–O–Si bridges, which activate the “dormant” Pr³⁺ ions on the surfaces of the nanoparticles. The luminescence efficiency of the as‐prepared core, core–shell, and core–shell‐SiO₂ NCs are comparatively analyzed, and the observed differences are justified on the basis of the surface modification surrounding the luminescent seed core NCs .     

FT-Raman and high-pressure infrared spectroscopic studies of dicalcium phosphate dihydrate (CaHPO4·2H2O) and anhydrous dicalcium phosphate (CaHPO4)

The FT-Raman spectra and the pressure dependence of the infrared spectra of the hydrated and anhydrous forms of dicalcium phosphate, CaHPO₄ · 2H₂O and CaHPO₄, have been studied. The hydrated salt exhibits a phase transition at 21 kbar (1.0 kbar=0.1 Gpa) but no high pressure transition was observed for anhydrous dicalcium phosphate. The O–H stretching frequencies of the water molecules in CaHPO₄·2H₂O all showed negative pressure dependences and correlate with the OO distances. The PO–H stretch increased with increasing pressure, indicating a strong hydrogen bond. The frequencies associated with the phosphate ion showed a normal pressure dependence.     

Additive assisted hydrothermal synthesis,characterization and optical properties of one dimensional DyPO4:Ce3+ nanostructures

One dimensional nanostructures of cerium doped dysprosium phosphate (DyPO₄:Ce³⁺) were synthesized via hydrothermal route in the presence of different surfactants [sodium dodecyl sulfate (SDS), dodecyl sulfosuccinate (DSS), polyvinyl pyrollidone (PVP)] and solvent [ethylene glycol and water]. The prepared nanostructures were characterized by Powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FE-SEM), Transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), UV-VIS-NIR absorption spectrophotometer and photoluminescence (PL) studies. The PXRD and FTIR results indicate purity, good crystallinity and effective doping of Ce³⁺ in nanostructures. SEM and TEM micrographs display nanorods, nanowires and nanobundles like morphology of DyPO₄:Ce³⁺. Energy-dispersive X-ray spectra (EDS) of DyPO₄:Ce³⁺nanostructures confirm the presence of dopant. UV-VIS-NIR absorption spectra of prepared compounds are used to calculate band gap and explore their optical properties. Luminescent properties of DyPO₄:Ce³⁺ was studied by using PL emission spectra. The effect of additives and solvents on the uniformity, morphology and optical properties of the nanostructures were studied in detail.     

Synthesis,characterization, and quantum chemical calculational studies on 3-<Emphasis Type="Italic">p</Emphasis>-methylphenyl-4-amino- 1, 2, 4-triazole-5-thione

The title compound of 3-p-methylphenyl-4-amino-1, 2, 4-triazole-5-thione was synthesized and characterized by elemental analysis, IR, electronic spectra, and X-ray single crystal diffraction. Quantum chemical calculations of the structure, natural bond orbital, and thermodynamic functions of the title compound were performed by using B3LYP/6-311G** and HF-6-311G** methods. Both the methods can well simulate the molecular structure. Vibrational frequencies were predicted, assigned and compared with the experimental values, and B3LYP/6-311G** method is superior to HF/6-311G** method to predict the vibrational frequencies. Electronic absorption spectra calculated by B3LYP/6-311G** method have some red shifts compared with the experimental ones and natural bond orbitals analyses indicate that the two absorption bands are mainly derived from the contribution of n → π^* and π → π^* transitions. On the basis of vibrational analyses, the thermodynamic properties of the title compound at different temperatures have been calculated, revealing the correlations between C ⁰ _p,m , S ⁰ _m , H ⁰ _m , and temperatures.     

Characterization and physical properties of Li2O-CaF2-P2O5 glass ceramics with Cr2O3 as a nucleating agent—Physical properties

In this paper, studies on various physical properties, viz., dielectric properties (dielectric constant, loss tan δ, a.c. conductivity σ) over a wide range of frequency and temperature, optical absorption, ESR at liquid nitrogen temperature and magnetic susceptibility at room temperature of Li₂O-CaF₂-P₂O₅: Cr₂O₃ glass ceramics, have been reported. The optical absorption, ESR and magnetic susceptibility studies indicate that the chromium ions exist in Cr⁵⁺, Cr⁴⁺ and Cr⁶⁺ states in addition to Cr³⁺ state in these samples. The dielectric constant and loss variation with the concentration of Cr₂O₃ have been explained on the basis of space charge polarization mechanism. The dielectric relaxation effects exhibited by these samples have been analysed by a graphical method and the spreading of dielectric relaxation has been established. The a.c. conductivity in the high-temperature region seems to be connected both with electronic and ionic movements.     

Synthesis and photoluminescence properties of tunable emission phosphors Ca4Si2O7F2:Ce3+

The Ce³⁺ activated phosphors Ca₄Si₂O₇F₂:Ce³⁺ are prepared by a solid state reaction technique. The UV–vis luminescence properties as well as fluorescence decay time spectra are investigated and discussed. The results revealed that there were two kinds of Ce³⁺ luminescence behavior with 408 and 470 nm emissions, respectively. Under 355 nm excitation, the Ce(1) emission (408 nm) is dominant at low doping concentration, and then the Ce(2) emission (470 nm) get more important with increasing of Ce³⁺ concentrations in the host. The phosphors Ca₄Si₂O₇F₂:xCe³⁺ show tunable emissions from blue area to green-blue area under near-ultraviolet light excitation, indicating a potential application in near-UV based w-LEDs.     

Synthesis, crystal structure and optical properties of an indium phosphate K3In3P4O16

An alkali-metal indium phosphate crystal, K₃In₃P₄O₁₆, has been synthesized by a high-temperature solution reaction and exhibits a new structure in the family of the alkali-metal indium phosphates system. Single-crystal X-ray diffraction analysis shows the structure to be monoclinic with space group P2₁/n, and the following cell parameters: a=9.7003(18), b=9.8065(18), c=15.855(3) Å, β=90.346(3)°, V=1508.2(5) Å³, Z=4, R=0.0254. It possesses three-dimensional anionic frameworks with tunnels occupied by K⁺ cations running along the a-axis. The emission and absorption spectra of the compound have been investigated. Additionally, the calculations of energy band structure, density of states, dielectric constants and refractive indexes have been performed with the density functional theory method. Also, the two-photon absorption spectrum is simulated by two-band model. The obtained results tend to support the experimental data.     

形貌可控的LaPO4:Eu3+荧光粉的制备与发光性能研究

分别以硝酸镧、多聚磷酸和磷酸二氢钠为原料,在无任何添加剂和模板的条件下,采用水热法分别合成微纳米球和纳米棒两种形貌的磷酸镧.通过场发射-扫描电子显微镜(FE-SEM),X射线衍射(XRD),红外光谱(FTIR)和荧光光谱(PL)等测试手段对以上不同形貌的样品的相结构以及微观形貌进行表征.FE-SEM测试结果表明:当以多聚磷酸为磷源时,在酸性条件下可以得到平均粒径约为2μm左右的磷酸镧微球;而当以磷酸二氢钠磷源时,在酸性条件下则可以得到纳米棒;两者的分散性良好.XRD测试结果表明:两种不同形貌的样品均为单斜晶系结构.荧光光谱分析可知:Eu3+的掺杂浓度相同时,球状样品的发光强度远大于棒状样品.     

Hexadecapropyloxy-substituted diphthalocyanine complexes of rare-earth elements: synthesis,spectroscopic and electrochemical studies

Hexadecapropyloxy-substituted diphthalocyanine complexes of rare-earth elements (REE = Lu, Tm, Sm) were synthesized. The new symmetrically substituted diphthalocyanine complexes prepared starting from 4,5-dipropyloxyphthalodinitrile (phthalogen) are characterized by better solubilities compared to the known hexadecamethyl-substituted diphthalocyanine complexes of the same REE. Spectral and electrochemical characteristics of the complexes were studied. The compounds can be used as materials for high-contrast electrochromic devices.     

Synthesis,spectroscopic studies,antimicrobial activity,and crystal structure of a Zn(II) complex based on Voriconazole

[Zn(FZ)₂Cl₂] (1) (FZ = Voriconazole, (2R,3S)-2-(2,4-difluorophenyl)-3(5-fluoropyrimidin-4-yl)-1-(1H-1,2,4-triazol-1-yl)butan-2-ol), has been obtained through the reaction of zinc chloride and FZ and has been characterized by FT-IR, UV–vis and fluorescence spectra, elemental analysis (EA), single crystal X-ray diffraction, powder X-ray diffraction and thermogravimetric analysis (TGA). FZ was also characterized by FT-IR, UV–vis spectra, single crystal X-ray diffraction and TGA. FZ crystallizes in the chiral space group P2₁ and 1 crystallizes in chiral space group P₁ with a mononuclear structure. In 1, there are three kinds of hydrogen bonding interactions and weak stacking interactions which generate a 3-D architecture. The primary antimicrobial results show that 1 exhibits potent activity against Aspergillus (Aspergillus niger, Aspergillus terreus, Aspergillus fumigatus and Aspergillus flavus) and Candida species (Candida albicans, Candida krusei, Candida glabrata and Cryptococcus neoformans), higher than that of free FZ. Fluorescence spectra of 1 and FZ have been discussed.     

Experimental and theoretical studies on vibrational spectra of 4-(2-furanylmethyleneamino)antipyrine, 4-benzylideneaminoantipyrine and 4-cinnamilideneaminoantipyrine

This work deals with the IR and Raman spectroscopy of 4-(2-furanylmethyleneamino) antipyrine (FAP), 4-benzylideneaminoantipyrine (BAP) and 4-cinnamilideneaminoantipyrine (CAP) by means of experimental and quantum chemical calculations. The equilibrium geometries, harmonic frequencies, infrared intensities and Raman scattering activities were calculated by density functional B3LYP method with the 6-31G(d) basis set. The comparisons between the calculated and experimental results covering molecular structures, assignments of fundamental vibrational modes and thermodynamic properties were investigated. The optimized molecular geometries have been compared with the experimental data obtained from XRD data, which indicates that the theoretical results agree well with the corresponding experimental values. For the three compounds, comparisons and assignments of the vibrational frequencies indicate that the calculated frequencies are close to the experimental data, and the IR spectra are comparable with some slight differences, whereas the Raman spectra are different clearly and the strongest Raman scattering actives are relative tightly to the molecular conjugative moieties linked through their Schiff base imines. The thermodynamic properties (heat capacities, entropies and enthalpy changes) and their correlations with temperatures were also obtained from the harmonic frequencies of the optimized strucutres.     

Synthesis and Infrared Multi‐band Absorption Properties of Core‐shell NaYF4:Yb3+, Er3+@SiO2 Nanoparticles

Due to the unique size effects, nanomaterials in infrared absorption have attracted much attention for their strong absorption in the infrared region. To achieve the infrared multi‐band absorption, we propose to synthesize a core‐shell structure nanomaterial consisting of NaYF₄:Yb³⁺, Er³⁺ core and a layer of SiO₂ as shell. A series of NaYF₄:Yb³⁺, Er³⁺ nanocrystals were synthesized through hydrothermal method by adjusting the ratio of citric acid(CA)‐to‐NaOH, and the effects of CA concentration, and NaOH concentration were studied in detail. NaYF₄:Yb³⁺, Er³⁺@SiO₂ nanoparticles were synthesized by sol‐gel method using TEOS as silica source. The results show that the core‐shell NaYF₄:Yb³⁺, Er³⁺@SiO₂ nanoparticles were successfully synthesized. Up‐conversion spectra of these nanoparticles were recorded with 980 nm laser excitation under room temperature. There are no changes of the emission centers of nanoparticles before or after silica coating, but the emission intensities of nanoparticles after silica coating are weakened. Furthermore, the property of infrared multi‐band absorption was tested through ultraviolet‐visible‐near infrared spectrophotometer and infrared absorption spectra. The results illustrate that the multi‐band infrared absorption nanomaterial was successfully synthesized.     

Synthesis, structure and theoretical studies of a new ternary non-centrosymmetric β-LaGaS3

New ternary β-LaGaS₃ has been synthesized from the stoichiometric mixture of elements by a conventional solid-state reaction at 1100 °C and annealed at 820 °C. This compound represents a new structure type that crystallizes in a non-centrosymmetric orthorhombic space group Pna2₁ (No.33) with a=10.405(1) Å, b=21.984(2) Å, c=6.0565(5) Å, and Z=12, and features the wavy GaS₄ tetrahedron chains that are separated by La³⁺ cations. Detailed structural differences between the title compound and its isomer, monoclinic α-LaGaS₃, are discussed. With the aid of WIEN2k package, the absorption spectra and electronic structures as well as the refractive indexes, absorption coefficients and reflectivities of two types of LaGaS₃ have been calculated. The calculated band gap and the absorption edge of β-LaGaS₃ agree well with the experimental measurements. And a weak NLO response of β-LaGaS₃ has been detected.     

Synthesis and gas sensitivities of SnO2 nanorods and hollow microspheres

SnO₂ urchin-like structures composed of nanorods with diameters of 10-15 nm and lengths of 50-70 nm have been hydrothermally synthesized via a H₂O₂-assisted route without any surfactant, using SnCl₂ as raw material. With the addition of methenamine (HMT), SnO₂ hollow microspheres with diameters of 2-3 μm and shell thickness of 60-140 nm were also prepared. The as-obtained products were examined using diverse techniques including X-ray powder diffraction (XRD), Raman spectroscopy, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), high-resolution TEM and photoluminescence spectra. The gas sensitivity experiments have demonstrated that the as-synthesized SnO₂ materials exhibit good sensitivity to alcohol vapors, which may offer potential applications in gas sensors.     

Spectroscopic studies of polymorphs of AlPO4 and SiO2

IR spectra of basic polymorphic forms of AlPO₄, measured at different temperatures, are presented. Diffuse reflectance spectroscopy has been used for high temperature measurements. According to the crystal structures of different AlPO₄ forms by means of factor group analysis, a number of modes and their activities have been determined. An attempt to assign bands to specific normal vibrational modes has been undertaken, comparing spectra of subsequent forms of AlPO₄ with each other. The obtained results have been discussed with regard to data referring to various isomorphous polymorphic forms of SiO₂, comparing, respectively, cristobalite with phosphocristobalite, berlinite with quartz, and phosphotridymite with tridymite (M. Handke and W. Mozgawa, Vib. Spectrosc. 5 (1993) 75; M. Handke, W. Mozgawa and M. Rokita, Michrochim. Acta [Suppl] 14 (1997) 511). Differences and similarities have been shown for the spectroscopic data and thus for structures of AlPO₄ and SiO₂.