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A new noncentrosymmetric (NCS) sulfide, Ba5In4Te4S7, was synthesized by a conventional solid-state reaction in evacuated closed silica tubes. The compound crystallizes in the orthorhombic space group Imm2 (44), with unit cell parameters a = 39.110(3) Å, b = 4.3763(3) Å, c = 7.3452(6) Å, Z = 2, and V = 1257.18(17) Å(3). The 3D framework of Ba5In4Te4S7 is composed of infinite 1(∞)[InS2Te2](5-) and 1(∞)[In2S3Te2](4-) anionic chains. The optical band gap of Ba5In4Te4S7 is 2.13 eV and it shows the UV-visible cutoff at 0.57 μm and the infrared transparency extends to 25 μm. The compound exhibits a powder second harmonic generation (SHG) signal at 2.05 μm with about half of the AgGaS2 at a particle size of 74-106 μm. According to first-principles calculation, the calculated major SHG tensor element is d32 = 18.8 pm V(-1). The SHG process of nonlinear optical response of Ba5In4Te4S7 originates from the electronic transitions from occupied S-3p and Te-5p states to unoccupied In-5s and In-5p states.

To investigate how the central diamagnetic cyanidometal influences the distant magnetic interaction of cyanide-bridged Fe(III)-M(II)-Fe(III) complexes, cis-[Cp(dppe)Fe(II)(NC)M(II)(L)2(CN)Fe(II)(dppe) Cp][PF6]2 (M = Os, L = bpy 1; M = Os, L = phen 2; M = Fe, L = bpy 3; M = Fe, L = phen 4), and their one-electron oxidation products 5–7 and two-electron oxidation products 8–11 were synthesized and fully characterized. The cyclic voltammetry of complexes 1–4 suggests that both NC-Os(II)(L)2-CN and NC-Fe(II)(L)2-CN have electronic communication ability. The electronic absorption spectroscopy suggests the presence of the central M(II) to the terminal Fe(III) and the terminal Fe(II) to the terminal Fe(III) metal to metal charge transfers (MMCTs) in 5-7 and the central M(II) to the terminal Fe(III) MMCTs in 8-11. Moreover, for the two-electron oxidation products the MMCT energy increases with the central metal in the order FeOsRu. The two-electron oxidation complexes 8 and 9 exhibit a strong antiferromagnetic coupling (J ≈ -26 cm(-1)) between the two distant Fe(III) ions although separated by the diamagnetic cyanidometal NC-Os(II)(L)2-CN bridge. To the best of our knowledge, this is the strongest magnetic coupling between the distant paramagnetic metal ions across a diamagnetic cyanidometal bridge reported by far. For the two-electron oxidation complexes 10 and 11 with the diamagnetic NC-Fe(II)(L)2-CN bridge, however, the distant two Fe(III) ions possess only very weak antiferromagnetic coupling (J = -0.15 and -0.19 cm(-1)). Combined with our previous reported results, it could be found that the magnetic coupling strength between the distant Fe(III) ions increases with the diamagnetic cyanidometal bridge in the order of FeRuOs.

In this paper, BPO4 and Ba2+-doped BPO4 powder samples were prepared by the sol-gel process using glycerol and poly(ethylene glycol) as additives. The structure and optical properties of the resulting samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM), diffuse reflection spectra, photoluminescence (PL) excitation and emission spectra, quantum yield, kinetic decay, and electron paramagnetic resonance (EPR), respectively. It was found that the undoped BPO4 showed a weak purple blue emission (409 nm, lifetime 6.4 ns) due to the carbon impurities involved in the host lattice. Doping Ba2+ into BPO4 resulted in oxygen-related defects as additional emission centers which enhanced the emission intensity greatly (> 10x) and shifted the emission to a longer-wavelength region (lambda(max) = 434 nm; chromaticity coordinates: x = 0.174, y = 0. 187) with a bluish-white color. The highest emission intensity was obtained ;when doping 6 mol % Ba2+ in BPO4, which has a quantum yield as high as 31%. The luminescent mechanisms of BPO4 and Ba2+-doped BPO4 were discussed in detail according to the existing models for silica-based materials.

Static and dynamic first hyperpolarizabilities have been studied by a DFT approach for a series of trinuclear heterometallic transition metal molecular clusters, [MAg2X4(C5H5NS)(PPh3)2]·CH2Cl2 (M = Mo, W; X = S, Se) with incomplete cubane-like configurations. Their nonlinear optical nature has been analyzed by using a two-level model. The large hyperpolarizabilities of about 100 × 10−30 esu of these metal clusters are generated by intermolecular charge transfers from the metal core to the pyridine-2-thiol ligand as well as by intramolecular charge transfers within the metal core. The conjoint effects of stereo π (3D) conjugation of the metal core and planar π (2D) conjugation of the C5H5NS ligand enhance these hyperpolarizabilities, while the presence of CH2Cl2 has a negative effect by lowering them. Since these complexes are all crystallized in noncentrosymmetric configurations, they are promising candidates as IR second-order nonlinear optical transition metal coordinated materials.

The dipole polarizability, static first hyperpolarizability and UV–Vis spectrum of the recently identified nano-sized tetrahedral cluster of Au 20 have been investigated by using time-dependent density functional response theory. We have discovered that the Au 20 cluster possesses remarkably large molecular second-order optical nonlinearity with the first hyperpolarizabilty ( β xyz ) calculated to be 14.3 × 10 −30 esu. The analysis of the low-energy absorption band suggests that the charge transfer from the edged gold atoms to the vertex ones plays the key role in nonlinear optical (NLO) response of Au 20 .

Reaction of VCL 3 , MnCl 2 and CrCl 3 +Zn with [Fe 2 S 2 (CO) 6 ] 2− , from reduction of [Fe 2 S 2 (CO) 6 ] by LiEt 3 BH, resulting in pentanuclear mixed metal clusters [VFe 4 S 4 (CO) 12 ] ( 1 ), [Et 4 N] 2 [MnFe 4 S 4 (CO) 12 ] ( 2 ) and [Et 4 N] 2 [CrFe 4 S 4 (CO) 12 ] ( 3 ), respectively. Complexes 1 , 2 and 3 have been characterized by elemental analysis, spectroscopy and the crystal structures of 1 and 2 have been determined by X-ray crystallography. The structures of 1 and 2 contain a penta-nuclear M–Fe–S core, [Fe 2 S 2 MS 2 Fe 2 ] z − (M=V, z =0 ( 1 ) and M=Mn, z =2 ( 2 )), consisting of two [Fe 2 S 2 ]-units chelating to a metal atom. The two [Fe 2 S 2 ] units are in ‘butterfly’ type configuration like the one in [Fe 2 S 2 (CO) 6 ] 2− . In 1 there are four V–Fe bonds of 2.822–2.865 A, but in 2 there were no Mn–Fe bonds found. V–S distances are 2.205–2.210 A and Mn–S bond lengths are 2.358–2.380 A. The novel structural configuration, IR spectra and synthesis were discussed.

Ab initio calculations of the first hyperpolarizabilities of (HCOOLi·H 2 O) 2 n supermolecules, as the building-blocks of lithium formate monohydrate (LFM) crystal with extended system, were performed for the first time. The dependence of the static β ijk 0 values on chain length was explored, and the frequency dependence of β ijk (−2 ω ; ω , ω ) was measured, and the influences of electron correlation and basis set on β ijk 0 were evaluated. Finally, we predicted the second-order nonlinear optical coefficients of LFM crystal. The β ijk 0 value of (HCOOLi·H 2 O) 2 n is linearly dependent on the chain length of supermolecule, which is quite unusual for an extended system connected by the O–Li bonds with ionic characters. Although the static component of β zzz 0 tensor is the static largest in these three components under study, the absolute value of frequency-dependent β zyy (−2 ω ; ω , ω ) element, transforming the smallest into the largest, is the most sensitive to frequency. After the fundamental wavelength is smaller than 500 nm, it is found that the β ijk (−2 ω ; ω , ω ) value is resonantly enhanced to a great extent due to the double frequency lies in the region of resonance. In addition, the β zxx 0 value goes from negative to positive with changes of electron correlation and basis set. Obviously, it is very necessary to take into account the effect of electron correlation, if the hyperpolarizability tensor components must be accurately calculated. Moreover, it is also very important whether it is adopted a complete basis set with diffuse and polarization functions. The calculated nonlinear coefficients at high level suggest that the scaled set reported by Robert seem more reasonable.

Crystals of [LaPb8O(OH)10(H2O)] (NO3)7 (I) and [LaPb8O(OH)10(H2O)] (NO3)7·2H2O (II) are hydrothermally synthesized under subcritical conditions from mixtures of Pb(NO3)2, H2O, and 0.5 and 1 equiv.

The novel iodate oxychloride, Bi2Te(IO3)O5Cl, has been hydrothermally synthesized and structurally characterized. The compound crystallizes in the polar monoclinic space group Cc with a = 22.037(8) Å, b = 5.256(2) Å, c = 15.142(5) Å, and β = 104.499(7)°. Three types of asymmetric chromophore structural units, that is the electron lone-paired [IO3](-) groups, the second-order Jahn-Teller effect (SOJT) [BiO6](9-) units, and the distorted [TeO6](6-) octahedra, coexist with cooperative dipole moment alignment along the c-axis direction of the crystal. This structure configuration gives the material a relatively large second harmonic generation (SHG) efficiency of approximately three times that of KDP for powder samples. Type I phase-matching at a wavelength of 1064 nm can be achieved as a result of the layered structure and large optical anisotropy of the crystal. First-principle density functional theory (DFT) calculations were performed to interpret relationships between the macroscopic optical properties and microscopic structures. The results indicate that the local dipole moments of the three types of chromophore units are simultaneously present in the compound with different contributions to the SHG effect. Additionally, thermal and optical properties of the compound were also characterized.

The potential energy surface and hyperpolarizabilities of the core (G0) and the first generation (G1) of polyamidoamide (PAMAM) dendrimer are studied by using the density functional theory with both the basis sets optimized for B3LYP method and the medium-size polarized GTO/CGTO basis sets for calculations of molecular polarizability. The inversion barrier of G1 is 941.4 cm −1 , which indicates that the back folding of the branches is very easy for this dendrimer construction. It is found that in most cases, the first hyperpolarizabilities β of G1 will increased when the molecular structure is distorted from its equilibrium arrangement. These results provide structural guidelines for the optimization of β by means of changing the dendrimer shape in different solvents.

Reaction of Co(CNS) 2 with Fe 2 S 2 (CO) 6 , LiBEt 3 H and PPh 3 in THFMeCN resulting in a novel cobalt carbonyl complex, Co(CO) 3 (PPh 3 ) 2 BEt 3 ( 1 ) and mixed-metal CoFeS cluster compound, [Et 4 N][Fe 2 Co(CO) 8 S(PPh 3 )] ( 2 ). The structures of 1 and 2 were determined from X-ray three dimension data. Structure studies reveal that 1 is a new cobalt carbonyl complex containing a novel BO bond of 1.601(5) A in which the oxygen atom is from metal carbonyl and the B atom is from BEt 3 and 2 contained a triangular pyramid mixed-metal CoFeS core [CoFe 2 S] − with CoS of 2.189, FeS of 2.208, CoFe of 2.56 and FeFe of 2.58 A. Theoretical calculation on 1 and 2 shows that BO bonding energy of complex 1 is lower than that of normal covalent bonding and 2 possesses a calculated nonlinear optical first molecular hyperpolarizability component of 28.5×10 −30 esu. The possible formation pathway of 1 and 2 was discussed.

The oriented-gas model based on the additivity hypothesis is widely used in predicting the macroscopic nonlinear optical susceptibility of a molecular crystal from molecular (hyper)polarizability calculations. Here, we argue that the intermolecular hydrogen bond interactions will break the additivity relationship for the first hyperpolarizability of urea hydrogen-bonded clusters on the basis of our high-level ab initio studies. The calculations at the HF level without electron correlation correction result in the underestimation of the hydrogen bond effect on the first hyperpolarizabilities to about 15% in the urea case. On the other hand, both HF and MP2 results show the additivity of linear polarizability of urea clusters. We hope that the study will be helpful to the areas of molecular design and simulation of novel nonlinear optical materials.

Compounds (IV) and (VII) are characterized by single crystal XRD, UV/VIS diffuse reflectance spectroscopy, second harmonic generation measurements, and DFT electronic structure calculations.

Two nonlinear optical crystal carbonates (Na4La2(CO3)5 and CsNa5Ca5(CO3)8 were successfully synthesized by hydrothermal method, and both of them crystallized in the same noncentrosymmetric hexagonal space group P63mc (No. 186). The structure of Na4La2(CO3)5 consists of a three-dimensional network made up of [CO3] triangles as well as irregular [Na(0.67)La(0.33)O10] and [NaO8] polyhedra. The structure of CsNa5Ca5(CO3)8 can be described as the standing-on-edge [CO3] groups connect the adjacent infinite [CaCO3]∞ layers in the ab plane to construct a framework with four types of channels running parallel to [010]. The Na, Cs, and [Na(0.67)Ca(0.33)] atoms reside in these channels. The measurement of second harmonic generation (SHG) by the method adapted from Kurtz and Perry indicated that Na4La2(CO3)5 and CsNa5Ca5(CO3)8 were phase-matchable in the visible region and exhibited SHG responses of approximately 3 and 1 × KH2PO4 (KDP). Meanwhile, they exhibited wide transparent region with short UV cutoff edge at about 235 and 210 nm, respectively, suggesting that these crystals as NLO materials may have potential applications in the UV region.

Pb(II) oxide hydroxide nitrates are prepared under subcritical hydrothermal conditions by adjusting the pH values of the Pb(NO3)2—NaOH reaction system.

A series of lead(II) nitrates have been synthesized by a hydrothermal method and adjusting the pH values of the reaction systems. Pb20O6(OH)16(NO3)12 and Pb2O(OH)NO3, crystallize in the centrosymmetric space group P1̅ and Pbca, respectively. The structure of Pb20O6(OH)16(NO3)12 features infinite cationic chains of [Pb20O6(OH)16]∞ running along c axis, and the nitrate groups as the counterions reside between adjacent chains, while the structure of Pb2O(OH)NO3 can be described as alternate stacking of cationic [Pb2O(OH)]∞ layers with anionic [NO3](-) layers along [001] direction by the weak Pb-O bonds, forming a 3D framework with 1D tunnels of 12-member rings (MRs). [Pb4(OH)4](NO3)4, crystallizing in the noncentrosymmetric space group Cc, has been studied as the nonlinear optical material for the first time. The second harmonic generation (SHG) measurement indicates that the SHG responses of [Pb4(OH)4](NO3)4 are 0.7 times that of KDP. Theoretical calculations confirmed the SHG efficiency of [Pb4(OH)4](NO3)4 originates from the cooperative effect of NO3(-) groups and lead oxygen polyhedras in the structure. Meanwhile, the relationship between pH value and ratio of Pb/OH(-) in the molecules presents a positive correlation, which results in the diversity of these structures under different pH value.

Nonlinear optical susceptibilities of a SHG material, 3-methoxy-4-hydroxy-benzaldehyde (MHBA), were investigated at both molecular and crystalline levels, by using the MP2 (second-order level of Moller–Plesset perturbation correction) method and the oriented-gas approximation. The results revealed that the electron donor group –OH and acceptor group –HCO play important roles in the magnitude of second-order polarizabilities. The studies of the oriented-gas model showed the crystal has large nonlinear optical coefficients, d 22 =23.8 d 36 KDP , d 21 =13.5 d 36 KDP , d 23 =29.1 d 36 KDP , d 25 =12.8 d 36 KDP , which agree well with the experimental results.

Classic tissue recombination studies have demonstrated that, in the early developing mouse tooth germ, the odontogenic potential, known as the tooth-inductive capability, resides initially in the dental epithelium and then shifts to the dental mesenchyme. However, it remains unknown if human embryonic dental tissues also acquire such odontogenic potential. Here we present evidence that human embryonic dental tissues indeed possess similar tooth-inductive capability. We found that human dental epithelium from the cap stage but not the bell stage was able to induce tooth formation when confronted with human embryonic lip mesenchyme. In contrast, human dental mesenchyme from the bell stage but not the cap stage could induce mouse embryonic second-arch epithelium as well as human keratinocyte stem cells, to become enamel-secreting ameloblasts. We showed that neither post-natal human dental pulp stem cells (DPSCs) nor stem cells from human exfoliated deciduous teeth (SHED) possess odontogenic potential or are odontogenic-competent. Our results demonstrate a conservation of odontogenic potential in mouse and human dental tissues during early tooth development, and will have an implication in the future generation of stem-cell-based bioengineered human replacement teeth.

While correlation of developmental stage with embryonic age of the human primary dentition has been well documented, the available information regarding the differentiation timing of the primary teeth was largely based on the observation of initial mineralization and varies significantly. In this study, we aimed to document precise differentiation timing of the developing human primary dentition. We systematically examined the expression of odontogenic differentiation markers along with the formation of mineralized tissue in each developing maxillary and mandibular teeth from human embryos with well-defined embryonic age. We show that, despite that all primary teeth initiate development at the same time, odontogenic differentiation begins in the maxillary incisors at the 15th week and in the mandibular incisors at the 16th week of gestation, followed by the canine, the first primary premolar, and the second primary premolar at a week interval sequentially. Despite that the mandibular primary incisors erupt earlier than the maxillary incisors, this distal to proximal sequential differentiation of the human primary dentition coincides in general with the sequence of tooth eruption. Our results provide an accurate chronology of odontogenic differentiation of the developing human primary dentition, which could be used as reference for future studies of human tooth development.

The two new title compounds (IV) and (V) are characterized by single crystal XRD, UV/VIS diffuse reflectance spectroscopy, second harmonic generation measurements, and DFT computations.

To investigate how the central metalloligand geometry influences distant or vicinal metal-to-metal charge-transfer (MMCT) properties of polynuclear complexes, cis- and trans-isomeric heterotrimetallic complexes, and their one- and two-electron oxidation products, cis/trans-[Cp(dppe)Fe(II)NCRu(II)(phen)2CN-Fe(II)(dppe)Cp][PF6]2 (cis/trans-1[PF6]2), cis/trans-[Cp(dppe)Fe(II)NCRu(II)(phen)2CNFe(III)-(dppe)Cp][PF6]3 (cis/trans-1[PF6]3) and cis/trans-[Cp(dppe)Fe(III)NCRu(II)(phen)2CN-Fe(III)(dppe)Cp][PF6]4 (cis/trans-1[PF6]4) have been synthesized and characterized. Electrochemical measurements show the presence of electronic interactions between the two external Fe(II) atoms of the cis- and trans-isomeric complexes cis/trans-1[PF6]2. The electronic properties of all these complexes were studied and compared by spectroscopic techniques and TDDFT//DFT calculations. As expected, both mixed valence complexes cis/trans-1[PF6]3 exhibited different strong absorption signals in the NIR region, which should mainly be attributed to a transition from an MO that is delocalized over the Ru(II)-CN-Fe(II) subunit to a Fe(III) d orbital with some contributions from the co-ligands. Moreover, the NIR transition energy in trans-1[PF6]3 is lower than that in cis-1[PF6]3, which is related to the symmetry of their molecular orbitals on the basis of the molecular orbital analysis. Also, the electronic spectra of the two-electron oxidized complexes show that trans-1[PF6]4 possesses lower vicinal Ru(II) → Fe(III) MMCT transition energy than cis-1[PF6]4. Moreover, the assignment of MMCT transition of the oxidized products and the differences of the electronic properties between the cis and trans complexes can be well rationalized using TDDFT//DFT calculations.

The excited-state proton transfer (ESPT) via proton transfer wires in green fluorescent protein (GFP) plays an important role on the spectroscopic of GFP. In this work, we use the proton transfer wires and the chromophore complex to simulate the tautomer structures of neutral state and the intermediate state in wt-GFP. And we employ the time-dependent density functional theory combined with the sum-over-states method to calculate the one- and two-photon absorption properties of these complexes in GFP. We obtain the large stokes shift from 383 nm to 500 nm in GFP when simulating the ESPT process by these isomerous H-bonding complexes. We find that the TPA spectrum of the H-bonding complex of the intermediate state agrees more with experimental measurement than that of the H-bonding complex of the neutral state. The TPA spectrum of GFP might be mainly dominated by the structure which is similar to the H-bonding complex of intermediate state. Further, we simulate another kind of complex which possess short-strong hydrogen bonds in proton transfer wires, and find that TPA properties of these complexes are much stronger than that of the complexes with the long distance proton wires from GFP.

A genetic engineering method is employed to design the second harmonic generation (SHG) materials with infrared transparency. The compounds of Ba2BiInA5 (A = S, Se, Te) are constructed in views of “genome” BiA5 pyramid and InA4 tetrahedron. Then, the crystal structures of these compounds are predicted or reproduced to show their non-centrosymmetry based on global optimization evolutionary methodology. Thirdly, the ab initio computations of band structures and simulations of optical properties are carried, and the nonlinear optical figure of merit in views of optical transparent range and the SHG parameters are surveyed for these crystals. Finally, we provide the substance evidences by the experimental synthesis, crystal structural determinations, and optical measurements for Ba2BiInA5 (A = S, Se) compounds.

Second-harmonic generation (SHG) materials only exist in solids that have no inversion center space groups, and they are constructed by the building blocks or chromophores of noncentrosymmetricity (NCS). In this chapter, we employed one or multiple chromophores that result from the coordination structure distortions of a d0 cation, polar displacement of d10 cation center, a stereochemically active lone pair (SCALP) of cations, and asymmetrical delocalization π-charge systems, as building blocks to obtain some new compounds with NCS space group. The single-crystal structures were characterized, and physical properties, in particular SHG responses, were measured for these compounds. The electronic structures and density of states were calculated by DFT method, and the SHG properties are simulated to gain an insight into the relations between structure and NLO properties for the materials. The electronic origination of large SHG responses was assigned in terms of the calculated results.

Generation of bio-engineered teeth by using stem cells will be a major approach for bioengineered implantation. Previous studies have demonstrated that dissociated tooth germ cells are capable of generating a tooth after reaggregation in vitro. However, the cellular and molecular mechanisms underlying this tooth regeneration are not clear. In this study, we dispersed E13.5 molar germ into single cells, immediately reaggregated them into cell pellet, then grafted the reaggregates under mouse kidney capsule for various times of culture. We investigated the morphogenesis and the expression of several developmental genes in dental epithelial cells in reaggregates of tooth germ cells. We found that dissociated tooth germ cells, after reaggregation, recapitulated normal tooth developmental process. In addition, dissociated dental epithelial cells retained the expression of Fgf8, Noggin, and Shh during reaggregation and tooth regeneration processes. Our results demonstrated that, despite of under dissociated status, dental epithelial cells maintained their odontogenic fate after re-aggregation with dental mesenchymal cells. These results provided important information for future in vitro generation of bio-engineered teeth from stem cells.

The title compounds are obtained quantitatively by reacting mixtures of M2O3 (M: Fe, In), H3BO3, and NH4H2PO4 in a molar ratio of 1:1:3 at 1153 K.

Explorations of the AI−MIII−BIII−PV−O quinary system under solid-state reactions led to an anhydrous cesium−chromium borophosphate−phosphate and an anhydrous cesium−iron borophosphate, namely, Cs2C...

SrTiO3 (STO) is attracting lots of research interests due to the rich physics and properties presented at its surfaces and the interfaces of STO with other transition metal oxides. Based on density functional theory methods, we have investigated the influence of hydrogen (H) atoms adsorption at the (001) surface of STO on the geometrical and electronic structures of the surface. We find that H adsorption induces significant antiferrodistortive (AFD) distortion of TiO6 octahedra at the surface. By calculating H adsorption energy, we show that AFD distortion makes a significant contribution to the stability of H adsorbed STO surfaces. The calculated energy position of O-H bond states by hybrid functional method is 9.9 eV below Fermi level, in agreement with experimental value of 10 eV. The electrons donated by H atoms first occupy several dxy bands and then start to fill in degenerate dyz/dxz bands, indicating the metallization of initially insulating STO. The band splitting and occupy sequence calculated here are consistent with recent angle-resolved photoemission spectroscopy experiments. Our results reveal that H adsorption changes the atomic and electronic structures and thus induce fascinating properties at the surface of STO.

In this paper, BPO4 and Ba2+-doped BPO4 powder samples were prepared by the sol-gel process using glycerol and poly(ethylene glycol) as additives. The structure and optical properties of the resulting samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM), diffuse reflection spectra, photoluminescence (PL) excitation and emission spectra, quantum yield, kinetic decay, and electron paramagnetic resonance (EPR), respectively. It was found that the undoped BPO4 showed a weak purple blue emission (409 nm, lifetime 6.4 ns) due to the carbon impurities involved in the host lattice. Doping Ba2+ into BPO4 resulted in oxygen-related defects as additional emission centers which enhanced the emission intensity greatly (> 10x) and shifted the emission to a longer-wavelength region (lambda(max) = 434 nm; chromaticity coordinates: x = 0.174, y = 0. 187) with a bluish-white color. The highest emission intensity was obtained ;when doping 6 mol % Ba2+ in BPO4, which has a quantum yield as high as 31%. The luminescent mechanisms of BPO4 and Ba2+-doped BPO4 were discussed in detail according to the existing models for silica-based materials.

Theoretical studies and simulations have been applied to explore novel nonlinear optical crystals in metal clusters. The structure-nonlinear optical property relationships of a series of metal cluster molecules have been investigated theoretically within the density functional theory framework. For example, the polarizability and hyperpolarizability of a set of three-nuclear metal cluster compounds of the Mo(W)/Cu(Ag, An) sulfur system are calculated to elucidate the influence of the geometric configuration and the element substitution effect; a set of potential second harmonic generation (SHG) metal cluster crystals are studied and simulated such as the MoAg(2)S5(Py)(PPh3)(2), MoS4Cu4I2(Py)(6) clusters. The results indicate that many of these crystals are promising SHG crystals that may be applied in the infrared (IR) spectroscopic region. The studies are useful to aid in screening, simulating and designing novel nonlinear optical crystals in metal cluster compounds, especially those to be applied in medium/far-IR region. (C) 2002 Elsevier Science B.V. All rights reserved.

We studied the electronic and magnetic properties of hole doped KTaO3/PbTiO3 interface using density functional theory methods. Ferromagnetic-nonmagnetic phase transition and metal-insulator phase transition occur simultaneously at the interface with ferroelectric polarization reversal. Furthermore, these two transitions are coupled with each other because hole doping with large concentration of holes gives rise to ferromagnetism. The interfacial magnetization, which is proportional to hole concentration at the interface, can be tuned by ferroelectric polarization, leading to strong intrinsic magnetoelectric effect at the interface of originally nonmagnetic KTaO3 and PbTiO3.

Low-dimensional mixed anion compounds Ba18F18In8S21 (1) and Ba9F10In4S10 (2), are synthesized and characterized. These compounds crystallize in the space group P42/ncm(138) with a = b = 22.0703(8) A, c = 12.6143(9) A, and V = 6144.4(6) A3 (Z = 4) for 1 and Pnma(62) with a = 12.5686(8) A, b = 19.2822(12) A, c = 12.5835(9) A, and V = 3049.6(3) A3 (Z = 4) for 2. Compound 1 contains the unusual one-dimensional fluorite type [Ba16F18] ionic region and [BaIn8S21] covalent region, whereas 2 has a two-dimensional fluorite type [Ba2F2] block and the unique tetranuclear [In4S10]8− anion. The first principles electronic structure calculation performed with density functional theory (DFT) indicates that the two compounds are both direct band semiconductors with a gap of 2.28 eV for 1 and 2.23 eV for 2.

A novel mechanism of magnetoelectric coupling at the KTaO3/BaTiO3 interfaces composed of nonmagnetic ferroelectric insulators is studied by density functional theory methods. We show that holes created by electronic reconstruction concentrate near the interface, which is significantly different from the distribution of holes in the LaAlO3/SrTiO3 model system (Chen H. H. et al., Phys. Rev. B, 79 (2009) 161402(R)). A large concentration of holes induces ferromagnetism at the interface. When ferroelectric polarization reverses, the ratio of the net change in magnetization to the total is about ten percent. This ratio is improved greatly compared with typical Fe/BaTiO3 heterostructures (Duan C. G. et al., Phys. Rev. Lett., 97 (2006) 047201), where the ratio is about one percent. The results provide an opportunity for searching multiferroic materials and offer the possibility to design spintronics devices.

Two non-linear optical crystalline carbonates (Na3Y(CO3)3 and Na3Gd(CO3)3) were synthesized under subcritical hydrothermal conditions, and both of them crystallized in the non-centrosymmetric space group Ama2 (40). Their crystal structures, analogous to shorite, can be described as alternate stackings of [Na(CO3)2]∞ and [Na2RE(CO3)2]∞ (RE = Y, Gd) layers, which are parallel to the bc plane. Second harmonic generation (SHG) studies indicated that Na3Y(CO3)3 and Na3Gd(CO3)3 have large SHG responses of approximately 3.57 and 3.54 times that of KH2PO4 (KDP), respectively, and the SHG responses were phase-matchable in the visible region. Furthermore, they exhibited wide transparent regions from UV to near IR with short UV cut-off edges at about 220 nm, suggesting that these crystals are promising UV non-linear optical (NLO) materials.

We theoretically study the second-order nonlinear optical properties of six fluorescent proteins (FPs), such as green fluorescent protein (GFP), BFP, enhanced BFP (eBFP), CFP, YFP, and DsRed. To begin with, the geometries of all these FP chromophores are optimized at B3LYP/6-311++G** level in a water medium and the polarized continuum model (PCM in water) method is adopted. Using a time-dependent density functional theory (TDDFT) method, the electronic structures and excited-state properties of chromophores are determined. Here we employ TDDFT combining with the sum-over-states (SOS) method to calculate the first-order hyperpolarizability for second-harmonic generation (SHG) optical process. Moreover, we discuss the origin of the nonlinear optical response and determine what caused the variation of first-order hyperpolarizability. Our calculations show that the charge transfers of π → π* in the central conjugated structure and p → π* charge transfers from the side chain R1 to conjugated structure of chromophores markedly affect the first-order hyperpolarizability.

The second harmonic generation (SHG) hyperpolarizabilities of phenylalanine and homopolypeptides are investigated by configuration interaction among singly excited configurations (CIS) technique combined with the sum-over-states (SOS) method. The geometries of peptides containing phenylalanine ( Phe )n(n = 1–8) are optimized by B3LYP/6-31g(d) method, and they form the special structures like β-sheet (a common protein secondary structure). It is found that the energy gaps of various peptides are reduced and the hyperpolarizabilities are increased with the peptide chains lengthened. We discuss the origin of the second-order nonlinear optical response in phenylalanine homopolypeptides and confirm that the π → π* transitions in the aromatic residue of phenylalanine make the most important contributions to the second-order polarizability. Our results strongly suggest that the hyperpolarizabilities are dominated from the propagation direction of peptide chains.

Two chiral dinuclear cyanide/isocyanide-bridged complexes (R)-[Cp(dppe)Fe-CN-Fe(dppp)Cp]PF6 (1[PF6]) and (R)-[Cp(dppe)Fe-NC-Fe(dppp)Cp]PF6 (2[PF6]), and their mono-oxidation products (R)-[Cp(dppe)Fe(II)-CN-Fe(III)(dppp)Cp] [PF6]2 (1[PF6]2) and (R)-[Cp(dppe)Fe(III)-NC-Fe(II)(dppp)Cp][PF6]2 (2[PF6]2) were synthesized and fully characterized. The electronic spectra of both the mixed-valence complexes 1[PF6]2 and 2[PF6]2 exhibit a strong and broad absorption band with two discernable peaks in the NIR region, which are attributed to Fe(II)-Fe(III) IVCT transitions. The attributions are supported by the DFT calculations. Under irradiation with a nanosecond laser at 1064 nm, the measured third-order NLO results of all four cyanide-bridged complexes showed that complexes 1(+) and 2(+) do not exhibit an NLO response, but their one-electron oxidation complexes 1(2+) and 2(2+) exhibit a strong NLO response due to a resonance enhanced effect. In addition, both complexes 1(2+) and 2(2+) display RSA and self-defocusing effects and show good optical limiting behavior in a broadband range.

We have replied to the comment about the stabilization of the singlet ground state and the sign of second hyperpolarizability for hydrogen- and metal-terminated graphene nanoribbons based on the calculated results of the open-shell singlet ground state. These new results again show the two opinions: i) that the (3,7)Be-AGNR has the largest static second hyperpolarizability and ii) that the tetra-coordinate carbons of M-GNRs make an important contribution toward enhancing the hyperpolarizabilities inferred from the original calculations based on the closed-shell singlet ground state, in spite of different values obtained from two methods of different levels.

We investigate the electronic and magnetic properties of GaN–ZnO nanoribbons with density functional theory methods. The obtained large binding energies suggest that these graphitic nanostructures are stable and can hence be effectively synthesized. Their calculated properties strongly depend on the edge atomic configuration: armchair nanoribbons are non-magnetic semiconductors and zigzag ones are half-metals with net magnetism depending on the ribbon width.

We have investigated the structural, electronic and carbon monoxide (CO) detection properties of the ZnO cluster-decorated single-walled carbon nanotubes (SWCNTs) by using density functional theory (DFT). The stable structures of hybrid ZnO/SWCNT materials are that the ZnO cluster plane is perpendicular to the surface of SWCNTs with the Zn atoms towards the SWCNTs (Zn atom above axial C-C bond or above the C atom). For the ZnO cluster-decorated semiconducting SWCNTs, the SWCNTs present p-type characteristics which may lead to the decrease of conductance upon illumination with ultraviolet (UV) light. The CO can be adsorbed on the hybrid ZnO/SWCNT materials due to the charge transfer between them. Compared with isolated ZnO clusters or bare SWCNTs, the ZnO/SWCNT network would have excellent CO detection ability due to their suitable adsorption energy and conductivity.

Graphitic GaN–ZnO is predicted theoretically. It is much softer than graphene and easier to wrap up into a nanotube. The g-GaN–ZnO and corresponding nanotubes have relatively uniform band gap independent of structures. Moreover, they are potential photocatalysts for water splitting and light-emitting in the UV light region.

The second-order polarizabilities and the UV-vis-IR spectra of a transition-metal complex Co(NH3)2(L-ala–gly–gly) have been studied by using the MP2 and TDHF methods. The complex has a maximum β component in the direction from the N(alanyl) group to the N(glycyl) groups. A transparent optical spectrum region from 0.55 to 5.5 µm was found, which offers potential applications as an optical material. The alkyl substitution of the glycyl group only slightly affected the β value and retained the IR transparent region but may cause the molecules to have a favorite packing fashion in the bulk crystal that leads to larger second-order nonlinear optical coefficients.