Solution combustion derived nanocrystalline Zn(2)SiO(4):Mn phosphors: a spectroscopic view

Manganese doped nanocrystalline willemite powder phosphors Zn(2-x)Mn(x)SiO(4) (0.1(6)A(1) ground state. The mechanism involved in the generation of a green emission has been explained in detail. The effect of Mn content on luminescence has also been studied.     

Designing ultra-highly efficient Mn2+-activated Zn2GeO4 green-emitting persistent phosphors toward versatile applications

Developing highly efficient green-emitting phosphors is very significant because human eyes are sensitive to green spectral region. Herein, Mn²⁺-activated Zn₂GeO₄ phosphors, which can emit bright green light with an ultrahigh internal quantum efficiency of 98.5%, were prepared by a solid-state reaction technology in ambient atmosphere. At 323 nm irradiation, the emission spectrum shows a narrow band centered at 534 nm, which is ascribed to the ⁴T₁ → ⁶A₁ transition of Mn²⁺, with a full width at half maxima of 49.5 nm. Through monitoring the temperature-dependent photoluminescence emission intensity and decay time of Mn²⁺, we explored the thermometric properties of the resultant compound and found maximum relative sensitivities of Zn₂GeO₄:0.02Mn²⁺ phosphor are 4.90% K^?1 and 0.74% K^?1, respectively. Furthermore, green afterglow phenomenon is observed in the designed phosphors, and its mechanism is verified by discussing the thermoluminescence. Because of the excellent luminescence behaviors, various multimode luminescent patterns for information encryption are designed, including anticounterfeiting and fingerprint identification. Furthermore, using the prepared Zn₂GeO₄:0.02Mn²⁺ as green-emitting components, a white-light-emitting diode with suitable color coordinates, high color rending index (>90), and low correlated color temperature (5,000–6,000 K) was fabricated. These results demonstrate that Mn²⁺-activated Zn₂GeO₄ phosphors are multifunctional green-emitting components for optical thermometry, anticounterfeiting, fingerprint detection, and solid-state lighting applications.     

Two-color emission of Zn2SiO4:Mn from ionic liquid mediated synthesis

Yellow emitting β-Zn₂SiO₄:Mn²⁺ and green emitting α-Zn₂SiO₄:Mn²⁺ nanoparticles are synthesized by nucleation applying a zinc-containing ionic liquid. As-prepared material is non-agglomerated and very uniform with a mean diameter of 32 nm. According to X-ray diffraction (XRD) two crystallographic different modifications of Zn₂SiO₄ can be realized by annealing of as-prepared and non-crystalline nanomaterial at 750 and 1000 °C. Surprisingly, these crystalline materials are still nanosized, non-agglomerated and redispersible. Scanning electron microscopy (SEM) and dynamic light scattering (DLS) confirm particle diameters of 18 nm (β-Zn₂SiO₄:Mn²⁺) and 14 nm (α-Zn₂SiO₄:Mn²⁺). Photoluminescence indicates Mn²⁺-related emission at an average wavelength of 579 nm and 528 nm, and a quantum yield of 7% and 12% for β-Zn₂SiO₄:Mn²⁺ and α-Zn₂SiO₄:Mn²⁺, respectively.     

A novel green template for the synthesis of mesoporous silica

Mesoporous pure silicas and functionalized silica with a narrow pore size distribution centered at 3.8 nm were prepared by a novel template, amphiphilic dendritic polyglycerol. The resulting silica materials were characterized by electron microscopy; nitrogen adsorption; (1)H, (13)C, and (29)Si solid-state cross-polarization magic-angle spinning NMR spectroscopy. It was shown that the template could be completely removed from the pure and functionalized silica in an environmentally friendly way by means of a simple water extraction procedure. Furthermore, it was shown that these materials could be easily functionalized, for example, by employing aminopropyl groups. Thus, a new environmentally friendly pathway to this fascinating class of silica material has been opened.     

A green chemical route for the synthesis of Mn3O4 nanoparticles

A novel environmental friendly, room temperature route using an ionic liquid 1-n-butyl-3-methylimidazolium hydroxide ([BMIM]OH) for the synthesis of Mn₃O₄ nanoparticles is presented. The product was characterized using Fourier transform infrared spectroscopy, X-ray powder diffraction, and transmission electron microscopy. Phase purity was confirmed by XRD, and X-ray line profile fitting determined a crystallite size of 42 ± 11 nm. TEM analysis revealed various morphologies. EPR measurements have indicated the existence of long-range interactions, due to the wide range of particle sizes and morphologies observed.      

(Zn, Mg)2GeO4:Mn2+ submicrorods as promising green phosphors for field emission displays: hydrothermal synthesis and luminescence properties

(Zn(1-x-y)Mg(y))(2)GeO(4): xMn(2+) (y = 0-0.30; x = 0-0.035) phosphors with uniform submicrorod morphology were synthesized through a facile hydrothermal process. X-Ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), photoluminescence (PL), and cathodoluminescence (CL) spectroscopy were utilized to characterize the samples. SEM and TEM images indicate that Zn(2)GeO(4):Mn(2+) samples consist of submicrorods with lengths around 1-2 μm and diameters around 200-250 nm, respectively. The possible formation mechanism for Zn(2)GeO(4) submicrorods has been presented. PL and CL spectroscopic characterizations show that pure Zn(2)GeO(4) sample shows a blue emission due to defects, while Zn(2)GeO(4):Mn(2+) phosphors exhibit a green emission corresponding to the characteristic transition of Mn(2+) ((4)T(1)→(6)A(1)) under the excitation of UV and low-voltage electron beam. Compared with Zn(2)GeO(4):Mn(2+) sample prepared by solid-state reaction, Zn(2)GeO(4):Mn(2+) phosphors obtained by hydrothermal process followed by high temperature annealing show better luminescence properties. In addition, codoping Mg(2+) ions into the lattice to substitute for Zn(2+) ions can enhance both the PL and CL intensity of Zn(2)GeO(4):Mn(2+) phosphors. Furthermore, Zn(2)GeO(4):Mn(2+) phosphors exhibit more saturated green emission than the commercial FEDs phosphor ZnO:Zn, and it is expected that these phosphors are promising for application in field-emission displays.     

A novel and efficient route for the preparation of atorvastatin

A novel and efficient synthetic method of atorvastatin was described.The key step of the synthesis was the construction of the olefin linkage between the chiral side chain and skeleton via a Horner-Wadsworth-Emmons reaction,resulting in the advanced intermediate of atorvastatin under hydrogenation of the olefin over Pd/C.This novel method is more useful for the practical synthesis of atorvastatin than its document reported methods.     

A facile synthesis to Zn(2)SiO(4):Mn(2+) phosphor with controllable size and morphology at low temperature

Sphere- and rod-shaped Zn(2)SiO(4):Mn(2+) phosphor nanocrystals were synthesized at 230 degrees C. The process consists of tuning the surfactant concentration in the oil/surfactant/ethanol system. Powder X-ray (XRD) and transmission electron microscopy (TEM) were used to characterize the phase purity, size and morphology. Photoluminescent (PL) spectra were collected and analyzed. Fourier transform infrared (FT-IR) spectra of the samples indicate the removal of surfactant in the phosphor nanoparticles. As a result, the sphere-shaped phosphor nanoparticles of 100 nm in size can be redispersed in ethanol ultrasonically. The suspension maintain stable for over 48 h.     

Low-Temperature Synthesis of Nanosize Zn2SiO4:Mn2+ Phosphor from the Precursor Sol in Supercritical Ethanol and its Photoluminescent Properties

Acetylcellulose (AC)/silica and polyvinylpyrrolidone (PVP)/silica composites were prepared by the sol–gel method from Si(OCH₃)₄-AC-HNO₃-H₂O-tetrahydrofuran-CH₃OC₂H₄OH and Si(OCH₃)₄-PVP-(CH₃COOH or NH₃)-H₂O-CH₃OH-CH₃OC₂H₄OH solutions. AC/silica composites were composed of micrometer-sized particles rich in silica and a matrix rich in AC, while PVP/silica composites were single-phase on the SEM length scale. The AC/silica composites exhibited elastic-plastic behavior, and had excellent machinability without chipping on cutting with an electric saw while the PVP/silica composites showed less plasticity and machinability. Youngs modulus and bending strength were increased by post-drying, 1.8–2.8 GPa and 49–88 MPa, respectively, for the AC/silica composites, and 1.0–3.9 GPa and 17–79 MPa, respectively, for the PVP/silica composites.     

Optical and Structural Properties of Zn2SiO4:Mn2+ from SLS Waste Bottle Obtained by a Solid State Method

In this studies, 2 wt.% Mn-doped Zn₂SiO₄ were synthesized from SLS waste glass, ZnO and MnO using conventional solid-state method. Structural and optical properties were examined as functions of sintering temperature. Density and linear shrinkage of samples increased with increasing in sintering temperature. X-Ray Diffraction pattern revealed that sintering temperature play an important role in enhancing crystallization of Zn₂SiO₄. It was found that the phase formation changed from amorphous to ȕ- Zn₂SiO₄ and then to α-Zn₂SiO₄ with the unsintered to sinter at 600 °C and 700 °C respectively. The morphology under FESEM characterization shows that the samples become more uniform with rectangular shape like as the sintering temperature increased. From UV-Vis spectroscopy, the results obtained showed that the intensive absorption occurred in the UV region, in the range of 250-γλ0 nm. Prominent green emission colours of α-Zn₂SiO₄ were observed centred at 527 nm while the yellow emission centred at η8η nm resulted from ȕ-Zn₂SiO at an excitation of 260 nm. However, red emission centred at 600 nm was observed for glass samples. These emissions come from the Mn-dopant and correspond to the ⁴T₁ – ⁶A₁ transition.     

A green route towards substituted 2-amino-4H-chromenes catalyzed by an organobase (TBD) functionalized mesoporous silica nanoparticle without heating

Research on Chemical Intermediates - 1,5,7-Triazabicyclo-[4,4,0]-dec-1-ene functionalized mesoporous silica nanoparticle promoted one-pot multicomponent synthesis of 2-amino-4H-chromenes from a...     

溶胶-凝胶法制备ZrO2/SiO2纳米复合材料的研究

利用溶胶-凝胶法制备了ZrO2/SiO2纳米复合物室温磷光材料,通过各条件的优化,最终确定溶剂为异丙醇、Zr摩尔掺杂百分含量为15%、550℃下煅烧3h得到的纳米ZrO2/SiO2复合物的室温磷光发光性能较好,其最大激发波长为280nm、发射波长为460nm,且磷光寿命为0.56s。     

Methylazacalix[4]pyridine: en route to Zn2+-specific fluoresence sensors

[structure: see text] Owing to the electronic nature of the bridging nitrogen atoms which can adopt different hybridizations and form various conjugations with the adjacent pyridine(s), methylazacalix[4]pyridine underwent conformation and cavity preorganization to highly selectively bind the Zn(2+) ion. Rigidification and coplanarity of the macrocyclic ring led to a great enhancement of fluorescence of the intrinsic fluorescent host molecule.     

A new and efficient chemoenzymatic route to both enantiomers of 4-hydroxycyclohex-2-en-1-one

[reaction: see text] A chemoenzymatic synthesis of both enantiomers of the pharmacologically interesting 4-hydroxycyclohex-2-en-1-one in three steps starting from 3-methoxycyclohex-2-en-1-one is described. Manganese(III) acetate-mediated acetoxylation followed by enzyme-mediated hydrolysis of alpha-acetoxy enone affords acetoxy enone 3 and hydroxy enone 4 with high enantiomeric excesses and in good yields. The reduction of the acetoxy and hydroxy enones furnished both enantiomers of 4-hydroxycyclohex-2-en-1-one in high enantiomeric excess.     

A novel and efficient route to the construction of the 4-oxa-tricyclo[4.3.1.0]decan-2-one scaffold

A short and efficient route to the synthesis of 4-oxa-tricyclo[4.3.1.0]decan-2-one scaffold 12 in good yield is reported. Essential to the synthesis was the implementation of selective protection of the catechol system in xanthone 2 with Ph₂CCl₂ and MOM groups. Subsequently, a biomimetic tandem Claisen/Diels-Alder reaction occurred to produce the desired tricyclic scaffold 11a as a single isomer. A rationalization of the excellent region and stereoselectivity of this transformation was also proposed.     

A green synthesis of spirooxindole derivatives catalyzed by SiO2@g-C3N4 nanocomposite

Research on Chemical Intermediates - In this study, SiO2 nanoparticles were immobilized onto the surface of g-C3N4 nanosheets. The characterization of SiO2@g-C3N4 nanocomposite has been done by...     

On the thermal stability of Fe2Mn0.5Zn0.5(C2O4)4

Heat of immersion and contact angle were measured for α-Si₃N₄. The electrostatic field strength, which was determined to be 0.42×10⁵ esu cm^?2, showed that the surface is much less polar than those of oxides. Slight increase of the heat of immersion in water with the increase of outgassing temperature is attributable to the rehydration of siloxane linkages which have been formed by dehydration of silanol groups on the surface. The heat of immersion in n-alkanes increased steeply with the number of carbon, n, from n=6 to 9, and became nearly constant for n>9, while in n-alkanols the heat began to rise at n=10 after the nearly constant values for n=4 to 8. The dispersion force contribution to the total surface free energy, γ^d_s, were estimated by contact angle and heat of immersion methods which have been well applied to the low energy surfaces, and found to be 25 mJ m^?2 from contact angle and 129 mJ m^?2 from the immersional heat in hexane.     

A simplified and efficient route to 2'-O, 4'-C-methylene-linked bicyclic ribonucleosides (locked nucleic acid).

A novel efficient method for the synthesis of locked nucleic acid (LNA) monomers is described. The LNA 5',3'-diols containing thymine, 4-N-acetyl- and 4-N-benzoylcytosine, 6-N-benzoyladenine, and 2-N-isobutyrylguanine as nucleobases were prepared via convergent syntheses. The method is based on the use of the common sugar intermediate 1,2-di-O-acetyl-3-O-benzyl-4-C-methanesulfonoxymethyl-5-O-methanesulfonyl-D-erythro-pentofuranose (8) that easily can be prepared from D-glucose in multigram scale. Four different nucleobases were stereoselectively coupled to 8 using a modified Vorbrüggen procedure to give the corresponding 4'-C-branched nucleoside derivatives. Subsequent ring closing furnished the protected LNA nucleosides. The 5'-O-mesyl groups were efficiently displaced by nucleophilic substitution using sodium benzoate. Saponification of the 5'-benzoates followed by catalytic removal of the 3'-O-benzyl groups afforded the free LNA diols. The exocyclic amino groups of adenosine and cytidine were selectively acylated to give 4-N-acetyl- or 4-N-benzoyl-LNA-C and 6-N-benzoyl-LNA-A. The isobutyryl group of guanine was retained during the preparation of 2-N-isobutyryl-LNA-G. The LNA-T diol and base-protected LNA diols can be directly converted into LNA-phosphoramidites for automated chemical synthesis of LNA containing oligonucleotides.     

A new emission band of Eu2+ and its efficient energy transfer to Mn2+ in Sr2Mg3P4O15:Mn2+, Eu2+

Eu(2+) singly and Eu(2+), Mn(2+) co-doped Sr(2)Mg(3)P(4)O(15) exhibit not only the well known blue emission band of Eu(2+) peaking at 448 nm but also a new band at 399 nm in violet. They are attributed to Eu(2+) on different Sr(2+) sites. The Eu(2+) for the violet band can transfer energy to the red emitting Mn(2+) more efficiently than Eu(2+) for the blue band. The new Eu(2+) band could enable Sr(2)Mg(3)P(4)O(15):Mn(2+), Eu(2+) to be a promising phosphor for enriching the red component of white LEDs.