Fluorescence detecting both organic and inorganic analytes has aroused tremendous scientific interests, because fluorescence techniques have high sensitivity and are easy to operate. A new threedimensional(3D) MOF {[(...Fluorescence detecting both organic and inorganic analytes has aroused tremendous scientific interests, because fluorescence techniques have high sensitivity and are easy to operate. A new threedimensional(3D) MOF {[(CH_(3))_(2)NH_(2)][Zn_(3)(bbip)(BTDI)1.5(OH)]·DMF·MeOH·3H_(2)O}n(JXUST-13, bbip = 2,6-bis(benzimidazol-1-yl)pyridine and H_(4)BTDI = 5,5-(benzo[c][1,2,5]thiadiazole-4,7-diyl)diisophthalic acid)with new 4,4,8-connceted topology has been successfully synthesized and structurally characterized. Importantly, JXUST-13 could recognize H_(2)PO_(4)-and acetylacetone(Acac) by obvious fluorescence blue shift and slight enhancement with the detection limits of 2.70 μmol/L and 0.21 mmol/L, respectively. In addition, JXUST-13 exhibits relatively good thermal stability, chemical stabilities as well as reusability, and the analytes could be distinguished by naked eye and fluorescence test paper. Remarkably, JXUST-13 is the first dual-responsive MOF sensor based on fluorescence blue shift for the detection of H_(2)PO_(4)-and Acac with good selectivity in a handy, economic, and environmentally friendly manner.展开更多
The influence of thermal treatment on Si 1-x Ge x/Si multiple-quantum wells (MQW) p-i-n photodiodes has been investigated by photocurrent spectroscopy combined with X-ray double crystal dif...The influence of thermal treatment on Si 1-x Ge x/Si multiple-quantum wells (MQW) p-i-n photodiodes has been investigated by photocurrent spectroscopy combined with X-ray double crystal diffraction.The cutoff wavelength is significantly reduced due to the Si-Ge interdiffusion and partial relaxation of the strained SiGe alloy.The values of the blue shift increase slowly with the annealing temperatures in the range of 750℃ to 850℃.However,the nonlinear changes in photocurrent intensities of the samples annealed at different temperatures have been observed,which is mainly dominated by the generation of misfit dislocations and the reduction of the point defects in the heating process.展开更多
Experiment on quantum well intermixing (QWI) of InGaAsP QWs by impurity free vacancy diffusion (IFVD) using SiO 2 encapsulation is reported.A maximum band gap wavelength blue shift as large as 200nm is realized.Furt...Experiment on quantum well intermixing (QWI) of InGaAsP QWs by impurity free vacancy diffusion (IFVD) using SiO 2 encapsulation is reported.A maximum band gap wavelength blue shift as large as 200nm is realized.Furthermore,an FP laser blue shifted 21nm by QWI is fabricated with characteristics comparable with the as grown one.展开更多
YPO4 and Eu doped YPO4 nanocrystals were prepared via a simple hydrothermal method. The phase purity, rnicrostructure, surface absorbed water and luminescence properties were characterized with X-ray diffraction （XRD...YPO4 and Eu doped YPO4 nanocrystals were prepared via a simple hydrothermal method. The phase purity, rnicrostructure, surface absorbed water and luminescence properties were characterized with X-ray diffraction （XRD）, transmission electron microscopy （TEM）, fluorescence spectrum, infrared spectroscopy, Raman spectroscopy and thermogravimetry analysis（TGA）. Combined with XRD and TEM analysis, it was found that YPO4 nanocrystals crystallized into a single phase of tetragonal （141/amd） zircon structure. YPO4 nanocrystals showed a size reduction with the reaction temperature decreasing. Considering the XRD, IR and Raman results, a lattice expansion and the unit cell symmetry enhancement were observed with the particle size decreasing. A dipole to dipole interaction model was applied to investigate the relationship of the variation of microstrucmre and the particle size. The emission spectrum of Eu doped YPO4 nanocrystals was also presented and the emission bands were clearly ascribed to the f to f transitions of Eu^3＋.展开更多
Capsulating vip into the nanometer voids of zeolites is a effective way to form novel host-vip material. In our work, stoichiometric SrAl2O4 : Eu2+, Dy3+ sol vip was prepared by sol-gel method and assembled into...Capsulating vip into the nanometer voids of zeolites is a effective way to form novel host-vip material. In our work, stoichiometric SrAl2O4 : Eu2+, Dy3+ sol vip was prepared by sol-gel method and assembled into the nanometer channels of zeolite ZSM-5 host through mechanical mixing, hydrothemial reaction and microwave heating reaction, respectively. After being reduced and diffused in a microwave muffle, the fluorescence spectra of the host-vip materials exhibit remarkable blue shifts in companison of that of SrAl2O4 : Eu2+, Dy3+ Some interesting phenomena in the assembled host-vip materials are that the after-low emission spectra exist two bands at about 400 nm and 517 nm and the relative strengths of these two hands can be adjusted by changing the assembly methods and the assembly concentration. These are attributed to the fact that the phosphor was capsuiated into the voids of zeolite ZSM-5 and generated the quantum size effect and the host-vip effect.展开更多
Black-coloured GaN nanoparticles with an average grain size of 50 nm have been obtained by annealing GaN nanoparticles under flowing nitrogen at 1200 ℃ for 30 min. XRD measurement result indicates an increase in the ...Black-coloured GaN nanoparticles with an average grain size of 50 nm have been obtained by annealing GaN nanoparticles under flowing nitrogen at 1200 ℃ for 30 min. XRD measurement result indicates an increase in the lattice parameter of the GaN nanoparticles annealed at 1200 ℃, and HRTEM image shows that the increase cannot be ascribed to other ions in the interstitial positions. If the as-synthesised GaN nanoparticles at 950 ℃ are regarded as standard, the thermal expansion changes nonlinearly with temperature and is anisotropic; the expansion below 1000 ℃ is smaller than that above 1000 ℃. This study provides an experimental demonstration for selecting the proper annealing temperature of GaN. In addition, a large blueshift in optical bandgap of the annealed GaN nanoparticles at 1200 ℃ is observed, which can be ascribed to the dominant transitions from the C（FT） with the peak energy at 3.532 eV.展开更多
A method of QWI （ quantum well intermixing） realizing through plasma-enhanced chemical vapordepositiom （PECVD） SiO2 film following ion implantation was investigated. PECVD 200 mn SiO2 film after 160 keV phosphorus...A method of QWI （ quantum well intermixing） realizing through plasma-enhanced chemical vapordepositiom （PECVD） SiO2 film following ion implantation was investigated. PECVD 200 mn SiO2 film after 160 keV phosphorus（P） ion implantation was performed to induce InP-based multiple-quantum-well （MQW） laser structural intermixing, annealing process was carried out at 780 ℃ for 30 seconds under N2 flue, the blue shift ofphotoluminescenee （PL） peak related to implanted dose ： 1 × 10^11, 1 × 10^12, 1×10^13 ,3 × 10^13 , 7× 10^13 ion/ cm^2 is 22 nm, 65 nm, 104 nm, 109 nm, 101 nm, respectively. Under the same conditions, by comparing the blue shift of PL peak with P ion implantation only, slight differentiation between the two methods was observed, and results reveal that the defects in the implanting layers generated by ion implantation are much more than those in SiO2 film. So, the blue shift results mainly from ion implantation. However, SiO2 film also may promote the quantum well intermixing.展开更多
MP2/6-31 + g(d) calculations were performed verifying the existences ofblue-shifting X - C ≡ C - CF_2 - H···OH_2 hydrogen bonds. Detailed analyses revealed that theinteraction energy and donor-acceptor...MP2/6-31 + g(d) calculations were performed verifying the existences ofblue-shifting X - C ≡ C - CF_2 - H···OH_2 hydrogen bonds. Detailed analyses revealed that theinteraction energy and donor-acceptor distance had good correlations with the substituent Hammettconstants. However, the extent of C―H bond contraction and the blue shift of the C―H stretchingvibration did not show any good correlation with the traditional substituent constants, indicatingthat certain more complicated mechanisms might be involved in the present systems. Nevertheless, itwas found that highly electron-withdrawing susbtituents were not favorable to the C―H bondcontraction, and it was suggested that the attractive interaction between water and the carbon of -CF_2H probably played an important role in the blue shift.展开更多
The electro optical characteristics of SrS∶Ce and SrGa 2S 4∶Ce as two kinds of hopeful blue TFEL phosphors have been intensively investigated. The color purity of SrGa 2S 4∶Ce is better than that of SrS∶Ce. ...The electro optical characteristics of SrS∶Ce and SrGa 2S 4∶Ce as two kinds of hopeful blue TFEL phosphors have been intensively investigated. The color purity of SrGa 2S 4∶Ce is better than that of SrS∶Ce. In this paper, the influence of Ga 3+ on photoluminescence (PL) characteristics of Ce 3+ is first reported. Ga 2S 3 was doped into SrS, then sintered. The emission spectra shift obviously towards short wavelength range with increase of Ga 3+ concentration. At the same time, the relative intensity of the excitation peaks corresponding to the interband absorption of SrS reduces, and the excitation efficiency corresponding to the transition from the ground state to the excited state of Ce 3+ ion increases. The ligand field around Ce 3+ is changed by doped Ga 3+ . The ionicity of the substituted become stronger and Ce 3+ -Ce 3+ interaction become weaker. These are favorite to blue emission.展开更多
The dihydrogen bonds B-H...H-X （X= the complexes of NH3BH3 with HF, HCl, F, Cl, Br, C, O, N） in the dimer （NH3BH3）2 and HBr, H2CO, H20, and CH3OH were theoretically studied. The results show that formation of the ...The dihydrogen bonds B-H...H-X （X= the complexes of NH3BH3 with HF, HCl, F, Cl, Br, C, O, N） in the dimer （NH3BH3）2 and HBr, H2CO, H20, and CH3OH were theoretically studied. The results show that formation of the dihydrogen bond leads to elongation and stretch frequency red shift of the BH and XH bonds, except that in the H2CO system, the CH bond blue shifts. For （NH3BH3）2 and the complexes of the halogenides, red shifts of the XH bonds are caused by the intermolecular hyperconjugation σ（BH）→σ^＊ （XH）. For the system of H2CO, a blue shift of the CH bond is caused by a decrease of the intramolecular hyperconjugation n（O→σ^＊ （CH）. In the other two systems, the red shift of OH bond is a secondary effect of the stronger traditional red-shifted H-bonds N-H... O. In all these systems, red shifts of the BH bonds are caused by two factors： negative repolarization and negative rehybridization of the BH bond, and decrease of occupancy on σ（BH） caused by the intermolecular hyperconjugation σ（BH）→σ^＊ （XH）.展开更多
Porous silicon prepared by pulse electro-etching is heat-treatedin O_2 atmosphere with an enhancement of its PI. peak and animprovement of its PL stability. The PL peak of a sample poroussilicon treated in O_2 atmosph...Porous silicon prepared by pulse electro-etching is heat-treatedin O_2 atmosphere with an enhancement of its PI. peak and animprovement of its PL stability. The PL peak of a sample poroussilicon treated in O_2 atmosphere at 1000 ℃ presents itself a three--peak structure and, compared with an un-- heat--treated sample,there exists blue shift of ～ 40 nm.展开更多
The ZnO quantum dots（QDs） were synthesized with improved chemical solution method.The size of the ZnO QDs is exceedingly uniform with a diameter of approximately 4.8 nm,which are homogeneously dispersed in ethanol.T...The ZnO quantum dots（QDs） were synthesized with improved chemical solution method.The size of the ZnO QDs is exceedingly uniform with a diameter of approximately 4.8 nm,which are homogeneously dispersed in ethanol.The optical absorption edge shifts from 370 nm of bulk material to 359 nm of QD materials due to the quantum size effect,while the photoluminescence peak shifts from 375 nm to 387 nm with the increase of the density of ZnO QDs.The stability of ZnO QDs was studied with different dispersion degrees at 0？C and at room temperature of 25？C.The agglomeration mechanisms and their relationship with the emission spectra were uncovered for the first time.With the ageing of Zn O QDs,the agglomeration is aggravated and the surface defects increase,which leads to the defect emission.展开更多
Two novel coordination compounds,1[Zn4（L1）4（NO3）2（H2O）2]（NO3）2·2H2O and 2[Mn2（L2）2（DMF）（H2O）3]（ClO4）2·DMF（HL1 = N＇-[（1E）-pyridine-2-ylmethylidene]pyrazine-2-carbohydrazide,H2L2 = 2-hydrox...Two novel coordination compounds,1[Zn4（L1）4（NO3）2（H2O）2]（NO3）2·2H2O and 2[Mn2（L2）2（DMF）（H2O）3]（ClO4）2·DMF（HL1 = N＇-[（1E）-pyridine-2-ylmethylidene]pyrazine-2-carbohydrazide,H2L2 = 2-hydroxy-3-methoxybenzaldehyde（pyrazin-2-ylcarbonyl）hydrazone）,based on the N-N bridged ligands were prepared and structurally characterized.Compound 1represents the[2＊2]molecular squares,in which both N atoms belonging to the N-N bridged ligands are connected to the Zn centers.The emission of compound 1 exhibits a blue shift,which can be assigned to strong electrostatic interaction between Zn^Ⅱ ions and the L1^-1.Compound 2represents a rare phenol-O bridged Mn2^Ⅱ complex.The magnetic investigation indicates weak antiferromagnetic interactions between the Mn^Ⅱ centers.展开更多
In recent years,Perovskite Light-Emitting Diodes(PeLEDs)have received considerable attention in academia.However,with the development of PeLEDs,commercial applications of full-color PeLED technology are largely limite...In recent years,Perovskite Light-Emitting Diodes(PeLEDs)have received considerable attention in academia.However,with the development of PeLEDs,commercial applications of full-color PeLED technology are largely limited by the progress of blue-emitting devices,due to the uncontrollably accurate composition,unstable properties,and low luminance.In this article,we add Cesium chloride(CsCl)to the quasi-two-dimensional(quasi-2D)perovskite precursor solution and achieve the relatively blue shifts of PeLED emission peak by introducing chloride ions for photoluminescence(PL)and electroluminescence(EL).We also found that the introduction of chlorine ions can make quasi-2D perovskite films thinner with smoother surface of 0.408 nm.It is interesting that the EL peaks and intensities of PeLED are adjustable under different driving voltages in high concentration chlorine-added perovskite devices,and different processes of photo-excited,photo-quenched,and photo-excited occur sequentially with the increasing driving voltage.Our work provides a path for demonstrating full-color screens in the future.展开更多
It is demonstrated that in all types of hydrogen bonds (X—H…Y) there is a balance between the long-range attractive orbital interactions and short-range Pauli/nucleus repulsions. When the proton acceptor approaches ...It is demonstrated that in all types of hydrogen bonds (X—H…Y) there is a balance between the long-range attractive orbital interactions and short-range Pauli/nucleus repulsions. When the proton acceptor approaches the proton donor from distance, the hydrogen bonding energy becomes more negative at relatively large distance, goes through a minimum, and then starts to become less negative when the short-range repulsive forces come into effect. Meanwhile, the X—H bond length increases at relatively large distances, goes through a maximum and starts to shorten when the short-range repulsive forces come into effect. Whether the hydrogen bond is red or blue shifted is dictated by the energy minimum position. If at the energy minimum position the X—H bond length is shorter than that for the free monomer, the hydrogen bond is blue shifted and vice versa. Further studies demonstrate that the recent report about the correlation of C—H bond lengths with proton donor-acceptor distance in F3C—H…OH2 and F3C—H…Cl- is not fully correct because the authors conducted an inappropriate comparison. Furthermore, it is shown for the first time that the Pauli/nucleus repulsion theory is applicable to the blue-shifted hydrogen bonds in the X—H…p complexes and the blue-shifted lithium bonds in the X—Li…Y complexes.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 22061019, 21861018, 22161019 and 12174172)the NSF of Jiangxi Province (No. 20202ACBL213001)+4 种基金Jiangxi Provincial Key Laboratory of Functional Molecular Materials Chemistry(No. 20212BCD42018)Fujian Key Laboratory of Functional Marine Sensing Materials,Minjiang University (No. MJUKF-FMSM202010)the Youth Jinggang Scholars Program in Jiangxi Province (No.QNJG2019053)the Two Thousand Program in Jiangxi Province (No.jxsq2019201068)the Special Foundation for Postgraduate Innovation in Jiangxi Province (No. YC_(2)020-B155)。
文摘Fluorescence detecting both organic and inorganic analytes has aroused tremendous scientific interests, because fluorescence techniques have high sensitivity and are easy to operate. A new threedimensional(3D) MOF {[(CH_(3))_(2)NH_(2)][Zn_(3)(bbip)(BTDI)1.5(OH)]·DMF·MeOH·3H_(2)O}n(JXUST-13, bbip = 2,6-bis(benzimidazol-1-yl)pyridine and H_(4)BTDI = 5,5-(benzo[c][1,2,5]thiadiazole-4,7-diyl)diisophthalic acid)with new 4,4,8-connceted topology has been successfully synthesized and structurally characterized. Importantly, JXUST-13 could recognize H_(2)PO_(4)-and acetylacetone(Acac) by obvious fluorescence blue shift and slight enhancement with the detection limits of 2.70 μmol/L and 0.21 mmol/L, respectively. In addition, JXUST-13 exhibits relatively good thermal stability, chemical stabilities as well as reusability, and the analytes could be distinguished by naked eye and fluorescence test paper. Remarkably, JXUST-13 is the first dual-responsive MOF sensor based on fluorescence blue shift for the detection of H_(2)PO_(4)-and Acac with good selectivity in a handy, economic, and environmentally friendly manner.
文摘The influence of thermal treatment on Si 1-x Ge x/Si multiple-quantum wells (MQW) p-i-n photodiodes has been investigated by photocurrent spectroscopy combined with X-ray double crystal diffraction.The cutoff wavelength is significantly reduced due to the Si-Ge interdiffusion and partial relaxation of the strained SiGe alloy.The values of the blue shift increase slowly with the annealing temperatures in the range of 750℃ to 850℃.However,the nonlinear changes in photocurrent intensities of the samples annealed at different temperatures have been observed,which is mainly dominated by the generation of misfit dislocations and the reduction of the point defects in the heating process.
文摘Experiment on quantum well intermixing (QWI) of InGaAsP QWs by impurity free vacancy diffusion (IFVD) using SiO 2 encapsulation is reported.A maximum band gap wavelength blue shift as large as 200nm is realized.Furthermore,an FP laser blue shifted 21nm by QWI is fabricated with characteristics comparable with the as grown one.
文摘YPO4 and Eu doped YPO4 nanocrystals were prepared via a simple hydrothermal method. The phase purity, rnicrostructure, surface absorbed water and luminescence properties were characterized with X-ray diffraction （XRD）, transmission electron microscopy （TEM）, fluorescence spectrum, infrared spectroscopy, Raman spectroscopy and thermogravimetry analysis（TGA）. Combined with XRD and TEM analysis, it was found that YPO4 nanocrystals crystallized into a single phase of tetragonal （141/amd） zircon structure. YPO4 nanocrystals showed a size reduction with the reaction temperature decreasing. Considering the XRD, IR and Raman results, a lattice expansion and the unit cell symmetry enhancement were observed with the particle size decreasing. A dipole to dipole interaction model was applied to investigate the relationship of the variation of microstrucmre and the particle size. The emission spectrum of Eu doped YPO4 nanocrystals was also presented and the emission bands were clearly ascribed to the f to f transitions of Eu^3＋.
文摘Capsulating vip into the nanometer voids of zeolites is a effective way to form novel host-vip material. In our work, stoichiometric SrAl2O4 : Eu2+, Dy3+ sol vip was prepared by sol-gel method and assembled into the nanometer channels of zeolite ZSM-5 host through mechanical mixing, hydrothemial reaction and microwave heating reaction, respectively. After being reduced and diffused in a microwave muffle, the fluorescence spectra of the host-vip materials exhibit remarkable blue shifts in companison of that of SrAl2O4 : Eu2+, Dy3+ Some interesting phenomena in the assembled host-vip materials are that the after-low emission spectra exist two bands at about 400 nm and 517 nm and the relative strengths of these two hands can be adjusted by changing the assembly methods and the assembly concentration. These are attributed to the fact that the phosphor was capsuiated into the voids of zeolite ZSM-5 and generated the quantum size effect and the host-vip effect.
基金Project supported by the Excellent Young Scientist Awarding Fund of Shandong Province,China(Grant No.2008BS04005)the China Postdoctoral Science Foundation(Grant No.20080441141)the Postdoctoral Innovation Program Special Fund of Shandong Province,China(Grant No.200803054)
文摘Black-coloured GaN nanoparticles with an average grain size of 50 nm have been obtained by annealing GaN nanoparticles under flowing nitrogen at 1200 ℃ for 30 min. XRD measurement result indicates an increase in the lattice parameter of the GaN nanoparticles annealed at 1200 ℃, and HRTEM image shows that the increase cannot be ascribed to other ions in the interstitial positions. If the as-synthesised GaN nanoparticles at 950 ℃ are regarded as standard, the thermal expansion changes nonlinearly with temperature and is anisotropic; the expansion below 1000 ℃ is smaller than that above 1000 ℃. This study provides an experimental demonstration for selecting the proper annealing temperature of GaN. In addition, a large blueshift in optical bandgap of the annealed GaN nanoparticles at 1200 ℃ is observed, which can be ascribed to the dominant transitions from the C（FT） with the peak energy at 3.532 eV.
基金Funded bythe National Natural Science Foundation of China(No.60276013)
文摘A method of QWI （ quantum well intermixing） realizing through plasma-enhanced chemical vapordepositiom （PECVD） SiO2 film following ion implantation was investigated. PECVD 200 mn SiO2 film after 160 keV phosphorus（P） ion implantation was performed to induce InP-based multiple-quantum-well （MQW） laser structural intermixing, annealing process was carried out at 780 ℃ for 30 seconds under N2 flue, the blue shift ofphotoluminescenee （PL） peak related to implanted dose ： 1 × 10^11, 1 × 10^12, 1×10^13 ,3 × 10^13 , 7× 10^13 ion/ cm^2 is 22 nm, 65 nm, 104 nm, 109 nm, 101 nm, respectively. Under the same conditions, by comparing the blue shift of PL peak with P ion implantation only, slight differentiation between the two methods was observed, and results reveal that the defects in the implanting layers generated by ion implantation are much more than those in SiO2 film. So, the blue shift results mainly from ion implantation. However, SiO2 film also may promote the quantum well intermixing.
文摘MP2/6-31 + g(d) calculations were performed verifying the existences ofblue-shifting X - C ≡ C - CF_2 - H···OH_2 hydrogen bonds. Detailed analyses revealed that theinteraction energy and donor-acceptor distance had good correlations with the substituent Hammettconstants. However, the extent of C―H bond contraction and the blue shift of the C―H stretchingvibration did not show any good correlation with the traditional substituent constants, indicatingthat certain more complicated mechanisms might be involved in the present systems. Nevertheless, itwas found that highly electron-withdrawing susbtituents were not favorable to the C―H bondcontraction, and it was suggested that the attractive interaction between water and the carbon of -CF_2H probably played an important role in the blue shift.
文摘The electro optical characteristics of SrS∶Ce and SrGa 2S 4∶Ce as two kinds of hopeful blue TFEL phosphors have been intensively investigated. The color purity of SrGa 2S 4∶Ce is better than that of SrS∶Ce. In this paper, the influence of Ga 3+ on photoluminescence (PL) characteristics of Ce 3+ is first reported. Ga 2S 3 was doped into SrS, then sintered. The emission spectra shift obviously towards short wavelength range with increase of Ga 3+ concentration. At the same time, the relative intensity of the excitation peaks corresponding to the interband absorption of SrS reduces, and the excitation efficiency corresponding to the transition from the ground state to the excited state of Ce 3+ ion increases. The ligand field around Ce 3+ is changed by doped Ga 3+ . The ionicity of the substituted become stronger and Ce 3+ -Ce 3+ interaction become weaker. These are favorite to blue emission.
基金ACKNOWLEDGMENT This work was supported Science Foundation of China by the National Natural （No.20873103）.
文摘The dihydrogen bonds B-H...H-X （X= the complexes of NH3BH3 with HF, HCl, F, Cl, Br, C, O, N） in the dimer （NH3BH3）2 and HBr, H2CO, H20, and CH3OH were theoretically studied. The results show that formation of the dihydrogen bond leads to elongation and stretch frequency red shift of the BH and XH bonds, except that in the H2CO system, the CH bond blue shifts. For （NH3BH3）2 and the complexes of the halogenides, red shifts of the XH bonds are caused by the intermolecular hyperconjugation σ（BH）→σ^＊ （XH）. For the system of H2CO, a blue shift of the CH bond is caused by a decrease of the intramolecular hyperconjugation n（O→σ^＊ （CH）. In the other two systems, the red shift of OH bond is a secondary effect of the stronger traditional red-shifted H-bonds N-H... O. In all these systems, red shifts of the BH bonds are caused by two factors： negative repolarization and negative rehybridization of the BH bond, and decrease of occupancy on σ（BH） caused by the intermolecular hyperconjugation σ（BH）→σ^＊ （XH）.
文摘Porous silicon prepared by pulse electro-etching is heat-treatedin O_2 atmosphere with an enhancement of its PI. peak and animprovement of its PL stability. The PL peak of a sample poroussilicon treated in O_2 atmosphere at 1000 ℃ presents itself a three--peak structure and, compared with an un-- heat--treated sample,there exists blue shift of ～ 40 nm.
基金Project supported by the FRFCU(Grant No.2016JBM066)863 Program(Grant No.2013AA032205)+1 种基金the National Natural Science Foundation of China(Grant Nos.61575019,51272022,and 11474018)RFDP(Grant Nos.20120009130005 and 20130009130001)
文摘The ZnO quantum dots（QDs） were synthesized with improved chemical solution method.The size of the ZnO QDs is exceedingly uniform with a diameter of approximately 4.8 nm,which are homogeneously dispersed in ethanol.The optical absorption edge shifts from 370 nm of bulk material to 359 nm of QD materials due to the quantum size effect,while the photoluminescence peak shifts from 375 nm to 387 nm with the increase of the density of ZnO QDs.The stability of ZnO QDs was studied with different dispersion degrees at 0？C and at room temperature of 25？C.The agglomeration mechanisms and their relationship with the emission spectra were uncovered for the first time.With the ageing of Zn O QDs,the agglomeration is aggravated and the surface defects increase,which leads to the defect emission.
基金supported by the National Basic Research Program of China(973 Program2012CB821702)+1 种基金the National Natural Science Foundation of China(21233009 and 21173221)the State Key Laboratory of Structural Chemistry,Fujian Institute of Research on the Structure of Matter,Chinese Academy of Sciences
文摘Two novel coordination compounds,1[Zn4（L1）4（NO3）2（H2O）2]（NO3）2·2H2O and 2[Mn2（L2）2（DMF）（H2O）3]（ClO4）2·DMF（HL1 = N＇-[（1E）-pyridine-2-ylmethylidene]pyrazine-2-carbohydrazide,H2L2 = 2-hydroxy-3-methoxybenzaldehyde（pyrazin-2-ylcarbonyl）hydrazone）,based on the N-N bridged ligands were prepared and structurally characterized.Compound 1represents the[2＊2]molecular squares,in which both N atoms belonging to the N-N bridged ligands are connected to the Zn centers.The emission of compound 1 exhibits a blue shift,which can be assigned to strong electrostatic interaction between Zn^Ⅱ ions and the L1^-1.Compound 2represents a rare phenol-O bridged Mn2^Ⅱ complex.The magnetic investigation indicates weak antiferromagnetic interactions between the Mn^Ⅱ centers.
基金supported by the National Key Research and Development Program of China(No.2018YFB2200103)the National Natural Science Foundation of China(Nos.61875186 and 61975196)+2 种基金the Project of the Natural Science Foundation of Beijing(No.Z160002)the Key Research Projects of Beijing Information Science and Technology University(BISTU)(Nos.2019-22,2019-23,2019-27)the Beijing Key Laboratory for Sensors of BISTU(No.2019CGKF007)。
文摘In recent years,Perovskite Light-Emitting Diodes(PeLEDs)have received considerable attention in academia.However,with the development of PeLEDs,commercial applications of full-color PeLED technology are largely limited by the progress of blue-emitting devices,due to the uncontrollably accurate composition,unstable properties,and low luminance.In this article,we add Cesium chloride(CsCl)to the quasi-two-dimensional(quasi-2D)perovskite precursor solution and achieve the relatively blue shifts of PeLED emission peak by introducing chloride ions for photoluminescence(PL)and electroluminescence(EL).We also found that the introduction of chlorine ions can make quasi-2D perovskite films thinner with smoother surface of 0.408 nm.It is interesting that the EL peaks and intensities of PeLED are adjustable under different driving voltages in high concentration chlorine-added perovskite devices,and different processes of photo-excited,photo-quenched,and photo-excited occur sequentially with the increasing driving voltage.Our work provides a path for demonstrating full-color screens in the future.
基金Project supported by the National Natural Science Foundation of China (No. 20272057).
文摘It is demonstrated that in all types of hydrogen bonds (X—H…Y) there is a balance between the long-range attractive orbital interactions and short-range Pauli/nucleus repulsions. When the proton acceptor approaches the proton donor from distance, the hydrogen bonding energy becomes more negative at relatively large distance, goes through a minimum, and then starts to become less negative when the short-range repulsive forces come into effect. Meanwhile, the X—H bond length increases at relatively large distances, goes through a maximum and starts to shorten when the short-range repulsive forces come into effect. Whether the hydrogen bond is red or blue shifted is dictated by the energy minimum position. If at the energy minimum position the X—H bond length is shorter than that for the free monomer, the hydrogen bond is blue shifted and vice versa. Further studies demonstrate that the recent report about the correlation of C—H bond lengths with proton donor-acceptor distance in F3C—H…OH2 and F3C—H…Cl- is not fully correct because the authors conducted an inappropriate comparison. Furthermore, it is shown for the first time that the Pauli/nucleus repulsion theory is applicable to the blue-shifted hydrogen bonds in the X—H…p complexes and the blue-shifted lithium bonds in the X—Li…Y complexes.
