Rapid screening of bacteria by low-cost and eco-friendly material-based approaches is still a major challenge. Herein, a colorimetric biosensor was designed for the ultrasensitive and rapid detection of Gram-positive bac-teria. The biosensor exploited polydopamine and polyethyleneimine (PDA-PEI)-modified papers for separating bacteria and carbon dots (CDs) for selective colorimetric detection of Gram-positive bacteria. Noble metal-free CDs can target Gram-positive bacteria by binding with peptidoglycan and possess peroxidase-like activity. Thus, they can avert the step of modifying recognition probes, facilitating biosensor fabrication, and reducing the cost. This biosensor can detect S. aureus as low as 1 cfu mL-1, L. monocytogenes as low as 5 cfu mL-1, and B. subtilis as low as 9 cfu mL-1 within 55 min. In addition, a portable device was constructed to enable convenient and on-site quantitative detection of Gram-positive bacteria. The feasibility of the biosensor was verified by detecting Gram-positive bacteria in eggshell and sausage samples with recoveries ranging from 91.2% to 110%.

设计并合成了荧光素酰腙类衍生物对羟基苯基荧光素酰腙(FHP),通过对荧光素的化学修饰,并采用酸碱以及二价铜离子为输入,实现了对由荧光素构成的二进制计算器加密的逻辑功能.该逻辑加密功能的实现是基于荧光素酰腙类衍生物对二价铜离子的特异性响应:在碱性环境中,二价铜离子催化FHP完全分解并释放出具有二进制计算器逻辑功能的荧光素分子;在酸性环境中,二价铜离子催化FHP部分分解并与二价铜离子配位形成稳定的二价铜离子配合物,该配合物既不能还原形成原化合物,也不能在碱性环境中释放出荧光素分子,导致该逻辑器件的逻辑功能被彻底破坏.基于该自毁装置的存在,使得该逻辑加密器件的安全性进一步提高.

We report a novel synthesis strategy for Y-branched TiO2 nanotubes on a pure titanium foil by electrochemical anodic oxidation in an NH4F organic electrolyte. Effects of temperature range, oxidation time, and morphology-dependent parameters of the Y-branched TiO2 nanotube arrays were investigated. We found that an optimized growth-temperature window between 20°C and 30°C resulted in Y-branched nanotubes with much better morphology and photoelectric performances. After annealing at 450°C for 1.5 h in air, a dominant crystal structure of these arrays was indexed to anatase.

Enhanced performance of small molecular weight organic solar cells based on CuPc/C60 and TiOPc/C60 with Ag nanoparticles fabricated on the ITO anode and MoO3 as the anode buffer layer has been demonstrated.Surface plasmon induced by the incorporation of Ag nanoparticles results in the increased absorption efficiency and photogenerated exciton dissociation probability of the photoactive layers.Meanwhile,the quenching of the photogenerated excitons at the organic/metal interface can be successfully restricted by the MoO3 anode buffer layer.Consequently,the short-circuit current is improved and the other parameters maintain unaffected,which leads to an enhanced power conversion efficiency of the devices.

A new material group, DPVBi and Bphen, are presented to form electroplex with their efficient white emission in a p-i-n OLED. The experimental results bear out that the interfacial phenomenon between DPVBi and Bphen originates from electroplex but not exciplex. By introducing p-i-n structure, the white OLEDs exhibits relatively high peak luminance of 9050 cd/m2, and power efficiency of 2.63 lm/W. Further more, the Commission Internationale De l'Eclairage coordinates of resulting emission varies gradually with increasing forward bias. Consequently, a consistent white color is obtained. It affords more opportunities in facilitating the fabrication process of white OLEDs.

Al-doped 6H-SiC nanowires (Al/6H-SiC) were successfully fabricated via catalyst-assisted pyro-lysis of polymeric precursor.The samples were characterized by HRTEM,EDS and XRD.The results showed that the doped concentrations were adjusted from 0.5% up to 1.25% with the Al concentrations in the precursors.The HRTEM pattern illustrated that the lattice fringe spacings are 0.26 nm and 0.25 nm.EDX shows the atom ratio of Si and C is 1∶1.The XRD pattern demonstrated that Al-doping causes a decrease in the lattice parameters with Al concentration as compared with standard values.The optical properties of single-crystalline 6H-SiC nanowires with different Al doping levels were characterized by Raman and absorption spectra.The Raman spectra reveal that the phonon energy of the single-crystalline SiC nanowire is 100 meV.We estimated the optical absorption band-gap of nanowires from optical band-edge absorption.Al doping results in a red-shift on the optical absorption edge of SiC nanowire,thus it demonstrates a reduction of optical band gap.

The luminescence properties of Ce3+ ions in yttrium aluminum garnet(YAG) powder have been studied.The addition of 5% NH4F flux is equivalent to decrease the preparation temperature by 200 ℃.Since the ionic radius of Ce3+(0.128 3 nm) is a little larger than that of Y3+(0.111 59 nm),one can expect that Ce3+ experiences a strong crystal field in YAG:Ce.If all the added Ce3+ ions enter into the crystal lattice,substitute the sites of Y3+ ions,and then are incorporated as Ce3+ at undisturbed Y3+ sites,the reagent need to absorb plentiful Joule heat.The content of cerium determines the preparation temperature,more cerium means higher preparation temperature.We consider that the NH4F flux has no effect on the growth of YAG:Ce crystallite because of its low melting point.In order to improve the fluorescence intensity of green-yellow-emitting phosphor based on YAG:Ce for white LED(light-emitting diode),the effect of BaF2 and MgF2 as charge compensators were studied separa-tely.But the charge compensating mechanism has seldom been reported before.When the charge compensator and NH4F were jointly added,the intensity of emission was enhanced.When the charge compensator is MgF2,the intensity of phosphor YAG:Ce has the strongest brightness.The photoluminescence intensities of YAG:Ce phosphor particles with Ba2+,Mg2+ doped were about 135%~142% of that of YAG:Ce phosphor particles without charge compensator.This result can be explained in terms of the environment of trivalent cerium in the crystal structure of YAG.On one hand,we postulate that the oxygen vacancy formed upon calcining in a reductive atmosphere is the most important intrinsic defect.A compensation mechanism expected for YAG:Ce with Mg2+ codoped is provided by the association of two Mg2+ ions with an oxygen vacancy.In this case,the introduction of Mg2+ ions in YAG:Ce takes place in accordance with the scheme:This scheme implies that at certain cerium concentrations a single oxygen vacancy can be compensated by two Mg2+ ions.On the other hand,Ce3+ and MgF2 dopants have counteracting effects on the lattice parameter of cubic YAG.Ce3+ ions,which replace Y3+ of YAG to form a substitutional solid solution,cause an increase in the lattice parameter as the ionic radius of Ce3+ is larger than that of Y3+,while Mg2+ ions leads to a decrease in the lattice parameter because the ionic radius of Mg2+(0.086 nm) is smaller than that of Y3+.Further more,Mg2+ can substitute Y3+ easily without disturbing the crystal lattice.The addition of BaF2 as charge compensator acts as the role of MgF2.Differently,Ce3+ and BaF2 dopants don't have counteracting effects on the lattice parameter of cubic YAG(the ionic radius of Ba2+is 0.135 nm,larger than Ce3+ and Y3+).The lattice parameter expands because of a repulsive interaction between cations.The effect of doping on the optical behavior of YAG is even more complex.To analyze the role of charge compensator on the luminescent emission property of YAG:Ce,the synthesized products were characterized by XRD,photoluminescence emission and excitation spectra(PLE).

With the development of far UV quasi-molecule laser lithography technique,the processing of CaF2 optical crystal lens material challenged traditional cool processing techniques.Combined with the fundamental properties of CaF2 crystal,the processing techniques was improved a lot in this study.Experimental results showed that high-quality optical crystals were processed by optimum technology parameters and the special processing method.

CaF_2 single crystals were grown by Bridgman method in different growing conditions.Growth defects and optical spectra properties of CaF_2 samples were studied.Experimental results show that water in the growing atmosphere induced several additional absorption bands.Among these,the broad one around 1500nm is ascribed to the two-times vibration of OH~-,and the peaks at 420nm and 590nm are induced by the formation of color centers due to the substitution of O~(2-) for F~-.Moreover,the presence of Ce~(3+) impurity causes the absorption band at 306nm.

Temperature dependence of direct conductivity in amorphous SiCN ceramics obtained by pyrolysis of the polymer precursor was investigated in the temperature range of room temperature to 1 373 K. The results indicate that the conductivity increases from 9.6×10~(-9)(Ω·cm)~(-1) at an ambient temperature to 1.62×10~(-3)(Ω·cm)~(-1) at 1 373 K. The experimental data were analyzed by Mott model and Arrhenius law. Distinct electrical conduction mechanisms are contributed to the conductivity in experimental temperature range including variable range hopping, hopping near the Feimi energy, hopping in the band tail state and the conduction in the extended band. X-ray diffraction pattern indicates that the structure of the samples annealed at (1 473 K) is amorphous. Infrared spectroscopy analysis indicates that Si—C, Si—N and C—N bonds are the dominant chemical bonds, and fewer C—H, Si—H and C—O bands are found.

利用发射波长为470nm的蓝光发光二极管作为基础光源,通过荧光粉转换方法制备白光发光二极管,荧光粉主要采用稀土激活的铝酸盐Y3Al5O12∶Ce3+ (YAG).在工作电流为15mA条件下,所研制的白光LED的法向光强为2 890mcd;色坐标为x=0.29,y=0.33;显色指数为77;流明效率为14.9 lm/W.研究制备了不同色温的白光LED,色温范围从2 700～8 000K,研究了色温与色坐标之间的对应关系.并且与国外同类产品进行比较,部分指标已经超过了国外同类产品水平.

The membranes of polydiacetylene backbone decorated with mannose can recognize Escherichia coli (E.coli) and bind with them. The binding leads to the color transition of the membranes which is readily visible to the naked eyes and can be quantified by visible absorption spectroscopy. The direct colorimetric detection by polydiacetylene membranes not only opens a new path for the use of these membranes in the area of biosensor development but also offers new possibilities for diagnostic applications and screening for binding ligand. In present paper, we utilized Langmuir-Blodgett technology to fabricate the mixed PDA/MPDA monolayers and measured the values of the colorimetric response when the mixed PDA/MPDA monolayers were incubated with various E.coli and physiological saline. On the basis of these measurements, we conclude the monolayers can be used to detect environmental E.coli. In order to understand the mechanism of the chromatic transition, the affinochromism properties of polydiacetylene are examined by Resonance Raman (RR) spectroscopy and Fourier Transform Infrared (FTIR) spectroscopy. The results of RR spectroscopy demonstrate the bands of the double and triple bonds simultaneously shift to higher wavenumber during the affinochromism. At the same time, the bands intensity ratio of the double bonds to the triple bonds changes from a value 1.12 in the blue film to a value of about 2.5 in the red film, which can be explained by that the electronic structure in the polymer backbone changes from a acetylene to butatriene form when the blue to red chromatic transformation occurs. In addition, the results of FTIR spectroscopy also show that the side chains of polymer backbone perform rearrangement during the affinochromism. In conclusion, we demonstrate a simple and rapid method to detect E.coli and give a possible explanation to the mechanism of the affinochromism through RR and FTIR spectroscopy.

The intermolecular interaction and complex of various molecules can influence their optical and electrical properties,especially,efficiency of fluorescence and stability for fluorescent materials. Fluorescence decay experiment can demonstrate energy transfer among molecules and intermolecular interaction. In this paper,Fluorescence decay of the blending of polyvinyl carbazole (PVC) and tris(8-hydroxyquinolinolato) aluminum (Alq) with weight ratio 100∶4 and 100∶10 were investigated. The decay experiment is pumped by YAG locking-mode laser,whose excitation wavelength is 355nm,and detected by streak camera. Detection wavelength is chose 480nm and 540nm. According to the photoluminescence spectra of PVC and Alq film,these two wavelength correspond to the radiation emission of PVC and Alq respectively. Fiting the decay curve using a single exponential decay function,we get the fluorescent decay time. For the blending ratio 100∶4,the decay time is 8.5ns at 460nm and 6.47ns at 540nm. For the blending ration 100∶10,it is 7.9ns at 480nm and 5.5ns at 540nm. For Alq film and PVC one,their fluorescent decay time are 16.4ns and 14ns respectively. The blending of PVC and Alq show a evident reduction in fluorescent decay time compared with PVC and Alq. Thus in addition to the energy transfer between PVC and Alq molecules,there is a second channel to exchange energy, and the dynamics in this relaxation can be faster than that of radiation transition. This decay experiment implied that the interaction of PVC and Alq molecules formed a new complex of PVC and Alq,or configuration change of molecule.

As potential materials for optical biosensor, the surface property of the monolayer film consisted of a mixture of 10,12 pentacosadiynoic acid(PDA) and its α D mannopyranoside (MPDA) at water gas interface has been investigated at different pH and temperature. The results show that the monolayer is rigid and more stable when pH=5 16～5 64 and subphase temperature below 14 ℃.