铂颗粒粒径效应:负载铂纳米颗粒的TiO2薄膜性质研究

制备了负载不同大小Pt纳米颗粒的TiO薄膜。利用TEM测定了Pt粒子的大小,XRD,UV—Vis和测量光电流等方法对TiO2复合膜进行了表征,以亚甲基蓝降解反应评价了Pt／TiO2薄膜的光催化活性。结果表明,在负载相同物质的量的Pt情况下,Pt颗粒的大小直接影响TiO2薄膜的性能,显示较强的粒径效应,当负载平均粒径约5nm的Pt粒子后,薄膜具有最高的光电流和光催化活性。     

Nanostructuring of thin Au films by means of short UV laser pulses

The particle size distribution, morphology and optical properties of the Au nanoparticle (NP) structures for surface enhanced Raman signal (SERS) application are investigated in dependence on their preparation conditions. The structures are produced from relatively thin Au films (10–20 nm) sputtered on fused silica glass substrate and irradiated with several pulses (6 ns) of laser radiation at 266 nm and at fluencies in the range of 160–412 mJ/cm². The SEM inspection reveals nearly homogeneously distributed, spherical gold particles. Their initial size distribution of the range of 20–60 nm broadens towards larger particle diameters with prolonged irradiation. This is accompanied by an increase in the uncovered surface of the glass substrate and no particle removal is observed. In the absorption profiles of the nanostructures, the broad peak centred at 546 nm is ascribed to resonant absorption of surface plasmons (SPR). The peak position, halfwidth and intensity depend on the shape, size and size distribution of the nanostructured particles in agreement with literature. From peak intensities of the Raman spectra recorded for Rhodamine 6G in the range of 300–1800 cm⁻¹, the relative signal enhancement by factor between 20 and 603 for individual peaks is estimated. The results confirm that the obtained structures can be applied for SERS measurements and sensing.     

Porosity depth profiling of spin-coated silica thin films produced by different precursors sols

The structural evolution of nanoporous silica thin films was studied by Doppler broadening spectroscopy (DBS), 2-3 gamma ratio of positronium (3γ-PAS) and Fourier transform infrared spectroscopy (FT-IR). Four series of silica films with thickness in the 300-600 nm range were deposited by spin coating on Si substrate changing the content of sacrificial porogen in the sol precursors. The effect on the porosity of different amount of porogen and of the thermal treatments in the 400-900 °C temperature range have been highlighted. The evolution of the porosity is discussed considering the removal of porogen and of the silanol Si-OH groups by thermal treatments as pointed out by FT-IR. Pores with size from less than 1 nm up to sizes larger than 2.0 nm have been detected. In samples with maximum porogen load oPs escaping was observed indicating onset of connected porosity. At temperatures higher than 700 °C a decrease of the porosity due to a progressive pore collapsing was evidenced. A strong correlation was found between the shift of the Si-O-Si transversal optical (TO₃) mode in the FT-IR spectra and the pore size in the porous silica films as revealed by DBS and 3γ-PAS.     

Lasing characteristics of Rhodamine B and Rhodamine 6G as a sensitizer in sol–gel silica

We report lasing characteristics of Rhodamine B (Rh. B) in sol–gel silica under excitation with frequency-doubled Nd:YAG laser and sensitization with Rhodamine 6G (Rh. 6G). The principle of radiative energy transfer (from Rh. 6G to Rh. B) has been utilized as a longitudinally Rh. 6G laser (at 585 nm)-pumped Rh. B laser process in the same sample. Rh. B offers a high photostable and efficient laser dye in sol–gel silica sensitized with Rh. 6G; 75,000 shots as a laser half-lifetime of the sample and 24% efficiency at pumping intensity 0.1 J/cm² of 532 nm. Wavelength shift occurs from 606 to 630 nm in the Rh. B laser with increasing its concentration from 1×10⁻⁴ to 8×10⁻⁴ M. The measured optical gain for Rh. B sensitized with Rh. 6G in sol–gel silica is higher than that in ethanol. A new effect has been observed; at 1×10⁻⁴ M of Rh. B and 0.5×10⁻⁴ M of Rh. 6G mixture, the emitted color of laser is changed by changing the pump intensity of frequency-doubled Nd:YAG laser.     

GaAs/SiO2纳米晶镶嵌薄膜的拉曼光谱与吸收光谱研究

采用射频磁控共溅射与高真空退火相结合的方法,分别在单晶硅片和光学石英玻璃片上制备了ＧａＡｓ／ＳｉＯ２纳米晶镶嵌薄膜样品。激光拉曼光谱的测量结果表明,退火态样品（４００℃,６０ｍｉｎ）的拉曼光谱特征峰呈现宽化和红移,红移量为９．５ｃｍ＾－１,对应薄膜中ＧａＡｓ纳米晶粒平均粒径约为３ｎｍ。样品的室浊吸收光谱测量结果表明,由于受量子限域效应的主导作用,与ＧａＡｓ块状单晶相比,样品光学吸收边呈现出明显的蓝     

Bi3.15Eu0.85Ti3O12铁电薄膜的结构与光学性能

采用化学溶液沉积法在石英衬底上制备了Bi_3.15Eu_0.85Ti₃O₁₂ (BEuT) 铁电薄膜,研究了 BEuT薄膜的结构和光学性能。XRD结果表明,不同温度退火的BEuT皆形成铋层状钙钛矿型结构,其晶粒尺寸随着退火温度的升高而增大,与SEM观察结果一致。对BEuT薄膜的拉曼光谱研究表明,Eu³⁺主要取代钙钛矿层中的Bi³⁺位。光学透过率曲线显示,在大于500 nm的波段,各BEuT薄膜的透过率均比较高,其禁带宽度约为 3.69 eV。BEuT薄膜的发光随着退火温度的升高而增强,这可归因于其结晶状况的改善。     

纳米多孔SiO2薄膜的制备与红外光谱研究

以正硅酸乙酯为原料,采用溶胶-凝胶法,结合旋转涂胶、超临界干燥工艺在硅片上制备了纳米多孔SiO2薄膜。XRD表明薄膜为无定形态;SEM显示薄膜具有多孔网络结构,其SiO2粒子直径为10~20nm。利用FTIR研究了薄膜的结构,纳米多孔SiO2薄膜含有Si—O—Si与Si—OR结构,呈疏水性;该SiO2薄膜热处理后因含有Si—OH基团而呈吸水性;用三甲基氯硅烷对热处理SiO2薄膜进行修饰可使其呈疏水性,修饰后的薄膜在N2中温度不高于450℃可保持其疏水性与多孔结构。     

密排银颗粒薄膜的制备及其SERS应用

银纳米颗粒通过自组装形成二维结构薄膜具有独特的光学性质,其提供的大量“热点”使其成为优越的表面增强拉曼散射(Surface enhanced Raman Scattering,SERS)基底.本文采用水/正己烷界面上自组装的方法得到了由密排的银纳米颗粒构成的薄膜,并以Rhodamine 6G为探针分子,比较了不同尺寸银...     

Grain size and its distribution in NiTi thin films sputter-deposited on heated substrates

Grain size and its distribution in NiTi thin films sputter-deposited on a heated substrate have been investigated using the small angle x-ray scattering technique. The crystalline particles have a small size and are distributed over a small range of sizes for the films grown at substrate temperatures 370 and 420℃. The results show that the sizes of crystalline particles are about the same. From the x-ray diffraction profiles, the sizes of crystalline particles obtained were 2.40nm and 2.81nm at substrate temperatures of 350 and 420℃, respectively. The morphology of NiTi thin films deposited at different substrate temperatures has been studied by atomic force microscopy. The root mean square roughness calculated for the film deposited at ambient temperature and 420℃ are 1.42 and 2.75nm, respectively.     

Measurement of nonlinear properties and optical limiting ability of Rhodamine6G doped silica and polymeric samples

The third order nonlinear optical properties of Rhodamine6G (Rh6G) doped silica and polymeric samples have been investigated using single beam z-scan technique under excitation by the second harmonic of Nd:YAG laser beam (532 nm). The nonlinear refractive index, nonlinear absorption coefficient, real and imaginary parts of third order nonlinear susceptibility in the samples of silica and poly-methylmethacrylate (PMMA) matrices are measured. Thermal contribution to the nonlinear refractive index in case of undoped silica samples has been calculated in order to have better accuracy of the material response contribution to third order nonlinearity. The comparative study of the optical limiting performance of Rh6G doped silica and polymeric samples show that Rh6G doped silica is relatively superior for optical limiting applications.     

Probing the phase transition behavior of acetonitrile confined in mesoporous silica by FT Raman spectroscopy

Phase transitions of acetonitrile confined in mesoporous silica SBA‐15 and mesocellular silica foam (MCF) having different pore diameters of 39.0, 39.9, 28.4, 8.7, and 4.6 nm with corresponding pore openings of 20.9, 12.1, 10.0, 8.7, and 4.6 nm were investigated by FT Raman spectroscopy. Melting and freezing temperature depressions were found for acetonitrile confined in mesoporous silica with pore opening sizes of 20.9, 12.1, 10.0 and 8.7 nm. A thermal hysteresis between the cooling and heating cycles was also observed. It appears that the smaller the pore opening, the larger the depression of melting or freezing temperature. Although two solid ( and ) phases exist in bulk acetonitrile, only the liquid →β phase transition was detected for acetonitrile confined in the nanopores of mesoporous silica. The solid‐to‐solid phase transition was not observed. For the mesoporous silica with the smallest pore size of 4.6 nm, neither the liquid nor the transition was observed for the confined acetonitrile. The results demonstrate that FT Raman spectroscopy is a useful technique for studying the phase transition behavior of organic compounds confined in silica‐based hosts. Copyright © 2011 John Wiley & Sons, Ltd.     

还原氮化对V2O5薄膜SERS效应的影响

探讨还原氮化后对V2O5薄膜SERS效应的影响。以乙酰丙酮氧钒(C10H14O5V)为V源,采用非水解溶胶-凝胶法制备V2O5凝胶,通过氨气还原氮化V2O5薄膜。利用XRD、FE-SEM、UV-VIS-NIR、RAMAN测试薄膜结构、光学性能及SERS效应。结果表明,氮化后V以氮氧化合物的形式存在,随着氮化温度升高,氮元素逐步替代氧元素。随着氮化温度升高,薄膜上晶粒逐渐增大,成板条状,晶体粒径达25 nm。经600℃还原氮化得到的薄膜的紫外可见近红外区域的吸收率最高,且禁带宽度相对于未氮化时的V2O5薄膜较小。利用R6G作为探针分子研究了薄膜的SERS效应,结果表明氮化温度600℃时薄膜具有显著的拉曼增强效应,且高于未氮化时的V2O5薄膜的拉曼增强效果,在620 cm^-1处拉曼信号峰强度达485 cps.     

同质与异质外延掺杂CVD金刚石薄膜的结构与性能

采用化学气相沉积(CVD)技术,以高温高压(HTHP)合成的(100)金刚石和p型(100)Si为衬底制备了硫掺杂和硼-硫共掺杂金刚石薄膜,利用原子力显微镜(AFM)、扫描隧道显微镜(STM)及隧道电流谱(CITS)等手段分析同质和异质外延CVD掺杂金刚石薄膜的结构和性能.结果表明:异Si衬底上CVD金刚石的形核密度低,薄膜表面比较粗糙,粗糙度达到18.5nm;同质HTHP金刚石衬底上CVD金刚石薄膜晶粒尺寸约为10—50nm,表面平整,表面粗糙度为1.8nm.拉曼测试和电阻测量的结果显示,在HTHP金刚 关键词： 金刚石 掺杂 外延     

基于表面增强拉曼光谱技术的金表面耐腐蚀性分析

金属表面耐腐蚀性能与其微观结构密切相关。以金为分析对象,采用不同粒径氧化铝抛光粉抛光处理金片表面,经扫描电镜和原子力显微镜观察,表明金片表面具备与实际工件类似的微观结构,在此基础上,研究金片表面微观划痕结构对表面增强拉曼散射(SERS)以及耐腐蚀性能的影响。以罗丹明B为探针分子,对不同特征尺寸的微观划痕进行SERS分析,获得了罗丹明B的SERS信号强度随划痕平均特征尺寸的变化规律。通过改变拉曼激发光偏振方向与划痕方向的夹角大小,发现SERS信号主要归因于激发光与划痕相互作用产生的横向表面等离激元。划痕平均特征尺寸在50 nm附近时,横向表面等离激元最强,之后随着划痕平均特征尺寸增加,横向表面等离激元逐渐变弱。另一方面,对具有不同特征尺寸微观划痕的金片进行电化学极化测试,获得了各样品的自腐蚀电位,发现金片的自腐蚀电位随着划痕平均特征尺寸增大而降低。结果表明,当划痕平均特征尺寸大于50 nm,金表面的SERS信号与自腐蚀电位间存在良好的线性对应关系,这为SERS技术用于工件耐蚀性分析提供了依据。通过在工件表面滴涂探针分子并使用便携式拉曼光谱仪测量有望可以对工件耐蚀性进行现场快速预判。     

Nanoporous structures on ZnO thin films

Porous structures were formed on ZnO thin films which were grown by an electrochemical deposition (ECD) method. The growth processes were carried out in a solution of dimethylsulfoxide (DMSO) zinc perchlorate, Zn(ClO₄)₂, at 120 ^°C on indium tin oxide (ITO) substrates. Optical and structural characterizations of electrochemically grown ZnO thin films have shown that the films possess high (0002) c$c$-axis orientation, high nucleation, high intensity and low FWHM of UV emission at the band edge region and a sharp UV absorption edge. Nanoporous structures were formed via self-assembled monolayers (SAMs) of hexanethiol (C₆SH) and dodecanethiol (C₁₂SH). Scanning electron microscope (SEM) measurements showed that while a nanoporous structure (pore radius 20 nm) is formed on the ZnO thin films by hexanathiol solution, a macroporous structure (pore radius 360 nm) is formed by dodecanethiol solution. No significant variation is observed in X-ray diffraction (XRD) measurements on the ZnO thin films after pore formation. However, photoluminescence (PL) measurements showed that green emission is observed as the dominant emission for the macroporous structures, while no variation is observed for the thin film nanoporous ZnO sample.     

掺杂和未掺杂氧化锌薄膜的拉曼光谱

利用拉曼光谱分别对不同衬底上,未掺杂和掺杂以及掺杂浓度不同的ZnO薄膜进行了系统的分析研究。其中ZnO薄膜均由溶胶-凝胶法制得,掺杂源为LiCl。测得的拉曼光谱显示,Pt/Ti/SiO2/Si衬底上生长的ZnO薄膜的拉曼特征峰(437cm-1)的强度明显高于SiO2/Si衬底上ZnO薄膜的拉曼特征峰的强度,说明Pt/Ti/SiO2/Si衬底上ZnO的晶化程度比SiO2/Si上ZnO的晶化程度高;但ZnO拉曼特征峰的位置和半高宽并没有发生变化,说明两种衬底上ZnO薄膜中应力大小没有发生变化。掺Li+后,580cm-1处的峰位向高频方向移动,且掺杂浓度越大频移量越大,说明掺杂已经在不同程度上引起了ZnO晶体中自由载流子浓度的变化。此外,还分析了掺Li+未在很大程度上引起ZnO晶格畸变的原因。     

银纳米粒子修饰三维碳纳米管阵列SERS实验

为了使表面增强拉曼散射(SERS)基底的三维聚焦体积内包含更多的“热点”,能吸附更多探针分子和金属纳米颗粒,以便获得更强的拉曼光谱信号,提出了银纳米粒子修饰垂直排列的碳纳米管阵列三维复合结构作为SERS基底,并对其进行了实验研究。利用化学气相沉积(CVD)方法制备了垂直排列的碳纳米管阵列;采用磁控溅射镀膜方法先在碳纳米管阵列上形成一层银膜,再通过设置不同的高温退火温度,使不同粒径的银纳米粒子沉积在垂直有序排列碳纳米管阵列的表面和外壁。SEM结果表明：在有序碳纳米管阵列的表面和外壁都均匀地负载了大量银纳米粒子,并且银纳米颗粒的粒径、形貌及颗粒间的间距随退火温度的不同而不同。采用罗丹明6G(R6G)分子作为探针分子,拉曼实验结果表明：R6G浓度越高,拉曼强度越强,但是R6G浓度的增加与拉曼强度增强并不呈线性变化;退火温度为450 ℃,银纳米颗粒平均粒径在100～120 nm左右,退火温度为400 ℃,银纳米颗粒平均粒径在70 nm左右,退火温度为450 ℃的拉曼信号强度优于退火温度400和350 ℃。     

Investigation on upconversion photoluminescence of Bi3TiNbO9:Er:Yb thin films

Bi₃TiNbO₉:Er³⁺:Yb³⁺ (BTNEY) thin films were fabricated on fused silica by pulsed laser deposition. It was demonstrated that different laser fluence and substrate temperature during growth of BTNEY upconversion photoluminescence (UC-PL) samples control the film’s grain size and hence influences the UC-PL properties. The average grain size of BTNEY thin films deposited on fused silica substrates with laser fluence 4, 5, 6, and 7 J/cm² are 30.8, 35.9, 40.6, and 43.4 nm, respectively. The 525 nm emission intensities increase with the deposition laser fluence and the emission intensities of BTNEY thin film deposited under 700 and 600 °C are almost 24 and 4 times, respectively, as strong as those of samples under 500 °C. The grain size of BTNEY thin film increases with the increasing temperature. UC-PL of BTNEY films is enhanced by increasing grain size of the films.     

SERS activity of carbon nanotubes modified by silver nanoparticles with different particle sizes

A two-dimensional (2D) surface-enhanced Raman scattering (SERS) substrate is fabricated by decorating carbon nanotube (CNT) films with Ag nanoparticles (AgNPs) in different sizes, via simple and low-cost chemical reduction method and self-assembling method. The change of Raman and SERS activity of carbon nanotubes/Ag nanoparticles (CNTs/AgNPs) composites with varying size of AgNPs are investigated by using rhodamine 6G (R6G) as a probe molecule. Meanwhile, the scattering cross section of AgNPs and the distribution of electric field of CNTs/AgNPs composite are simulated through finite difference time domain (FDTD) method. Surface plasmon resonance (SPR) wavelength is redshifted as the size of AgNPs increases, and the intensity of SERS and electric field increase with AgNPs size increasing. The experiment and simulation results show a Raman scattering enhancement factor (EF) of 10⁸ for the hybrid substrate.     

Structure and Morphology of SBA-15 Thin Films on Different Substrates

Well-ordered hexagonal mesoporous silica thin films, SBA-15 type, were synthesized with Pluronic P123 and tetraethyl orthosilicate in a diluted ethanol-hydrochloric acid solution. Films deposited on a broad range of distinct substrates by a sol-gel dip-coating method resulted in transparent and adherent samples. Transmission electron microscopy images revealed, predominantly, well-ordered regions of hexagonal arrays of cylindrical mesopores parallel to the substrate. X-ray reflectivity showed similar lattice parameters for all analyzed films, with a (h00) preferred orientation. The films presented diverse shrinkage susceptibilities, which were tested after different polymer removal procedures. Calcined films have 342 m²/g surface area, 0.130 cm³/g pore volume, and 6.8 nm pore diameter. The wetting characteristics of the substrates in water and alcoholic solutions were evaluated. The films showed different structural properties, mostly related to the mean surface roughness of the substrates and to the drying process.