Sensitivity Enhancement of Surface Plasmon Resonance Imaging Using Periodic Metallic Nanowires

A nanowire-mediated surface plasmon resonance (SPR) imaging is numerically investigated for enhanced sensitivity. The results calculated by rigorous coupled-wave analysis present that interplays between localized surface plasmons and surface plasmon polaritons contribute to sensitivity enhancement. Compared to conventional thin film-based SPR imaging measurement, an optimal nanowire structure can provide sensitivity enhancement by 3.44 times as well as highly linear detection property for quantification of surface reactions of interests. This paper demonstrates the potential and limitation for a highly sensitive, label-free, and real-time SPR imaging sensor based on periodic metallic nanowires.     

金属纳米颗粒光力增强与稳定捕获研究

基于有限元算法和Maxwell应力张量法,分析了紧聚焦高斯光束照明下金基底表面的金纳米球所受光力。利用无结构的平整金基底,被捕获的金纳米颗粒和金基底之间能够产生间隙表面等离激元和局域表面等离激元共振效应,将电磁场局域在金球与金基底之间的纳米间隙内,增强了金纳米球所受光力以及光阱刚度。通过研究入射光的偏振态、金纳米球的半径、基底类型以及聚焦光束焦点到基底表面距离对光力的影响,得到了实现基底附近金纳米球稳定捕获以及获得最大光力的优化方案。     

Strong Photoacoustic Signal Enhancement by Coating Gold Nanoparticles with Melanin for Biomedical Imaging

Photoacoustics is a powerful biomedical imaging and detection technique, because it is a noninvasive, nonionizing, and low‐cost method facilitating deep tissue penetration. However, suitable contrast agents need to be developed to increase the contrast for in vivo imaging. Gold nanoparticles are often discussed as potential sonophores due to their large absorption cross‐section and their tunable plasmon resonance. However, disadvantages such as toxicity and low photoacoustic efficiency in the tissue transparency window prevail, preventing their clinical application. As a result, there remains a strong need to develop colloidal photoacoustic contrast agents which absorb in the tissue transparency window, exhibit high photoacoustic signal, and are biocompatible. Here, a facile synthetic approach is presented to produce melanin shells around various gold nanoparticle geometries, from spheres to stars and rods. These hybrid particles show excellent dispersability, better biocompatibility, and augmented photoacoustic responses over the pure melanin or pristine gold particles, with a rod‐shape geometry leading to the highest performance. These experimental results are corroborated using numerical calculations and explain the improved photoacoustic performance with a thermal confinement effect. The applicability of melanin coated gold nanorods as gastrointestinal imaging probes in mouse intestine is showcased.     

氧化锡纳米线的光致发光性能分析

通过热蒸发沉积法在常压、900°C高温条件下,合成了氧化锡纳米线结构。利用扫描电子显微镜、透射电子显微镜及选区电子衍射对样品的表面形貌和微结构进行了表征,X射线衍射、傅里叶变换红外光谱进一步证明所制纳米结构为金红石型氧化锡单晶结构。在77K和300K温度条件下,研究了所制氧化锡纳米线及其在氧气气氛中退火后的光致发光性能。     

Synthesis and Photoluminescence of GaN Nanowires with Nb Catalyst

Large-scale GaN nanowires are successfully synthesized by ammoniating Ga2O3 films on Nb layer deposited on Si（111） substrates at 850 ℃. X-ray diffraction （XRD）, scanning electron microscopy （SEM）, field-emssion transmission electron microscope（FETEM）, Fourier transformed infrared spectrum（FTIR） are used to characterize the structural and morphological properties of the as-synthesized GaN nanowires. The results reveal that the nanowires are pure hexagonal GaN wurtzite structure with a length of about several microns and a diameter between 50 nm and 100 nm. Finally, discussed briefly is the formation mechanism of gallium nitride nanowires.     

SnO2纳米线的低温生长及光致发光研究

在550℃下,通过Au-Ag合金助催热蒸发氧化亚锡,制备了25nm的Sn02纳米线.测试了Sn02纳米线的室温光致发光谱,其四个发光峰中,418nm的峰足新发现的峰,它是孪晶纳米线的面缺陷造成的.SnO2纳米线的低温生长机制遵从VLS生长机制,且与5nO粉末的应用有一定的关系.Sn02纳米线的较小尺度与气相因子的低温度低浓度化学反应有关.     

SnO2纳米线的低温生长及光致发光研究

在550℃下,通过Au-Ag合金助催热蒸发氧化亚锡,制备了25nm的Sn02纳米线.测试了Sn02纳米线的室温光致发光谱,其四个发光峰中,418nm的峰足新发现的峰,它是孪晶纳米线的面缺陷造成的.SnO2纳米线的低温生长机制遵从VLS生长机制,且与5nO粉末的应用有一定的关系.Sn02纳米线的较小尺度与气相因子的低温度低浓度化学反应有关.     

掺锂氧化锌纳米线的光致发光特性

氧化锌（ZnO）是直接宽带隙半导体材料,有高达60meV的激子束缚能,是下一代短波长光电材料的潜在材料。首先制备了优良的多孔氧化铝（Anodic Aluminum Oxide）有序孔洞阵列;以其为模板,采用直流电化学沉积的方法,在其规则排列的孔中沉积得到锌的纳米线;然后将其在高温下氧化,得到氧化锌的纳米线。XRD图显示Li掺杂前后的ZnO纳米线具有较好的晶态结构。对Li掺杂前后的ZnO纳米线进行光学特性测量,结果表明,ZnO纳米线有两个发光峰,分别位于382nm和508nm处;Li掺杂较大地改善了ZnO纳米线的发光性能,本征发光峰移到395nm处,蓝绿发光强度也有了很大程度的提高。     

Photoluminescence study of ZnO varistor stability

Photoluminescence (PL) measurements were carried out on commercial ZnO varistor samples that were electrically stressed and/or annealed at different temperatures. Changes in the intensity of green and yellow luminescence centers were studied as a function of annealing treatment. It was found that the ZnO luminescence (green and yellow) decrease with increase in annealing temperature, reach a minimum at 700°C, and increase again beyond 800°C. Furthermore, these green and yellow luminescence bands observed in the PL spectra are quenched in the ZnO varistor samples, compared to pure ZnO. In an electrically stressed ZnO varistor sample, the luminescence intensity was found to be higher compared to the as-sintered varistor sample. Annealing of the stressed varistor sample resulted in a decrease of the luminescence intensity. These PL observations are consistent with previous deep level transient spectroscopy and doppler positron annihilation spectroscopy results. All of the experimental results are consistent with the ion migration model of degradation and can be explained using a grain boundary defect model.     

基于微流体的ZnO纳米线的合成

微流控芯片在纳米材料的合成方面具有突出的优势,在芯片中通过微流体的操控制备ZnO纳米线,并利用扫描电子显微镜(SEM)、X射线衍射仪(XRD)和能谱仪(EDS)对制备得到的ZnO纳米线的表面形貌、晶体结构及成分进行表征。实验结果表明,在具有微腔室结构的微通道中可以构建浓度梯度,从而在单一通道中制备得到形貌及尺寸不同的致密ZnO纳米线,成为高效探索纳米材料合成条件的便捷手段。分别以玻璃片、ZnO种子层和ZnO纳米线为载体,对异硫氰酸荧光素标记的羊抗牛IgG抗体进行荧光检测,发现ZnO纳米线可显著增强荧光信号。     

一维硅氧线的水热法制备及光致发光

以SiO粉末为原料,采用水热法成功地制备出一维纳米硅氧线,并通过扫描电子显微镜(SEM)和透射电子显微镜(TEM)观察该一维硅氧线的形貌,可知其直径为100～200 nm,长度可以达到几十微米.X射线能谱仪(EDS)定量分析了该一维材料的成分,表明该纳米线由硅和氧两种元素组成.荧光光谱法测试了硅氧线的发光光谱,表明在426和446nm处有较强的发光.通过不同条件下的对比实验得到制备该纳米线的最佳条件,同时根据实验结果提出了该方法制备硅氧线的生长机理.     

二氧化锡纳米线自催化生长及其发光特性研究

在没有添加任何催化剂情况下,通过热蒸发锡粉制备了二氧化锡纳米线.利用扫描电子显微镜,X射线衍射和透射电镜对上述纳米线进行了结构表征.实验结果表明二氧化锡纳米线直径在100～400 nm,长度达数十微米.PL分析表明当激发波长为325 nm时,在581 nm处出现较强的黄色发光峰;在激发波长为250 nm时,在可见光区域579 nm处形成较强的发光峰,同时伴随一个385 nm处较弱的发光峰.二氧化锡纳米线的生长机制符合气-目生长模式.     

一维硅氧线的水热法制备及光致发光

以SiO粉末为原料,采用水热法成功地制备出一维纳米硅氧线,并通过扫描电子显微镜(SEM)和透射电子显微镜(TEM)观察该一维硅氧线的形貌,可知其直径为100～200 nm,长度可以达到几十微米.X射线能谱仪(EDS)定量分析了该一维材料的成分,表明该纳米线由硅和氧两种元素组成.荧光光谱法测试了硅氧线的发光光谱,表明在426和446nm处有较强的发光.通过不同条件下的对比实验得到制备该纳米线的最佳条件,同时根据实验结果提出了该方法制备硅氧线的生长机理.     

回力标形状的ZnO纳米棒的制备和光致发光特性(英文)

在1 050°C条件下,利用碳热蒸发的方法在NiO覆盖的Si(100)衬底上制备了回力标形状的ZnO纳米棒,这是一种新的ZnO的纳米结构。通过结构分析,发现这种回力标形状的ZnO纳米棒具有纤锌矿结构。室温的光致发光图谱中有两个发光峰:380nm附近的弱近紫外发光峰和524nm及575nm附近较宽的绿光发光峰。拉曼谱以及X电子能量谱也用于研究其性质。最后讨论了缓冲层的作用及ZnO纳米棒的生长机理。     

自催化方式制备ZnO纳米线及光致发光特性

采用化学气相沉积法,不用催化剂,在Si(111)基片上制备了ZnO纳米线。扫描电子显微镜(SEM)表征发现ZnO纳米线的直径在100nm左右。X射线衍射(XRD)图谱上只存在ZnO的(002)衍射峰。室温下光致发光谱(PL)中出现了389nm和357nm的紫外峰以及五个蓝光峰(450,468,474,481和491nm)。389nm峰为自由激子复合发射357nm峰是在LO声子的参与下,自由载流子碰撞形成自由激子过程的发光行为;468nm峰系电子从氧空位形成的浅施主能级向价带跃迁发光;450nm峰系电子从导带向锌空位形成的浅受主能级跃迁发光;474,481和491nm峰是声子伴线。     

Pre-avalanche Ultraviolet Photoconduction Properties of Transitional-Metal-Doped ZnO Nanowires

The ultraviolet (UV) photoelectric characteristics of transitional metal (Cu) doped ZnO nanowires produced by the self-catalytic vapor–liquid–solid (VLS) method were investigated by performing a series of photoconduction and time-resolved measurements. The photocurrent voltage characteristics obtained on the nanowires configured as two-terminal metal–semiconductor–metal photodetectors exhibited a nonmonotonic behavior attributed to the interplay of several limiting mechanisms: Schottky contacts and trapping/detrapping effects that take place at low and intermediate (pre-avalanche) bias regimes, respectively. In the intermediate biases, the photocurrent was power-law dependent, i.e., changed with voltage as and for excitation wavelengths of 365 nm, 302 nm, and 254 nm, respectively. The dependence of the exponent on the wavelength of the light is analyzed and explained based on the detailed consideration of the contribution of different deep-defect Cu levels formed within the band gap of ZnO. The study will be important to those working in the area of ZnO-based nanophotodetectors, optical switches, and sensors.     

Efficiency Enhancement of Organic Solar Cells by Using Shape‐Dependent Broadband Plasmonic Absorption in Metallic Nanoparticles

It is been widely reported that plasmonic effects in metallic nanomaterials can enhance light trapping in organix solar cells (OSCs). However, typical nanoparticles (NP) of high quality (i.e., mono‐dispersive) only possess a single resonant absorption peak, which inevitably limits the power conversion efficiency (PCE) enhancement to a narrow spectral range. Broadband plasmonic absorption is obviously highly desirable. In this paper, a combination of Ag nanomaterials of different shapes, including nanoparticles and nanoprisms, is proposed for this purpose. The nanomaterials are synthesized using a simple wet chemical method. Theoretical and experimental studies show that the origin of the observed PCE enhancement is the simultaneous excitation of many plasmonic low‐ and high‐order resonances modes, which are material‐, shape‐, size‐, and polarization‐dependent. Particularly for the Ag nanoprisms studied here, the high‐order resonances result in higher contribution than low‐order resonances to the absorption enhancement of OSCs through an improved overlap with the active material absorption spectrum. With the incorporation of the mixed nanomaterials into the active layer, a wide‐band absorption improvement is demonstrated and the short‐circuit photocurrent density (J_sc) improves by 17.91%. Finally, PCE is enhanced by 19.44% as compared to pre‐optimized control OSCs. These results suggest a new approach to achieve higher overall enhancement through improving broadband absorption.     

退火对溅射ZnO薄膜光吸收性能的影响

利用射频磁控溅射制备了高c轴取向的ZnO薄膜,采用X-射线衍射仪、扫描电镜和紫外-可见光分光光度计研究了退火对ZnO薄膜的结构和光吸收性能的影响。结果表明,退火可以改善ZnO薄膜的质量和光吸收性能。退火后薄膜的结构、形貌和光吸收性能得到改善,薄膜中缺陷减少,晶粒长大致密化,尺寸较均匀;紫外吸收峰变窄,强度增加,吸收边变得陡峭并向长波方向移动,光学带隙降低。450℃退火的ZnO薄膜具有最佳的结晶质量和紫外吸收性能。     

纳米晶ZnO:Dy3+粉体的制备和发光性质

通过固相反应法制备了ZnO:Dy3 纳米粉末,样品的X射线衍射、透射电镜和选区电子衍射证实了ZnO:Dy3 纳米粉末属于六方纤锌矿多晶结构.研究了光致发光谱与激发波长和掺杂离子浓度的依赖关系.结果表明,从ZnO:Dy3 纳米粉末的光致发光光谱中首次发现除了Dy3 的4f→4f跃迁外,出现了Dy掺入ZnO后产生的两个缺陷A和B的宽谱带发射峰,峰值分别在600和760nm,半高宽分别约为200和100nm.在ZnO的激子激发下(385nm),峰值760nm的发光强度远远大于峰值在600nm的发光强度.样品的发射光谱中峰值的相对强度变化依赖于激发波长和Dy3 的掺杂浓度.当在Dy3 4f→4f激发下(454nm),光谱中只有Dy3 的4f态间的特征发射,而缺陷A,B不发光.     

Cu掺杂ZnO薄膜的结构及发光特性

采用溶胶-凝胶旋涂法在玻璃衬底上制备了不同Cu掺杂量的ZnO薄膜。用显微镜和X射线衍射(XRD)研究了Cu掺杂对ZnO薄膜形貌和微结构的影响。结果表明,制备得到的ZnO薄膜具有应变小和c轴择优取向。室温下测量了样品Zn1-xCuxO的光致发光(PL)谱,发现所有样品的PL谱中均观察到435nm左右的蓝光发光带,发光带强度与Cu的掺杂量有关;当x=0.06时,Zn1-xCuxO薄膜的PL谱中出现了较强的蓝光发射。分析了掺杂量对发光性能的影响,并对样品的发光机制进行了探讨,推断出蓝光峰来源于电子由导带底到锌空位(VZn)能级的跃迁及锌填隙(Zni)能级到价带顶的跃迁,它们可通过改变Cu的掺杂量予以控制。