近红外光热转换纳米晶研究进展

近红外光热转换纳米晶材料因其在近红外区(普遍位于780~1 400 nm)的高效光热转换性能,已广泛应用于光热杀死癌细胞、肿瘤治疗、海水淡化等领域。因其多样的液相制备方法和形貌控制、纳米结构复合、逐渐提高的光热转换效率以及表面易于药物修饰等优点,该材料在光热成像诊断、光热治疗等领域引起了学术界的广泛关注。本文综述了近红外光热转换纳米晶的研究进展,主要包括贵金属纳米晶、铜硫族半导体纳米晶、碳相关纳米晶以及这些纳米晶材料构成的复合结构,同时介绍了具有较高光热转换效率的表面等离子体共振(SPR)材料的研究进展,尤其是双模态SPR性质的耦合在光热转换领域的应用前景。基于其性能协同耦合的特性,双模态表面等离子体共振耦合的复合纳米晶将是近几年光热转换纳米晶发展的重要方向。     

纳米 Au 球壳材料的制备及其近红外光热转换性质

报道了一种采用湿化学法,以Ag纳米球为模板合成纳米Au球壳水溶胶的新方法,并对这种材料的光热转换性质进行了研究。TEM分析表明,Au纳米颗粒呈球壳结构,粒径约为20nm,粒径分布比较均匀,无明显硬团聚体存在。随着氯金酸加入量的增加,Au球壳的吸收峰位置从可见区(-400nm)逐渐红移至近红外区(-800nm)。测量了不同浓度的Au球壳水溶胶经近红外激光照射后的温度变化。结果表明,经1．9W／mm^2的808nm近红外光照射10min,温度最高升高了5．5℃。由于800—1200nm是人体组织的透射窗口,肿瘤细胞在42℃左右即可被杀死,这种纳米Au球壳材料有望在利用光热转换的红外热疗中得到应用,并有可能利用光动力实现药物释放。     

金纳米星/双锥的可控制备、光热转换及体外光热治疗

采用种子生长法,分别制备了金纳米星和金纳米双锥,利用透射电子显微镜、紫外-可见(UV-Vis)分光光度计等对样品进行了表征,并评价了金纳米星和金纳米双锥的光热转换性能、生物相容性以及体外光热治疗性能。结果表明,金纳米星和金纳米双锥的UV-Vis吸收峰位于808 nm和815 nm左右。在808 nm激光辐照下,光热转换效率分别为48.43%和53.68%。细胞实验表明,金纳米星和金纳米双锥具有良好的生物相容性。808 nm激光辐照5 min后,MCF-7细胞存活率分别降至22.54%和13.73%;且在同等条件下,金纳米双锥具有更加优异的光热治疗性能,是一种安全、高性能的肿瘤光热治疗用纳米探针材料。     

金纳米颗粒溶液的光热转换效率测量

激光照射金属材料表面会引起材料内部性质的变化,金属材料会对光产生吸收并可以将其转化为热能,导致材料表面温度的变化.金属材料的不同形貌、尺寸对光的能量转换效应是不同的,光热转换效率是材料吸收光能转换成热能的重要参数.在材料尺寸相同条件下光热转换效率大小与入射波长、激光器的功率密度、溶液浓度等因素有关.本文选取金纳米棒材料作为研究对象,通过改变入射波长、激光功率等条件研究金纳米棒光热转化效率,借此建立一种微观物质的能量转换的测量研究方法.     

铝基银纳米阵列制备及其紫外-可见-近红外光吸收特性

基于阳极氧化铝模板,采用真空蒸镀技术,制备了高度有序的周期性银纳米球阵列.阵列几何结构参数调控实验发现,通过控制蒸镀厚度,可实现对阵列中银纳米球尺寸(直径)和间距的有效调控,进而有效实现对紫外-可见-近红外各波段吸收峰位和峰宽的调制.吸收光谱测试显示,该纳米阵列在紫外、可见和近红外波段都具有明显的电磁波吸收特性.时域有限差分理论模拟结合实验分析不同波段光吸收特性的物理机制,紫外超窄强吸收为银、铝介电环境非对称诱发的法诺共振,可见波段吸收源自于银纳米粒子局域表面等离子体共振,近红外波段强吸收为银纳米球阵列表面晶格共振所激发.     

玻璃基底上不规则银纳米结构的生长及其光学性质的研究

以经过硅烷化后玻璃片为基底,之后吸附金纳米种子,采用柠檬酸钠为还原剂,在荧光灯照射条件下还原硝酸银,制备出基底表面具有银纳米粒子聚集结构的材料。采用透射电镜、扫描电镜和紫外可见分光光度计对产物的形貌和性质进行了表征,并考察银纳米粒子的形貌对其薄膜基底SERS活性的影响。结果表明：随着光照时间增加至16 h,金种子长大为平均粒径110 nm的不规则状多晶银纳米粒子,且出现双层粒子堆积。基底上纳米粒子的吸收光谱上出现了由银粒子的表面等离子体激元偶极子耦合引发的强烈吸收峰：随着光照时间的变化,耦合峰在600～813 nm波段内移动。光照时间为12 h后得到的SERS活性基底具有最强的SERS信号。     

芯帽纳米颗粒的光热性质

贵金属纳米结构中的光热效应在肿瘤光热治疗、光热成像、纳米药物等领域具有重要的应用价值.各向异性的芯帽纳米结构以其丰富的可调结构参数和对激发光偏振态敏感的特性,可灵活地在近红外波段获得理想的光学吸收性质,从而可以实现温度的高效调节.本文基于有限元方法研究了颗粒物纳米结构参数对其光热效果的作用规律,数值结果表明:通过对结构参数的微量改变(包括金壳厚度、芯壳比、芯径、金属表面覆盖率等)可实现温度的显著调整;在偏振态的旋转范围(30?—70?)内可快速地产生大温变光热的准线性调整.其不弱于纳米芯壳和纳米棒结构的光热性能可为纳米光热生医研究提供一种新的选择.     

纳米金复合炸药的设计及其近红外光吸收性质研究

金纳米粒子具有较大光吸收截面和光谱选择性,在激光点火含能材料中具有极大的应用潜力。本文根据目前实验中所制备的纳米金属复合炸药的结构和尺寸,构建了三种复合炸药的光吸收模型,分别为Au核RDX壳球形纳米粒子,Au-RDX-Au-RDX均匀相间的球形纳米粒子,以及RDX核Au壳的纳米粒子。利用离散偶极近似方法(DDA)对纳米金复合炸药的近红外吸收光谱进行了分析,并考虑了多种模型核壳尺寸及周围环境介质对光吸收性质的影响。获得了近红外光辐照下,纳米复合结构的最佳结构尺寸参数。结果表明,当制备成纳米级Au核RDX壳球形粒子时,其对近红外光(800 nm)波长具有较高的光吸收,相应的核壳尺寸约为60 nm和20 nm左右,且在水中的吸收要比在空气中的吸收强。     

玻璃基底上不规则银纳米结构的生长及其光学性质的研究

以经过硅烷化后玻璃片为基底，之后吸附金纳米种子，采用柠檬酸钠为还原剂，在荧光灯照射条件下还原硝酸银，制备出基底表面具有银纳米粒子聚集结构的材料。采用透射电镜、扫描电镜和紫外可见分光光度计对产物的形貌和性质进行了表征，并考察银纳米粒子的形貌对其薄膜基底SERS活性的影响。结果表明：随着光照时间增加至16 h，金种子长大为平均粒径110 nm的不规则状多晶银纳米粒子，且出现双层粒子堆积。基底上纳米粒子的吸收光谱上出现了由银粒子的表面等离子体激元偶极子耦合引发的强烈吸收峰：随着光照时间的变化，耦合峰在600～813 nm波段内移动。光照时间为12 h后得到的SERS活性基底具有最强的SERS信号。     

光热膨胀材料的光谱特性分析及微型光热驱动机构研究

光热膨胀材料的光谱特性是影响微型光热驱动机构性能的关键因素,该文在理论分析的基础上,采用单积分球测量法对四种聚合物材料的反射光谱及吸收特性进行了实验测量,据此选择制作光热驱动机构的最佳光热膨胀材料,发现掺杂染料的高密度聚乙烯(HDPE)材料在600～690 nm的范围内有较强烈的吸收.选取HDPE作为光热膨胀材料,设计制作了一种长度1 500 μm的微型光热驱动机构,并采用自行研制的CCD显微监控和视频运动测量系统进行了驱动机构的驱动性能测量实验.研究结果表明,在10 mW/650 nm的半导体激光器驱动下,该微型光热驱动机构可以产生18.7 μm的光热偏转量,说明其具有良好的光谱吸收和光热转换特性,可望在微光机电系统(MOEMS)中获得广泛应用.     

Gold Nanocages as Effective Photothermal Transducers in Killing Highly Tumorigenic Cancer Cells

Numerous gold nanostructures have the potential for photothermal therapy in cancers. Here, gold nanocages and gold nanoshells are synthesized, the sizes of which are fine‐tuned for a response at 750 nm wavelength. Their photothermal therapeutic efficiency is compared at gold concentration of 100 lg mL^?1 using a near‐infrared laser (750 nm). The biocompatibility for varying concentrations of gold (1 to 100 lg mL^?1) is performed in a normal cell line and laser‐mediated cell cytotoxicity for varying time intervals (7.5 and 10 min) is carried out in breast cancer cells. This study shows that when analyzed under similar conditions, the gold nanocages show better biocompatibility and are more efficient in near‐infrared absorption and photothermal conversion in comparison with conventional gold nanoshells. When subjected to photothermal laser ablation of breast cancer cell line for 7.5 min and 10 min, the nanocages are able to induce 62.92 ± 3.25% and 96.41 ± 3.04% reduction in cell viability, respectively, in comparison to nanoshells, in which a 43.35 ± 1.91% and 79.89 ± 4.74% reduction in cell viability is observed. The current study shows that the gold nanocages can outperform gold nanoshells and effectively kill cancer cells without any significant cytotoxic effect on normal cells.     

Synthesis,characterization, and toxicity of hollow gold nanoshells

Hollow gold nanoshells (HGN) with a diameter of 50–70 nm and tunable optical properties within the near-infrared region were synthesized from a substitution reaction using a sacrificial template, in which the morphological properties of the HGN were affected by the synthesis conditions. Using EDX line scan, the composition of the structure was determined to verify if the sacrificial template is completely consumed or residues remain after the chemical synthesis, obtaining that the final HGN structure contains about 11% of the remaining silver that showed no significant effect on the cell viability of a hNS1 cell line, but resulted as toxic on a C6 glioma cell line at high concentrations. The photothermal properties were evaluated using a NIR laser, which despite its low power showed the conversion of light into heat. This study was conducted to evaluate the potential of these nanostructures as therapeutic agents with an emphasis on toxicity.     

Enhancement of the 808 nm Photothermal Effect of Gold Nanorods by Thiol‐Induced Self‐Assembly

Gold (Au) nanomaterials are promising photothermal agents for the selective treatment of tumor cells owing to the strong capability to convert near‐infrared (NIR) irradiation into heat energy. One basic issue for practical photothermal therapy is the enhancement of photothermal effect in NIR region. Here, various low‐molecular‐weight thiols are applied to induce one‐dimensional (1D) self‐assembly of Au nanorods (NRs), which leads to the redshift of absorption peak towards NIR region. As a result, the 1D assembled Au NRs exhibit improved photothermal effect at 808 nm in comparison to unassembled Au NRs.     

Optimal design of gold nanoshells for optical imaging and photothermal therapy

Gold nanoshells are of great interest in optical imaging based on their light scattering properties and photothermal therapy due to their light absorption properties. Strong light scattering is essential for optical imaging, while effective photothermal therapy requires high light absorption. In this article, the optimal core radii and shell thicknesses of silica–gold and hollow gold nanoshells, possessing maximal light scattering and absorption at wavelengths between 700 and 1100 nm, are obtained using the Mie theory of a coated sphere. The results show that large-sized gold nanoshells of high aspect ratios (the aspect ratio is defined as the ratio of core radius to shell thickness) are the efficient contrast agents for optical imaging, while smaller gold nanoshells of high aspect ratios are the ideal therapeutic agents for photothermal therapy. From the comparison of the numerical results for silica–gold and hollow gold nanoshells, the latter are seen to offer a little superior light scattering and absorption at smaller particle size. Fitting expressions for the optimal core radii and shell thicknesses are also obtained, which can provide design guidelines for experimentalists to optimize the synthetic process of gold nanoshells.     

Surface Plasmon Resonance and Field Enhancement of Au/Ag Alloyed Hollow Nanoshells

We investigate the nanostructure, surface plasmon resonance （SPR） absorption and nonlinear enhancement of Au/Ag alloyed hollow nanoshells prepared by the replacement reaction of Ag nanoparticles in a HAuCI4 aqueous solution. As the volume of HAuCl4 increases from OmL to 0.S mL, the SPR band of the Au/Ag alloyed nanoshells is tuned from 430nm to 780nm, and the third-order nonlinear optical susceptibility is enhanced nearly by an order of magnitude, which indicates a large enhancement of local field in the Au/Ag alloyed hollow nanoshells with hole defects.     

Seed-mediated shape evolution of gold nanomaterials: from spherical nanoparticles to polycrystalline nanochains and single-crystalline nanowires

We studied the kinetics of the reduction of a gold precursor (HAuCl₄) and the effect of the molar ratio (R) of sodium citrate, which was introduced from a seed solution, and the gold precursor on the shape evolution of gold nanomaterials in the presence of preformed 13 nm gold nanoparticles as seeds. The reduction of the gold precursor by sodium citrate was accelerated due to the presence of gold seeds. Nearly single-crystalline gold nanowires were formed at a very low R value (R = 0.16) in the presence of the seeds as a result of the oriented attachment of the growing gold nanoparticles. At a higher R value (R = 0.33), gold nanochains were formed due to the non-oriented attachment of gold nanoparticles. At a much higher R value (R = 1.32), only larger spherical gold nanoparticles grown from the seeds were found. In the absence of gold seeds, no single-crystalline nanowires were formed at the same R value. Our results indicate that the formation of the 1D nanostructures (nanochains and nanowires) at low R values is due to the attachment of gold nanoparticles along one direction, which is driven by the surface energy reduction, nanoparticle attraction, and dipole–dipole interaction between adjacent nanoparticles.     

Bimetallic Au–Ag nanochains as SERS substrates

Au–Ag bimetallic nanochains were prepared using pulsed laser ablation in liquid medium. Synthesis was performed by ablating silver target in a gold colloidal suspension. The plasmon characteristics of the nanostructures are found to be sensitive to ablation duration. AFM and TEM images indicate that almost all nanoparticles, both Au and Ag in the suspension participate in the growth process. An attempt was also made to realize plasmon hybridization by reducing the volume of the suspension by simple evaporation. The nanochains were tested for application as SERS substrates by using crystal violet as probe molecules.     

聚吡咯修饰的金纳米棒对肿瘤的光学相干层析成像的影响

聚吡咯(PPy)制备简单、生物相容性好,且在近红外(NIR)光谱范围内有很强的吸收,可作为一种良好的光热治疗试剂;同时,其NIR光吸收性质也可用于增强光学相干层析成像(OCT)的对比效果。因此,采用PPy对传统的OCT对比试剂——金纳米棒(GNR)进行表面修饰,有望获得对比效果更好且生物毒性较小的新型OCT对比试剂。选用吡咯为起始原料,在GNR表面进行一步简单的氧化聚合反应即可制备得到PPy修饰的金纳米棒(GNR-PPy)。利用紫外-可见吸收光谱,拉曼光谱和透射电子显微镜对制备的样品进行了分析和表征。构建小鼠荷瘤模型,以研究GNR-PPy对肿瘤OCT图像对比度的增强效果。采用中心波长为840 nm的OCT系统对注射了纳米粒子的肿瘤区域进行OCT成像。结果表明,肿瘤组织注射了GNR-PPy后,OCT信号衰减非常明显;与注射了GNR的OCT图像相比,840 nm光在GNR-PPy的OCT图像中的穿透深度明显更低。从OCT图像中抽提出一维的衰减曲线对OCT图像进行定量分析,发现注射有GNR-PPy肿瘤组织的OCT信号衰减系数明显高于注射了GNR的组织。表明,相对于GNR,GNR-PPy具有更好的OCT信号对比效果,这在增强肿瘤成像效果方面具有潜在应用价值。     

Advantages of using gold hollow nanoshells in cancer photothermal therapy

Lots of studies have been conducted on the optical properties of gold nanoparticles in the first region of near infrared(650 nm–950 nm), however new findings show that the second region of near-infrared(1000 nm–1350 nm) penetrates to the deeper tissues of the human body. Therefore, using the above-mentioned region in photo-thermal therapy(PTT) of cancer will be more appropriate. In this paper, absorption efficiency is calculated for gold spherical and rod-shaped nanoshells by the finite element method(FEM). The results show that the surface plasmon frequency of these nanostructures is highly dependent on the dimension and thickness of shell and it can be adjusted to the second region of near-infrared. Thus, due to their optical tunability and their high absorption efficiency the hollow nanoshells are the most appropriate options for eradicating cancer tissues.     

Synthesis and photo physical properties of Au @ Ag (core @ shell) nanoparticles disperse in poly vinyl alcohol matrix

Synthesis of core @ shell (Au @ Ag) nanoparticle with varying silver composition has been carried out in aqueous poly vinyl alcohol (PVA) matrix. Core gold nanoparticle (~15 nm) has been synthesized through seed-mediated growth process. Synthesis of silver shell with increasing thickness (~1–5 nm) has been done by reducing Ag⁺ over the gold sol in the presence of mild reducing ascorbic acid. Characterization of Au @ Ag nanoparticles has been done by UV–Vis, High resolution transmission electron microscope (HRTEM) and energy dispersive X-ray (EDX) spectroscopic study. The blue shift of surface plasmon resonance (SPR) band with increasing mole fraction of silver has been interpreted due to dampening of core, i.e. Au SPR by Ag. The dependence of nonlinear optical response of spherical core @ shell nanoparticles has been investigated as a function of relative composition of each metal. Simulation of SPR extinction spectra based on quasi-static theory is done. A comparison of our experimental and the simulated extinction spectra using quasi-static theory of nanoshell suggests that our synthesized bimetallic particles have core @ shell structure rather than bimetallic alloy particles.