Plasmonic Effect on the Optical Properties in a Hybrid V-Type Three-Level Quantum Dot-Metallic Nanoparticle Nanosystem

We investigated theoretically the exciton–plasmon coupling effects on the population dynamics and the absorption properties of a hybrid nanosystem composed of a metal nanoparticle (MNP) and a V-type three-level semiconductor quantum dot (SQD), which are created by the interaction with the induced dipole moments in the SQD and the MNP, respectively. Excitons of the SQD and the plasmons of the MNP in such a hybrid nanosystem could be coupled strongly or weakly to demonstrate novel properties of the hybrid system. We also find that the gain happens in such a hybrid system, because of the coherent interaction between the SQD and the MNP. Our results show that the non-linear optical response of the hybrid nanosystem can be greatly enhanced or depressed due to the exciton–plasmon couplings.     

The Interactions of Glutathione-Capped CdTe Quantum Dots with Trypsin

Due to their unique fluorescent properties, quantum dots present a great potential for biolabelling applications; however, the toxic interactions of quantum dots with biopolymers are little known. The toxic interactions of glutathione-capped CdTe quantum dots with trypsin were studied in this paper using synchronous fluorescence spectroscopy, fluorescence emission spectra, and UV–vis absorption spectra. The interaction between CdTe quantum dots and trypsin resulted in structure changes of trypsin and inhibited trypsin's activity. Fluorescence emission spectra revealed that the quenching mechanism of trypsin by CdTe quantum dots was a static quenching process. The binding constant and the number of binding sites at 288 and 298 K were calculated to be 1.98 × 10⁶ L mol⁻¹ and 1.37, and 6.43 × 10⁴ L mol⁻¹ and 1.09, respectively. Hydrogen bonds and van der Waals' forces played major roles in this process.     

Luminescence Enhancement of Carboxyl-Coated CdTe Quantum Dots by Silver Nanoparticles

Metallic nanoparticles (NPs) have been used to improve the sensibility of biosensors and bioassays either by enhancing radiative emission or inducing quenching process on fluorescent probes. The aim of this research was to study the interaction of silver and silver-pectin NPs with water-dispersed carboxyl-coated cadmium telluride (CdTe) quantum dots (QDs). Metallic NPs were observed to change the emission of these fluorophores through local field effects. In a solution-base platform, an increase of 82 % was observed for the CdTe emission due to the interaction of QDs and silver-pectin NPs. QDs interaction with silver NPs without pectin was also investigated and a smaller emission enhancement of 20 % was detected. We observed that the NPs’ nature and QDs’ surface charge and concentration are important parameters for NPs-QDs interaction. Moreover, the presence of the pectin polymer shows to be a key component to the observed fluorescence enhancement.     

Modification of Spontaneous Emission Rates of Self-assembled CdSe Quantum Dots by Coupling to Hybrid Optical Nanoantennas

Plasmonics - The spontaneous emission of a light source can be modified by tailoring its local density of optical states. Indeed, this concept has been commonly utilized to enhance the spontaneous...     

Photon Statistics of a Hybrid Quantum Dot-Metal Nanoparticle Cluster

A theoretical study of photon statistics of an optically driven quantum dot located near a metal nanoparticle cluster (composed of one or two nanoparticles) is presented. Considering the system in the weak Rabi frequency regime, an analytical formula for anti-bunching time is derived. Using a photon Green’s function method based on the exact quantization of electromagnetic field in a dissipative medium, the dependence of the anti-bunching time on the geometrical parameters (quantum dot radius and quantum dot distance from the metal nanoparticle) is studied. The results show that these geometrical parameters have pronounced impacts on the photon statistics. Furthermore, our findings reveal that the quantum dot dipole orientation possesses an important role in the quantum dot photon emission.     

Detecting the Quantity of Acrylamide in Potato Chips Utilizing CdTe Surface Functionalized Quantum Dots with Fluorescence Spectroscopy

International Journal of Peptide Research and Therapeutics - According to the classification of the International Agency for Research on Cancer (IARC), acrylamide is a compound in “probably...     

Quantum Dots in Cell Biology

Quantum dots are semiconductor nanocrystals that have broad excitation spectra, narrow emission spectra, tunable emission peaks, long fluorescence lifetimes, negligible photobleaching, and ability to be conjugated to proteins, making them excellent probes for bioimaging applications. Here the author reviews the advantages and disadvantages of using quantum dots in bioimaging applications, such as single-particle tracking and fluorescence resonance energy transfer, to study receptor-mediated transport.     

在光动力疗法中应用的量子点

概述了现存的主要量子点的构成及其特点,阐述了量子点的性质主要由量子点的成分、结构、包覆和尺寸所决定。并重点讨论量子点在光动力疗法中,量子点直接代替传统光敏剂、量子点的荧光共振能量转移、量子点作为宽禁带半导体材料TiO2的敏化剂等三种不同应用中,对量子点的要求,通过讨论指出由于其特性,量子点将在光动力疗法中得到更广泛的应用,也对在光动力疗法中应用的量子点的毒性及其他可能产生的问题提出了展望。     

量子点在生物学中的研究进展

量子点作为一种新型的荧光标记物近年来已在生物学中获得广泛应用。本文总结了量子点的主要光学特性,其中包括荧光激发和发射光谱特性、量子产额、光漂白特性和荧光寿命等。重点综述了量子点在细胞标记、活体和组织成像、组合标记和光动力学治疗等生物学中的应用及其最新研究进展。同时讨论了量子点在应用中可能存在的细胞毒性等主要问题,最后对量子点在生物学中的应用前景作了展望。     

CdSe/ZnS-SA量子点细胞毒性的初步研究

目的：探讨链亲和素修饰的CdSe/ZnS核壳结构量子点（CdSe/ZnS-SA）对稳定转染pcDNA3.1/APP595/596质粒的人胚肾（HEK293）细胞的短期毒性作用.方法：将CdSe/ZnS-SA量子点与稳定转染pcD-NA3.1/APP595/596质粒的HEK293细胞共培育,在倒置荧光显微镜下观察细胞形态学变化;MTT法测定细胞活性;流式细胞术检测细胞凋亡率.结果：终浓度为2.5 nmol/L-20 nmol/L的CdSe/ZnS-SA量子点与HEK293细胞分别共育8h、16h、24 h后,细胞的形态无明显改变;终浓度为2.5 nmol/L-25 nmol/L的CdSe/ZnS-SA量子点与HEK293细胞分别共育8h、16 h、24 h,各处理组与对照组间,各处理组间的吸光度值、细胞凋亡率差异均无统计学意义（P＞0.05）.结论：一定浓度范围的CdSe/ZnS-SA量子点在短期内对稳定转染pcDNA3.1/APP595/596质粒的HEK293细胞无明显的毒性作用,具有较好的生物相容性.     

量子点在癌症研究中的应用

半导体量子点具有长时间、多目标和灵敏度高等独特的光化学性质,这些特性使量子点成为细胞标记和生物应用中得到了广泛的应用。利用量子点目标定位癌细胞,对于寻找癌变部位具有指导的作用。近年来,利用量子点作为光动力学治疗癌症的能量供体也得到了一定的研究。简单地介绍了量子点独特的光学性质,并从量子点标记癌细胞、可视化癌细胞表面功能和在光动力学治疗癌症等方面综述了量子点在癌症诊断和治疗中的应用。     

综述——基于纳米材料的生物检测与医学诊断技术：功能化量子点在肿瘤活体成像中的应用

量子点表面经生物分子或药物分子修饰而具有生物功能．功能化量子点具有独特的光学性质和生物相容性,在生物医学光学诊断和治疗领域具有广泛的应用．本文简要介绍了功能化量子点制备及修饰方法,综合评述了量子点在肿瘤活体诊断和治疗中的应用,包括活体淋巴结成像、血管动态成像、肿瘤成像和抗肿瘤药物示踪等,讨论了功能化量子点在肿瘤活体诊断和治疗中的应用前景以及面临的挑战．     

Synthesis,Characterization, and Functionalization of Hybrid Au/CdS and Au/ZnS Core/Shell Nanoparticles

Plasmonic nanoparticles are an attractive material for light harvesting applications due to their easily modified surface, high surface area and large extinction coefficients which can be tuned across the visible spectrum. Research into the plasmonic enhancement of optical transitions has become popular, due to the possibility of altering and in some cases improving photo-absorption or emission properties of nearby chromophores such as molecular dyes or quantum dots. The electric field of the plasmon can couple with the excitation dipole of a chromophore, perturbing the electronic states involved in the transition and leading to increased absorption and emission rates. These enhancements can also be negated at close distances by energy transfer mechanism, making the spatial arrangement of the two species critical. Ultimately, enhancement of light harvesting efficiency in plasmonic solar cells could lead to thinner and, therefore, lower cost devices. The development of hybrid core/shell particles could offer a solution to this issue. The addition of a dielectric spacer between a gold nanoparticles and a chromophore is the proposed method to control the exciton plasmon coupling strength and thereby balance losses with the plasmonic gains. A detailed procedure for the coating of gold nanoparticles with CdS and ZnS semiconductor shells is presented. The nanoparticles show high uniformity with size control in both the core gold particles and shell species allowing for a more accurate investigation into the plasmonic enhancement of external chromophores.     

Effect of CdTe Quantum Dots Size on the Conformational Changes of Human Serum Albumin: Results of Spectroscopy and Isothermal Titration Calorimetry

Quantum dots (QDs) are recognized as some of the most promising candidates for future applications in biomedicine. However, concerns about their safety have delayed their widespread application. Human serum albumin (HSA) is the main protein component of the circulatory system. It is important to explore the interaction of QDs with HSA for the potential in vivo application of QDs. Herein, using spectroscopy and isothermal titration calorimetry (ITC), the effect of glutathione-capped CdTe quantum dots of different sizes on the HSA was investigated. After correction for the inner filter effect, the fluorescence emission spectra and synchronous fluorescence spectra showed that the microenvironment of aromatic acid residues in the protein was slightly changed when the glutathione (GSH)–cadmium telluride (CdTe) QDs was added, and GSH–CdTe QDs with larger particle size exhibited a much higher effect on HSA than the small particles. Although a ground-state complex between HSA and GSH–CdTe QDs was formed, the UV–vis absorption and circular dichroism spectroscopic results did not find appreciable conformational changes of HSA. ITC has been used for the first time to characterize the binding of QDs with HSA. The ITC results revealed that the binding was a thermodynamically spontaneous process mainly driven by hydrophobic interactions, and the binding constant tended to increase as the GSH–CdTe QDs size increased. These findings are helpful in understanding the bioactivities of QDs in vivo and can be used to assist in the design of biocompatible and stable QDs.     

量子点的制备及其在生物医学中的研究

量子点是近几年发展起来的新型纳米材料,虽然研究起步较晚,但因其独特的电学和光学性质而成为人们关注的热点,在生物医学等多个领域有突破性的研究进展。本文主要介绍量子点的性质、制备方法及其在生物医学中的应用进展和存在的问题。     

Plasmonic Coupling in Er3+:Au Tellurite Glass

In this paper, we report on luminescence and absorbance effects of Er⁺³:Au-doped tellurite glasses synthesized by a melting-quenching and heat treatment technique. After annealing times of 2.5, 5.0, 7.5, and 10.0 h, at 300 °C, the gold nanoparticles (GNP) effects on the Er⁺³ are verified from luminescence spectra and the corresponding levels lifetime. The localized surface plasmon resonance around 800 nm produced a maximum fluorescence enhancement for the band ranging from 800 to 840 nm, corresponding to the transitions ⁴H_11/2 → ⁴I_13/2 (805 nm) and ⁴S_3/2 → ⁴I_13/2 (840 nm), with annealing time till 7.5 h. The measured lifetime of the levels ⁴H_11/2 and ⁴S_3/2 confirmed the lifetime reduction due to the energy transfer from the GNP to Er⁺³, causing an enhanced photon emission rate in these levels.     

Neurexin/Neuroligin Interaction Kinetics Characterized by Counting Single Cell-Surface Attached Quantum Dots

We report what to our knowledge is a new method to characterize kinetic rates between cell-surface-attached adhesion molecules. Cells expressing specific membrane receptors are surface-labeled with quantum dots coated with their respective ligands. The progressive diminution in the total number of surface-diffusing quantum dots tracked over time collectively reflects intrinsic ligand/receptor interaction kinetics. The probability of quantum dot detachment is modeled using a stochastic analysis of bond formation and dissociation, with a small number of ligand/receptor pairs, resulting in a set of coupled differential equations that are solved numerically. Comparison with the experimental data provides an estimation of the kinetic rates, together with the mean number of ligands per quantum dot, as three adjustable parameters. We validate this approach by studying the calcium-dependent neurexin/neuroligin interaction, which plays an important role in synapse formation. Using primary neurons expressing neuroligin-1 and quantum dots coated with purified neurexin-1β, we determine the kinetic rates between these two binding partners and compare them with data obtained using other techniques. Using specific molecular constructs, we also provide interesting information about the effects of neurexin and neuroligin dimerization on the kinetic rates. As it stands, this simple technique should be applicable to many types of biological ligand/receptor pairs.