Polydopamine dots as an ultrasensitive fluorescent probe switch for Cr(VI) in vitro

Because of the great demand for fluorescent materials, fluorescent dyes, semiconductor quantum dots, and carbon‐based quantum dots have been studied extensively. However, the poor photostability and potential biological toxicity need to be resolved. In this study, we demonstrated the synthesis of a new biomass quantum dot, the polydopamine dot (PDADs), via a simple hydrothermal method under an acidic environment. This new biomass quantum dot showed not only remarkable photoluminescence properties (quantum yield = 0.93) but also a high stability and low toxicity. Moreover, these PDADs could be used as a fluorescent probe for the rapid detection of Cr(VI) (response time = 0.01 s). The detection limit (1 × 10^?11 M ) is the lowest detection limit reported for Cr(VI) fluorescent probes. The mechanism efficient quenching progress could have been due to the fast redox progress between the PDADs and Cr(VI). Moreover, we also showed a practical application of PDADs for Cr(VI) detection in vitro . © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44784.     

Simplistic hydrothermal synthesis approach for fabricating photoluminescent carbon dots and its potential application as an efficient sensor probe for toxic lead(II) ion detection

The past decade has witnessed a variety of members of the carbon family along with exposure of carbon dots due to their magnificent properties in sensing, bioimaging, catalytic applications, biomedical fields, and so on. Herein, we report the simple hydrothermal method to fabricate photoluminescent doped carbon quantum dots for the detection of noxious lead(II) ions. Lead(II) ion is very venomous for both the environment and human health for which its detection is demanded area in the research field. The as-prepared carbon dots show excellent photostability, low toxicity and significant photoluminescence properties along with good water solubility. Along with these properties, carbon dots have a quantum yield of approximately 15%. In the practical field of application, these carbon dots have been used as sensing probes for the detection of lead(II) ions with a detection limit of 60 nmol·L^–1. The fluorescence intensity of carbon dots was remarkably quenched in the presence of the lead(II) ion selectively among all the tested metal ions. Furthermore, we have studied the Stern–Volmer relationship for lead(II) quenching along with the explanation of the probable quenching mechanism. Ability of the doped carbon dots in heavy metal ions sensing in an environmental sample was demonstrated.     

The Influence of a Continuum Background on Carrier Relaxation in InAs/InGaAs Quantum Dot

We have investigated the ultra-fast carrier dynamics in Molecular Beam Epitaxy (MBE)-grown InAs/InGaAs/GaAs quantum dots (QDs) emitting at 1.3 μm by time resolved photoluminescence (TRPL) upconversion measurements with a time resolution of about 200 fs. Changing the detection energies in the spectral region from the energy of the quantum dots excitonic transition up to the barrier layer absorption edge, we have found that, under high excitation intensity, the intrinsic electronic states are populated mainly by carriers directly captured from the barrier.     

One-Pot Synthesis of Biocompatible CdSe/CdS Quantum Dots and Their Applications as Fluorescent Biological Labels

We developed a novel one-pot polyol approach for the synthesis of biocompatible CdSe quantum dots (QDs) using poly(acrylic acid) (PAA) as a capping ligand at 240°C. The morphological and structural characterization confirmed the formation of biocompatible and monodisperse CdSe QDs with several nanometers in size. The encapsulation of CdS thin layers on the surface of CdSe QDs (CdSe/CdS core–shell QDs) was used for passivating the defect emission (650 nm) and enhancing the fluorescent quantum yields up to 30% of band-to-band emission (530–600 nm). Moreover, the PL emission peak of CdSe/CdS core–shell QDs could be tuned from 530 to 600 nm by the size of CdSe core. The as-prepared CdSe/CdS core–shell QDs with small size, well water solubility, good monodispersity, and bright PL emission showed high performance as fluorescent cell labels in vitro. The viability of QDs-labeled 293T cells was evaluated using a 3-(4,5-dimethylthiazol)-2-diphenyltertrazolium bromide (MTT) assay. The results showed the satisfactory (>80%) biocompatibility of as-synthesized PAA-capped QDs at the Cd concentration of 15 μg/ml.     

Interaction of Water-Soluble CdTe Quantum Dots with Bovine Serum Albumin

Semiconductor nanoparticles (quantum dots) are promising fluorescent markers, but it is very little known about interaction of quantum dots with biological molecules. In this study, interaction of CdTe quantum dots coated with thioglycolic acid (TGA) with bovine serum albumin was investigated. Steady state spectroscopy, atomic force microscopy, electron microscopy and dynamic light scattering methods were used. It was explored how bovine serum albumin affects stability and spectral properties of quantum dots in aqueous media. CdTe–TGA quantum dots in aqueous solution appeared to be not stable and precipitated. Interaction with bovine serum albumin significantly enhanced stability and photoluminescence quantum yield of quantum dots and prevented quantum dots from aggregating.     

Fluorophosphate glasses doped with PbSe quantum dots and their nonlinear optical characteristics

A new fluorophosphate glass matrix containing PbSe quantum dots characterized by a narrow size distribution (ΔR/R ∼ 5–7%, where R is the size of a quantum dot) is prepared under heat treatment. It is demonstrated that fluorophosphate glasses can be doped by introducing (ZnSe + PbO) or PbSe into the composition of the glass. The optical absorption spectra of the quantum dots corresponding to the strong quantum confinement regime are studied over a wide range of quantum-dot sizes (4–18 nm). The nonlinear optical absorption is investigated at a wavelength of 1.54 μm. It is revealed that the introduction of (ZnSe + PbO) rather than of PbSe into the composition of the glass improves the bleaching contrast owing to a more uniform distribution of the quantum dots over the volume of the glass sample.     

Synthesis and Spectral Studies of CdTe–Dendrimer Conjugates

In order to couple high cellular uptake and target specificity of dendrimer molecule with excellent optical properties of semiconductor nanoparticles, the interaction of cysteine-capped CdTe quantum dots with dendrimer was investigated through spectroscopic techniques. NH₂-terminated dendrimer molecule quenched the photoluminescence of CdTe quantum dots. The binding constants and binding capacity were calculated, and the nature of binding was found to be noncovalent. Significant decrease in luminescence intensity of CdTe quantum dots owing to noncovalent binding with dendrimer limits further utilization of these nanoassemblies. Hence, an attempt is made, for the first time, to synthesize stable, highly luminescent, covalently linked CdTe–Dendrimer conjugate in aqueous medium using glutaric dialdehyde (G) linker. Conjugate has been characterized through Fourier transform infrared spectroscopy and transmission electron microscopy. In this strategy, photoluminescence quantum efficiency of CdTe quantum dots with narrow emission bandwidths remained unaffected after formation of the conjugate.     

Synthesis of Aqueous CdTe/CdS/ZnS Core/shell/shell Quantum Dots by a Chemical Aerosol Flow Method

This work described a continuous method to synthesize CdTe/CdS/ZnS core/shell/shell quantum dots. In an integrated system by flawlessly combining the chemical aerosol flow system working at high temperature (200–300°C) to generate CdTe/CdS intermediate products and an additional heat-up setup at relatively low temperature to overcoat the ZnS shells, the CdTe/CdS/ZnS multishell structures were realized. The as-synthesized CdTe/CdS/ZnS core/shell/shell quantum dots are characterized by photoluminescence spectra, X-ray diffraction (XRD), energy-dispersive X-ray spectra (EDS), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). Fluorescence and XRD results confirm that the obtained quantum dots have a core/shell/shell structure. It shows the highest quantum yield above 45% when compared to the rhodamine 6G. The core/shell/shell QDs were more stable via the oxidation experiment by H₂O₂.     

Quantum dot-aptamer nanoprobes for recognizing and labeling influenza A virus particles

The fluorescence labeling of viruses is a useful technology for virus detection and imaging. By combining the excellent fluorescence properties of quantum dots (QDs) with the high affinity and specificity of aptamers, we constructed a QD-aptamer probe. The aptamer A22, against the hemagglutinin of influenza A virus, was linked to QDs, producing the QD-A22 probe. Fluorescence imaging and transmission electron microscopy showed that the QD-A22 probe could specifically recognize and label influenza A virus particles. This QD labeling technique provides a new strategy for labeling virus particles for virus detection and imaging.     

Temperature-Dependent Site Control of InAs/GaAs (001) Quantum Dots Using a Scanning Tunneling Microscopy Tip During Growth

Site-controlled InAs nano dots were successfully fabricated by a STMBE system (in situ scanning tunneling microscopy during molecular beam epitaxy growth) at substrate temperatures from 50 to 430°C. After 1.5 ML of the InAs wetting layer (WL) growth by ordinal Stranski–Krastanov dot fabrication procedures, we applied voltage at particular sites on the InAs WL, creating the site where In atoms, which were migrating on the WL, favored to congregate. At 240°C, InAs nano dots (width: 20–40 nm, height: 1.5–2.0 nm) were fabricated. At 430°C, InAs nano dots (width: 16–20 nm, height: 0.75–1.5 nm) were also fabricated. However, these dots were remained at least 40 s and collapsed less than 1000 s. Then, we fabricated InAs nano dots (width: 24–150 nm, height: 2.8–28 nm) at 300°C under In and As₄ irradiations. These were not collapsed and considered to high crystalline dots.     

Single-dot Spectroscopy of GaAs Quantum Dots Fabricated by Filling of Self-assembled Nanoholes

We study the optical emission of single GaAs quantum dots (QDs). The QDs are fabricated by filling of nanoholes in AlGaAs and AlAs which are generated in a self-assembled fashion by local droplet etching with Al droplets. Using suitable process parameters, we create either uniform QDs in partially filled deep holes or QDs with very broad size distribution in completely filled shallow holes. Micro photoluminescence measurements of single QDs of both types establish sharp excitonic peaks. We measure a fine-structure splitting in the range of 22–40μeV and no dependence on QD size. Furthermore, we find a decrease in exciton–biexciton splitting with increasing QD size.     

Impacts of Post-metallisation Processes on the Electrical and Photovoltaic Properties of Si Quantum Dot Solar Cells

As an important step towards the realisation of silicon-based tandem solar cells using silicon quantum dots embedded in a silicon dioxide (SiO₂) matrix, single-junction silicon quantum dot (Si QD) solar cells on quartz substrates have been fabricated. The total thickness of the solar cell material is 420 nm. The cells contain 4 nm diameter Si quantum dots. The impacts of post-metallisation treatments such as phosphoric acid (H₃PO₄) etching, nitrogen (N₂) gas anneal and forming gas (Ar: H₂) anneal on the cells’ electrical and photovoltaic properties are investigated. The Si QD solar cells studied in this work have achieved an open circuit voltage of 410 mV after various processes. Parameters extracted from dark I–V, light I–V and circular transfer length measurement (CTLM) suggest limiting mechanism in the Si QD solar cell operation and possible approaches for further improvement.     

Fluorescence-based assay formats and signal amplification strategies for DNA microarray analysis

DNA microarrays are powerful tools for the high throughput analysis of nucleic acids due to their parallel detection capabilities. To realize the apparent power of DNA microarray, an efficient assay format is essential and a variety of assay formats have been developed for nucleic acid detection on microarrays. Many of them employ fluorescence-based methods because fluorescence detection is straightforward and easy to implement. Herein we broadly review fluorescence-based assay formats with a focus on PCR-associated target preparation. For the heterogeneous assay of nucleic acid on DNA microarrays, sensitivity is one of the most important factors and special emphasis has been given to recently developed signal amplification strategies aimed at achieving high sensitivity.     

Single InGaAs Quantum Dot Coupling to the Plasmon Resonance of a Metal Nanocrystal

We report the observation of coupling of single InGaAs quantum dots with the surface plasmon resonance of a metal nanocrystal, which leads to clear enhancement of the photoluminescence in the spectral region of the surface plasmon resonance of the metal structures. Sharp emission lines, typical for single quantum dot emission, are observed, whereas for reference samples, only weak continuous background emission is visible. The composite metal–semiconductor structure is prepared by molecular beam epitaxy utilizing the principle of strain-driven adatom migration for the positioning of the metal nanocrystals with respect to the quantum dots without use of any additional processing steps.     

Direct Interband Light Absorption in Strongly Prolated Ellipsoidal Quantum Dots’ Ensemble

Within the framework of adiabatic approximation, the energy levels and direct interband light absorption in a strongly prolated ellipsoidal quantum dot are studied. Analytical expressions for the particle energy spectrum and absorption threshold frequencies in three regimes of quantization are obtained. Selection rules for quantum transitions are revealed. Absorption edge and absorption coefficient for three regimes of size quantization (SQ) are also considered. To facilitate the comparison of obtained results with the probable experimental data, size dispersion distribution of growing quantum dots by the small semiaxe in the regimes of strong and weak SQ by two experimentally realizing distribution functions have been taken into account. Distribution functions of Lifshits–Slezov and Gaussian have been considered.     

石墨烯量子点修饰柔性硅纳米线阵列用于NO2检测

将化学刻蚀法与金属辅助刻蚀法相结合,制备了形貌统一、分布均匀的高质量柔性硅纳米线阵列结构,用石墨烯量子点对其表面进行修饰,得到了表面稳定且具有强载流子传输能力的柔性石墨烯量子点/硅纳米线核?壳结构阵列,用其制备气敏设备检测NO2. 结果表明,基于该阵列的电阻式气敏设备对NO2的检测灵敏性及可重复性极高,检测浓度极限达20 mg/m3;不同弯曲度的柔性石墨烯量子点/硅纳米线阵列的气敏特性未大幅度降低,弯曲90o时响应电流峰值为未弯曲时的70%.     

A quantum dots and superparamagnetic nanoparticle-based method for the detection of HPV DNA

Background

The recent advance in nanomaterial research field prompts the development of diagnostics of infectious diseases greatly. Many nanomaterials have been developed and applied to molecular diagnostics in labs. At present, the diagnostic test of human papillomavirus (HPV) relies exclusively on molecular test. Hereon, we report a rapid and facile quantum dots (QDs) and superparamagnetic nanoparticle-based hybridization assay for the detection of (HPV) 16 infections which combines the merits of superparamagnetic nanoparticles and QDs and wholly differs from a conventional hybridization assay at that the reaction occurs at homogeneous solution, and total time for detection is no more than 1 h.

Methods

The probes were labeled with superparamagnetic nanoparticles and QDs. Sixty cervical swab samples were used to perform a hybridization assay with these probes, and the results were compared with type-specific polymerase chain reaction (PCR) method.

Results

The statistic analysis suggests that there is no significant difference between these two methods. Furthermore, this method is much quicker and easier than the type-specific PCR method.

Conclusion

This study has successfully validated the clinical performance of our hybridization assay. The advantages in the time of detection and ease of process endow this method with great potential in clinical usage, especially mass epidemiological screening.     

Magnetic-Fluorescent Nanocomposites Fe3O4@SiO2@ZnSe: Preparation and Characterization

Fe₃O₄@SiO₂@ZnSe composite nanoparticles with superparamagnetism and luminescence have been prepared by a facile chemical method. Nontoxic fluorescent ZnSe quantum dots were assembled around the Fe₃O₄-silica core–shell nanocomposite via chemical bonds formed between –COOH and –NH₂. Transmission electron microscopy images show that the nanocomposites are approximately spherical and between 50 nm and 80 nm in size. The bifunctional nanocomposites exhibit superparamagnetic behavior and good fluorescence intensity. Magnetic attraction test, vibrating sample magnetometer at 300 K, UV–visible absorption and fluorescence emission spectroscopy were applied to characterize the magnetic/fluorescent properties of the nanocomposites.     

CdSe@ZnS量子点荧光传感器在水体铜离子污染检测中的应用

使用微流控技术连续合成CdSe@ZnS核壳型量子点,并使用巯基丙酸对其进行表面改性,制备出可以被铜离子淬灭的水溶性CdSe@ZnS核壳型量子点。随后以聚乙烯醇（PVA）水凝胶为骨架,将改性后的量子点通过氢键作用力负载于骨架上,得到制备工艺简单、热稳定性高的复合荧光传感器件。该传感器的荧光强度随水溶液中铜离子浓度呈线性负相关关系,检测灵敏度可达20 μmol/L。其简便的操作和敏感的响应使之与原子吸收分光光度法形成优势互补,适用于水体铜离子污染的原位检测。该负载方法具有一定普适性,提供了将任意量子点制成器件应用于某种金属离子检测的新方式,实现了可回收的、环境友好的重金属离子快速检测目的。     

量子点荧光纳米材料的化学合成及其在潜手印显现中的应用

随着纳米科技的发展,将量子点荧光纳米材料作为一种新型显现试剂并应用于潜手印显现技术已引起了研究者的浓厚兴趣。合成出高质量、高荧光性能的量子点是拓展其在手印显现方面广泛应用的前提条件。本文针对量子点荧光纳米材料的化学法合成及其在潜手印显现领域中的应用进展进行了较为详尽的归纳和总结。