Size‐Dependent Thermochromism through Enhanced Electron–Phonon Coupling in 1 nm Quantum Dots

1 nm CuO quantum dots (QDs) were produced in size‐controlled super‐micropores of a silica matrix. The reversible color change of the QDs from pale blue to deep green was clearly observed in a wide temperature range from 298 to 673 K. This particular thermochromism is ascribed to an enhanced bandgap shift depending on temperature with a strong electron–phonon coupling in the confined space of the 1 nm QDs.     

A Simple Synthesis of an N‐Doped Carbon ORR Catalyst: Hierarchical Micro/Meso/Macro Porosity and Graphitic Shells

Replacing platinum as an oxygen reduction catalyst is an important scientific and technological challenge. Herein we report a simple synthesis of a complex carbon with very good oxygen reduction reaction (ORR) activity at pH 13. Pyrolysis of magnesium nitrilotriacetate yields a carbon with hierarchical micro/meso/macro porosity, resulting from in situ templating by spontaneously forming MgO nanoparticles and from etching by pyrolysis gases. The mesopores are lined with highly graphitic shells. The high ORR activity is attributed to a good balance between high specific surface area and mass transport through the hierarchical porosity, and to improved electronic conductivity through the graphitic shells. This novel carbon has a high surface area (1320 m²g^?1), and high nitrogen content for a single precursor synthesis (～6 %). Importantly, its synthesis is both cheap and easily scalable.     

量子点传感器测定水中微量银离子

选择铋试剂Ⅱ作为硫化镉(cds)量子点的修饰剂,合成了表面修饰的量子点,利用其有效官能团与银离子作用,导致修饰的量子点的荧光增强作用,建立了测定银离子的方法,开发了新型的银离子的传感器。结果表明,对水中银离子测定的线性范围为0.01~5.0μmol.L-1,相关系数为0.999 3,检测限达到1.6 nmol.L-1,对实际水样的分析获得了较满意的结果。     

The Influence of Surface Modification on the Photoluminescence of CdTe Quantum Dots: Realization of Bio‐Imaging via Cost‐Effective Polymer

To impart biocompatibility, stability, and specificity to quantum dots (QDs)—and to reduce their toxicity—it is essential to carry out surface modification. However, most surface‐modification processes are costly, complicated, and time‐consuming. In addition, the modified QDs often have a large size, which leads to easy aggregation in biological environments, making it difficult to excrete them from in vivo systems. To solve these problems, three kinds of conventional polymers, namely, polyvinyl alcohol (PVA, neutral), sodium polystyrene sulfonate (PSS, negative charged), and poly(diallyl dimethyl ammonium chloride) (PDDA, positive charged) were selected to modify the surface of QDs at low cost via a simple process in which the size of the QDs was kept small after modification. The effect of polymer modification on the photoluminescence (PL) properties of the QDs was systematically investigated. High quantum yields (QYs) of 65 % were reached, which is important for the realization of bio‐imaging. Then, the cytotoxicity of CdTe QD–polymer composites was systematically investigated via MTT assay using the Cal27 and HeLa cell lines, especially for high concentrations of QD–polymer composites in vitro. The experimental results showed that the cytotoxicity decreased in the order CdTe‐PDDA>CdTe>CdTe‐PSS>CdTe‐PVA, indicating that PSS and PVA can reduce the toxicity of the QDs. An obvious cytotoxicity of CdTe‐PVA and CdTe‐PSS was present until 120 h for the Cal27 cell line and until 168 h for the HeLa cell line. At last, the Cal27 cell line was selected to realize bio‐imaging using CdTe‐PSS and CdTe‐PVA composites with different emission colors under one excitation wavelength.     

Sensitive and Selective Determination of 2,4,6-Trichlorophenol Using a Molecularly Imprinted Polymer Based on Zinc Oxide Quantum Dots

Novel core-shell molecularly imprinted polymers were prepared based on zinc oxide quantum dots for the determination of 2,4,6-trichlorophenol by fluorescence. Principally, ZnO quantum dots and 2,4,6-trichlorophenol were chosen as the core substrate and the template molecule, respectively. The specific recognition sites for 2,4,6-trichlorophenol were obtained during the polymerization process in presence of 3-aminopropyltriethoxysilane and tetraethylorthosilicate. Molecularly imprinted ZnO quantum dots were characterized by transmission electron microscopy and Fourier transform infrared spectroscopy and the optical properties were evaluated by spectrofluorometry. Under the optimal conditions, molecularly imprinted ZnO quantum dots were successfully applied to the sensitive determination and selective recognition of 2,4,6-trichlorophenol in water. A linear relationship was obtained to cover the concentration range of 0–160?µmol?L^?1 with a correlation coefficient of 0.9931 calculated by the Stern–Volmer equation. The products were used for the determination of 2,4,6-trichlorophenol in the water from local rural areas and the results strongly supported that the molecularly imprinted ZnO quantum dots were suitable for the determination of 2,4,6-trichlorophenol in real examples.     

Research Update of Emergent Sulfur Quantum Dots in Synthesis and Sensing/Bioimaging Applications

Due to their unique optical property, low toxicity, high hydrophilicity, and low cost, sulfur quantum dots (SQDs), an emerging luminescent nanomaterial, have shown great potential in various application fields, such as sensing, bioimaging, light emitting diode, catalysis, and anti-bacteria. This minireview updates the synthetic methods and sensing/bioimaging applications of SQDs in the last few years, followed by discussion of the potential challenges and prospects in their synthesis and sensing/bioimaging applications, with the purpose to provide some useful information for researchers in this field.     

CdX(X=Se,Te,Te/ZnS)量子点脂质体的制备及毒性比较

在水相中以巯基乙酸(mercaptoacetic acid, MA)为稳定剂合成了CdSe、CdTe、CdTe/ZnS量子点及谷胱甘肽(glutathione, GSH)为稳定剂合成了CdTe量子点,然后通过卵磷脂和胆固醇修饰制得相应的量子点脂质体。溶血实验证实GSH修饰量子点的溶血率低于MA修饰的量子点45%;脂质体修饰后,量子点的溶血率＜5%,达到生物医用材料要求。不同表面修饰的量子点对小鼠毒性存在明显差异,荧光显微镜观察组织切片证实量子点在小鼠体内主要分布在肺、肾、胸腺等组织中,而脂质体量子点在脑组     

Visible-Light-Mediated Oxidative Amidation of Aldehydes by Using Magnetic CdS Quantum Dots as a Photocatalyst

A magnetic CdS quantum dot (Fe₃O₄/polydopamine (PDA)/CdS) was synthesized through a facile and convenient method from inexpensive starting materials. Characterization of the prepared catalyst was performed by means of FTIR spectroscopy, XRD, SEM, TEM, energy-dispersive X-ray spectroscopy, and vibrating-sample magnetometer techniques. Fe₃O₄/PDA/CdS was found to be a highly active photocatalyst for the amidation of aromatic aldehydes by using air as a clean oxidant under mild conditions. The photocatalyst can be recovered by magnetic separation and successfully reused for five cycles without considerable loss of its catalytic activity.     

Energy Transfer Between Eu3+ Ions and CdS Quantum Dots in Sol-Gel Derived CdS/SiO2 : Eu3+ Gel

We have investigated the energetic correlation between rare-earth ions and semiconductor nanocrystals, using europium ion (Eu³⁺) doped silica (SiO₂) gel with adsorbed cadmium sulfide (CdS) particles. Samples were prepared by a sol-gel technique, in which several methods for the precipitation of CdS colloids were attempted. The fluorescence intensities were compared for different gels, with and without CdS particles. The intrinsic emission lines due to ⁵D₀ ⁷F_J(J = 0–4) transitions of Eu³⁺ were observed, which were enhanced for 24 h-immersed gel (dried at 50°C). From the results on the decay dynamics of fluorescence, we proposed the model that surface-trapped electrons on CdS particles nonradiatively excited 4f electrons in Eu³⁺ ions due to an energy transfer process.     

Continuous‐Flow Synthesis of CdSe Quantum Dots: A Size‐Tunable and Scalable Approach

In recent years, continuous‐flow/microreactor processing for the preparation of colloidal nanocrystals has received considerable attention. The intrinsic advantages of microfluidic reactors have opened new opportunities for the size‐controlled synthesis of nanocrystals either in the laboratory or on a large scale. Herein, an experimentally simple protocol for the size‐tunable continuous‐flow synthesis of rather monodisperse CdSe quantum dots (QDs) is presented. CdSe QDs are manufactured by using cadmium oleate as cadmium source, selenium dioxide as selenium precursor, and 1‐octadecene as solvent. Exploiting selenium dioxide as selenium source and 1‐octadecene as solvent allows execution of the complete process in open air without any requirement for air‐free manipulations using a glove box or Schlenk line. Continuous‐flow processing is performed with a stainless steel coil of 1.0 mm inner diameter pumping the combined precursor solution through the reactor by applying a standard HPLC pump. The effect of different reaction parameters, such as temperature, residence time, and flow rate, on the properties of the resulting CdSe QDs was investigated. A temperature increase from 240 to 260 °C or an extension of the residence time from 2 to 20 min affords larger nanocrystals (range 3–6 nm) whereas the size distribution does not change significantly. Longer reaction times and higher temperatures result in QDs with lower quantum yields (range 11–28 %). The quality of the synthesized CdSe QDs was confirmed by UV/Vis and photoluminescence spectroscopy, small‐angle X‐ray scattering, and high‐resolution transmission electron microscopy. Finally, the potential of this protocol for large‐scale manufacturing was evaluated and by operating the continuous‐flow process for 87 min it was possible to produce 167 mg of CdSe QDs (with a mean diameter of 4 nm) with a quantum yield of 28 %.     

3,4-Dinitrobenzamide Functionalized CdTe/ZnTe Quantum Dots as a Nanoprobe for Imaging Glutathione S-Transferase in Living Cells

A novel fluorescent nanoprobe for glutathione S‐transferase (GST) has been developed by incorporating 3,4‐dinitrobenzamide (a specific substrate of GST) onto CdTe/ZnTe quantum dots. The probe itself displays a low background signal due to the strong quenching effect of the electron‐withdrawing unit of 3,4‐dinitrobenzamide on the quantum dots. However, GST can efficiently catalyze the nucleophilic substitution of reduced glutathione on the p‐nitro group of the nanoprobe, leading to a large fluorescence enhancement. Most notably, this enhancement shows high selectivity and sensitivity towards GST instead of the other biological substances. With this nanoprobe, a simple fluorescence imaging method for intracellular GST has been established, and its applicability has been successfully demonstrated for imaging GST in different living cells, which reveals that A549 cells express GST about 3 times higher than NIH‐3T3 and Hela cells.     

室温水相合成CdTe/CdS核/壳结构量子点

开发了一种以聚乙烯吡咯烷酮为分散剂和稳定剂经条件温和的室温水相合成光谱可调的水溶性CdTe/CdS核/壳结构量子点的方法:向新鲜制备的CdTe量子点溶液中加入硫源,继续反应即可生成CdS壳层,通过控制硫源的浓度即可控制CdS壳层厚度,从而调节光谱性质和增强稳定性.采用XRD、TEM、HRTEM、荧光光谱以及紫外-可见光...     

Mediated Drug Release from Nanovehicles by Black Phosphorus Quantum Dots for Efficient Therapy of Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is an intractable disease involving a sticky mucus layer and nanoagents with mucus-penetrating capability offer a new way to deliver drugs. However, drug release from nanovehicles requires optimization to enhance the therapeutic effects of COPD therapy. Herein, black phosphorus quantum dots (BPQDs) are combined with PEGylated chitosan nanospheres containing the antibiotic amikacin (termed PEG@CS/BPQDs-AM NPs). As a drug-delivery system, the hydrophilicity of PEG and positive charge of CS facilitate the penetration of nanovehicles through the mucus layer. The nanovehicles then adhere to the mucous membrane. Furthermore, the BPQDs degrade rapidly into nontoxic PO₄³⁻ and acidic H⁺, thereby promoting the dissociation of PEGylated CS nanospheres, accelerating the release of AM, decreasing the vitality of biofilms for ease of eradication. Our results reveal that drug delivery mediated by BPQDs is a feasible and desirable strategy for precision medicine and promising for the clinical therapy of COPD.     

Long-Range Transport in an Assembly of ZnO Quantum Dots: The Effects of Quantum Confinement,Coulomb Repulsion and Structural Disorder

We have studied the storage and long-range transport of electrons in a porous assembly of weakly coupled ZnO quantum dots permeated with an aqueous and a propylene carbonate electrolyte solution. The number of electrons per ZnO quantum dot is controlled by the electrochemical potential of the assembly; the charge of the electrons is compensated by ions present in the pores. We show with optical and electrical measurements that the injected electrons occupy the S, P, and D type conduction electron levels of the quantum dots; electron storage in surface states is not important. With this method of three-dimensional charge compensation, up to ten electrons per quantum-dot can be stored if the assembly is permeated with an aqueous electrolyte. The screening of the electron charge is less effective in the case of an assembly permeated with a propylene carbonate electrolyte solution. Long-range electron transport is studied with a transistor set-up. In the case of ZnO assemblies permeated with an aqueous electrolyte, two quantum regimes are observed corresponding to multiple tunnelling between the S orbitals (at a low occupation) and P orbitals (at a higher occupation). In a ZnO quantum-dot assembly permeated with a propylene carbonate electrolyte solution, there is a strong overlap between these two regimes.     

紫外-可见吸收、荧光光谱研究CdTe/CdS量子点与盐酸药根碱的相互作用及其应用

合成了巯基乙酸（TGA）修饰的壳核型CdTe/CdS量子点（TGA-CdTe/CdS QDs）。 利用紫外-可见光谱吸收、荧光光谱研究TGA-CdTe/CdS QDs与盐酸药根碱（JH）的相互作用机理。 在pH值为7.4的tris-HCl缓冲溶液介质中,QDs与JH相互作用后使QDs的荧光呈线性猝灭,并有良好的线性关系（r=0.999 1）,线性范围0.011~10 mg/L,检出限（3σ）为3.3×10-3 mg/L,因此可以作为一种快速、简便、定量测定盐酸药根碱的新方法。     

Tuning Optical Properties of Si Quantum Dots by π‐Conjugated Capping Molecules

The absorption and photoluminescence (PL) properties of silicon quantum dots (QDs) are greatly influenced by their size and surface chemistry. Herein, we examined the optical properties of three Si QDs with increasing σ–π conjugation length: octyl‐, (trimethylsilyl)vinyl‐, and 2‐phenylvinyl‐capped Si QDs. The PL photon energy obtained from as‐prepared samples decreased by 0.1–0.3 eV, while the PL excitation (PLE) extended from 360 nm (octyl‐capped Si QDs) to 400 nm (2‐phenylvinyl‐capped Si QDs). A vibrational PL feature was observed in all samples with an energy separation of about 0.192±0.013 eV, which was explained based on electron–phonon coupling. After soft oxidization through drying, all samples showed blue PL with maxima at approximately 410 nm. A similar high‐energy peak was observed with the bare Si QD sample. The changes in the optical properties of Si QDs were mainly explained by the formation of additional states arising from the strong σ–π conjugation and QD oxidation.