Toxicity of CdTe Quantum Dots on Yeast Saccharomyces Cerevisiae

Along with the widespread development of their bioapplications, concerns about the biosafety of quantum dots (QDs) have increasingly attracted intensive attention. This study examines the toxic effect and subcellular location of cadmium telluride (CdTe) QDs with different sizes against yeast Saccharomyces cerevisiae. The innovative approach is based on the combination of microcalorimetric, spectroscopic, electrochemical, and microscopic methods, which allows analysis of the toxic effect of CdTe QDs on S. cerevisiae and its mechanism. According to the values of the half inhibitory concentration (IC(50) ), CdTe QDs exhibit marked cytotoxicity in yeast cells at concentrations as low as 80.81 nmol L(-1) for green-emitting CdTe QDs and 17.07 nmol L(-1) for orange-emitting CdTe QDs. QD-induced cell death is characterized by cell wall breakage and cytoplasm blebbing. These findings suggest that QDs with sizes ranging from 4.1 to 5.8 nm can be internalized into yeast cells, which then leads to QD-induced cytotoxicity. These studies provide valuable information for the design and development of aqueous QDs for biological applications.     

Biocompatible Semiconductor Quantum Dots as Cancer Imaging Agents

Approximately 1.7 million new cases of cancer will be diagnosed this year in the United States leading to 600 000 deaths. Patient survival rates are highly correlated with the stage of cancer diagnosis, with localized and regional remission rates that are much higher than for metastatic cancer. The current standard of care for many solid tumors includes imaging and biopsy with histological assessment. In many cases, after tomographical imaging modalities have identified abnormal morphology consistent with cancer, surgery is performed to remove the primary tumor and evaluate the surrounding lymph nodes. Accurate identification of tumor margins and staging are critical for selecting optimal treatments to minimize recurrence. Visible, fluorescent, and radiolabeled small molecules have been used as contrast agents to improve detection during real‐time intraoperative imaging. Unfortunately, current dyes lack the tissue specificity, stability, and signal penetration needed for optimal performance. Quantum dots (QDs) represent an exciting class of fluorescent probes for optical imaging with tunable optical properties, high stability, and the ability to target tumors or lymph nodes based on surface functionalization. Here, state‐of‐the‐art biocompatible QDs are compared with current Food and Drug Administration approved fluorophores used in cancer imaging and a perspective on the pathway to clinical translation is provided.     

In Vivo NIR-II Fluorescence Lifetime Imaging of Whole-Body Vascular Using High Quantum Yield Lanthanide-Doped Nanoparticles

Second near infrared (NIR-II, 1000–1700 nm) fluorescence lifetime imaging is a powerful tool for biosensing, anti-counterfeiting, and multiplex imaging. However, the low photoluminescence quantum yield (PLQY) of fluorescence probes in NIR-II region limits its data collecting efficiency and accuracy, especially in multiplex molecular imaging in vivo. To solve this problem, lanthanide-doped nanoparticles (NPs) β-NaErF₄: 2%Ce@NaYbF₄@NaYF₄ with high PLQY and tunable PL lifetime through multi-ion doping and core–shell structural design, are presented. The obtained internal PLQY can reach up to 50.1% in cyclohexane and 9.2% in water under excitation at 980 nm. Inspired by the above results, a fast NIR-II fluorescence lifetime imaging of whole-body vascular in mice is successfully performed by using the homebuilt fluorescence lifetime imaging system, which reveals a murine abdominal capillary network with low background. A further demonstration of fluorescence lifetime multiplex imaging is carried out in molecular imaging of atherosclerosis cells and different organs in vivo through NPs conjugating with specific peptides and different injection modalities, respectively. These results demonstrate that the high PLQY NPs combined with the homebuilt fluorescence lifetime imaging system can realize a fast and high signal-to-noise fluorescence lifetime imaging; thus, opening a road for multiplex molecular imaging of atherosclerosis.     

Ultrasmall Near‐Infrared Non‐cadmium Quantum Dots for in vivo Tumor Imaging

The high tumor uptake of ultrasmall near‐infrared quantum dots (QDs) attributed to the enhanced permeability and retention effect is reported. InAs/InP/ZnSe QDs coated by mercaptopropionic acid (MPA) exhibit an emission wavelength of about 800 nm (QD800‐MPA) with very small hydrodynamic diameter (<10 nm). Using 22B and LS174T tumor xenograft models, in vivo and ex vivo imaging studies show that QD800‐MPA is highly accumulated in the tumor area, which is very promising for tumor detection in living mice. The ex vivo elemental analysis (Indium) using inductively coupled plasma (ICP) spectrometry confirm the tumor uptake of QDs. The ICP data are consistent with the in vivo and ex vivo fluorescence imaging. Human serum albumin (HSA)‐coated QD800‐MPA nanoparticles (QD800‐MPA‐HSA) show reduced localization in mononuclear phagocytic system‐related organs over QD800‐MPA plausibly due to the low uptake of QD800‐MPA‐HSA in macrophage cells. QD800‐MPA‐HSA may have great potential for in vivo fluorescence imaging.     

A Red Emissive Two‐Photon Fluorescence Probe Based on Carbon Dots for Intracellular pH Detection

Intracellular pH is closely related with many biological processes, including cellular proliferation, apoptosis, endocytic processes, signal transduction, and enzymatic activity. The use of fluorescent probes has become an essential method for intracellular pH detection, but existing fluorescent probes have substantial limitations, such as requiring tedious synthetic preparation, suffering from an inappropriate response range and insufficiently long emission wavelength. In this work, a red emissive two‐photon fluorescence probe based on carbon dots (pH‐CDs) is fabricated using a facile one‐pot hydrothermal method for the monitoring of intracellular pH. pH‐CDs possess a variety of superior properties, including high selectivity, excellent photostability, and low cytotoxicity. Furthermore, they exhibit a pH‐sensitive response in the range of 1.0–9.0 and a linear range of 3.5–6.5, which is desirable for tracking the pH value in living cells. It is demonstrated that the pH‐dependent fluorescence signal is regulated via switching between aggregation and disaggregation of CDs. More importantly, pH‐CDs can be successfully applied to sense and visualize pH fluctuation in cells, tissue, and zebrafish. These findings suggest that the as‐prepared pH‐CDs probe has significant potential for practical application in living systems.     

快速热退火对多层Ge量子点晶体质量的影响

使用超高真空化学气相淀积(UHV/CVD)设备在Si衬底上生长多层Ge量子点,用双晶X射线衍射(DCXRD)、拉曼光谱(Raman)等手段表征在不同条件下快速热退火的Ge量子点材料的组分、应力等特性,研究了快速热退火对多层Ge量子点晶体质量的影响.结果表明:随着退火温度的升高,量子点中Ge的组分下降,量子点应变的弛豫程...     

稳定剂对水相制备CdTe量子点的荧光性能和细胞毒性影响研究

用巯基乙酸(TGA)、半胱氨酸(L-Cys)和谷胱甘肽(GSH)这三种巯基稳定剂在水相中制备了CdTe量子点(QDs).红外光谱(FTIR)分析结果表明,三种稳定剂都成功地利用Cd2+与巯基之间的配位与QDs相结合并起到保护及稳定的作用.利用荧光光谱对不同QDs的荧光性能进行了研究,结果表明当采用GSH作为稳定剂时,QDs的生长速率较快,且最大发射波长能够达到约680nm;L-Cys-CdTe的生长速率次之,也能生成具有较大发射波长的QDs;TGA-CdTe的生长速率最慢,且最大发射波长只能达到约620nm,但是其荧光强度较高,适于制备对荧光强度要求较高的QDs.通过MTT(噻唑蓝)比色法对细胞存活率进行测定,同时利用显微镜对细胞形貌进行观察,结果表明各量子点都具有一定的细胞毒性,但TGA-QDs对细胞的伤害作用更大,以20μg/mL的浓度对细胞培养24h后,细胞存活率只有52.6%.     

Graphene Quantum Dots for Optical Bioimaging

Graphene quantum dots (GQDs) have shown great potential in bioimaging applications due to their excellent biocompatibility, low cytotoxicity, feasibility for surface functionalization, physiological stability, and tunable fluorescence properties. This Review first introduces the intriguing optical properties of GQDs that are suitable for biological imaging, and is followed by the GQDs' synthetic strategies. The emergent and latest development methods for tuning GQDs' optical properties are further described in detail. The recent advanced applications of GQDs in vitro, particularly in cell imaging, targeted imaging, and theranostic nanoplatform fabrication, are included. The applications of GQDs for in vivo bioimaging are also covered. Finally, the Review is concluded with the challenges and prospectives that face this nascent yet exciting field.     

Memristive Devices with Highly Repeatable Analog States Boosted by Graphene Quantum Dots

Memristive devices, having a huge potential as artificial synapses for low‐power neural networks, have received tremendous attention recently. Despite great achievements in demonstration of plasticity and learning functions, little progress has been made in the repeatable analog resistance states of memristive devices, which is, however, crucial for achieving controllable synaptic behavior. The controllable behavior of synapse is highly desired in building neural networks as it helps reduce training epochs and diminish error probability. Fundamentally, the poor repeatability of analog resistance states is closely associated with the random formation of conductive filaments, which consists of oxygen vacancies. In this work, graphene quantum dots (GQDs) are introduced into memristive devices. By virtue of the abundant oxygen anions released from GQDs, the GQDs can serve as nano oxygen‐reservoirs and enhance the localization of filament formation. As a result, analog resistance states with highly tight distribution are achieved with nearly 85% reduction in variations. In addition the insertion of GQDs can alter the energy band alignment and boost the tunneling current, which leads to significant reduction in both switching voltages and their distribution variations. This work may pave the way for achieving artificial neural networks with accurate and efficient learning capability.     

Near‐Unity Quantum Yields from Chloride Treated CdTe Colloidal Quantum Dots

Colloidal quantum dots (CQDs) are promising materials for novel light sources and solar energy conversion. However, trap states associated with the CQD surface can produce non‐radiative charge recombination that significantly reduces device performance. Here a facile post‐synthetic treatment of CdTe CQDs is demonstrated that uses chloride ions to achieve near‐complete suppression of surface trapping, resulting in an increase of photoluminescence (PL) quantum yield (QY) from ca. 5% to up to 97.2 ± 2.5%. The effect of the treatment is characterised by absorption and PL spectroscopy, PL decay, scanning transmission electron microscopy, X‐ray diffraction and X‐ray photoelectron spectroscopy. This process also dramatically improves the air‐stability of the CQDs: before treatment the PL is largely quenched after 1 hour of air‐exposure, whilst the treated samples showed a PL QY of nearly 50% after more than 12 hours.     

Tailoring the Heterostructure of Colloidal Quantum Dots for Ratiometric Optical Nanothermometry

Colloidal quantum dots (QDs) are a fascinating class of semiconducting nanocrystals, thanks to their optical properties tunable through size and composition, and simple synthesis methods. Recently, colloidal double‐emission QDs have been successfully applied as competitive optical temperature sensors, since they exhibit structure‐tunable double emission, temperature‐dependent photoluminescence, high quantum yield, and excellent photostability. Until now, QDs have been used as nanothermometers for in vivo biological thermal imaging, and thermal mapping in complex environments at the sub‐microscale to nanoscale range. In this Review, recent progress for QD‐based nanothermometers is highlighted and perspectives for future work are described.     

圆偏振光诱导CdTe量子点再生长及其对光致发光的影响

实验研究了以3-巯基丙酸为配体合成的水溶性CdTe量子点经过非偏振光与圆偏振光照射处理后, 量子点的再生长变化规律。采用光致发光谱、紫外-可见吸收光谱、透射电子显微镜与X射线衍射等表征手段分析表明: 非偏振光会促进CdTe量子点的光氧化, 导致量子点尺寸缩小, 荧光发光峰位蓝移, 且发光效率降低; 而圆偏振光增强了配体的光氧化, 在量子点表面形成CdS层, 导致量子点尺寸进一步增大, 荧光发光峰红移, 且发光效率提升。进一步讨论了CdTe量子点与配体之间的键合作用, 相关光化学反应机制及其对量子点光致发光性质的影响。