Search

Primary alkylamines are generally used as ligands for the synthesis of colloidal II–VI group quantum dots (QDs). However, knowledge of the effects of these ligands on the nanocrystalline structure in the literature is scarce and often contradictory. Herein, the structural evolution of CdSe QDs synthesized with primary alkylamines of different chain lengths and concentrations and at various reaction temperatures has been investigated. Absorption spectroscopy, XRD, HRTEM and Fourier transform imaging were applied to characterize the structure of the CdSe QDs. The results demonstrate that CdSe QDs preferentially form the wurtzite structure with shorter-chain and higher-concentration primary alkylamines at higher reaction temperatures. In contrast, the zinc blende structure is formed in the presence of longer-chain and lower-concentration primary alkylamines at lower reaction temperatures. By precisely controlling the experimental conditions, CdSe QDs with a pure zinc blende phase have been successfully achieved. [ABSTRACT FROM AUTHOR]

Intracellular viscosity plays an important role in regulating cellular morphology and physiology and is closely related to a host of diseases. Especially, the changes in mitochondrial viscosity will cause some common diseases such as hyperlipidemia, Alzheimer's disease and cancer. In this work, we report the design of a red-emissive molecular rotor for the detection of mitochondrial viscosity in live cells. The probe showed fascinating performance, such as specific targeting to mitochondria, high sensitivity to viscosity, and rapid fluorescence response, especially the dual response mode of fluorescence intensity and fluorescence lifetime. By using this probe, we realized monitoring of the mitochondrial viscosity variations in live cells under different physiological processes. Our study offers an opportunity to discover potential tools for mitochondria-related physiology and pathology investigation. [ABSTRACT FROM AUTHOR]

As a specific biological marker for the occurrence and progression of tumor cells, detection of telomerase activity is of great importance for the physiological research of tumors. However, in situ measurement of telomerase activity in living cells still remains a challenge. Herein, we report a precisely designed oligonucleotide-functionalized gold nanoparticle probe that has realized high-efficiency detection of telomerase activity for cellular imaging toward the identification of tumors. Our method has achieved intracellular imaging of telomerase activity and shows good performance towards the distinction of tumor cells from normal ones. Moreover, the method reported here for tracking tumor cells in blood has wide applications in cancer diagnosis. This strategy offers an opportunity for cancer diagnosis, guiding therapy and evaluating prognosis. [ABSTRACT FROM AUTHOR]

A ratiometric fluorescent probe with a large emission shift was developed for the accurate measurement of hydrogen peroxide (H2O2) in sophisticated pyroptosis signaling pathways. The results reported here demonstrate that H2O2, as a principal member of ROS, is a critical upstream signaling molecule in regulating pyroptosis. [ABSTRACT FROM AUTHOR]

E3 ligases play a critical role in ubiquitin (Ub) conjugation cascades, and any aberration in their activity is associated with a number of diseases. Advancement in our knowledge of understanding the roles of HECT E3s requires biochemical tools such as activity-based probes (ABPs). In this study we developed a novel dehydroalanine (Dha)-based E2-Ub ABP using a strategy that is a combination of practical hydrazide-based native chemical ligation and sequential Dha formation. The probe could be used for labeling HECT E3s not only in vitro but also in endogenous cellular contexts. Our easy-to-implement method is expected to be useful for the preparation of Dha based Ub family E2 conjugate ABPs. [ABSTRACT FROM AUTHOR]

Telomerase is repressed stringently in normal cells but highly activated in tumours to maintain their uncontrollable growth. We report a ratiometric fluorescence strategy for visualising telomerase activity for tumour identification. Using our strategy, tumour cells and tissues can be differentiated from normal cells and tissues by the naked eye. [ABSTRACT FROM AUTHOR]

Fluorescent paper sensors are widely used in the assays of environment, food and medicine; however, their applications usually have been limited due to the narrow color-change range and insensitivity of the color variation to dosage of target analytes. In this paper, we report a ratiometric fluorescent probe-based paper sensor regulated by the optimum proportion of gold nanoclusters stabilized by bovine serum albumin and fluorescent graphene oxide to achieve the maximum consecutive color change for visual determination of glucose in human serum. The oxidation of hydrogen peroxide produced by glucose quenches the red fluorescence emission of gold nanoclusters and unveils a consecutive color change from pink to blue with the corresponding dosage of glucose. This colorimetric paper sensor printed with the probe ink exhibits a dosage-sensitive allochromatic capability for the blood glucose concentration of 4–10 mM in human serum (normal concentration: 4.4–6.6 mM). The method reported here can open a window in predicting diseases related to abnormal glucose levels. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H2S) is a key signaling molecule in the cytoprotection, vascular mediation and neurotransmission of living organisms. In-depth understanding of its production, trafficking, and transformation in cells is very important in the way H2S mediates cellular signal transductions and organism functions; it also motivates the development of H2S probes and imaging technologies. A fundamental challenge, however, is how to engineer probes with sensitivity and cellular penetrability that allow detection of spontaneous production of H2S in the entire cell space and live animals. Here, we report a rationally designed molecular switch capable of accessing all intracellular compartments, including the nucleus, lysosomes and mitochondria, for H2S detection. Our probe comprised three functional domains (H2S sensing, fluorescence, and biomembrane penetration), could enter almost all cell types readily, and exhibit a rapid and ultrasensitive response to H2S (≤120-fold fluorescence enhancement) for the dynamic mapping of spontaneously produced H2S as well as its distribution in the whole cell. In particular, the probe traversed blood/tissue/cell barriers to achieve mapping of endogenous H2S in metabolic organs of a live Danio rerio (zebrafish). These results open-up exciting opportunities to investigate H2S physiology and H2S-related diseases. [ABSTRACT FROM AUTHOR]

Luminescent chemosensors for hydrogen sulphide (H2S) are of great interest because of the close association of H2S with our health. However, current probes for H2S detection have problems such as low sensitivity/selectivity, poor aqueous-solubility or interference from background fluorescence. This study reports an ultrasensitive and time-gated “switch on” probe for detection of H2S, and its application in test paper for visualization of exhaled H2S. The complex probe is synthesized with a luminescent Tb3+ centre and three ligands of azido (–N3) substituted pyridine-2,6-dicarboxylic acid, giving the probe high hydrophilicity and relatively fast reaction dynamics with H2S because there are three –N3 groups in each molecule. The introduced –N3 group as a strong electron-withdrawing moiety effectively changes the energy level of ligand via intramolecular charge transfer (ICT), and thus breaks the energy transferring from ligand to lanthanide ion, resulting in quenching of Tb3+ luminescence. On addition of H2S, the –N3 group can be reduced to an amine group to break the process of ICT, and the luminescence of Tb3+ is recovered at a nanomolar sensitivity level. With a long lifetime of luminescence of Tb3+ centre (1.9 ms), use of a time-gated technique effectively eliminates the background fluorescence by delaying fluorescence collection for 0.1 ms. The test paper imprinted by the complex probe ink can visualize clearly the trace H2S gas exhaled by mice. [ABSTRACT FROM AUTHOR]

A green and efficient synthesis of aqueous CdTe quantum dots (QDs) embedded in inorganic salt enabled by co-precipitation is demonstrated, providing a new type of solid-state conversion material with emission colors covering green to red spectral regions. CdTe QDs were synthesized in the water phase, followed by incorporation into inorganic salt with the assistance of ethanol. Due to the protection of the tight matrix, the resulting composites exhibit good stability and processability as well as high photoluminescence properties. A white light emitting diode (WLED) applying the composites as a red color conversion layer with good luminescence properties is also fabricated, suggesting the promising application of the composites in solid-state lighting systems. [ABSTRACT FROM AUTHOR]

We have developed a selective upconversion switching method for the ratiometric fluorescence detection of nitrite using upconversion nanoparticles (UCNPs) and an efficient nitrite reaction. The green emission (λem = 539 nm) of NaYF4:Yb3+,Er3+ nanoparticles can be selectively quenched by the neutral red (NR) dye due to the spectral overlap between the emission at 539 nm and the absorption of NR, while its red emission (λem = 654 nm) remains unchanged. Nitrite reacts specifically and strongly with NR to form diazonium salt and lose the diazonium group, which sharply decreases the absorption of NR. Thus, the green emission of NaYF4:Yb3+,Er3+ can be recovered by increasing the amount of nitrite, leading to visible color changes from red to orange-yellow and finally green under excitation at 980 nm. The increase in the ratio of emission intensities (I539/I654) is quantitatively correlated to the concentration of nitrite ions. Moreover, the developed method has been successfully applied to nitrite detection in real samples such as drinking water, natural water and meat foods. In particular, the upconversion sensors can efficiently avoid background optical interference and thus show potential for the detection of nitrite salts in complex samples. [ABSTRACT FROM AUTHOR]

Herein, for the detection of highly explosive 2,4,6-trinitrotoluene (TNT) instantly and on-site, a fluorescence ratiometric probe using a dual-emission nanohybrid has been developed. The nanohybrid comprises blue-colored fluorescent graphene oxide (FGO) being conjugated with red-emitting manganese-doped ZnS nanocrystals (ZnS:Mn NCs), the latter being functionalized with hexamethylenediamine. The blue fluorescence of FGO is insensitive to TNT and is used as an internal reference, whereas the red fluorescence of ZnS:Mn NCs can be selectively quenched by TNT through electron transfer, resulting in a unique red–purple–blue color response as the amount of TNT is increased. Thus, the probe could be used for the quantitative measurement of TNT based on the fluorescence ratiometric method. We demonstrated that the nanohybrid probe exhibited high visual detection sensitivity and reliability in comparison with single-color fluorescence quenching probes. A fluorescence test paper was prepared using the nanohybrid probe and was demonstrated to detect TNT residues directly on various surfaces including rubber, a person's fingers and manila envelopes with a visual detection limit as low as 5.68 ng mm−2, showing its promising application for security screening. [ABSTRACT FROM AUTHOR]

A chemically reactive Raman probe has been developed for ultrasensitively monitoring and imaging the in vivo generation of femtomolar oxidative species as induced by anti-tumor drugs in living cells. [ABSTRACT FROM AUTHOR]