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Semiconductor nanocrystals (NCs) possess unique photoluminescent properties which can be used to design fluorescence probes for chemo/biosensing applications. Several have recently emerged that offer excellent turn-on or ratiometric fluorescence chemosensory protocols by sophisticated procedures, but it has been challenging to realize all of these advantages in a single construct. Herein, we develop an intrinsic dual-emitting Mn-doped ZnS nanocrystal-based probe that achieves this goal with turn-on and ratiometric fluorescence response for the determination of organophosphate (diethylphosphorothioate, DEP). The probe relies on the modification of dopamine dithiocarbamate on the surface of NCs and the modulation of dual emission through a photoinduced electron transfer process, which makes use of red fluorescence of Mn(2+) ions doped in the NCs as specific recognition for the target analyte and blue defect emission of the NCs as stable internal reference. In presence of DEP, the red emission of the probe is thus enhanced by switching off the electron transfer pathway, while the blue emission is almost unchanged. With the addition of different amounts DEP, the two emission intensity ratios gradually vary and display color changes from dark-blue to purple to red. Thus, this method generates turn-on and ratiometric fluorescence signals for quantitative and visual detection of the analyte. Significantly, the dual-emitting probe has been used to fabricate paper-based test strips for visual detection of DEP residues, which validate the method for its rapid, on-site, and visual identification.

A fluorescent probe was synthesized and demonstrated to be highly selective and sensitive in the reaction with copper (II) ion, generating a large variation of the fluorescence intensity in a dose-response manner. The probe contains a dansyl moiety as fluorophore and a multidentate ligand for copper (II) ion recognition. The reaction of the molecular probe with copper (II) ion proceeds rapidly and irreversibly in a 1 to 1 stoichiometric way, leading to the production of stable copper (II) complex, which subsequently results in the quenching of fluorescence. The detection limit for copper (II) ion was measured to be about 2ppb. It was also shown that the probe has high selectivity for copper (II) ion and good anti-interference ability against other transition metal ions. The herein reported very simple and reliable fluorescence probe could be employed for copper (II) ion detection in many aspects., (Copyright © 2014 Elsevier B.V. All rights reserved.)

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]

Stimuli‐responsive photonic crystals (PCs) have been extensively studied due to their potential in fabrication of anti‐counterfeiting devices and information storage. In this work, using Ca2+ ionic crosslinker, a cholesteric liquid crystalline network (CLCN) based PC able to simultaneously present visible and fluorescence pattern by moisture treatment is designed and prepared. The circularly polarized light from helical structure of CLCN makes the reflected pattern distinguishable under different circular polarizer, implying the unique advantage of this novel coating as anti‐counterfeiting devices. More importantly, due to the thermochromic property of the liquid crystal monomers, permanent pattern is achievable by chemically crosslinking specific region at different temperature. By integrating chemically crosslinking and physically ionic crosslinking, a permanent pattern and a dynamic humidity responsive pattern can be incorporated in a single device, indicating the great potential of this novel photonic coating in information storage. [ABSTRACT FROM AUTHOR]

Imitating the structures and behaviors of natural creatures is of great significance to scientists to explore novel materials for practical applications. However, the design and fabrication of biomimetic devices with complex and outstanding performances is still on the way. A bilayer film composed of liquid crystalline networks (LCN) film and hydrochromic aggregation‐induced‐emission molecule‐doped hydrophilic layer is prepared. Under different relative humidity, the composite film can deform and change fluorescence color simultaneously. The influence of the content of the hydrophilic matrix on the fluorescent property and humidity‐responsive behaviors of the bilayer film is investigated. Thanks to the mechanical anisotropy provided by uniform‐aligned LCN film, different modes of deformation of the bilayer film are achievable, like bending, curling, and twisting. More importantly, due to the independence of the LCN film and the non‐mesogenic molecules brought by this bimorph strategy, complex alignment of the LCN film and modification by immiscible molecules are realized in a single LCN actuator. Based on the functional composite film, artificial flowers showing synergistic blooming and shape‐changing is prepared. By regulating the molecular alignment of the LC mesogens of the LCN film, the artificial flowers can imitate various blooming behaviors of natural flowers like confederate jasmine and jade lotus. [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]

Since the first discovery of luminescent graphene oxide (GO), exponentially increasing investigations on the tunable structures and surfaces for modulating its optical properties have struggled to expand applications in imaging, sensing, biomedical diagnostics, and so on. Here, the latest works on reconstructing or modifying the structures and surfaces of GO to achieve diverse luminescence are systematically reviewed, including fluorescence, electroluminescence, and chemiluminescence. Moreover, the fundamental difficulties of the investigations and applications of luminescent GO nanomaterials are clarified to inspire more constructive thoughts for expanding their application boundaries. [ABSTRACT FROM AUTHOR]

Abstract In recent years, copper nanoclusters (Cu NCs) have attracted a great deal of research interests, because the fluorescence intensity will be significantly enhanced after they aggregate, which makes them an ideal material for constructing chemical sensors. The current Cu NCs based sensor researches focus mainly on the control of surface modification and aggregation conditions. Herein, we report a method for direct detection of Cu2+ ions through in situ cluster formation and aggregation. Glutathione was used as both reducing agent and stabilizing agent, while tetrahydrofuran as the poor solvent. When the analyte of Cu2+ ions were added to the mixed solution, they were reduced and aggregated to generate bright orange emission. The method is easy to operate and the reaction complete within 2 min. The detection limit for Cu2+ ions is as low as 0.17 μM. Based on these findings, we successfully achieved the determination of copper content in naturally occurring mineral. Therefore, the method reported here provides a convenient and sensitive way to perform qualitative analysis of Cu2+ ions. Highlights • A rapid and sensitive method for Cu2+ ions detection was developed. • The method was based on the formation and aggregation of Cu nanoclusters. • Glutathione was used as both reducing agent and stabilizing agent, while tetrahydrofuran as the poor solvent. • Proposed method has been successfully applied in naturally occurring mineral. [ABSTRACT FROM AUTHOR]

Fluorescent test papers are promising for the wide applications in the assays of diagnosis, environments and foods, but unlike classical dye-absorption-based pH test paper, they are usually limited in the qualitative yes/no type of detection by fluorescent brightness, and the colorimetry-based quantification remains a challenging task. Here, we report a single dual-emissive nanofluorophore probe to achieve the consecutive color variations from blue to red for the quantification of blood glucose on its as-prepared test papers. Red quantum dots were embedded into silica nanoparticles as a stable internal standard emission, and blue carbon dots (CDs) were further covalently linked onto the surface of silica, in which the ratiometric fluorescence intensity of blue to red is controlled at 5:1. While the oxidation of glucose induced the formation of Fe 3+ ions, the blue emission of CDs was thus quenched by the electron transfer from CDs to Fe 3+ , displaying a serial of consecutive color variations from blue to red with the dosage of glucose. The high-quality test papers printed by the probe ink exhibited a dosage-sensitive allochromatic capability with the clear differentiations of ~5, 7, 9, 11 mM glucose in human serum (normal: 3–8 mM). The blood glucose determined by the test paper was almost in accordance with that measured by a standard glucometer. The method reported here opens a window to the wide applications of fluorescent test paper in biological assays. [ABSTRACT FROM AUTHOR]