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Targeted imaging is playing an increasingly important role in the early detection and precise diagnosis of cancer. This need has motivated research into sensory nanomaterials that can be constructed into imaging agents to serve as biosensors. Graphene quantum dots (GQDs) as a valuable nanoprobe show great potential for use in two-photon biological imaging. However, most as-prepared GQDs exhibit a low two-photon absorption cross-section, narrow spectral coverage, and "one-to-one" signal conversion mode, which greatly hamper their wide application in sensitive early-stage cancer detection. Herein, a versatile strategy has been employed to fabricate an aptamer Sgc8c-functionalized hybrid as a proof-of-concept of the signal amplification strategy for targeted cancer imaging. In this study, GQDs with two-photon imaging performance, and silica nanoparticles (SiO2 NPs) as nanocarriers to provide amplified recognition events by high loading of GQD signal tags, were adopted to construct a two-photon hybrid-based signal amplification strategy. Thus, the obtained hybrid (denoted SiO2@GQDs) enabled extremely strong fluorescence with a quantum yield up to 0.49, excellent photostability and biocompatibility, and enhanced bright two-photon fluorescence up to 2.7 times that of bare GQDs (excitation at 760 nm; emission at 512 nm). Moreover, further modification with aptamer Sgc8c showed little disruption to the structure of the SiO2@GQDs-hybrid and the corresponding two-photon emission. Hence, SiO2@GQDs–Sgc8c showed specific responses to target cells. Moreover, it could be used as a signal-amplifying two-photon nanoprobe for targeted cancer imaging with high specificity and great efficiency, which exhibits a distinct green fluorescence compared to that of GQDs–Sgc8c or SiO2@GQDs. This signal amplification strategy holds great potential for the accurate early diagnosis of tumors and offers new tools for the detection a wide variety of analytes in clinical application. [ABSTRACT FROM AUTHOR]

In this communication, we report a low-dimensional perovskite-related structure based on Cu(I) organometallic halide with strong green cluster-centred emission and near-unity photoluminescence quantum yield. The 0D [Rb(18-crown-6)]2Cu4I6 was sucessfully applied for X-ray imaging screens which exhibit high spatial resolution of 16.8 lp mm−1 and low detection limit of 458 nGy s−1. [ABSTRACT FROM AUTHOR]

Fluorescent organic nanoparticles (FONs) with intriguing features have emerged as a kind of inspiring contrast reagent for various biomedical applications. However, the formation of preassembled nanoparticles requires stimuli (such as light, pH, heat, etc.), which hampers their application in all circumstances. The challenge lies in understanding and then exploring a simple and feasible method to prepare FONs without any external stimuli. Herein, we designed a novel in situ strategy to fabricate cobalt oxyhydroxide (CoOOH) nanoflake-loaded pyrene-based fluorescent organic nanoparticles (PyFONs), enabling sensitive monitoring and precision imaging of ascorbic acid (AA) in living cells. The pyrene-based FONs were constructed via a facile one-step co-precipitation method and used as the signal output. The π–π stacking-directed self-assembly process provides a brightness at 468 nm of the pyrene excimer emission accompanied by an almost disappeared monomer peak around 370–400 nm. The CoOOH nanoflakes were then in situ grown on the surface of PyFONs to serve as both an effective quencher and a recognition unit for AA. The as-synthesized PyFONs@CoOOH showed weak fluorescence signals via Förster resonance energy transfer (FRET). Subsequently, the turn-on fluorescence responses were triggered during CoOOH nanoflake reduction to Co2+ by AA, which resulted in the decomposition and collapse of the CoOOH nanoflakes. Owing to the specific oxidation–reduction reaction between the enediol group of AA and CoOOH on the surface of the PyFONs@CoOOH nanoprobe, excellent sensitivity and selectivity for AA detection was obtained with a wide linear relationship from 2.0 μM to 500 μM. The detection limit was calculated to be as low as 0.21 μM (S/N = 3). More importantly, the PyFONs@CoOOH nanoprobe also presented excellent sensitivity and selectivity for AA analysis in biological fluids, as well as for bioimaging of endogenous AA in living cells. Consequently, the proposed sensing systems can serve as a powerful tool to monitor and image AA and show broad potential applications in clinical diagnostics and drug screening. [ABSTRACT FROM AUTHOR]

Three new silver–chalcogenide clusters protected by naphthyl ligands are described in this work, namely [Ag14(SCH2C10H7)6(CF3COO)8(DMAc)6] (1), [Ag30(SCH2C10H7)18(CrO4)2(DMAc)2 (CF3COO)8] (DMAc = dimethylacetamide) (2) and {Ag12(SCH2C10H7)6(CF3COO)4(CH3CN)6(Cr2O7)}n (3). Their crystal structures were studied by X-ray crystallography, and they show hollow-core–shell (1), template-core–shell (2) and 1D infinite (3) structures, respectively. The luminescence properties of cluster 1 were investigated, which showed interesting thermochromic variation from red to bright yellow. Moreover, the chromate ions were proven to act as templates in forming the silver clusters through a series of experiments to prepare compounds 2 and 3, which could be considered as derivatives of cluster 1. [ABSTRACT FROM AUTHOR]

Up to now, the successful fabrication of efficient specific reaction-based sensing systems for amplification signal-enhanced detection of reactive species remains an unsolved problem. To address this issue, we describe herein a universal β-cyclodextrin polymer (β-CDP)-based sensing platform that uses an amplified fluorescence assay for sensitive detection of glutathione (GSH) and trypsin activity. More specifically, the negatively charged peptide Py-GC adsorbed on the surfaces of MnO2 nanotubes via electrostatic interaction. Upon addition of GSH, MnO2 was reduced to Mn2+ and Py-GC was separated far from the nanoquencher, generating an activated fluorescence signal. It was worth noting that free pyrene could easily enter the hydrophobic cavity of β-CDP, accompanied by significant fluorescence enhancement. The nanoprobe exhibits high sensitivity and selectivity to GSH as well as excellent biocompatibility, making it a promising probe for imaging of endogenous GSH in living cells. As a proof-of-principle, we use this approach to quantify trypsin activity on the basis of the trypsin-catalyzed hydrolysis reaction of cytochrome c (Cyt c) in human serum. As a universal βCDP-based signal amplification reporter, this prototype can be applied to a sensitive and versatile sensing platform for multi-analyses by selecting suitable switched-reagents, thus inspiring the new strategies for bioanalysis. [ABSTRACT FROM AUTHOR]

Thermally activated delayed fluorescence (TADF) emitters are attractive for display and lighting applications. Here, a series of highly efficient blue TADF emitters including 3,5-bis((3,6-di-tert-butyl-9H-carbazol-9-yl)phenyl)(pyridin-4-yl)methanone (4BPy-mDTC), (3,5-bis(3,6-di-tert-butyl-9H-carbazol-9-yl)phenyl)(pyridin-3-yl)methanone (3BPy-mDTC), (3,5-bis(3,6-di-tert-butyl-9H-carbazol-9-yl)phenyl)(pyridin-2-yl)methanone (2BPy-mDTC) and (3,5-bis(3,6-di-tert-butyl-9H-carbazol-9-yl)phenyl)(phenyl)methanone (BP-mDTC) were designed and synthesized. The molecular structures feature two meta carbazole substituents attached to a benzoylpyridine (BPy) group or to a benzophenone (BP) group. These compounds show high thermal stability (Td = 371–439 °C), blue emissions (458–488 nm), high photoluminescence quantum yields (PLQY) (75–96%) in thin films and very small energy gaps between S1 and T1 (ΔEST) of 0.01–0.05 eV. In addition, they all reveal TADF properties including small ΔEST, two components in the transient PL decays, prompt emission and temperature-dependent delayed emission. The BPy series appears to give much higher photoluminescence quantum yields (PLQY ＞ 92%) than BP-mDTC (75%) plausibly due to the more rigid structure caused by the interaction between pyridine nitrogen and the aromatic C–H bond. Furthermore, 4BPy-mDTC shows a more delayed component compared to 3BPy-mDTC and 2BPy-mDTC. The electroluminescent devices based on 4BPy-mDTC and 2BPy-mDTC as the dopant emitters exhibit sky blue emission with maximum external quantum efficiencies (EQEs) over 28%, and current and power efficiency and maximum luminance up to 67.0 cd A−1, 60.1 lm W−1 and 20 000 cd m−2, respectively. The presence of the pyridine ring and the position of the nitrogen atom in the molecules are critical for the high quantum yield and device efficiency. The PLQY EQE and luminance are dramatically improved by changing the phenyl into a pyridine group in the dopant in these devices. [ABSTRACT FROM AUTHOR]

A thermally activated delayed fluorescent (TADF) material containing two meta carbazolyl groups on the phenyl ring of the benzoyl-4-pyridine moiety was prepared and its luminescence showed a colour change from blue to green by external stimuli. The organic-blue-light-emitting device using this TADF dopant provided a high external quantum efficiency of 18.4%. [ABSTRACT FROM AUTHOR]

The reactions of flexible supramolecular synthons with a pendant ethynide arm attached to a heteroaryl skeleton and different silver(I) salts under solvent evaporation conditions yielded four silver-organic frameworks. In 1-4, the Ag7, Ag8 and Ag9 aggregates are fused together through trifluoroacetate groups and/or Ag-N coordination bonds to generate a 2D layer, and finally linked into 3D supramolecular networks by argentophilic interactions or hydrogen bonding. The diversities of the present structures also indicate that both solvent and the anionic component play vital roles in the assembly of silver(I)- ethynide complexes. In addition, their luminescence behaviors have been studied in the solid state. [ABSTRACT FROM AUTHOR]

Targeted imaging is playing an increasingly important role in the early detection and precise diagnosis of cancer. This need has motivated research into sensory nanomaterials that can be constructed into imaging agents to serve as biosensors. Graphene quantum dots (GQDs) as a valuable nanoprobe show great potential for use in two-photon biological imaging. However, most as-prepared GQDs exhibit a low two-photon absorption cross-section, narrow spectral coverage, and "one-to-one" signal conversion mode, which greatly hamper their wide application in sensitive early-stage cancer detection. Herein, a versatile strategy has been employed to fabricate an aptamer Sgc8c-functionalized hybrid as a proof-of-concept of the signal amplification strategy for targeted cancer imaging. In this study, GQDs with two-photon imaging performance, and silica nanoparticles (SiO 2 NPs) as nanocarriers to provide amplified recognition events by high loading of GQD signal tags, were adopted to construct a two-photon hybrid-based signal amplification strategy. Thus, the obtained hybrid (denoted SiO 2 @GQDs) enabled extremely strong fluorescence with a quantum yield up to 0.49, excellent photostability and biocompatibility, and enhanced bright two-photon fluorescence up to 2.7 times that of bare GQDs (excitation at 760 nm; emission at 512 nm). Moreover, further modification with aptamer Sgc8c showed little disruption to the structure of the SiO 2 @GQDs-hybrid and the corresponding two-photon emission. Hence, SiO 2 @GQDs-Sgc8c showed specific responses to target cells. Moreover, it could be used as a signal-amplifying two-photon nanoprobe for targeted cancer imaging with high specificity and great efficiency, which exhibits a distinct green fluorescence compared to that of GQDs-Sgc8c or SiO 2 @GQDs. This signal amplification strategy holds great potential for the accurate early diagnosis of tumors and offers new tools for the detection a wide variety of analytes in clinical application.