Facile high-quantum-yield sulfur-quantum-dot-based photoluminescent probe for nifedipine detection.

Monitoring of dihydropyridine drugs, such as nifedipine (NIF), has attracted considerable attention owing to the side effects arising from the consumption of such drugs. Herein, a highly sensitive and facile fluorescence-sensing platform based on a high-quantum-yield sulfur quantum dot (SQDs) probe for NIF detection is proposed. Based on the principle of the inner filter effect, the rapid detection of NIF with high sensitivity is successfully realized on the basis of the change in the fluorescence signal due to the quenching effect of NIF on SQDs. The results show a good linear relationship between the NIF concentration and fluorescence intensity within the range of 5-150 µmol/L, with a low detection limit of 1.63 µmol/L (S/N = 3). Moreover, because no surface modification or establishment of any coupling between the receptor and the fluorophore is necessary, this approach provides considerable flexibility and simplicity for the construction of a fluorescence sensor and substantially reduces the detection time. A systematic investigation was conducted to verify the applicability of this method for the analysis of pharmaceutical components in NIF tablets. This study not only promotes the design and development of a fluorescence analysis platform for NIF detection, but also facilitates the fabrication of novel SQD-based fluorescence-sensing systems for the molecular detection of drugs. Proposal for a facile nifedipine assay method based on the inner filter effect of nifedipine to high-quantum-yield sulfur quantum dots, and realizing nifedipine detection in tablets and human urine samples.

Whole brain segmentation with full volume neural network.

Whole brain segmentation is an important neuroimaging task that segments the whole brain volume into anatomically labeled regions-of-interest. Convolutional neural networks have demonstrated good performance in this task. Existing solutions, usually segment the brain image by classifying the voxels, or labeling the slices or the sub-volumes separately. Their representation learning is based on parts of the whole volume whereas their labeling result is produced by aggregation of partial segmentation. Learning and inference with incomplete information could lead to sub-optimal final segmentation result. To address these issues, we propose to adopt a full volume framework, which feeds the full volume brain image into the segmentation network and directly outputs the segmentation result for the whole brain volume. The framework makes use of complete information in each volume and can be implemented easily. An effective instance in this framework is given subsequently. We adopt the 3D high-resolution network (HRNet) for learning spatially fine-grained representations and the mixed precision training scheme for memory-efficient training. Extensive experiment results on a publicly available 3D MRI brain dataset show that our proposed model advances the state-of-the-art methods in terms of segmentation performance.

Highly Conductive Ligand-Free Cs2 PtBr6 Perovskite Nanocrystals with a Narrow Bandgap and Efficient Photoelectrochemical Performance.

Design of high-performance all-inorganic halide perovskites, especially lead-free perovskites, is key to the broadening of its application prospects. Herein, the authors report the synthesis of ligand-free cesium platinum (IV) bromide nanocrystals (Cs2 PtBr6 NCs), a new kind of vacancy-ordered lead-free perovskite nanomaterial, by a facile one-pot method. The Cs2 PtBr6 NCs exhibits a narrow band gap of 1.32 eV covering the entire visible range, which is supported by density functional theory calculations. Together with their high conductivity, matching energy levels with the work function of carbon electrodes, and excellent environmental stability, this NC displays a cathodic photocurrent density as high as 335 µA cm-2 , two orders of magnitude higher than other perovskites in aqueous solutions without the need of other electron acceptors. These combined properties suggest that the Cs2 PtBr6 NCs have great potentials in a wide range of photoelectronic and photoelectrochemical sensing applications.

Size-focusing results in highly photoluminescent sulfur quantum dots with a stable emission wavelength.

Sulfur quantum dots (SQDs) are a new kind of functional nanomaterial, but several challenges still exist in relation to their synthesis and application, such as low-yield and time-consuming synthetic methods, low photoluminescence quantum yields (PLQYs), and the non-selectivity of their detection mechanisms. Herein, we report the drastic enhancement of the fluorescence performance of water-soluble SQDs via the one-pot synthesis of size-focusing QDs using ultrasound microwave radiation. The synthetic period has been greatly shortened to 2 h via the present process. Notably, the proposed SQDs exhibit a highly stable emission wavelength with a record high PLQY of 58.6%. The mechanistic study indicates that size-focusing is a key factor relating to the proposed high-performance SQDs. As they also have robust stability, the proposed SQDs show a wide range of potential applications. Inspired by the characteristic properties of the SQDs and specific analytes, a simple SQD-based fluorescence sensing platform, via a redox-reaction-mediated mechanism, has been successfully developed for the rapid and selective detection of Ce(iv). In addition, this system has been effectively applied to some Ce(iv)-related biological assays, such as ascorbic acid (AA) analysis. This work is an important breakthrough in the SQD field, opening up avenues for solving the challenging problems relating to SQD-based probes, enriching the fundamental understanding of them, and greatly extending their applications, especially in biomedicine.

Pre-oxidation of Gold Nanoclusters Results in a 66 % Anodic Electrochemiluminescence Yield and Drives Mechanistic Insights.

Gold nanoclusters (AuNCs) are attractive electrochemiluminescence (ECL) emitters because of their excellent stability, near IR emission, and biocompatibility. However, their ECL quantum yield is relatively low, and our limited fundamental understanding has hindered rational improvement of this parameter. Herein, we report drastic enhancement of the ECL of ligand-stabilized AuNCs by on-electrode pre-oxidation with triethylamine (TEA) as a co-reactant. The l-methionine-stabilized AuNCs resulted in a record high ECL yield of 66 %. This strategy was successfully extended to other AuNCs, and it is more effective for ligand shells that allow more effective electron transfer. In addition, excitation of the pre-oxidized ECL required a lower potential than conventional methods, and no additional instrument was required. This work opens avenues for solving a challenging problem of AuNC-based ECL probes and enriches fundamental understanding, greatly broadening their potential applications.