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Coal-based Carbon Dots (C-CDs) have gradually become a research focus due to the abundant raw materials and low preparation cost. Still, before coal-based carbon dots are widely used, a systematic biological toxicity study is the basis for the safe utilization of C-CDs. However, the level of toxicity and the mechanism of toxicity of C-CDs for organisms are still unclear. To ensure the safe utilization of C-CDs, the present study investigated C-CD nanomaterials as stressors to probe their biotoxic effects on plant, bacterial, and animal cells as well as the photocatalytic oxidative properties of C-CDs. The results showed that low concentrations of C-CDs could promote various growth indicators of wheat, and high concentrations of C-CDs had significant inhibitory effects on wheat growth; C-CDs had significant toxic effects on (S. aureus) at specific concentrations and were light-related; meanwhile, at concentrations of 1–5000 μg/mL, C-CDs were almost not toxic to HeLa cells; however, when irradiated at 365 nm, even low concentrations of C-CDs were toxic to cells by the mechanism that C-CDs could generate singlet oxygen (1O2) by photocatalytic oxidation under 365 nm excitation light, resulting in enhanced toxicity of C-CDs to cells. [ABSTRACT FROM AUTHOR]

The accurate prediction of traffic flow is paramount for the advancement of intelligent transportation systems. Despite this, current prediction models only account for either temporal or spatial features in isolation, without considering their interaction, impeding the model's ability to express itself. In light of this, we propose the graph differential equations network (GDENet), an approach that can effectively mine spatiotemporal correlation. Specifically, we propose a spatiotemporal feature integrator (STFI), which alleviates the error caused by the deviation of the sampling distribution from the overall distribution. By incorporating temporal information into the model for training and combining it with spatial features, we thoroughly explore the spatiotemporal intrinsic association. When compared to state-of-the-art methods, our proposed algorithm reduces memory consumption and elevates computational efficiency and the practical value. We conduct experiments with real-world datasets, and our proposed model outperformed advanced prediction models. [ABSTRACT FROM AUTHOR]

Understanding the freezing mechanism of a complex fluid drop is of interest from both fundamental study and application viewpoints. Whereas a water drop is frozen into a peach-like crystal due to the volume expansion upon freezing, the shape of a frozen complex fluid drop is still mysterious. In this work, we investigate the freezing dynamics of a nanosuspension drop in two different schemes, i.e., sessile and deposited. We find that the top of a frozen nanosuspension drop can either be a singular tip or flat plateau depending on the thermal condition onset of icing nucleation. Illustrated using a Hele–Shaw cell experiment, we attribute such intriguing freezing behaviors to the interplay between nanoparticles and two types of ice, i.e., dendritic ice formed in the recalescence stage and planar ice formed in the isothermal stage. Specifically, microcells constructed by dendritic ice lead to the failure of global freezing segregation, which yields the formation of the flat plateau. The fundamental understanding and the ability to control the shape of a frozen complex fluid drop have numerous promising applications in additive manufacturing, microelectronic systems, and others. [ABSTRACT FROM AUTHOR]

The complementary sequence of genetically-modified marker sequence cauliflower mosaic virus 35S promoter (Ca MV 35S) DNA was trimmed and designed into sequences S1 and S2, which were separately modified onto the surfaces of room-temperature phosphorescent (RTP) quantum dots (QDs), forming QDs-S1 (P1) and QDs-S2 (P2), respectively. P1 and P2 were used as phosphorescent responsive units and identifying units. The target DNA sequence was added to induce P1 and P2 assembly aggregation, and the phosphorescence was self-quenched. Also, with the reduction of phosphorescence lifetime, a novel phosphorescent exciton energy transfer nano-probe system was built, which was used to quantitatively detect the genetically modified marker sequence Ca MV 35S in Maize (Zea mays L.). This simple and marker-free biological sensing method had a linear range of 10–200 nM for detecting the target DNA sequence (R = 0.991) and a detection limit (3σ) of 0.48 nM. Owing to the phosphorescence properties of QDs, this method is not affected by the background fluorescence and scattering light in biological fluids, and it is very feasible for the recognition and detection of genetically-modified marker sequences in biological samples. [ABSTRACT FROM AUTHOR]

A majority of traditional array sensors combine several sensing units, which can hardly be miniaturized. In order to solve the deficiency, it is suggested to design a sensing unit, which can obtain multidimensional information. Herein, taking the three-dimensional (3D) optical properties including phosphorescence (Ph), fluorescence (FL) and resonance light scattering (RLS) of the Mn–ZnS quantum dots (QDs) as signals, single-unit 3-signal mucopolysaccharide (MPS) sensors on the basis of Mn–ZnS QD/poly(diallyldimethylammonium chloride) (PDC) nanohybrids (Mn–ZnS+ QDs) were built with positively-charged poly(diallyldimethylammonium chloride) (PDC) as a receptor. These 3D sensors took advantage of the static interactional difference between Mn–ZnS+ QDs and different mucopolysaccharides (MPSs), and utilized different responses of Ph, FL and RLS to differentiate and identify four MPSs including heparan sulfate (Hep), hyaluronic acid (Hya), dermatan sulfate (Der) and chondroitin sulfate (Cho). Since the static interactional difference can be discriminated in virtue of the linear discriminating analysis, single-unit 3D sensors were constructed for differentiating MPSs of different types and concentrations. The three-dimensional sensor can still identify and analyze the target mucopolysaccharide in the presence of biological sample matrix, showing its good application prospects. [ABSTRACT FROM AUTHOR]

Action mechanism and Hg2+ detection with photoresponsive oxidase-like P-NCDs. [Display omitted] • Triethylenetetraminehexaacetic acid as a single raw material. • One-step hydrothermal synthesis of long-lived room-temperature phosphorescent P-NCDs. • The photosensitive oxidase-mimetic activity of P-NCDs was demonstrated. • P-NCDs generate singlet oxygen through energy transfer under illumination. • Photo-stimulated colorimetric sensor for Hg2+ determination by "off-on" TMB molecules. Developing novel photoresponsive oxidase mimics is highly useful for environmental pollution monitoring and biological sensing. Herein, long-life room-temperature phosphorescent nitrogen-doped carbon quantum dots (P-NCDs) were synthesized from triethylenetetramine hexaacetic acid via a simple one-step hydrothermal method. The P-NCDs showed high photoresponsive oxidase-like activity. On this basis, a P-NCD-based photostimulated colorimetric sensing system was developed and used to detect Hg2+ in environmental and biological samples. P-NCDs under 365 nm UV lamp irradiation converted dissolved oxygen, via triplet excited state (T 1) exciton transfer, to singlet oxygen (1O 2), which then oxidized 3,3′,5,5′-tetramethylbenzidine (TMB), leading to a color changing reaction. Cysteine can suppress the catalysis of P-NCDs, and its specific complexation with Hg2+ can recover the oxidation activity of P-NCDs. Hence, efficient colorimetric Hg2+ detection with a linear range of 0.01–14 μM and a detection limit of 3.1 nM was achieved by detecting the color change of TMB. The feasibility of this strategy was validated through real sample analysis. Our study broadens the application scope of phosphorescent nanomaterials into colorimetric sensing. [ABSTRACT FROM AUTHOR]

A simple phosphorescence method is proposed for quercetin detection based on Al 3+ -amplified room-temperature phosphorescence (RTP) signals of 3-mercaptopropionic acid (MPA)-capped Mn-doped ZnS quantum dots (QDs). The sensor was established based on some properties as follows. Al 3+ can interact with carboxyl groups on the surface of MPA-capped Mn-doped ZnS QDs via chelation, which will lead to the aggregation of QDs and amplification of RTP signals, After the addition of quercetin, it can form more stable complex with Al 3+ in alkaline aqueous solution and dissociate Al 3+ from the surface of Mn-doped ZnS QDs, which will result in significant recovery of RTP intensity of the MPA-capped Mn-doped ZnS–Al 3+ system. Under the optimized conditions, the change of RTP intensity was proportional to the concentration of quercetin in the range from 0.1 to 6.0 mg L −1 , with a high correlation coefficient of 0.996 and a detection limit of 0.047 mg L −1 . The proposed method is potentially suitable for detection of quercetin in real samples without complicated pretreatment. [ABSTRACT FROM AUTHOR]

A selective system was developed to detect heparin in aqueous solutions by using MPA(3-Mercaptopropionic Acid)-capped Mn-doped ZnS quantum dots (QDs)/polybrene (hexadimethrine bromide) hybrids as a sensitive room temperature phosphorescence (RTP) nanosensor. In this system, the RTP intensity of QDs was remarkably enhanced via electrostatic self-assembly after the addition of polybrene. The addition of heparin into the system was competitively bound to polybrene and enable to deprive it from the surface of QDs, as a result, the RTP intensity of Mn-doped ZnS QDs/polybrene hybrids was reduced with the increased of heparin concentration. Based on this effect, a selective system was proposed to detect heparin. Under the optimal conditions, the change of RTP intensity was proportional to the heparin concentration from 0.05 to 1.4 U mL −1 (about 0.38–10.76 μg mL −1 ) and the limit of detection (LOD) was 0.021 U mL −1 (about 0.16 μg mL −1 ). This proposed nanosensor is simple and relatively free of interference from coexisting substances, which can be applied to detect heparin in heparin injection and human serum. In addition, a new pathway was also provided based on the assembly of QDs with other cationic homopolymers for further design of biosensors and detection of biomolecules. [ABSTRACT FROM AUTHOR]

Quantum dot (QD) nanohybrids provide an effective route to explore the new properties of materials and are increasingly used as highly valuable sensitive (bio) chemical probes. Interestingly, the room-temperature phosphorescence (RTP) of 3-mercaptopropionic acid (MPA)-capped Mn-doped ZnS QDs could be remarkably enhanced by the addition of protamine. Based on the above finding, a simple, sensitive, and selective method for rapid detection of protamine was successfully designed. With this method, protamine as a cationic peptide interacts electrostatically with MPA-capped Mn-doped ZnS QDs to form MPA-capped Mn-doped ZnS QD/protamine complexes, which leads to the aggregation of QDs and enhances the RTP intensity. Under the optimized conditions, the RTP intensity change was linearly proportional to the concentration of protamine in the range 0.2–3.0 μg ml −1 , and the limit of detection was 0.14 μg ml −1 . The proposed method was successfully applied to detect protamine in protamine sulfate injection and human serum samples with satisfactory results, and the recovery ranged from 96.5 to 105.6%. [ABSTRACT FROM AUTHOR]

A “turn off–on” switch mode was established by using the interaction between acridine orange (AO) and DNA as an input signal and using the room temperature phosphorescence (RTP) reversible change of 3-mercaptopropionic acid (MPA)-capped Mn-doped ZnS quantum dots (QDs) as an output signal in biological fluids. AO was absorbed into the surface of Mn-doped ZnS QDs via electrostatic attraction and, thus, formed a ground-state complex through photoinduced electron transfer (PIET). This complex quenched the phosphorescence of Mn-doped ZnS QDs and then rendered the system into the “turn-off” mode. Along with the addition of DNA and embedded binding with DNA, AO was competitively induced to fall off from the surface of Mn-doped ZnS QDs and embed into the double helix structure of DNA. As a result, the RTP of Mn-doped ZnS QDs was recovered and the system consequently was rendered into “turn-on” mode. In this case, a new biosensor for DNA detection was built and has a detection limit of 0.033 mg L −1 and a detection range from 0.033 to 20 mg L −1 . What is more, this kind of biosensor does not require complex pretreatments and is free from the interference from autofluorescence and scattering light. Thus, this biosensor can be used to detect DNA in biological fluids. [ABSTRACT FROM AUTHOR]

Image classification has always been a hot research direction in the world, and the emergence of deep learning has promoted the development of this field. Convolutional neural networks (CNNs) have gradually become the mainstream algorithm for image classification since 2012, and the CNN architecture applied to other visual recognition tasks (such as object detection, object localization, and semantic segmentation) is generally derived from the network architecture in image classification. In the wake of these successes, CNN-based methods have emerged in remote sensing image scene classification and achieved advanced classification accuracy. In this review, which focuses on the application of CNNs to image classification tasks, we cover their development, from their predecessors up to recent state-of-the-art (SOAT) network architectures. Along the way, we analyze (1) the basic structure of artificial neural networks (ANNs) and the basic network layers of CNNs, (2) the classic predecessor network models, (3) the recent SOAT network algorithms, (4) comprehensive comparison of various image classification methods mentioned in this article. Finally, we have also summarized the main analysis and discussion in this article, as well as introduce some of the current trends. [ABSTRACT FROM AUTHOR]

A reasonable grasping strategy is a prerequisite for the successful grasping of a target, and it is also a basic condition for the wide application of robots. Presently, mainstream grippers on the market are divided into two-finger grippers and three-finger grippers. According to human grasping experience, the stability of three-finger grippers is much better than that of two-finger grippers. Therefore, this paper's focus is on the three-finger grasping strategy generation method based on the DeepLab V3+ algorithm. DeepLab V3+ uses the atrous convolution kernel and the atrous spatial pyramid pooling (ASPP) architecture based on atrous convolution. The atrous convolution kernel can adjust the field-of-view of the filter layer by changing the convolution rate. In addition, ASPP can effectively capture multi-scale information, based on the parallel connection of multiple convolution rates of atrous convolutional layers, so that the model performs better on multi-scale objects. The article innovatively uses the DeepLab V3+ algorithm to generate the grasp strategy of a target and optimizes the atrous convolution parameter values of ASPP. This study used the Cornell Grasp dataset to train and verify the model. At the same time, a smaller and more complex dataset of 60 was produced according to the actual situation. Upon testing, good experimental results were obtained. [ABSTRACT FROM AUTHOR]

The direction synthesis of biofunctional nanomaterials with DNA as the template is of high application value. By using phosphorothioate-thymine single-stranded DNA (PS-T-ssDNA) as the template and through synthetic conditions optimization, novel low-toxicity and environment-friendly ssDNA-functionalized room-temperature phosphorescent quantum dots (PS-T-ssDNA RTP QDs) were prepared at low temperature (37 °C). Then, the quantitative RTP-based mercury(II) (Hg 2+ ) detection was achieved by utilizing the specific identifying ability of T-base-pair Hg 2+ (T-Hg 2+ -T) and its photoinduced electron transfer. This RTP sensor in Hg 2+ detection had a linear range of 0.02 to 0.8 μM and a detection limit of 4.8 nM. The dependence on RTP of QDs effectively avoids interference from background fluorescence and scattering light in the environment or biological samples. This sensor also possessed an RTP stability and a long service life and did not require sample pretreatment. Thus this sensor is suitable for environmental and quantitative Hg 2+ detection in biological samples.

The thiol-capped CdTe nanocrystals were obtained by a clean chemical approach with hydrazine hydrate. In alkaline aqueous solution, hydrazine hydrate reduced commercial tellurium to be active reactant, and further reduced to negative bivalent telluride for the preparation of CdTe nanocrystals. The resulting CdTe nanocrystals were characterized by UV-Vis absorption spectra, photoluminescence spectra, X-ray diffraction, and high-resolution transmission electron microscopy. The synthesized CdTe nanocrystals were stable with relatively strong photoluminescence in neutral and close neutral range, and further combined with living Corynebacterium glutamicum without any post-preparative treatment. The conjugation samples were observed on laser confocal microscope, and the photoluminescence signals can only be detected at the positions of Corynebacterium glutamicum, which suggests that the CdTe nanocrystals have been combined with Corynebacterium glutamicum successfully.

Here we report the formation and spectroscopic properties of cadmium sulfide (CdS) nanocrystal systems: individual nanocrystal and CdS aggregates. The optical absorption and luminescence spectra of the aggregated CdS nanocrystals and individual nanocrystal show exciton aggregate and individual exciton characteristics. Although it is not Bose-Einstein condensation, such aggregated quantum dots (QDs) seem to supply us opportunity to study the interactions and condensation of excitons in multi-QDs system, not in the separated QDs system.