Carbon dots (CDs) are photoluminescent nanomaterials with wide-ranging applications. Despite their photoactivity, it remains unknown whether CDs degrade under illumination and whether such ...photodegradation poses any cytotoxic effects. Here, we show laboratory-synthesized CDs irradiated with light degrade into molecules that are toxic to both normal (HEK-293) and cancerous (HeLa and HepG2) human cells. Eight days of irradiation photolyzes 28.6-59.8% of the CDs to <3 kilo Dalton molecules, 1431 of which are detected by high-throughput, non-target high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry. Molecular network and community analysis further reveal 499 cytotoxicity-related molecules, 212 of which contain polyethylene glycol, glucose, or benzene-related structures. Photo-induced production of hydroxyl and alkyl radicals play important roles in CD degradation as affected by temperature, pH, light intensity and wavelength. Commercial CDs show similar photodegraded products and cytotoxicity profiles, demonstrating that photodegradation-induced cytotoxicity is likely common to CDs regardless of their chemical composition. Our results highlight the importance of light in cytocompatibility studies of CDs.
Large-scale targeted exploration of metal-organic frameworks (MOFs) with characteristics such as specific surface chemistry or metal-cluster family has not been investigated so far. These definitions ...are particularly important because they can define the way MOFs interact with specific molecules (
e.g.
their hydrophilic/phobic character) or their physicochemical stability. We report here the development of algorithms to break down the overarching family of MOFs into a number of subgroups according to some of their key chemical and physical features. Available within the Cambridge Crystallographic Data Centre's (CCDC) software, we introduce new approaches to allow researchers to browse and efficiently look for targeted MOF families based on some of the most well-known secondary building units. We then classify them in terms of their crystalline properties: metal-cluster, network and pore dimensionality, surface chemistry (
i.e.
functional groups) and chirality. This dynamic database and family of algorithms allow experimentalists and computational users to benefit from the developed criteria to look for specific classes of MOFs but also enable users - and encourage them - to develop additional MOF queries based on desired chemistries. These tools are backed-up by an interactive web-based data explorer containing all the data obtained. We also demonstrate the usefulness of these tools with a high-throughput screening for hydrogen storage at room temperature. This toolbox, integrated in the CCDC software, will guide future exploration of MOFs and similar materials, as well as their design and development for an ever-increasing range of potential applications.
Large-scale targeted exploration of metal-organic frameworks (MOFs) with characteristics such as specific surface chemistry or metal-cluster family has not been investigated so far.
A novel ratiometric fluorescence molecularly imprinted sensor based on a dual-emission quantum dot hybrid was fabricated and used as an alternative analytical tool for the detection of tetracycline. ...In the synthesis process, red-emitting quantum dots (r-QDs) and green-emitting quantum dots (g-QDs) were modified by two different methods. Afterward, a stepwise precipitation polymerization imprinting reaction was performed to prepare the novel ratiometric fluorescence molecularly imprinted sensor (MIP–g/r-QD sensor). The MIP–g/r-QD sensor integrated the advantages of molecularly imprinted polymers and ratiometric fluorescence probes. The specific recognition sites in the polymer layers could adsorb tetracycline molecules, and then they caused fluorescence quenching behavior of g-QDs via an electron transfer process. Under the optimal conditions, a linear relationship was obtained covering the range from 10 to 160 μmol/L, with a correlation coefficient of 0.9976 and a high imprinting factor of about 3.3. Moreover, the novel MIP–g/r-QD sensor was successfully applied to detect tetracycline in milk samples. This work provides a new way to fabricate an efficient ratiometric fluorescence molecularly imprinted sensor based on quantum dots for convenient, fast, and highly selective and sensitive detection of organic molecules.
Graphical abstract
A novel ratiometric fluorescence molecularly imprinted sensor based on a dual-emission quantum dot hybrid was fabricated and used as an alternative analytical tool for the detection of tetracycline. AIBN azoisobutyronitrile, EGDMA ethylene glycol dimethacrylate, KH-570 3-(methacryloyloxy)propyltrimethoxysilane, OVDAC octadecyl-4-vinylbenzyldimethylammonium chloride, PDDA poly(diallyldimethylammonium chloride), QD quantum dot, TEOS tetraethoxysilane
Solid electrode processes fall in the central focus of electrochemistry due to their broad-based applications in electrochemical energy storage/conversion devices, sensors and electrochemical ...preparation. The electrolytic production of metals, alloys, semiconductors and oxides
via
the electrochemical reduction of solid compounds (especially solid oxides) in high temperature molten salts has been well demonstrated to be an effective and environmentally friendly process for refractory metal extraction, functional materials preparation as well as spent fuel reprocessing. The (electro)chemical reduction of solid compounds under cathodic polarizations generally accompanies a variety of changes at the cathode/melt electrochemical interface which result in diverse electrolytic products with different compositions, morphologies and microstructures. This report summarizes various (electro)chemical reactions taking place at the compound cathode/melt interface during the electrochemical reduction of solid compounds in molten salts, which mainly include: (1) the direct electro-deoxidation of solid oxides; (2) the deposition of the active metal together with the electrochemical reduction of solid oxides; (3) the electro-inclusion of cations from molten salts; (4) the dissolution-electrodeposition process, and (5) the electron hopping process and carbon deposition with the utilization of carbon-based anodes. The implications of the forenamed cathodic reactions on the energy efficiency, chemical compositions and microstructures of the electrolytic products are also discussed. We hope that a comprehensive understanding of the cathodic processes during the electrochemical reduction of solid compounds in molten salts could form a basis for developing a clean, energy efficient and affordable production process for advanced/engineering materials.
The electrochemical reduction mechanisms of solid compounds in molten salts influence the chemical composition, the microstructure of the electrolytic products and the energy efficiency of the electrolysis.
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•The recent advances in use of surfactant for soil remediation are reviewed.•The mechanisms of surfactant-based soil remediation are discussed.•A review on the application of ...different types of surfactants is made.•The future research direction of surfactant-based technologies is suggested.
Due to the great harm caused by soil contamination, there is an increasing interest to apply surfactants to the remediation of a variety of contaminated soils worldwide. This review article summarizes the findings of recent literatures regarding remediation of contaminated soils/sites using surfactants as an enhancing agent. For the surfactant-based remedial technologies, the adsorption behaviors of surfactants onto soil, the solubilizing capability of surfactants, and the toxicity and biocompatibility of surfactants are important considerations. Surfactants can enhance desorption of pollutants from soil, and promote bioremediation of organics by increasing bioavailability of pollutants. The removal of heavy metals and radionuclides from soils involves the mechanisms of dissolution, surfactant-associated complexation, and ionic exchange. In addition to the conventional ionic and nonionic surfactants, gemini surfactants and biosurfactants are also applied to soil remediation due to their benign features like lower critical micelle concentration (CMC) values and better biocompatibility. Mixed surfactant systems and combined use of surfactants with other additives are often adopted to improve the overall performance of soil washing solution for decontamination. Worldwide the field studies and full-scale remediation using surfactant-based technologies are yet limited, however, the already known cases reveal the good prospect of applying surfactant-based technologies to soil remediation.
The dynamics, duration, and nature of immunity produced during SARS-CoV-2 infection are still unclear. Here, we longitudinally measured virus-neutralising antibody, specific antibodies against the ...spike (S) protein, receptor-binding domain (RBD), and the nucleoprotein (N) of SARS-CoV-2, as well as T cell responses, in 25 SARS-CoV-2-infected patients up to 121 days post-symptom onset (PSO). All patients seroconvert for IgG against N, S, or RBD, as well as IgM against RBD, and produce neutralising antibodies (NAb) by 14 days PSO, with the peak levels attained by 15-30 days PSO. Anti-SARS-CoV-2 IgG and NAb remain detectable and relatively stable 3-4 months PSO, whereas IgM antibody rapidly decay. Approximately 65% of patients have detectable SARS-CoV-2-specific CD4
or CD8
T cell responses 3-4 months PSO. Our results thus provide critical evidence that IgG, NAb, and T cell responses persist in the majority of patients for at least 3-4 months after infection.
•Total factor carbon emissions performance change for Chinese transportation sector is investigated.•The impact of regional heterogeneity is incorporated.•Metafrontier non-radial Luenberger carbon ...emission performance index is proposed.•Carbon emissions performance growth is mainly driven by technological innovation.
This study examines and decomposes dynamic changes in total factor carbon emissions performance within the transportation sector in China, incorporating the impact of regional heterogeneity. For this purpose, we combine the metafrontier approach with the non-radial Luenberger productivity indicator to propose a new definition named the metafrontier non-radial Luenberger carbon emission performance index (MNLCPI). This total factor index includes the efficiency change, best-practice gap change, and metafrontier technology gap change indexes. This method is capable of measuring dynamic changes in total factor carbon emissions performance over time via the production frontier framework and can incorporate group heterogeneity and non-radial slack into its measurement of total factor carbon emission performance. Empirical results applying this method show a 6.2% increase in overall total factor carbon emissions performance for the 2000–2012 period. This growth in carbon emissions performance is mainly driven by technological innovation, and different growth patterns are observed across China’s three main areas in transport sector.
Covalent organic frameworks (COFs) are distinguished from other organic polymers by their crystallinity
, but it remains challenging to obtain robust, highly crystalline COFs because the ...framework-forming reactions are poorly reversible
. More reversible chemistry can improve crystallinity
, but this typically yields COFs with poor physicochemical stability and limited application scope
. Here we report a general and scalable protocol to prepare robust, highly crystalline imine COFs, based on an unexpected framework reconstruction. In contrast to standard approaches in which monomers are initially randomly aligned, our method involves the pre-organization of monomers using a reversible and removable covalent tether, followed by confined polymerization. This reconstruction route produces reconstructed COFs with greatly enhanced crystallinity and much higher porosity by means of a simple vacuum-free synthetic procedure. The increased crystallinity in the reconstructed COFs improves charge carrier transport, leading to sacrificial photocatalytic hydrogen evolution rates of up to 27.98 mmol h
g
. This nanoconfinement-assisted reconstruction strategy is a step towards programming function in organic materials through atomistic structural control.
Nitriles are widely existed in many bioactive compounds, and they can be easily transformed into other functional groups. Therefore, the synthesis of nitriles under cyanide-free conditions is of ...significant importance. Recent advances for the synthesis of nitriles through photoinduced C—C bond cleavage of cycloketone oximes classified by the type of C—X bond forming are summarized. Various compounds possessing nitriles can be efficiently accessed via this method.
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