Palladium-Catalyzed Arylation of C(sp2)-H Bonds and C(sp3)-H Bonds with 4-Amino-benzotriazole as the Bidentate Directing Group.

The arylation of C(sp2)-H and C(sp3)-H bonds in carboxylic acids catalyzed by Pd(II) with 4-aminobentriazole as the directing group was investigated. In addition to activation of the C(sp2)-H bond, selective arylation of alkyl carboxylic acids and amino acids in the ß position can also be achieved. This strategy involved a 5,5-bicyclic Pd intermediate complex whose structure was determined by X-ray single crystal diffraction analysis. Importantly, the DG (directing group) can be easily removed under mild conditions.

A new FRET-based fluorescent probe: Colorimetric and ratiometric detection of hypochlorite and anti-counterfeiting applications.

Hypochlorite (ClO-), as the main component of widely used disinfectants in daily life, comes into closer contact with the human body, which can lead to a number of diseases. The high-performance method is increasingly needed to detect ClO- in our daily life. In this report, we successfully synthesized a FRET ratiometric fluorescent probe (NDAC) containing benzoxadiazole moieties and coumarin moieties bound via ethylenediamine. As expected, NDAC has excellent selectivity and anti-interference ability toward ClO-, and the ratio of fluorescence intensity (I471 nm/I533 nm) has a very good linear relationship with the concentration of ClO-, with a wide linear range (2.5-1750 µM) and low detection limit (0.887 µM). Furthermore, we have successfully applied it for the quantitative detection of ClO- in water samples in daily life. At the same time, there is a very clear change in the fluorescence color after the reaction of the NDAC with ClO-. The blue/green value (B/G) of this color change also shows a very good linear relationship to ClO- (5.0-1000 µM). Therefore, the NDAC has also been successfully used for test strip detection and quantitative detection of ClO- in actual samples through smartphone-based fluorescence image analysis, and this method can provide faster, more convenient and more accessible detection. In addition, NDAC sensors also have potential applications in the field of information anti-counterfeiting.

Synthesis of Benzo[a]carbazoles and Dibenzo[c,g]carbazoles via Sequential Gold Catalysis and Photomediated Cyclization.

Herein, we report a reaction protocol for the construction of benzo[a]carbazole and dibenzo[c,g]carbazole frameworks. The detailed gold catalytic reaction conditions developed for the challenging intermolecular carbon nucleophilic addition to internal alkynes are realized, giving the desired alkyne hydroarylation products in good yields. The resulting trisubstituted alkenes are able to undergo photomediated cyclization, furnishing the desired carbazole molecules with excellent yields and high efficiency.

One-Pot Synthesis of Polycyclic Sultams Enabled by Gold-Catalyzed Hydroamination of o-Alkynylbenzenesulfonamides and Subsequent Iodine(III)-Mediated Counteranion-Assisted Intramolecular Annulation.

Herein we present a facile and efficient one-pot synthetic protocol for the construction of polycyclic sultams. This protocol involves gold-catalyzed intramolecular hydroamination of o-alkynylbenzenesulfonamides followed by HTIB-mediated counteranion-assisted intramolecular annulation. The transformation tolerates a wide range of functional groups, resulting in the formation of highly functionalized and valuable polycyclic sultam skeletons in moderate to excellent yields. These polycyclic sultams are widely used as key building blocks in organic science.

A new ratiometric fluorescent probe for rapid and highly selective detection of Cysteine in bovine serum.

As one of the most fundamental thiol compounds in the human body, cysteine (Cys) is involved in maintaining redox balance. Abnormal Cys levels can lead to various diseases. In this work, we successfully synthesized a fluorescent probe (CTBA) that can specifically detect Cys using acrylate as the reaction site, and CTBA has met the selectivity and anti-interference for Cys detection under optimized conditions. The linear range for Cys detection is between 0.05 and 100 µM and the detection limit is 0.0381 µM. Finally, this probe is used to detect the Cys content in three bovine serum samples and the test results are satisfactory.

A novel dual-function fluorescent probe for the detection of cysteine and its applications in vitro.

A fluorescent probe of both colorimetric and ratiometric type for highly selective and sensitive detection of Cys (cysteine) is very important in biological analysis. In this work, a new colorimetric and ratiometric fluorescent probe ((E)-2-(2-(5-(4-(acryloyloxy)phenyl)furan-2-yl)vinyl)-3-methylbenzo[d]thiazol-3-ium iodide, LP-1) was designed and synthesized for the detection of Cys. The reaction mechanism of LP-1 toward Cys involves a conjugate addition reaction between Cys and the α,ß-unsaturated carbonyl group, leading to the formation of an intermediate thioether, followed by intramolecular cyclization to produce the desired compounds LP-1-OH. At this point, the ICT process is activated, significantly increasing the fluorescence intensity of the molecules. Meanwhile, LP-1 is highly selective and sensitive to Cys identification under optimized experimental conditions. LP-1 shows a good linear relationship in the range of Cys concentration from 0.40 µM to 40 µM (R2 = 0.9942) and the limit of detection (LOD) of Cys is 0.19 µM. In addition, we have developed a simple, portable and low-cost smartphone-based high-sensitivity Cys detection method based on naked eye obvious color detection. LP-1 also has low cell toxicity and can be successfully used for biological imaging of Cys, suggesting that it is a promising biological application tool for Cys detection.

Natural and anthropogenic controls on environmental change during the Holocene based on a multi-proxy record obtained from subalpine peatland in southern China.

The interactions between past climate, human activity and environmental change in subtropical mountainous areas are poorly understood due to the lack of reliable records in South China. In this study, the evolution of the East Asian summer monsoon (EASM) during the Holocene, and the interactions between regional human activity and environmental change, were studied using multi-proxy records from a subalpine peat core recovered from South China. The chronology of this peat core has been well-constrained by 10 AMS 14C dates of peat stems. A series of proxy indicators, including carbon isotopes (δ13C), loss on ignition (LOI), magnetic susceptibility (MS), the chemical index of alteration (CIA), and geochemical elements from the Shiwangutian (SWGT) peatland were used to reconstruct the palaeohydrological changes during the Holocene. Regional moisture levels showed a generally arid-wet-arid pattern, and three phases of climatic change were detected as follows. 1) Between 11,600 and 9000 cal yr BP, the EASM was weak and a relatively dry climate developed. 2) Between 9000 and 4000 cal yr BP, the prevalence of humid climatic conditions was associated with a strong summer monsoon. 3) After 4000 cal yr BP, the climate shifted to relatively dry conditions. Further comparisons and analysis suggested that solar insolation, migration of the Intertropical Convergence Zone (ITCZ), and El Niño-Southern Oscillation (ENSO) activity played an important role in determining the variations in Holocene EASM intensity. In addition, the increase in both MS and heavy metal concentrations over the last 1000 years is consistent with an increase in the population of Hunan Province. Therefore, it can be inferred that population growth and the associated expansion of cropland and mining led to an increase in soil erosion and metal tool use. These findings suggest that the impact of human activity generally outweighed the natural climatic controls on the environment and landscape in the mountainous region of southern China over the last 1000 years.

A novel fluorescent molecule based on 1,2,3-triazole for determination of palladium (II) and hydrazine hydrate in aqueous system.

In recent years, hydrazine hydrate has been widely used in various fields as fuel and chemical raw materials, etc. However, hydrazine hydrate is also a potential threat to living body and natural environment. The effective method is urgently needed to detect hydrazine hydrate in our living environment. Secondly, as a precious metal, palladium has attracted more and more attention because of its excellent properties in industrial manufacturing and chemical catalysis. However, its potential danger is also slowly approaching, so it is necessary to find an excellent way to detect palladium, too. Herein, a fluorescent molecule, 4,4',4'',4'''-(1,4-phenylenebis(2H-1,2,3-triazole-2,4,5-triyl)) tetrabenzoic acid (NAT), was synthesized. Firstly, NAT has very high selectivity and sensitivity for determination of Pd2+, because Pd2+ can coordinate well with carboxyl oxygen of NAT. The detection performance of Pd2+ is that the linear range is from 0.06 to 4.50 µM and the detection limit is 16.4 nM. Furthermore, the chelate (NAT-Pd2+) can continue to be used for quantitative determination of hydrazine hydrate with a linear range of 0.05-6.00 µM and the detection limit is 19.1 nM. The interaction time of NAT-Pd2+ and hydrazine hydrate is about 10 min. Of course, it also has good selectivity and strong anti-interference ability for many common metal ions, anions and amine like compounds. At last, the ability of NAT to quantitatively detect Pd2+ and hydrazine hydrate in actual samples has also been verified and the results are very satisfactory.

CUDM: A Combined UAV Detection Model Based on Video Abnormal Behavior.

The widespread use of unmanned aerial vehicles (UAVs) has brought many benefits, particularly for military and civil applications. For example, UAVs can be used in communication, ecological surveys, agriculture, and logistics to improve efficiency and reduce the required workforce. However, the malicious use of UAVs can significantly endanger public safety and pose many challenges to society. Therefore, detecting malicious UAVs is an important and urgent issue that needs to be addressed. In this study, a combined UAV detection model (CUDM) based on analyzing video abnormal behavior is proposed. CUDM uses abnormal behavior detection models to improve the traditional object detection process. The work of CUDM can be divided into two stages. In the first stage, our model cuts the video into images and uses the abnormal behavior detection model to remove a large number of useless images, improving the efficiency and real-time detection of suspicious targets. In the second stage, CUDM works to identify whether the suspicious target is a UAV or not. Besides, CUDM relies only on ordinary equipment such as surveillance cameras, avoiding the use of expensive equipment such as radars. A self-made UAV dataset was constructed to verify the reliability of CUDM. The results show that CUDM not only maintains the same accuracy as state-of-the-art object detection models but also reduces the workload by 32%. Moreover, it can detect malicious UAVs in real-time.

Heavy Metal Contamination and Ecological Risk Assessments in Urban Mangrove Sediments in Zhanjiang Bay, South China.

With the acceleration of industrialization and urbanization, increasing attention has been paid to the problem of heavy metal pollution in mangroves and its ecological restoration. Urban mangroves can be used to measure the impact of human activities on the urban ecological environment because mangroves are sensitive to human activities. However, studies on the evaluation of heavy metal elements in urban mangroves are still limited. Consequently, this study selected the urban mangroves in a central commercial area of Zhanjiang Bay as a case study to investigate the content and distribution of the heavy metals (Co, V, Cu, Pb, Ni, As, Cd, and Hg) in mangrove surface sediments. Risk levels and possible sources of heavy metals were evaluated based on multivariate statistical analysis methods and pollution indices. The results showed that the average concentrations of heavy metals for Co, V, Cu, Pb, Ni, As, Cd, and Hg were 2.91, 29.96, 18.24, 20.07, 7.86, 5.0, 0.20, and 0.09 mg/kg, respectively. Cd, Cu, and Hg were most prominent within the Zhanjiang Bay mangrove sediments, whereas other metals showed a low contamination factor of therm. Cd displayed a high potential ecological risk followed by Hg and Cu. The sampling site, the sewage outlet sampling site, exhibited the highest pollution degree followed by the surrounding area of the sewage outlet sampling site. Those polluted heavy metals could arise from anthropogenic sources, including domestic sewage and automobile exhaust emission. Correlation analysis between the heavy metals and physicochemical properties indicated that fine particles and organic matter play a key role in controlling heavy metal enrichment.

4-Aminobenzotriazole (ABTA) as a Removable Directing Group for Palladium-Catalyzed Aerobic Oxidative C-H Olefination.

4-Aminobenzotriazole (ABTA) was applied as an effective removable directing group (DG) in Pd-catalyzed C-H activation for the first time. Compared with the widely applied pyridine and quinoline analogs, ABTA showed significantly improved reactivity, achieving aerobic oxidative C-H olefination in excellent yields (up to 95% vs <50% with other reported DGs under identical conditions). Using this new strategy, macrocyclization was achieved to give cyclic peptides in good yields with easy ABTA removal under mild conditions, highlighting the promising potential of this new DG.

Impact of intensive mariculture activities on microplastic pollution in a typical semi-enclosed bay: Zhanjiang Bay.

Microplastic (MP) was investigated in Zhanjiang Bay, a semi-enclosed bay in south China and famous for considerable mariculture industry, to evaluate whether mariculture activities accelerated MP pollution. The MP abundances ranged from 0 to 2.65 n/m3 (number/m3), showing seasonal variances with higher levels in May and September and lower levels in January. In the inner part of the bay, a significantly high MP abundance and predominance of foam were found during the oyster breeding period, and pollution sources were prone to be single and extensive. This suggested that MPs were strongly influenced by the intensive plastic products for oyster culturing, especially during breeding. Moreover, plastic cages used for culturing were the main source of MPs in the central part of the bay. By conducting statistical analysis for eight representative bays, the economic growth, social development, agriculture structure, and aquaculture development were supposed to influence the local MP pollution level.

A novel benzotriazole derivate with Twisted intramolecular charge transfer and Aggregation Induced emission features for proton determination.

Molecules with Aggregation-Induced Emission (AIE) effects could show strong emission in solid or aggregate form, thus they are suitable for applications in the field of solid luminescent materials. According to former reporting, AIE molecules are always J-aggregates. In this study, a new benzotriazole derivate with electron donor-acceptor structure was synthesized. (E)-4-(2-(1H-benzo[d] [1,2,3] triazol-1-yl) vinyl)-N, N-dimethylaniline (BTADA) has both TICT and AIE effect, even though it is H-aggregate. Furthermore, BTADA could respond to proton in solution and solid form. Due to its multiple binging sites, proton would bind to benzotriazole and dimethylaniline moiety successively when BTADA was exposed to acid, and the fluorescent color changed from green to yellow then blue as the concentration of proton increased. Such phenomena indicate BTADA has potential usage in proton detection.

Coastal currents regulate the distribution of the particulate organic matter in western Guangdong offshore waters as evidenced by carbon and nitrogen isotopes.

The δ13C, δ15N and C/N ratio of the particulate organic matter (POM) in western Guangdong waters were determined to evaluate the impacts of the coastal currents on the POM in spring and summer. The predominance of photosynthetic organic matter in the nearshore was triggered by nutrients brought by the coastal currents in spring and summer, while the proportion of terrestrial organic matter in the offshore was very high in spring but low in summer. In spring, the weaker and narrower coastal currents carried insufficient nutrients (phosphate deficiency) to the offshore and prohibited phytoplankton production. This scenario contributes to the dominance of terrestrial organic matter transported by the cyclonic circulation beyond the coastal currents in the offshore in spring. The Bayesian mixing model reveals that the proportion of terrestrial organic matter (with 75.8% of C3 plants) in the offshore was higher in spring than in summer (with 33.7% of C3 plants).

Achieving Aliphatic Amine Addition to Arylalkynes via the Lewis Acid Assisted Triazole-Gold (TA-Au) Catalyst System.

Transition metal catalyzed intermolecular hydroamination of the arylalkynes with aliphatic amine is generally problematic due to the good coordination between amine and metal cation. With the combination of 1,2,3-triazole coordinated gold(I) catalyst (TA-Au) and Zn(OTf)2 cocatalyst, this challenging transformation was achieved with good to excellent yields and regioselectivity. Compared to previously reported methods, this approach offered an alternative catalyst system to achieve this fundamental chemical transformation with high efficiency and practical conditions.

Accelerated atrazine degradation and altered metabolic pathways in goat manure assisted soil bioremediation.

The intensive and long-term use of atrazine in agriculture has resulted in serious environmental pollution and consequently endangered ecosystem and human health. Soil microorganisms play an important role in atrazine degradation. However, their degradation efficiencies are relatively low due to their slow growth and low abundance, and manure amendment as a practice to improve soil nutrients and microbial activities can solve these problems. This study investigated the roles of goat manure in atrazine degradation performance, metabolites and bacterial community structure. Our results showed that atrazine degradation efficiencies in un-amended soils were 26.9-35.7% and increased to 60.9-84.3% in goat manure amended treatments. Hydroxyatrazine pathway was not significantly altered, whereas deethylatrazine and deisopropylatrazine pathways were remarkably enhanced in treatments amended with manure by encouraging the N-dealkylation of atrazine side chains. In addition, goat manure significantly increased soil pH and contents of organic matters and humus, explaining the change of atrazine metabolic pathway. Nocardioides, Sphingomonas and Massilia were positively correlated with atrazine degradation efficiency and three metabolites, suggesting their preference in atrazine contaminated soils and potential roles in atrazine degradation. Our findings suggested that goat manure acts as both bacterial inoculum and nutrients to improve soil microenvironment, and its amendment is a potential practice in accelerating atrazine degradation at contaminated sites, offering an efficient, cheap, and eco-friendly strategy for herbicide polluted soil remediation.

Construction of Stable Helical Metal-Organic Frameworks with a Conformationally Rigid "Concave Ligand".

A helical metal-organic framework was prepared by using a conformationally rigid tetratopic benzoic acid ligand with binding units pointing toward each other (concave ligand). To avoid the obvious intramolecular interactions between binding units, matching spacing groups were applied to introduce atropic repulsion, thereby allowing the formation of extended frameworks for the first time. With this new ligand design, a helical-shaped MOF with significantly improved air and moisture stability was successfully prepared, thus providing a new strategy for ligand design toward porous material constructions.

Spatiotemporal variation, speciation, and transport flux of TDP in Leizhou Peninsula coastal waters, South China Sea.

Phosphorus (P) plays key role in phytoplankton primary production in coastal water. In this study, seawater samples collected within China's Leizhou Peninsula coastal waters from October 2017 to July 2018 were examined to determine the seasonal variation, speciation, and transport flux of total dissolved phosphorus (TDP) linked to hydrographic features. TDP concentration and speciation had significant seasonal variations (P < 0.01), and the annual mean TDP concentration was 0.42 ± 0.25 µmol·L-1. High concentrations of TDP occurred in coastal waters adjacent to Zhanjiang Bay and Jianjiang River estuary, whereas low TDP concentrations were found across large offshore areas. Dissolved inorganic and organic P were the main TDP bulk species in different seasons, comprising up to 55.5 ± 7.9% and 46.5 ± 22.6%, respectively. The Beibu Gulf was annually subjected to 3.5 × 109 mol flux of TDP through the Qiongzhou Strait. Coastal currents, river plumes, and human activities were responsible for the dynamic variations in P species.

Effects of two ecological earthworm species on tetracycline degradation performance, pathway and bacterial community structure in laterite soil.

This study explored the change of tetracycline degradation efficiency, metabolic pathway, soil physiochemical properties and degraders in vermiremediation by two earthworm species of epigeic Eisenia fetida and endogeic Amynthas robustus. We found a significant acceleration of tetracycline degradation in both earthworm treatments, and 4-epitetracycline dehydration pathway was remarkably enhanced only by vermiremediation. Tetracycline degraders from soils, earthworm intestines and casts were different. Ralstonia and Sphingomonas were potential tetracycline degraders in soils and metabolized tetracycline through direct dehydration pathway. Degraders in earthworm casts (Comamonas, Acinetobacter and Stenotrophomonas) and intestines (Pseudomonas and Arthrobacter) dehydrated 4-epitetracycline into 4-epianhydrotetracycline. More bacterial lineages resisting tetracycline were found in earthworm treatments, indicating the adaptation of soil and intestinal flora under tetracycline pressure. Earthworm amendment primarily enhanced tetracycline degradation by neutralizing soil pH and consuming organic matters, stimulating both direct dehydration and epimerization-dehydration pathways. Our findings proved that vermicomposting with earthworms is effective to alter soil microenvironment and accelerate tetracycline degradation, behaving as a potential approach in soil remediation at tetracycline contaminated sites.