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Portable and sensitive detection of carbendazim (CBD) is highly desirable for food safety and environmental protection. Herein, a portable immunosensor for the sensitive detection of CBD is proposed based on alkaline phosphatase (ALP)-labeled and secondary antibody-modified gold nanoparticles (AuNPs). The quantification is based on ALP catalyzing the dephosphorylation of glucose-1-phosphate disodium salt to generate glucose, thus converting the concentration of CBD into glucose, thereby realizing the portable detection of CBD by personal glucose meter. Benefiting from signal amplification strategy that integrates the large specific surface area of AuNPs, the enzymatic reactions of terminal deoxynucleotidyl transferase and ALP, a low detection limit of 0.37 ng/mL for CBD is achieved. When this portable method is used to analyze citrus fruit, canned citrus, and cabbage, good-consistency results are obtained with the UPLC-MS/MS method. The good performance demonstrates the great potential of this portable method for CBD monitoring in resource-poor settings.

Nobiletin, a polymethoxyflavone mainly found in citrus fruits, have been reported to exhibit various beneficial biological activities for human health. It is an important bioactive compound in traditional Chinese medicine, Pericarpium Citri Reticulatae and Fructus Aurantii. To detect the contents of nobiletin in citrus and herb samples, we developed an indirect competitive enzyme-linked immunosorbent assay (icELISA) based on monoclonal antibodies. It possessed a median inhibition concentration (IC50) of 2.43 ± 0.19 ng/mL and a working range of 0.52–12.3 ng/mL. The assay exhibited the average recoveries of 72.5–85.3% in citrus peel, pulp and juice samples. Moreover, eleven citrus cultivars samples and four herb samples were also detected by the icELISA. The nobiletin content varied in different citrus cultivars samples and herb samples, which were confirmed by the ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS). These results indicated that the developed immunoassay was suitable for detecting nobiletin in citrus and herb samples.

Photothermal reagent-mediated portable detection platforms using thermometers as signal readers have received extensive attention due to their simplicity, low cost, and practicality. However, exploitation photothermal reagent with excellent photothermal conversion effect, convenient to synthesize, preferably without any modification for biosensing application, is still challenging. Herein, a simple and rapid seed-mediated in situ synthesis strategy has been developed for the preparation of gold nanostars (AuNSs) with remarkable photothermal conversion effect. By simply changing the seed size and component concentrations involved in the in situ synthesis process, AuNSs have adjustable geometries, allowing the photothermal conversion to be tuned to a high level optimal for biosensing. Meanwhile, an accurate understanding of the photothermal conversion mechanism is obtained by studying the relationship between the morphology of AuNSs and the photothermal effect. Subsequently, using ascorbic acid (AA) as a model target, the preliminary application of AuNSs in constructing a portable photothermal detection platform has been demonstrated. This in situ preparation strategy of AuNSs not only exhibits remarkable photothermal conversion effect, but also avoids complicated and time-consuming synthesis and modification. Therefore, it has great potential to be extended to portable detection of other targets by simply converting the concentration of the target to that of AA.

An eco-benign effective in-situ decomposed nanofluid dispersive liquid-phase microextraction was developed to determine myclobutanil, flusilazole, hexaconazole, penconazole, epoxiconazole, paclobutrazol and diniconazole in tea drinks and fruit juices by HPLC. Various new nanofluids were prepared using multi-walled carbon nanotubes (MWCNTs) and hydrophilic deep eutectic solvents (DESs), with acetic acid/ DL-lactic acid/glycerol/propylene glycol/ethylene glycol/urea and choline chloride used as hydrogen-bond provider and receiver respectively. The nanofluids was decomposed in-situ in sample solutions, while MWCNTs and DESs served as adsorbent and carrier/stabilizer/dispersing agent, respectively. The optimal parameters influencing the extracting performance were identified by one-factor-at-a-time. The new approach was excellent with relative recovery, linear range, detection limit, quantification limit, and inter- and intra-day RSDs of 70.03-107.14%, 10-10000 μg/L, 3.34-8.30 μg/L, 10-25 μg/L

The detection of carbendazim (CBZ) is important for food safety and human health. However, most current analytical methods require large instruments and highly trained operators. In order to solve this problem, herein, an innovative portable and quantitative photothermal assay platform relying on a thermometer readout for the detection of CBZ has been developed. Gold nanoparticles (AuNPs), which exhibit a strong distance-dependent photothermal effect under specific laser irradiation, were utilized as indicators. The CBZ aptamer was introduced to protect AuNPs from salt-mediated aggregation. When CBZ is present, the binding event between CBZ and aptamer leads to the loss of the aptamer protective effect on AuNPs, and AuNP aggregation occurs. Under 650-nm laser irradiation, the increase in temperature associated with an AuNP-dependent photothermal effect is highly related to the CBZ concentration. Having the advantages of user-friendliness, low cost, quick response, and portability, this method has great potential for on-site applications.

This study examines a new type of inorganic gel plugging fluid that can solidify and plug into lost circulation zones. This approach resolves the difficulty of forming an effective slug in a leakage passage using a plugging agent. Difficulty forming such a slug leads to a low plugging success rate. Tests were performed to examine sample characteristics, such as the suspension stability, rheology, microstructure, and strength. Analysis of the hydration mechanism of the solidifier was performed. This study shows that activators, e.g., NaOH, Na2CO3 and Na2SiO3, can condition the rheology by changing the thickness of the hydration film of charged particles in the system. An alkaline environment can disperse the solidifier vitreum so that it dissolves and develops structures, enabling the working fluid to solidify and form plugs. Field tests at Well X demonstrate that this system can condition the additives based on actual conditions when circulation loss occurs in an oil/gas well. The pressure bearing capacity of the well increases from an equivalent circulation density (ECD) of 1.02 g/cm3–1.61 g/cm3, thus satisfying the requirements to continue drilling. The development of this system provides a new solution for the treatment of circulation loss and establishes a correlation between basic research and industrial application of the relevant materials.

An innovative colorimetric method based on enzyme-induced gold nanoparticle aggregation was developed to detect the activity of alkaline phosphatase (ALP), and it was further applied to construct an aptasensor to monitor ochratoxin A (OTA) concentrations. In the presence of ALP, the substrate ascorbic acid 2-phosphate was hydrolyzed to generate ascorbic acid (AA). Subsequently, reduction of MnO2 nanosheets by AA produced manganese ions, which mediated gold nanoparticle aggregation. The color of the detection solution changed from brown-red to purple to blue as the ALP concentration increased, and a detection limit of 0.05 U·L-1 was achieved. Furthermore, this strategy was successfully utilized to devise a target-responsive aptasensor for colorimetric detection of an important mycotoxin, OTA, which causes food poisoning and has various toxic effects on humans. The proposed method offers high sensitivity with a detection limit as low as 5.0 nM together with high specificity. When applied to analyze red wine and grape juice samples, no complex sample pretreatment or bulky instruments were required. Overall, a colorimetric platform based on enzyme-induced gold nanoparticle aggregation was successfully established to improve the simplicity and sensitivity of ALP and OTA detection. This platform appears highly promising for mycotoxin-related food safety monitoring.

China is one of the most important diversity centres of the genus Citrus L. and is particularly rich in pummelo germplasm. In this study, the flavonoids in the peels and pulps of 28 Chinese local pummelos and four grapefruits were determined by optimised Ultra Performance Liquid Chromatography (UPLC), and their antioxidant capacities were evaluated using 2,2-diphenyl-1-picrylhydrazyl radicals (DPPH), ferric reducing/antioxidant power (FRAP) and superoxide anion methods. We found that naringin was the predominant flavonoid in pummelo, while naringin and neohesperidin were the predominant flavonoids in grapefruit. The fruit peels of Citrus paradisi cvs. Rio Red and Cocktail had the highest contents of naringin (9871.69 mg/kg FW) and neohesperidin (7011.15 mg/kg FW), respectively. Overall, C. paradisi cvs. Cocktail, Rio Red and Changshanhuyou, Citrus grandis cvs. 28-19, Chandler, and Hongxinyou contained more flavonoids and exhibited higher antioxidant capacities and are potentially good sources of phytochemicals and natural antioxidants.

The evolution of diborane accompanying H 2 release during the decomposition of transition metal borohydrides reduces the purity of evolved hydrogen and results in capacity loss during cycling. To solve the problem, a small amount of LiNH 2 is doped into a 3LiBH 4 /MnF 2 composite and the decomposition properties are investigated. The results show that after doping LiNH 2 , the formation of diborane during decomposition is effectively suppressed meanwhile the decomposition temperature is significantly reduced. Around 5 wt.% pure hydrogen can be released at 95–140 °C from 5 wt.% LiNH 2 -doped 3LiBH 4 /MnF 2 composite. These improvements in the decomposition performance are mainly attributed to the prevention of the formation of B–H–B bonds for B 2 H 6 and the destabilization of B–H bonds in borohydrides by the interaction of BH 4 − and NH 2 − .