Determination of trichlorfon using a molecularly imprinted electrochemiluminescence sensor on multi-walled carbon nanotubes decorated with silver nanoparticles

Fabrication of BSA-protected AgNPs modified MIL-53(Al) as SERS substrate for trace determination of diquat and dipterex

Ultrasensitive Surface-enhanced Raman spectroscopy (SERS) method for the detection of diquat/dipterex was established using bovine serum albumin (BSA)-protected silver nanoparticles (AgNPs) modified MIL-53(Al) (named as BSA/MIL-53(Al)/AgNPs). Compared with unmodified AgNPs, BSA/MIL-53(Al)/AgNPs significantly enhanced the Raman signals of diquat and dipterex and the enhancement factors (EFs) were 1.58 × 107 and 2.34 × 107, respectively. The TEM, XRD, TGA, XPS, UV-vis and FT-IR were utilized to characterize BSA/MIL-53(Al)/AgNPs and the binding of the substrate with diquat/dipterex. The optimal measurement conditions were investigated in detail by single factor experiment and response surface model. The impacts of common pesticides and coexisting substances on the determination of diquat/dipterex were studied. Under optimum conditions, linear calibration curves for detecting diquat/dipterex were established with a limit of detection (LOD) of 0.17/0.89 pmol L-1 (3S0/S). The SERS approaches were used to detect diquat and dipterex in several fruits and vegetables. The recovery was 97.10 %-104.82 % with the relative standard deviation (RSD) of 1.04 %-4.15 % (n = 5).

Construction of CuNCs/AgNPs based fluorescent platform for specific enzyme-free detection of trichlorfon

BACKGROUND

As a common organophosphorus pesticide, trichlorfon (TC) is being extensively used in agriculture due to its high efficiency in plant diseases and insect pest control. However, TC should be monitored in a timely manner due to its severe threat to public health. Currently reported fluorescence methods for TC detection largely depend on enzyme inhibition effect, which suffers from their intrinsic defects such as poor selectivity, complexity, or high cost. Hence, it is of essential value to develop a facile and low-cost fluorescence approach to achieve specific enzyme-free detection of TC.

RESULTS

In this work, L-cysteine protected copper nanoclusters (CuNCs) with good stability were prepared as the fluorescence sensing probe. Under alkaline conditions, TC tends to be hydrolyzed to produce dichloroacetaldehyde, which was directly employed as an effective reducing agent to in-situ synthesize silver nanoparticles (AgNPs). The fluorescence of L-cys-CuNCs was quenched by AgNPs through the inner filter effect (IFE), realizing specific enzyme-free determination of TC. Besides, portable and visual detection of TC was achieved depending on a smartphone sensing platform. This method was further employed to monitor TC in cherry tomatoes, potatoes, and cultivated soil samples with satisfying results, illustrating its high potential in monitoring TC in real samples. Overall, this method possesses the attractive superiorities of simplicity, cost efficiency, and specificity for the detection of TC.

SIGNIFICANCE

The strategy has the following advantages. (i) Specific enzyme-free detection of TC was achieved based on CuNCs/AgNPs fluorescent platform. (ii) AgNPs, as CuNCs fluorescence quencher, was directly in-situ synthesized using the hydrolysis products of TC, which avoids adding extra reducing agent and provides a possibility for the waste utilization of TC. (iii) A portable and low-cost smartphone sensing platform was constructed for visually specific determination of TC.

Solid-state electrochemiluminescence sensor based on TiO2@CdSe and Ru(bpy)32+@Ag NPs for ultrasensitive detection of malathion

To sensitively monitor trace-level of malathion (MAT) in vegetable samples, an ultrasensitive solid-state electrochemiluminescence (ECL) sensor was proposed based on TiO2@CdSe and Ru(bpy)32+@Ag NPs. In this system, the introduction of Ag NPs enhanced the initial ECL signal of Ru(bpy)32+- tripropylamine (TPrA). When TiO2@CdSe was introduced into the system, the ECL signal was further enhanced, which may be due to the synergistic effect of the two complexes. Based on the fact that the addition of MAT causes ECL strength to decrease, a ECL sensor for the ultrasensitive trace detection of MAT has been successfully established. Under the optimized conditions, a wide liner detection range of MAT concentrations from 4.0 × 10-14 to 4.0 × 10-9 mol L-1 and a low detection limit (S/N = 3) of 1.3 × 10-14 mol L-1 were obtained. The ECL sensor has been applied to the detection of vegetable samples and satisfactory results were obtained.

De novo synthesis of a novel hapten and development of a monoclonal antibody-based immunoassay for the detection of dichlorvos and trichlorfon

The absence of high-affinity antibodies has hindered the development of satisfactory immunoassays for dichlorvos (DDVP) and trichlorfon (TCP), two highly toxic organophosphorus pesticides. Herein, the de novo synthesis of a novel anti-DDVP hapten was introduced. Subsequently, a specific anti-DDVP monoclonal antibody (Mab) was produced with satisfying affinity to DDVP (IC50: 12.4 ng mL-1). This Mab was highly specific to DDVP, and TCP could readily convert into DDVP under mild alkaline conditions. Leveraging this insight, an indirect competitive ELISA was successfully developed for simultaneous detection of DDVP and TCP. The limit of detection in rice, cabbage and apple for DDVP /TCP was found to be 12.1/14.6 μg kg-1, 7.3/8.8 μg kg-1 and 6.9/8.3 μg kg-1, respectively. This study not only provides an effective strategy for producing a high-quality anti-DDVP Mab but also affords a reliable and cost-effective tool suitable for high-throughput detection of DDVP and TCP in food samples.

An electrochemiluminescence sensor based on Ag NPs amplifying PDDA-modified TbPO4:Ce NWs signal for sensitive detection of lincomycin

The residue of lincomycin in water will not only aggravate the drug resistance of bacteria but also cause damage to the human body through biological accumulation. In this work, an electrochemiluminescence (ECL) aptasensor for the detection of lincomycin was constructed based on polydimethyldiallylammonium chloride (PDDA) functionalized Ce-doped TbPO4 nanowires (PDDA-TbPO4:Ce NWs) and silver nanoparticles (Ag NPs). TbPO4:Ce NWs were used as the luminophore, and PDDA was used to functionalize the luminophore to make the surface of the luminophore positively charged. The negatively charged silver nanoparticles were combined with PDDA-TbPO4:Ce NWs by electrostatic interaction. Ag NPs accelerated the electron transfer rate and promoted the ECL efficiency, which finally increased the ECL intensity of TbPO4:Ce NWs by about 4 times. Under the optimal conditions, the detection limit of the ECL sensor was as low as 4.37 × 10-16 M, and the linear range was 1 × 10 - 15 M to 1 × 10 - 5 M, with good selectivity, stability, and repeatability. The sensor can be applied to the detection of lincomycin in water, and the recovery rate is 97.7-103.4 %, which has broad application prospects.

Strong cathode electroluminescence biosensor based on CeO2 functionalized PCN-222@Ag NPs for sensitive detection of p-Tau-181 protein

Electrochemiluminescence (ECL) biosensors provide a convenient and high sensitivity method for early disease diagnosis. However, creating luminophore arrays relying on powerful ECL signals remains a daunting task. Porphyrin-centered metal organic frameworks (MOFs) exhibit remarkable potential in ECL sensing applications. In this paper, based on a simple one-pot synthesis method, PCN-222@Ag NPs doped with CeO2 was synthesized to enhance the ECL performance. Due to the strong catalytic ability of CeO2, the ECL signal strength of the new material PCN-222@CeO2@Ag NPs is much higher than that of the PCN-222@Ag NPs and PCN-222. The luminous properties of PCN-222@CeO2@Ag NPs become more intense and stable due to the excellent electronic conductivity of Ag NPs. Based on the fact that CuS@PDA composite can quench the ECL signal of PCN-222@CeO2@Ag NPs, we constructed a novel sandwich ECL immune sensor for the detection of phosphorylated Tau 181 (p-Tau-181) protein. The ECL sensor has a great linear relationship with p-Tau-181 protein concentration, ranging from 1 pg/mL to 100 ng/mL. The detection limit is as low as 0.147 pg/mL. This work provides new ideas for developing sensitive ECL sensors for the p-Tau-181 protein, the marker of Alzheimer's disease.