Search

The rapid and sensitive surface-enhanced Raman scattering (SERS) detection of molecular biomarkers from real samples is still a challenge because the intrinsically trace analytes may have a low molecular affinity for metal surfaces. Herein, we develop a smart signal conversion and amplification strategy based on silver–gold–silica core-satellite structure nanoparticles (Ag@Au@SiO2 NPs) to sensitively detect low adsorptive vitamin E using SERS, which has been considered a biomarker of neuromuscular disorders when its abnormal content is measured in the serum of patients. Through the reducibility of vitamin E, Ag+ ions are rapidly reduced to Ag atoms, resulting in the epitaxial growth of Ag nanocrystals on gold nanoparticles forming satellite particle–particle gap-narrowed Ag@Au@SiO2 NPs. The generated strong plasmonic field dramatically enhances the Raman signal of the Raman reporter molecule 4-aminothiophenol (4-ATP) and the detected vitamin E molecules at an estimated level of 58.19 nmol L−1. The sensitivity of this operational SERS strategy provides tremendous prospects for the screening of neuromuscular disorders. [ABSTRACT FROM AUTHOR]

A fluorescent probe based on single metal–organic framework material without additional fluorophores and active sites can significantly improve the stability of the probe for detection, and has very important application value in environmental analysis and detection. In this paper, a simple and rapid fluorescence detection method was established with Zn-MOF, which realized the highly sensitive detection of tetracycline antibiotics and NH4+ in water. The prepared Zn-MOF has abundant pores and can exist stably in water. When tetracycline antibiotics are present in Zn-MOF aqueous solution, based on the unique coordination ability between Zn and N, tetracycline antibiotics rich in N will be adsorbed into the pore canals of MOF, and aggregation-induced luminescence will occur. The original non-fluorescent Zn-MOF will immediately produce yellow fluorescence, realizing the detection of tetracycline antibiotics in water, with the limit of detection reaching 0.017 μM in a linear range of 0.02–13 μM. Zn-MOF is further used for the detection of tetracycline antibiotics in actual samples of milk and honey. Oxytetracycline (OTC) with the best fluorescence response of tetracycline antibiotics was coated on Zn-MOF to synthesize OTC@Zn-MOF fluorescent probe. NH4+ will replace the original ligand of Zn-MOF, which will disintegrate MOF and release OTC, resulting in a fluorescence decrease. Therefore, NH4+ can be detected with low limit of detection (0.038 μM) in a linear range of 0 to 3 mM. The probe is expected to be able to detect ammonia in the environment. [ABSTRACT FROM AUTHOR]

Fenton-like reaction systems have been proven to be efficient as powerful promoters in advanced oxidation processes (AOPs) due to their generated reactive oxygen species (ROS), such as ˙OH and ˙O2−, which can further oxidize a specific chromogenic substrate like 3,3′,5,5′-tetramethylbenzidine (TMB) to generate sensitive color readout and thereby demonstrate more potential in the colorimetric analysis field. However, the inherent drawback of the low rate-limiting step of Fe3+/Fe2+ conversion in the Fenton-like reaction and its resultant inefficiency for H2O2 decomposition hinder its practical applications. We herein communicate an analyte-activated catfish effect based catalysis strategy to promote the Fenton-like reaction, in which dopamine, like a catfish, was added to activate the Fenton-like reaction. By definition, the conversion rate of Fe3+ to Fe2+ in the proposed Fenton-like reaction can be significantly accelerated through a specific DA-mediated electron transfer process which further promotes the reaction activity in the Fenton-like reaction to generate more ˙OH and ˙O2− radicals. As a result, the produced ˙OH and ˙O2− radicals in such a reaction system can significantly oxidize TMB indicator into its oxidation product (TMBox) and therefore indicate the corresponding target-dependent color and photothermal signal readout, enabling the successful fabrication of a more sensitive and stable colorimetric and photothermometric DA sensor. More significantly, this strategy can greatly advance the practical application of Fenton-like reactions in the fields of colorimetric and photothermometric bioassays. [ABSTRACT FROM AUTHOR]

Developing a rapid, low-cost, and multimode detection method for heavy metal ions remains a compelling goal for many applications, including food safety, environmental and biological analysis. This study investigated the influence of Hg2+ on the peroxidase-like activity of gold nanoparticles (GNPs) decorated on carbon dots (CDs) from lysine (denoted as GNP@CDs). A new type of Hg2+-triggered peroxidase-like activity of GNP@CDs was discovered, which could catalyze the oxidation of the colorless 3,3′,5,5′-tetramethylbenzidine (TMB) into blue TMB. Based on the regulation of the catalytically triggered activity, a sensitive colorimetric method for the detection of Hg2+ was developed, with a linear range of 7–150 nM, providing a limit of detection as low as 3.7 nM. The sensor is simple and rapid, and was successfully applied to the detection of Hg2+ enrichment in chlorella, suggesting a promising application in biological analysis. [ABSTRACT FROM AUTHOR]

The metal–organic framework (MOF-74) series has the most open metal sites. The metal ions have different bonding strengths with the ligand in MOF-74 and the bond of the ligand can be successively broken to obtain highly active heteroparticles by controlling the temperature, which is difficult to achieve using traditional methods. Magnetic NiCo/Fe3O4-MOF-74, which is fabricated using trimetallic NiCoFe-MOF-74 as a precursor, is simple and rational in comparison with the traditional magnetic core and tunable MOF shell hybrid composites that are formed using a step-by-step assembly strategy. After thermal treatment under a specific atmosphere, NiCo/Fe3O4-MOF-74 shows higher stability, strong magnetism and more active metal sites compared to the original MOF. NiCo/Fe3O4-MOF-74 shows excellent enrichment capability for the removal of tetracycline, with a high removal efficiency that reached 94.1% within 5 min, which is much higher than that of NiCoFe-MOF-74. The main interaction between the adsorbent and analyte is most likely attributed to the open metal sites that can form a stable metal–ligand with the antibiotic molecules. Furthermore, the material can be reused five times without considerable loss. The prepared material has potential applications for removing antibiotics with high efficiency at low cost. Therefore, the experiments described in this study provide a route to a broad class of MOF-based materials for detecting organic contaminants. [ABSTRACT FROM AUTHOR]

Herein, a simple strategy for constructing activity-controllable nanozymes is proposed based on the glutathione (GSH)-gated surface chemistry of citrate-capped Pt nanoparticles (PtNPs). PtNPs have been shown to have oxidase-like activity that can effectively catalyze the oxidation of 3,3′,5,5′-tertamethylbenzidine (TMB) by O2, resulting in a typical color reaction from colorless to blue. We found that GSH can inhibit the oxidase-like activity of PtNPs as a molecule-gated surface chemistry element, resulting in a dramatic decrease of the oxidation of TMB. The addition of copper ions (Cu2+) could oxidize GSH into glutathione disulfide (GSSG), resulting in the distinct suppression of GSH-modulated PtNP surface chemistry and oxidase-like activity inhibition, which further results in a significant acceleration of TMB oxidation and the obvious recovery of intense blue color. Furthermore, the color-based detection signal associated with the redox of TMB indicator here was found to show good fluorescence and a photothermal effect and exhibit sensitive and selective response toward the proposed molecule-gated surface chemistry and Cu2+ target. On the basis of this phenomenon, we successfully constructed a three-in-one sensor for Cu2+ with a triple signal readout, colorimetric, photothermal (temperature), and fluorescence, depending on the proposed in situ modulation method for PtNP catalysis. The applicability of the three-in-one sensor was also demonstrated by measuring Cu2+ in human serum with a standard addition method, and the results are of satisfactory accuracy as confirmed by ICP-MS measurements. [ABSTRACT FROM AUTHOR]

A novel and highly sensitive photoelectrochemical biosensor for the detection of glucose based on ternary nanocomposites of Au/CuS/TiO2 (Au/CuS/TiO2) has been fabricated. Highly ordered TiO2 nanotube arrays (TiO2 NTs) were prepared by anodization of Ti foils, and CuS nanoparticles (NPs) and Au NPs were deposited on TiO2 NTs by the successive ionic layer adsorption and reaction (SILAR) method. The resultant Au/CuS/TiO2 exhibited excellent photoelectrochemical behavior as a glucose sensor under white light illumination due to the remarkable photocatalytic capabilities of TiO2 and CuS, and the surface plasmonic resonance (SPR) effect of Au NPs. The fabricated Au/CuS/TiO2 non-enzymatic photoelectrochemical sensor showed brilliant catalytic activity, favourable selectivity, good reproducibility and long-term stability for glucose detection under optimized conditions. The linear range was 0.1–3 μM (R = 0.9942) with a detection limit of 0.03 μM (S/N = 3). Moreover, the proposed sensor detected glucose in human serum samples. Thus, Au/CuS/TiO2 appears to be a promising photocatalyst for a non-enzymatic glucose sensor. [ABSTRACT FROM AUTHOR]

A fluorescent probe based on single metal-organic framework material without additional fluorophores and active sites can significantly improve the stability of the probe for detection, and has very important application value in environmental analysis and detection. In this paper, a simple and rapid fluorescence detection method was established with Zn-MOF, which realized the highly sensitive detection of tetracycline antibiotics and NH 4 + in water. The prepared Zn-MOF has abundant pores and can exist stably in water. When tetracycline antibiotics are present in Zn-MOF aqueous solution, based on the unique coordination ability between Zn and N, tetracycline antibiotics rich in N will be adsorbed into the pore canals of MOF, and aggregation-induced luminescence will occur. The original non-fluorescent Zn-MOF will immediately produce yellow fluorescence, realizing the detection of tetracycline antibiotics in water, with the limit of detection reaching 0.017 μM in a linear range of 0.02-13 μM. Zn-MOF is further used for the detection of tetracycline antibiotics in actual samples of milk and honey. Oxytetracycline (OTC) with the best fluorescence response of tetracycline antibiotics was coated on Zn-MOF to synthesize OTC@Zn-MOF fluorescent probe. NH 4 + will replace the original ligand of Zn-MOF, which will disintegrate MOF and release OTC, resulting in a fluorescence decrease. Therefore, NH 4 + can be detected with low limit of detection (0.038 μM) in a linear range of 0 to 3 mM. The probe is expected to be able to detect ammonia in the environment.

Developing a rapid, low-cost, and multimode detection method for heavy metal ions remains a compelling goal for many applications, including food safety, environmental and biological analysis. This study investigated the influence of Hg 2+ on the peroxidase-like activity of gold nanoparticles (GNPs) decorated on carbon dots (CDs) from lysine (denoted as GNP@CDs). A new type of Hg 2+ -triggered peroxidase-like activity of GNP@CDs was discovered, which could catalyze the oxidation of the colorless 3,3',5,5'-tetramethylbenzidine (TMB) into blue TMB. Based on the regulation of the catalytically triggered activity, a sensitive colorimetric method for the detection of Hg 2+ was developed, with a linear range of 7-150 nM, providing a limit of detection as low as 3.7 nM. The sensor is simple and rapid, and was successfully applied to the detection of Hg 2+ enrichment in chlorella, suggesting a promising application in biological analysis.

A novel and highly sensitive photoelectrochemical biosensor for the detection of glucose based on ternary nanocomposites of Au/CuS/TiO2 (Au/CuS/TiO2) has been fabricated. Highly ordered TiO2 nanotube arrays (TiO2 NTs) were prepared by anodization of Ti foils, and CuS nanoparticles (NPs) and Au NPs were deposited on TiO2 NTs by the successive ionic layer adsorption and reaction (SILAR) method. The resultant Au/CuS/TiO2 exhibited excellent photoelectrochemical behavior as a glucose sensor under white light illumination due to the remarkable photocatalytic capabilities of TiO2 and CuS, and the surface plasmonic resonance (SPR) effect of Au NPs. The fabricated Au/CuS/TiO2 non-enzymatic photoelectrochemical sensor showed brilliant catalytic activity, favourable selectivity, good reproducibility and long-term stability for glucose detection under optimized conditions. The linear range was 0.1-3 μM (R = 0.9942) with a detection limit of 0.03 μM (S/N = 3). Moreover, the proposed sensor detected glucose in human serum samples. Thus, Au/CuS/TiO2 appears to be a promising photocatalyst for a non-enzymatic glucose sensor.

A simple and mild strategy was proposed to develop a novel electrochemical sensor based on zirconia/ordered macroporous polyaniline (ZrO2/OMP) and further used for the detection of methyl parathion (MP), one of the organophosphate pesticides (OPPs). Due to the strong affinity of phosphate groups with ZrO2 and the advantages of OMP such as high catalytic activity and good conductivity, the developed sensor showed a limit of detection as low as 2.28 × 10(-10) mol L(-1) (S/N = 3) by square-wave voltammograms, and good selectivity, acceptable reproducibility and stability. Most importantly, this novel sensor was successfully applied to detect MP in real samples of apple and cabbage. It is expected that this method has potential applications in electrochemical sensing platforms with simple, sensitive, selective and fast analysis.

Based on Ru(bpy)(3)(2+)-Au nanoparticles decorated multi-walled carbon nanotubes composites and a molecularly imprinted polymer (MIP), we propose a novel molecularly imprinted electrochemiluminescence (ECL) sensor to selectively determine isoniazid (INH). The MIP is synthesized through electrochemical copolymerization of acrylamide and N,N'-methylene diacrylamide in the presence of INH template molecules. The enhanced ECL intensity is linear in the range of 0.1 to 110 μg cm(-3) and the detection limit is 0.08 μg cm(-3) (3σ) INH with relative standard deviation 3.8% (n = 6) for 8 μg cm(-3). As a result, the sensor has been successfully applied to the determination of INH in human urine and pharmaceutical samples. Moreover, the possible ECL mechanism is discussed.

Electrochemiluminescence (ECL) of Ru(bpy)(3)(2+) using metabolites of catecholamines: homovanillic acid (HVA) and vanillylmandelic acid (VMA) as co-reactants were investigated in aqueous solution for the first time. When HVA and VMA were co-existent in the buffer solution containing Ru(bpy)(3)(2+), ECL peaks were observed at a potential corresponding to the oxidation of Ru(bpy)(3)(2+), and the ECL intensity was increased noticeably when the concentrations of HVA and VMA were at lower levels. The linear calibration range was from 8.0 × 10(-5) to 1.0 × 10(-9) M for HVA and VMA. The detection limit (S/N = 3) of HVA and VMA was 4.0 × 10(-10) M. The formation of the excited state Ru(bpy)(3)(2+*) was confirmed to result from the reaction between Ru(bpy)(3)(3+) and the intermediates of HVA or VMA radicals. Moreover, it was found that the ECL intensity was quenched significantly when the concentrations of HVA and VMA were relatively higher. The mechanism of self-quenching processes involved in the Ru(bpy)(3)(2+)-HVA and -VMA ECL systems are proposed in this study.

A novel idea on the basis of 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin (THPP) functionalized carbon nanotubes (CNTs) film was developed to simulate the chromatographic separation, which was able to rapidly and simultaneously detect dihydroxybenzene isomers based on their different oxidation potentials and corresponding currents. The mechanism involved in the recognition and isolation of the dihydroxybenzene isomers was explored and confirmed by UV spectra and density functional theory. It was proven that the current method for simultaneously detecting and isolating dihydroxybenzene isomers was ascribed to the priority of porphyrin film to induce oxidation of the three kinds of isomers, and the priority depends to a large extent on the different tendencies of dihydroxybenzene to interact with the peripheral hydroxyl group and with the extended π-conjugated ring of porphyrin. Most important of all, porphyrin functionalized CNTs film allows for the formation of well-defined interface and provides an advantageous and high-performance platform for the simultaneous determination and isolation of dihydroxybenzene isomers.

The novel phenomenon of cathodic electrochemiluminescence on a gold electrode in tris(bipyridine) ruthenium(II) (Ru(bpy)(3)(2+)) solution is described for the first time. A cathodic electrochemiluminescence (ECL) was found to mainly occur at 0.4-0.8 V with continuous potential scanning from 0.2-1.4 V and the ECL peak was observed around 0.68 V, which was quite different from generally reported Ru(bpy)(3)(2+) ECL. Our group speculated that Ru(bpy)(3)(2+) possibly reacts with the gold electrode in the acidic phosphate buffer solution (PBS) to generate luminescence. The possible ECL mechanism was discussed according to the presented results. Moreover, it is revealed that the Au as co-reactant in the Ru-system contributed dominantly to the whole ECL. Therefore, the reaction between Ru(bpy)(3)(2+) and the newly formed Au implied that the inert metal Au could become a promising material for ECL investigations.