Thiomalate Research Articles

Membrane chromatographic test system for the determination of bisphenol A in drinking water based on the use of an aptamer

A membrane test system has been developed for the rapid determination of bisphenol A in drinking water, utilizing a conjugate of gold nanoparticles with an aptamer that specifically binds the target analyte, and a conjugate of mercaptosuccinic acid with a carrier protein impregnated in the test zone of the strip. The working principle of the test system is based on the binding of free gold nanoparticles in the test zone, which are formed as a result of the competitive interaction of the aptamer with bisphenol A and its release from the surface of the gold nanoparticles. Conjugates of gold nanoparticles with aptamers of different compositions were obtained and tested. Optimal conditions were selected to achieve a low detection limit for bisphenol A. The developed test system allows for the detection of bisphenol A within 15 minutes with a detection limit of 13.5 ng/mL. The suitability of the test system was confirmed by testing drinking water; the detection rate of bisphenol A ranged from 88.2 to 101.3%.

Sn-Pb Perovskite with Strong Light and Oxygen Stability for All-Perovskite Tandem Solar Cells.

Research on mixed Sn-Pb perovskite solar cells (PSCs) is gaining significant attention due to their potential for high efficiency in all-perovskite tandem solar cells. However, Sn2+ in Sn-Pb perovskite is susceptible to oxidation, leading to a high defect density. The oxidation primarily occurs through two pathways: one involving a reaction with oxygen, and the other related to iodine defects, which generate I2 and further accelerate the oxidation of Sn2⁺, greatly reducing stability. First, to tackle the photo-stability issues caused by iodine defects, amber acid (AA) is screened as the additive. The Carboxyl group on AA can strongly coordinate with Sn2+, reinforcing the Sn─I bond and electrostatically interacting with negatively charged defects. This interaction inhibits the photoinduced formation of I2 and the subsequent oxidation of Sn2+, thereby enhancing the stability of Sn─Pb PSCs under continuous illumination. Building on the foundation of AA, a reductive sulfhydryl group is introduced to synthesize thiomalic acid (TA). It inhibits the formation of Sn4+ in both the perovskite precursor and the perovskite film, thereby improving air stability while maintaining strong photostability. Consequently, single PSCs achieved a champion efficiency of 22.7%. The best-performing two-terminal all-perovskite tandem solar cell achieved a power conversion efficiency of 28.6% with improved operational stability.

Strong enhancement on tetrabromobisphenol A removal in natural water matrix by adding cysteine into Cu(II)/peroxymonosulfate system over the wide pH range of 4–12: Efficiency and mechanism

Although Cu(II) can trigger peroxymonosulfate (PMS) oxidation of pollutants, it is only effective under alkaline environments and is susceptible to interference by aqueous matrix components. In this study, cysteine, a natural thiol and amino acid, was found to greatly improve the performance of tetrabromobisphenol A (TBBPA) elimination in the Cu(II)/PMS system across a broad pH range of 4.0–12.0. The cysteine/Cu(II)/PMS system achieved a 94.34 % elimination of TBBPA within 10 min at pH 7.0, which had a 7.55-fold increase in efficiency relative to the Cu(II)/PMS system, and superior to the previously-reported hydroxylamine and gallic acid-enhanced Cu(II)/PMS systems. Cu(III)-(cysteine)2, as opposed to radicals, was the main reactive species leading to the removal of TBBPA, contributing at least 91.53 %. Cysteine first coordinated with Cu(II) through sulfhydryl groups (−SH) and rapidly converted Cu(II)-(cysteine)2 to Cu(I)-(cysteine)2, then Cu(III)-(cysteine)2 was formed finally by the further oxidation of PMS on Cu(I)-(cysteine)2. This enhancement was further extended to other thiols including cysteamine, β-mercaptoethanol and mercaptosuccinic acid. Four potential degradation pathways of TBBPA were inferred from the determined nine degradation intermediates. A marked decline in the toxicity of the reaction solutions was observed after the elimination of TBBPA. Furthermore, the cysteine/Cu(II)/PMS system shown high anti-interference performance with common cations and anions (Ca(II), Mg(II), NO3–, SO42–, HCO3– and Cl–), humic acid and actual water samples. Overall, this study provided a promising approach to extend the working pH range of Cu(II)/PMS system and its anti-interference capability with actual water matrix, which was favorable for its potential utilization in water treatment.

Preparation and Application of Weak Cation Exchange Resin Based on Thiol Click Reaction.

Using poly(styrene-divinylbenzene) microspheres as stationary phase matrix and mercaptosuccinic acid as a modifier, a new weak cation exchange resin was synthesized by thiol click reaction. The conditions for thiol-chlorine click reaction and thiol-alkene click reaction were optimized. The surface morphology and chemical composition of the modified microspheres were characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, and an elemental analyzer. The stationary phase can achieve the separation of six common cations within 25min. A homemade weak cation chromatographic column was used to determine the impurities of Na+ and K+ and the content of tetramethylammonium ions in tetramethylammonium hydroxide samples. The method showed a good linear correlation in the range of 0.1-500.0mg/L with correlation coefficients of 0.9998-0.9999, and the limits of detection (signal-to-noise ratio ≥ 3) were 0.01-0.20mg/L. The intra-day relative standard deviations (RSDs) were in the range of 1.1%-4.4%, and the inter-day RSDs were in the range of 0.8%-14.8%. The spiked recoveries were in the range of 91.92%-119.86%. The results showed that the prepared stationary phase exhibited effective separation ability and good reproducibility, which was suitable for the analysis of the impurities of Na+, K+, and the content of tetramethylammonium in the tetramethylammonium reagents.

Defect-Engineered MOF-801/Sodium Alginate Aerogel Beads for Boosting Adsorption of Pb(II).

Metal-organic frameworks (MOFs) are attractive adsorbents for heavy metal capture due to their superior stability, easy modification, and adjustable pore size. However, their inherent microporous structure poses challenges in achieving a higher adsorption capacity. Defect engineering is considered a simple method to create hierarchical MOFs with larger pores. Here, we employed l-aspartic acid as a mixed linker to bind Zr4+ clusters in competition with fumaric acid of MOF-801 to create defects, and the pore size was increased from 4.66 to 15.65 nm. Mercaptosuccinic acid was subsequently used as a postexchange ligand to graft the resultant MOF-801 by acid-ammonia condensation to further expand the pore size to 22.73 nm. Notably, the -NH2, -COOH, and -SH groups contributed by these two ligands increased the adsorption sites for Pb(II). The obtained defective MOF-801 with larger pores was thereafter loaded onto sodium alginate to form aerogel beads as adsorbents, and an adsorption capacity of 375.48 mg/g for Pb(II) was achieved, which is ∼51 times that of pristine MOF-801. The aerogel beads also exhibited outstanding reusability with a removal efficiency of ∼90.23% after 5 cycles of use. The adsorption mechanism of Pb(II) included ion-exchange interaction, as well as chelation interactions of Pb-O, Pb-NH2, and Pb-S. The versatile combination of defect engineering and composite beads provides novel inspirations for MOF modification for boosting heavy metal adsorption.

Enhancing water purification efficiency with zirconium-mercaptosuccinic acid metal-organic framework integrated mixed matrix membranes: Synthesis, comprehensive characterization, and performance insights

The development of metal-organic framework (MOF) based membranes has shown great potential to address the bottlenecks in industrial wastewater treatment. This study emphasized a novel approach involving a zirconium-based MOF (Zr-MA-MOF) with mercaptosuccinic acid (MA) as a ligand for fabricating mixed matrix membranes (MMMs). These MMMs were fabricated using a polyethersulfone (PES) matrix embedded with different nanofiller loadings of 0.25, 0.5, 0.75, and 1.0 wt%. Consequently, this study investigated the impact of Zr-MA-MOF loadings on the membrane morphology and functional performance, particularly focusing on pure water flux, rejection of salts, heavy metals, and dyes, antifouling properties, and long-term stability. The MMM with a loading of 0.75 wt% Zr-MA-MOF emerged as a standout performer, delivering an exceptional water flux of 71 Lm−2h−1 and rejection efficiencies of 80, 74, and 99 % for divalent magnesium sulfate (MgSO4), monovalent sodium chloride (NaCl), and dyes (including methylene blue, congo red, and rose bengal), respectively. The heavy metal rejection capabilities of the Zr-MA-MOF membrane were equally remarkable, with rejection rates of 90, 92, and 94 % for arsenic, chromium, and aluminum ions, respectively. Furthermore, a flux recovery ratio of 92 % showcased the great potential for sustainable industrial applications. These findings revealed that the integration of Zr-MA-MOF into membrane technology holds great potential for water treatment processes, catering to both human consumption and industrial applications for diverse wastewater treatment needs.

PARAFAC under non-negativity constraint is adapted to recover the underlying Beer-Lambert law of the excitation-emission fluorescence matrix measurements acquired from analyte-triggered semiconductor QDs photoluminescence modulation. When and why?

BackgroundAnalyte-triggered semiconductor quantum dots (QDs) modulation in the presence of non-consistently responsive fluorescent species represents a challenging analytical issue in concrete multi-way data handling. QDs with heterogeneous sizes and/or uneven distribution of functional moieties on their surfaces exhibit significant fluctuations in the fluorescent response components, known as chemical rank, across different excitation/emission modes. This phenomenon may lead to a substantial deviation from the proportionality prescribed by Beer-Lambert law. Nonetheless, even in the presence of such deviation, a multi-way model may be successfully selected after determining a proper chemical rank in a QDs system. ResultsWe show that in a valid PARAllel FACtor (PARAFAC) model under properly determined chemical rank, meaningfully resolved pure spectral profiles can be reached for each fluorescent responsive constituent in the original excitation-emission fluorescence matrix (EEFM) measurements. This was thoroughly illustrated by applying PARAFAC trilinear decomposition of a three-way data array of two distinct datasets acquired from semiconductor QDs sensing systems with low-rank trilinear assumption. The first dataset, presented here for the first time, comprises EEFM measurements of the ligand-driven quenching of thiomalic acid (TMA)-capped AgInS2 (AIS) QDs by vomitoxin. The second dataset, employed for illustrative purposes, comprises EEFM measurements of the quenching, via cation bridging, of glutathione (GSH)-capped CdTe QDs by Pb(II). The results of this study enabled the determination of vomitoxin at a ppb level in real samples of fish feeds, showcasing the efficacy of the PARAFAC model in resolving spectral signatures (loadings) and pure concentration profiles (scores). SignificancePARAFAC under a properly examined chemical rank can be easily adapted for retrieval the underlying Beer-Lambert law of the original EEFM measurements with a low-rank trilinear structure through the chemically meaningful information either when (i) no deviation of Beer-Lambert law was observed as deeply discussed in connection with the dataset acquired from vomitoxin-driven molecular sensing through TMA-capped AIS QDs, or when (ii) substantial deviations of the Beer-Lambert law are evident, as discussed in connection with the dataset collected from sensing ionic species through Pb(II) bridging of GSH-capped CdTe QDs.

Multi-ligand strategy for enhanced removal of heavy metal ions by thiol-functionalized defective Zr-MOFs

Given the significant global concern about heavy metal pollution, the development of effective adsorbents to capture pollutants has become an urgent issue. In this work, thiol-functionalized defective Zr-MSA-DMSA was designed by mixing 2,3-dimercaptosuccinic acid and mercaptosuccinic acid, which was applied for the rapid and efficient removal of M(II) (i.e., Pb(II), Hg(II), Cd(II)) from wastewater. Zr-MSA-DMSA exhibited excellent adsorption performance, and the maximum adsorption capacities for Pb(II), Hg(II), and Cd(II) were 715.2 mg g−1, 862.7 mg g−1, and 450.5 mg g−1. In actual wastewater, Zr-DMSA-MSA exhibited up to 97 % M(II) removal efficiency and excellent anti-interference ability. It also maintained good structural stability after five adsorption/regeneration cycles. Thus, the abundant oxygen vacancies and unsaturated adsorption sites on Zr-MSA-DMSA significantly improved the adsorption performance of M(II). Spectral analysis and DFT calculations confirmed that Zr-MSA-DMSA mainly relied on the coordination of sulfur and oxygen atoms, electrostatic attraction and a large number of defective sites to achieve the adsorption of M(II). Fixed bed experiments showed that Zr-MSA-DMSA exhibited a depletion time of 10500 min and a volume of 7.0 L. In summary, Zr-MSA-DMSA holds significant potential for treating heavy metal wastewater and provides potential applications for defect engineering.

Improvement of fluorescence properties by surface modification of CdS-ZnS quantum dots by thiol compounds and its application as a sensitive fluorescence probe for copper ion detection.

The capped CdS-ZnS quantum dots (QDs) were synthesized with various thiol capping agents of glycolic acid (TGA), mercaptosuccinic acid (MSA), and L-cysteine (LCY) and used as fluorescence probe for determination of Cu (II) ions. The method of two-level three-factor full-factorial experiment design was used to achieve the best optical fluorescence emission. Results revealed that Cu (II) ions can effectively quench the emission of QDs, and the fluorescence intensity is linearly decreased with increasing Cu (II) ion concentration. The limit of detection for CdS-ZnS@ QDs capped with TGA, MSA, and LCY was obtained at 1.15 ×10-7, 1.32 ×10-7, and 2.19 ×10-7mol L-1, respectively, with linear dynamic range of 3.13 ×10-6 to 1.41 ×10-4mol L-1. Luminescence quantum yields of CdS-ZnS@LCY, CdS-ZnS@MSA, and CdS-ZnS@TGA were obtained at 4.17, 1.92, and 2.47, respectively. Results indicated that no significant quenching occurred in the presence of the other metal ions. The binding constant (Kb) of capped CdS-ZnS@ QDs with Cu2+ and the other metal ions was also investigated and discussed. The Kb value for Cu2+ was obtained considerably more than that the other ions. This work presents a new and sensitive method for determination of Cu2+ ion.

Effect of non‐selenium glutathione peroxidase activity of peroxiredoxin 6 on beef tenderness: underlying mechanisms

SummaryThis study investigated the effect of non‐selenium glutathione peroxidase (NSGPx) activity of Peroxiredoxin 6 (Prdx6) on beef tenderness. Longissimus thoracis et lumborum (LTL) muscle from six cattle were obtained at 30 min post‐mortem. Samples from each muscle were randomly assigned to each of four treatment groups: being incubated in H2O2 (simulation of oxidative stress), mercaptosuccinic acid (MA; inhibiting NSGPx activity), N‐acetyl‐L‐cysteine (NAC; inhibiting oxidative stress and increasing NSGPx activity), and saline (control), respectively. Results indicated that cells increased the expression of Prdx6 and NSGPx activity to resist oxidative stress. The inhibition of NSGPx activity group (MA) significantly decreased the Warner‐Bratzler shear force and increased the degradation of desmin. Moreover, both the H2O2 and the MA treatment significantly increased the Ca2+ concentration in the sarcoplasm, cell apoptotic rate, and caspase 9 and 3 activity. These results demonstrated that inhibiting NSGPx activity of Prdx6 could accelerate beef tenderization by promoting mitochondrial apoptosis.

Fluorescent and colorimetric dual-readout platform for tuberculosis point-of-care detection based on dual signal amplification strategy and quantum dot nanoprobe

Rapid and accurate diagnosis of tuberculosis (TB) is of great significance to control the spread of this devastating infectious disease. In this work, a sensitive and low-cost point-of-care testing (POCT) detection platform for TB was developed based on recombinase polymerase amplification (RPA)-catalytic hairpin assembly (CHA)-assisted dual signal amplification strategy. This platform could achieve homogeneous fluorescent and visual diagnosis of TB by using CdTe quantum dots (QDs) signal reporter. In the presence of target DNA (IS1081 gene fragment), RPA amplicons blocked by short oligonucleotide strands could trigger CHA signal amplification, leading to the Ag+ releasing from C–Ag+-C structure and the fluorescence quenching of CdTe QDs by the released Ag+. Furthermore, the detection performance of CdTe QDs modified by 3-mercaptopropionic acid (MPA) or thiomalic acid (TMA) (MPA-capped QDs and TMA-capped QDs) was systematically compared. Experimental results demonstrated that TMA-capped QDs exhibited better detection sensitivity due to their stronger interaction with Ag+. The limits of detection (LODs) of fluorescence and visual analysis were as low as 0.13 amol L−1 and 0.33 amol L−1. This method was successfully applied to the clinical sputum samples from 36 TB patients and 20 healthy individuals, and its quantitative results were highly consistent with those obtained by real-time fluorescent quantitative polymerase chain reaction (RT-qPCR). The proposed approach has the advantages of high sensitivity and specificity, simple operation and low cost, and is expected to be applied in clinical TB screening and diagnosis.

Insights into flotation separation mechanism of chalcopyrite from galena using mercaptosuccinic acid as a novel depressant: Experimental and MDS studies

The separation of polymetallic sulfide ores by flotation is a difficult task in the mineral processing industry. In this investigation, a small-molecule organic compound, mercaptosuccinic acid (MSA), was used as a new depressant for inhibiting galena in chalcopyrite flotation. Micro-flotation and surface wettability tests indicated that MSA pronouncedly weakened the floatability of galena but not chalcopyrite, resulting in marked differences in their flotation recovery. Findings of Fourier transform infra-red (FT-IR) spectroscopy measurements and reagent adsorption trials showed that MSA was strongly adsorbed on galena, resulting in the inability of the collector to effectively interact with galena. Atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS) analyses further corroborated that MSA showed a greater affinity for galena than chalcopyrite, this behavior markedly altered the superficial chemical environment of galena. Molecular dynamic simulations (MDS) showed that MSA increased the concentrations of H2O molecules on galena, which enhanced the surface hydrophilicity of galena.

The effect of sulfur atom on the biomedical properties of metal organic frameworks (MOF) prepared from mercaptosuccinic acid (MSA) and dimercaptosuccinic acid (DMSA) with Co(II), Ni(II), and Cu(II) ions

Metal-organic frameworks (MOFs) were prepared at room temperature using natural occurring succinic acid derivatives, mercaptosuccinic acid (MSA), and dimercaptosuccinic acid (DMSA), as organic linker with Co(II), Ni(II), and Cu(II) as metal ions. The porosity, thermal, and structural properties of MSA- and DMSA-based Co(II), Ni(II) and Cu(II) MOFs were characterized and DMSA-Cu(II) MOFs were found to have higher surface area and lower pore size values, 73.7 m2/g, and 12.7 nm, respectively. The metal ion amount in MSA and DMSA-based MOF structures via Atomic Absorption Spectroscopy (AAS) analysis revealed an increased amount of Metal ions with the increasing number of −SH groups in the MOF structures. The antioxidant activities of DMSA-based MOFs were measured higher than MSA-based MOFs by ABTS•+scavenging assay. DMSA-Cu(II) MOFs showed higher antioxidant activity with 4.58 ± 0.13 μmol trolox g−1. Both MSA- and DMSA-MOFs presented hemocompatible behavior at concentrations < 100 µg/mL. Also, against B. subtilis and S. aureus bacteria strains, DMSA-Cu(II) MOFs showed higher antimicrobial activity than all the other prepared MSA- and DMSA-based MOFs with a MIC value of 31 µg/mL and MBC value of 125 µg/mL for both bacteria strains. Moreover, the MSA- and DMSA-MOFs at 250 μg/mL concentration retain about 80 % cell viability for L929 fibroblast cells at 24 incubation time.

Selective and efficient immobilization of cadmium in soil by layered double hydroxides intercalated with the mercaptosuccinic acid

Cadmium (Cd) contamination in cropland poses a significant threat to the quality of agricultural products, but even though in-situ remediation has been extensively applied, non-selective immobilization remains an issue. In order to develop a material that specifically immobilizes Cd in soil, a layered double hydroxide, intercalated with mercaptosuccinic acid (MSA-CFA), was synthesized through co-precipitation. In this case, the MSA-CFA's maximum adsorption capacity was increased from the 513.8 mg·g−1 for unintercalated hydrotalcite CFA to 692.6 mg·g−1. Besides, MSA-CFA efficiently removed 99.25 % of Cd from soil water-extract solution and immobilized up to 70.03 % of bio-available Cd. However, interestingly, its immobilization effects on beneficial metal elements Fe, Mn and Zn were milder, being equivalent to 2/7, 5/7 and 1/2 that of lime, respectively. Moreover, XRD and XPS techniques revealed isomorphous substitution with calcium and sulfhydryl complexation during the Cd adsorption by MSA-CFA. Compared with CFA, the increased adsorption capacity of MSA-CFA for Cd was due to intercalated MSA acting as a new adsorption site, while the enhanced selectivity was contributed by sulfhydryl's affinity for Cd. Altogether, MSA-CFA showed great promise as a competitive and highly efficient candidate amendment in Cd-contaminated soil remediation.

SERS-Based Microneedle Biosensor for In Situ and Sensitive Detection of Tyrosinase.

Tyrosinase (TYR) emerges as a key enzyme that exerts a regulatory influence on the synthesis of melanin, thereby assuming the role of a critical biomarker for the detection of melanoma. Detecting the authentic concentration of TYR in the skin remains a primary challenge. Distinguished from ex vivo detection methods, this study introduces a novel sensor platform that integrates a microneedle (MN) biosensor with surface-enhanced Raman spectroscopy (SERS) technology for the in situ detection of TYR in human skin. The platform utilized dopamine (DA)-functionalized gold nanoparticles (Au NPs) as the capturing substrate and 4-mercaptophenylboronic acid (4-MPBA)-modified silver nanoparticles (Ag NPs) acting as the SERS probe. Here, the Au NPs were functionalized with mercaptosuccinic acid (MSA) for DA capture. In the presence of TYR, DA immobilized on the MN is preferentially oxidized to dopamine quinone (DQ), a process that results in a decreased density of SERS probes on the platform. TYR concentration was detected through variations in the signal intensity emitted by the phenylboronic acid. The detection system was able to evaluate TYR concentrations within a linear range of 0.05 U/mL to 200 U/mL and showed robust anti-interference capabilities. The proposed platform, integrating MN-based in situ sensing, SERS technology, and TYR responsiveness, holds significant importance for diagnosing cutaneous melanoma.

Light-triggered reactions in a new “light” of nanoparticles engineering

This study presents an innovative light-triggered synthesis of nanoparticles (NPs) utilizing UV radiation (λ = 254 nm), thiols (non-toxic mercaptosuccinic acid, MSA), and metal ions (Cu2+, Zn2+, Cd2+, Se4+). Efficient formation of various nanoparticles is achieved by exposing a precursor blend of metal ions and thiols (MSA) to ultraviolet light in compact volumes, like UV-transparent 96-well plates (50 – 300 μL per well) or plastic tubes (1.5 – 50 mL). This process effectively produces different types of nanoparticles, including fluorescent zinc-cadmium quantum dots (ZnCd QDs), non-fluorescent copper nanoparticles (CuNPs), and selenium nanoparticles (SeNPs). The scalability of the method allows for easy upscaling using larger test tubes or downsizing by depositing precursors (10 – 100 μL) on a paper matrix, where UV treatment not only induces NP formation in solution but also facilitates their anchoring to the paper surface. The developed one-pot in situ approach offers a cost-effective, user-friendly, and energy-efficient method for NP production and chemical engineering on paper surfaces. The technique is promising for a wide range of applications, such as interferometric measurement using ZnCd QDs, bactericidal effects of CuNPs against methicillin-resistant Staphylococcus aureus (MIC100 = 0.14 mg/mL), and visible light switchable (ON/OFF) nanozymatic reactors employing SeNPs. We suggest light-triggered chemistry based on thiols and metal ions for effective “soft” synthesis of various nanoparticles and NPs-based devices.

MXene nanosheet-derived N, S-codoped graphene quantum dots for ultrasensitive and selective detection of 3-nitro-l-tyrosine in human serum

3-Nitro-l-tyrosine (3NT) is an oxidative stress metabolite associated with neurodegenerative diseases such as Parkinson's disease and rheumatoid arthritis. In this study, the N, S-co-doped graphene quantum dots (NSGQDs) derived from nitrogen-doped Ti3C2Tx MXene nanosheet via the hydrothermal method in the presence of mercaptosuccinic acid was synthesized as an optical sensing probe to detect 3NT in human serum. Tetramethyl ammonium hydroxide, the nitrogen source and delamination agent, was used to prepare nitrogen-doped MXene nanosheets via one step at room temperature. The as-prepared NSGQDs are uniform with an average size of 1.2 ± 0.6 nm, and can be stable in aqueous solution for at least 90 d to serve as the fluorescence probe. The N atoms in N-MXene reduce the restacking and aggregation of MXene nanosheets, while the sulfur dopant in NSGQDs increases the quantum yield from 6.2 to 12.1 % as well as enhances the selectivity of 3NT over the other 12 interferences via coordination interaction with nitro group in 3NT. A linear range of 0.02–150 μM in PBS and 0.05–200 μM in human serum with a recovery of 97–108 % for 3NT detection is observed. Moreover, the limit of detection can be lowered to 4.2 and 7 nM in PBS and 1 × diluted human serum, respectively. Results obtained clearly indicate the potential application of the N–Ti3C2Tx derived NSGQD for effective detection of 3NT, which can open a window for the synthesis of doped GQDs via 2D MXene materials for ultrasensitive and selective detection of other biometabolites and biomarkers of neurodegenerative diseases in biological fluids.

Exploring the probing capacities of MSA capped CdTe semiconductor quantum dots as optical chemsensors via analytical and isotherms modeling for selective Hg2+ detection

Heavy metal ions bioaccumulation can cause severe damage to environment and human health. Hence, the development of an effective detection assay of trace amounts of these ions is of great importance. Here, CdTe quantum dots (QDs) capped with mercaptosuccinic acid (MSA) ligands have been synthesized in aqueous solution with significant stability and good fluorescence properties. Photophysical characterization was performed using FTIR, XRD, HRTEM and UV–Vis. Absorption, PL and PLRT techniques, seeking their subsequent application as fluorescent probes for metal cations. CdTe-MSA QDs showed selective sensitivity toward Hg2+ ions by monitoring quantitative fluorescence quenching with increasing analyte content. Under optimal conditions, the linear range for the detection was 0.2–6 μM with a detection limit of 0.05 μM. According to the Stern–Volmer model, it can be inferred that a static quenching mechanism via Hg2+ selective binding to MSA carboxylate groups is operating with electron transfer process. Excess of mercuric ions further decreased and red shifted the fluorescence possibly due to competitive cation exchanges. To further explain the corresponding ligation mechanisms, adsorption behavior study was conducted via several isotherms as well as statistical physics models. The pseudo-first-order model can describe the adsorption kinetics of Hg2+ on CdTe-MSA QDs more accurately and the experimental data fitted well the Langmuir isotherm model of monolayer adsorption on homogeneous surface. Furthermore, this spontaneous process conforms to the Hill model as a physisorption with an adsorption energy of 32 kJ.mol−1 associated with the electrostatic interactions and hydrogen bonding. The developed system was assayed in the Hg2+ trace amount detection in real tap water and showed satisfactory accuracy performance meeting analytical requirements. The relevant results demonstrated that CdTe-MSA QDs could be deployed as promising Hg2+ fluorescent chemosensing system with high sensitivity and selectivity over wide linear detection range that have great potential for real water samples analysis.

Mechanistic elucidation of the catalytic activity of silver nanoclusters: exploring the predominant role of electrostatic surface.

The core and the ligand shell of metal nanoclusters (MNCs) have an influential role in modulating their spectroscopic signatures and catalytic properties. The aspect of electrostatic interactions to regulate the catalytic properties of MNCs has not been comprehensively addressed to date. Our present work conclusively delineates the role of the metal core and the electrostatic surface of MNCs involved in the reduction of nitroarenes. A facile surface modification of mercaptosuccinic acid (MSA)-templated AgNCs has been selectively achieved through Mg2+ ions (Mg-AgNCs). Microscopic studies suggest that the size of Mg-AgNCs is ∼3.3 nm, which is considerably higher than that of MSA-templated AgNCs (∼1.75 nm), confirming the formation of a nano-assembled structure. Our spectroscopic and microscopic experiments revealed that the negatively charged AgNCs efficiently catalyze the reduction of 4-nitrophenol (4-NP) with a rate constant of 0.23 ± 0.01 min-1. However, upon surface modification, the catalytic efficiency almost doubles due to the formation of Mg-AgNCs. Catalysis through AgNCs and Mg-AgNCs collectively portrays the role of the core and electrostatic surfaces. Furthermore, the role of electrostatic interaction has been substantiated by varying the ionic strength of the medium, as well as employing different molecular systems. A quantitative assessment of the Debye screening length asserts the correlation between the ionic strength of the medium and the role of electrostatic interactions involved herein. This highly enhanced catalytic aspect has been utilized for the real sample analysis, wherein AgNCs unexpectedly outperform Mg-AgNCs. This approach of real sample analysis also emanates the role of electrostatics involved. This comprehensive investigation represents the influential role of the core and ligand shell of MNCs as well as the role of electrostatics on its catalytic activities, which is relevant for the rational design of highly efficient catalysts.

A sensitive immunosensor for the detection of alkaline phosphatase as a biomarker for fracture healing

Fractures occur at all ages and are highly prevalent. At the same time, there is a problem of delayed healing after fracture, and drugs are often taken to promote healing. Alkaline phosphatase (ALP) is an important indicator for assessing fracture healing, and achieving its quantification would be helpful in evaluating fracture recovery in patients on medication. Here, we present an ultrasensitive immunosensor based on NH2-MIL-101(Cr)@AuNPs/rGO nanocomposites. The poor conductivity of metal–organic skeletons (MOF) limits their electrochemical applications. In this study, NH2-MIL-101(Cr) was used as a carrier for the in situ reductive growth of gold nanoparticles (AuNPs) on its surface. Then NH2-MIL-101(Cr)@AuNPs were synergized with reduced graphene oxide (rGO) to amplify the electrochemical signals. The obtained NH2-MIL-101(Cr)@AuNPs/rGO nanocomposites exhibited electrical conductivity and stability. Mercaptosuccinic acid introduces a sufficiently large number of carboxyl groups by binding to AuNPs, providing abundant binding sites for ALP antibodies. The immunosensor used differential pulse voltammetry (DPV) for electrochemical analysis, and could capture the concentration response in the range of 10-12 −10-5 g mL−1 with a relatively low detection limit of 1.64 pg mL−1. In addition, the sensor has been successfully applied to the detection of ALP in massively diluted serum of fracture patients before and after drug administration.