Search Results (84)

In the present study, (E)-1-(2-(pyridin-2-yl)benzo[d]thiazol-6-yl)-3-(3,4,5-trimethoxyphenyl)prop-2-en-1-one (4) was designed and synthesized via a three-step reaction sequence. Initially, 6-acetylbenzo[d]thiazol-2(3H)-one (1) was hydrolyzed to the corresponding 5-acetyl-2-aminothiophenol 2 and then cyclized with pyridine-2-carbaldehyde. The final product was synthesized by a base-catalyzed aldol condensation of 1-(2-(pyridin-2-yl)benzo[d]thiazol-6-yl)ethan-1-one (3) and 3,4,5-trimethoxybenzaldehyde and was comprehensively characterized. Full article

Silver nanoparticles are metallic particles with very small dimensions and excellent optical, electrical and biological properties. Lately, they have shown promising results in biosensing applications. In the material’s fabrication, the synthesis parameters remain the main aspect to be considered once a certain application is targeted. Therefore, this work presents the synthesis of silver nanoparticles using a chemical reduction based on various volumes of reducing and stabilizing agents. The multiple synthesis methods proposed were tested and optimized in order to achieve the best results for further biosensing applications. In this regard, sodium borohydride (NaBH₄) was used as reducing agent in volumes of 400 μL and 1 mL, while trisodium citrate (TSC) was proposed in much smaller volumes of 10, 20, and 50 μL. The optical and morphological analysis obtained from UV-VIS and TEM microscopy confirmed the formation of nanoparticles in case of all synthesis. The average diameters of silver nanoparticles were in the range between 21 and 27 nm, with high homogeneity for the samples with 20 and 50 μL of TSC. FT-IR analysis confirmed the TSC functionalization on the AgNPs’ surface. SERS analysis and the bulk sensitivity method also showed good surface results, leading to the assumption that both reducing and stabilizing agents can influence the final properties of the material. LSPR biosensing of para-aminothiophenol was tested, and was proven to have detection capabilities at concentrations as low as 10⁻⁷ M. Overall, the results proved that the synthesis method with a smaller amount of reducing agent and a moderate quantity of stabilizing agent has superior properties for biosensing applications. Full article

Caffeine is a natural alkaloid consumed primarily for its stimulant and metabolic effects. Some everyday products, such as coffee, tea, soft drinks, sports supplements, and even pain relievers, contain caffeine. However, excessive caffeine consumption, greater than 400 mg per day, can cause adverse effects. Therefore, this work presents an electrochemical sensor based on a molecularly imprinted polymer (MIP) electropolymerized on gold nanoparticles functionalized with p-aminothiophenol (AuNPs-pATP) for caffeine quantification. AuNPs-pATP synthesized show a spherical morphology with an average diameter of 2.54 nm. Stages of MIP formation were monitored by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) using a potassium ferrocyanide redox probe, where the following were observed: (i) an increase in conductivity upon modification of the GCE with AuNPs-pATP, (ii) the blocking of active sites during the electropolymerization step, and (iii) the release of specific cavities upon template removal, revealing consistent differences between the MIP and the control polymer (NIP). SEM images revealed three-dimensional spherical cavities on MIP surface, while the NIP showed a more compact rough surface. Caffeine quantification was performed using square wave voltammetry (SWV) with LOD of 0.195 µmol L⁻¹ and LOQ of 0.592 µmol L⁻¹. Interference studies indicated high selectivity and a high density of caffeine-specific binding sites in the MIP. Additionally, MIP sensor demonstrated reusability, good reproducibility, and stability, as well as promising results for analysis in soft drink and sports supplement samples. Full article

This work presents the development of carbon nanotubes functionalised with carboxylic acid groups (CNT-COOH) as an oxygen-sensitive electrochemical platform for parallel multi-analyte enzymatic biosensing. The platform was constructed by depositing carboxylic-acid-functionalised single-walled carbon nanotubes covalently onto nanostructured gold electrodes modified with a self-assembled monolayer of 4-aminothiophenol. Atomic force microscopy characterization revealed that the nanotubes attached via their ends to the surface and had a predominantly horizontal orientation. Glucose oxidase, lactate oxidase, glutamate oxidase, and tyrosinase were immobilised onto the electrodes to create selective biosensor for lactate, glucose, glutamate, and dopamine, respectively. A key finding is that incorporating catalase significantly extends the linear detection range for analytes by mitigating the accumulation of hydrogen peroxide. The resulting multifunctional biosensor demonstrated its capability for the simultaneous and independent measurement of glucose, lactate as the key bioanalytes under uniform conditions in blood plasma samples, highlighting its potential for applications in health and food technologies. Full article

The detection of Fe²⁺ in environmental water sources is critical due to its biological relevance and potential toxicity at elevated levels. Herein, we report a plasmon-driven catalytic sensing nanoplatform based on p-aminothiophenol (pATP)-functionalized silver nanoparticles (AgNPs) for the selective and sensitive detection of Fe²⁺. The nanoplatform exploits the inhibition of the plasmon-driven catalytic conversion of pATP to 4,4-dimercaptoazobenzene (DMAB), monitored via surface-enhanced Raman scattering (SERS) spectroscopy. The catalytic efficiency was quantified by the intensity ratio between the formed DMAB-specific Raman band and the common aromatic ring vibration band of pATP and DMAB. This ratio decreased proportionally with increasing Fe²⁺ concentration over a range of 100 µM to 1.5 mM, with a calculated limit of detection of 39.7 µM. High selectivity was demonstrated against common metal ions, and excellent recovery rates (96.6–99.4%) were obtained in real water samples. Mechanistic insights, supported by chronopotentiometric measurements under light irradiation, revealed a competitive oxidation pathway in which Fe²⁺ preferentially consumes plasmon-generated hot holes over pATP. This mechanism clarifies the observed catalytic inhibition and supports the design of redox-responsive SERS sensors. The platform offers a rapid, low-cost, and portable solution for Fe²⁺ monitoring and holds promise for broader applications in detecting other redox-active analytes in complex environmental matrices. Full article

Several benzothiazole (BT) derivatives have recently been explored in medicinal chemistry, and they are frequently reported in the literature. The interest in this kind of heterocyclic compounds and their structural hybrids has been increasing, as shown by several reviews reported over the last decade. In this context, we found that about 70 articles related to the synthesis of BT derivatives that studied their biological activities were published in the last five years. From this, we prepared a review on the synthesis and biological activity studies about this topic. In this bibliographic review it was found that medicinal chemists also explore BT derivatives in search of anticancer and anti-Alzheimer’s candidates. This review comprehends 70 articles, published between 2020 and 2024, related to the synthesis of BT derivatives with the purpose of assessing their biological activities. On the other hand, BT derivatives have been explored as molecular species that perform two or more biological actions, called multifunctional drugs. Some accounts related to the structure–activity relationship which provide a framework for drug discovery and design are also discussed. The synthetic methods of BT synthesis include the use of biocatalysts, solvent-free conditions, photocatalysts, and catalysts supported on nanoparticles. Studies also explore renewable energy sources such as microwave, UV, and visible-light and mechanochemical sources. Full article

The determination of formaldehyde is of paramount importance, as it is present in numerous locations throughout life. In this study, aminophenol-modified gold nanoparticles (ATP-AuNPs) with different relative positions of hydroxyl and amino groups were synthesized for the detection of formaldehyde. They were characterized by transmission electron microscopy (TEM), ultraviolet–visible (UV-Vis) spectroscopy and Fourier transform infrared (FTIR) spectroscopy tests. The results demonstrated that the position plays a crucial role in the composites, which exhibit good stability when the sulfhydryl group and amino group transition from the para position to the neighboring position. Furthermore, the para position was identified as the optimal configuration for formaldehyde detection. When it was used to detect formaldehyde in ultrapure and Li River water, the limit of detection (LOD) was calculated to be 1.03/1.15 mM, respectively. This work not only provides a novel ATP-AuNP sensor but also highlights its practical situations. Full article

Schiff base reactions are widely used in pharmacy, catalysis, and volatile aldehyde detection. However, common biomarker sensing methods struggle to monitor this reaction process precisely due to their sensitivity, their time-consuming nature, and complex substrates. Here, we introduce the Nanoparticle-on-Mirror structure for in situ monitoring this reaction process through the application of a Au nanoparticle-p-Aminothiophenol-Au thin-film platform by surface-enhanced Raman scattering (SERS). Owing to the exposure of -NH₂ groups and the local ultra-strong electromagnetic field in the nanocavity, the Schiff base reactions process can be rapidly monitored within two minutes. Meanwhile, the monitoring platform can detect benzaldehyde molecules as low as 10⁻⁶ M, showing excellent SERS performance. Notably, the Au-nanoparticle-p-Aminothiophenol-Au thin-film platform exhibited anti-interference and specificity, being able to identify BA in the presence of interference. The use of the Au-nanoparticle-p-Aminothiophenol-Au thin-film platform provides a sensing method for Schiff base reactions with accuracy and simplicity of operation, achieving a balanced approach for low-cost and high-performance real-time monitoring, which is expected to be applied in various catalytic reaction process monitoring and catalyst design processes. Full article

The adsorption of p-aminothiophenol (PATP) on metallic nanostructures is a very interesting phenomenon that depends on many factors, and because of that, PATP is an increasingly important probe molecule in surface-enhanced Raman spectroscopy (SERS) due to its strong interaction with Ag and Au, its intense SERS signal, and its significance in molecular electronics. In our study, the SERS spectra of PATP on silver colloids were investigated and we considered several factors, such as the effect of the adsorbate concentration, the nature of the metallic nanoparticles, and the excitation wavelength. Differences between the SERS spectra recorded at high and low concentrations of PATP were explained and DFT calculations of different species were performed in order to support the experimental results. Additionally, time-dependent density-functional theory (TD-DFT) calculations were used to simulate the UV spectra of each species and to determine the MOs involved in each transition. The presence of different species of PATP adsorbed onto the metal surface gave rise to the acquisition of simultaneous SERS signals from those species and the consequent overlapping of some bands with new SERS bands coming from the dimerization of PATP. This work helped to discern which species is responsible for each SERS spectrum under particular experimental conditions. Full article

A highly sensitive, selective and recyclable histidine detection method based on magnetic Fe₃O₄@mTiO₂ (M-TiO₂) nanocomposites with SERRS was developed. Mesoporous M-TiO₂ nanoparticles were functionalized with 4-aminothiophenol and then coupled with histidine through an azo coupling reaction in 5 min, producing the corresponding azo compound. The strong and specific SERRS response of the azo product allowed for ultrasensitive and selective detection for histidine with an M-TiO₂ device loaded with Ag NPs due to the molecular resonance effect and plasmonic effect of Ag NPs under a 532 nm excitation laser. The sensitivity was further enhanced with the magnetic enrichment of M-TiO₂. The limit of detection (LOD) was as low as 8.00 × 10⁻¹² mol/L. The M-TiO₂ demonstrated applicability towards histidine determination in human urine without any sample pretreatment. Additionally, the M-TiO₂ device can be recycled for 3 cycles with the photodegradation of the azo product under UV irradiation due to TiO₂-assisted and plasmon-enhanced photocatalysis. In summary, a multifunctional and recyclable M-TiO₂ device was synthesized based on azo coupling and SERRS spectroscopy for ultra-sensitive and specific histidine sensing. In addition, the proposed system demonstrated the potential for the multiplex determination of toxic compounds in the fields of food safety, industrial production and environmental protection, which benefit from the fingerprint property and universality of SERRS. Full article

Surface-enhanced Raman scattering (SERS) provides an alternative rapid detection method for pesticide residues in food, but fenvalerate possesses poor affinity to the novel metal substrate, thus restricting its analysis. To break this bottleneck, a SERS-active platform with an Ag/rGO composite structure was engineered using a facile method for fenvalerate detection. Ag nanoparticles with a 60 nm diameter can grow evenly on the top and bottom of rGO layers under intense ultrasonic oscillation, and rGO in hybrid material acts as an ideal hotspot holder between the gaps of Ag nanoparticles, not only allowing the interaction area to be enhanced both electromagnetically and chemically but also enabling the capture and enrichment of fenvalerate pesticide molecules into the “hotspot” area to improve detection sensitivity. Ag/rGO composite substrate possesses superior SERS performance with an ultralow detectable concentration of 4-aminothiophenol (10⁻¹⁰ M) and good reproducibility, endowing the material with a better enhancement effect than pure Ag nanoparticles. When used as the SERS substrate for fenvalerate detection, Ag/rGO composite material showed excellent performance in both experiments and theoretical calculation, with the limit of detection (LOD) of fenvalerate being as low as 1.69 × 10⁻⁵ mg/kg and a detection model with an R² of 99.2%, demonstrating its exciting potential as a SERS substrate for pesticides detection. Full article

Heterocycles, compounds featuring heteroatoms like nitrogen, sulfur, and oxygen, are integral in fields such as synthesis, pharmacology, and medicine. Among these, benzothiazoles, formed by fusing thiazole with benzene, hold significant prominence. Their unique reactivity, especially at the carbon position between nitrogen and sulfur, has sparked wide interest. Notably, 2-substituted benzothiazoles exhibit diverse biological activities, including anticonvulsant, antimicrobial, and antioxidant properties, making them valuable in drug discovery. This review unveils an array of mesmerizing methods employed by chemists to prepare these compounds using 2-aminothiophenol as one of the precursors with other varied reactants. From novel strategies to sophisticated methodologies, each section of this review provides a glimpse into the fascinating world of synthetic chemistry of 2-substituted benzothiazoles. Delving into the diverse synthetic applications of 2-substituted benzothiazoles, this paper not only enriches our understanding of their synthesis but also sparks the imagination with the possibilities for future advancements. Full article

Molecularly imprinted polymers (MIPs) have garnered significant attention as a promising material for engineering specific biological receptors with superior chemical complementarity to target molecules. In this study, we present an electrochemical biosensing platform incorporating MIP films for the selective detection of the interleukin-1β (IL-1β) biomarker, particularly suitable for mobile point-of-care testing (POCT) applications. The IL-1β-imprinted biosensors were composed of poly(eriochrome black T (EBT)), including an interlayer of poly(3,4-ethylene dioxythiophene) and a 4-aminothiophenol monolayer, which were electrochemically polymerized simultaneously with template proteins (i.e., IL-1β) on custom flexible screen-printed carbon electrodes (SPCEs). The architecture of the MIP films was designed to enhance the sensor sensitivity and signal stability. This approach involved a straightforward sequential-electropolymerization process and extraction for leaving behind cavities (i.e., rebinding sites), resulting in the efficient production of MIP-based biosensors capable of molecular recognition for selective IL-1β detection. The electrochemical behaviors were comprehensively investigated using cyclic voltammograms and electrochemical impedance spectroscopy responses to assess the imprinting effect on the MIP films formed on the SPCEs. In line with the current trend in in vitro diagnostic medical devices, our simple and effective MIP-based analytical system integrated with mobile POCT devices offers a promising route to the rapid detection of biomarkers, with particular potential for periodontitis screening. Full article

Capsaicinoids, mostly from chili peppers, are widely used in daily life. Capsaicinoids are considered to be markers for the identification of illegal cooking oil (ICO), which is a serious threat to public health. The identification of capsaicinoids can help reveal food-related fraud, thereby safeguarding consumers’ health. Here, a novel and ultrasensitive method was established with a signal amplification strategy for the detection of capsaicinoids. AuNPs@Fe₃O₄ nanocomposites were functionalized with 4-aminothiophenol (4-atp). After diazotization, 4-atp on AuNPs@Fe₃O₄ reacted with capsaicinoids and formed capsaicinoids-azo-atp-AuNPs@Fe₃O₄. Ultimately, capsaicinoids-azo-atp-AuNPs@Fe₃O₄ was dropped onto the surface of a screen-printed carbon electrode (SPCE) and detected via the differential pulse voltammetry (DPV) method. AuNPs@Fe₃O₄ nanocomposites increased the specific surface area of the electrode. Moreover, the diazotization–coupling reaction enriched the analytes on the electrode surface. Liquid–liquid extraction was used for sample pretreatment. Under a pH value of 9.0 and concentration of 0.20 mol/L for the supporting electrolyte, the linearity of capsaicinoids in ICO is from 0.10 to 10.00 ng/mL, and the limit of detection (S/N = 3) is 0.05 ng/mL. This method is ultra-sensitive, reliable, and cost-effective for the detection of capsaicinoids. Herein, this method provides a promising tool for the identification of ICO. Full article

1,4-Benzothiazines are the main building blocks of the naturally occurring pheomelanin pigments, and their chromophoric properties have been strongly related to the well-known phototoxicity of these pigments, partly responsible for the high incidence of melanoma and other skin cancers in red-haired people. However, some peculiar features of the 1,4-benzothiazine chromophore could be functionally exploited in several sectors. Within this context, in this perspective, an overview of the very recently reported applications of the 1,4-benzothiazine chromophore in pH sensing, filter permeability control, smart packaging, electrochromic device fabrication, bioimaging, photocatalysis, and HPLC detection systems is provided, together with a brief presentation of recently developed synthetic approaches to the 1,4-benzothiazine scaffold, with the aim of emphasizing the still-undervalued multifunctional opportunities offered by this class of compounds. Full article