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Surface functional groups of molybdenum disulfide (MoS2) quantum dots (QDs) can play a fundamental role in their optical properties. Nonetheless, the use of fluorescent MoS2 QDs as optical probes still requires further investigation regarding their surface properties and functional groups. Because such features depend on the synthesis procedures employed, which influence the nanomaterials' morphologies and structure, it becomes essential to understand the influences of the synthesis parameters on the material properties. Here, we demonstrate how to tune the surface properties of MoS2 QDs by alterations in the synthesis parameters and how they influence the copper ions (Cu2+) detection. Different stoichiometric ratio (Mo:S) between sodium molybdate:l-cysteine and reaction times of 7 or 17 h were used on the syntheses of MoS2 QDs, resulting in changes in the amount of partially oxidized functional groups (SO3/SO3H/SO42–/S2O22–) and oxygen functionalities (Mo–O/MoO/–COOH), according to Fourier transformed infrared and X-ray photoelectron spectroscopies analyses. The results show that the partially oxidized functionalization and sulfur-based groups of MoS2 QDs were obtained and led to remarkable changes in the photoluminescence (PL) properties, with quantum yields ranging from 7.0 to 13.1%. At the optimal synthesis condition, the MoS2 QDs could detect Cu2+ in water with a limit of detection (LoD) as low as 0.07 μM. Additionally, the MoS2 QDs obtained demonstrated the ability to discriminate Cu2+ from other common metal ions by using Principal Component Analysis (PCA). The sensing performance was attributed to the surface functional group tuning, which can be tailored by the synthesis parameters to enhance the LoD, quantum yield, or affinities toward different heavy metals. [ABSTRACT FROM AUTHOR]

Electrospun nanofibrous membranes have garnered significant attention in antimicrobial applications, owing to their intricate three-dimensional network that confers an interconnected porous structure, high specific surface area, and tunable physicochemical properties, as well as their notable capacity for loading and sustained release of antimicrobial agents. Tailoring polymer or hybrid-based nanofibrous membranes with stimuli-responsive characteristics further enhances their versatility, enabling them to exhibit broad-spectrum or specific activity against diverse microorganisms. In this review, we elucidate the pivotal advancements achieved in the realm of stimuli-responsive antimicrobial electrospun nanofibers operating by light, temperature, pH, humidity, and electric field, among others. We provide a concise introduction to the strategies employed to design smart electrospun nanofibers with antimicrobial properties. The core section of our review spotlights recent progress in electrospun nanofiber-based systems triggered by single- and multi-stimuli. Within each stimulus category, we explore recent examples of nanofibers based on different polymers and antimicrobial agents. Finally, we delve into the constraints and future directions of stimuli-responsive nanofibrous materials, paving the way for their wider application spectrum and catalyzing progress toward industrial utilization. [ABSTRACT FROM AUTHOR]

Cellulose nanocrystal (CNC) thin films have gained attention for application in green optoelectronics devices. However, the dependence on plasticizers, external cross-linkers, or auxiliary polymers can impair the full exploration of the nanomaterials' properties. Herein, we report on the evaluation of a surface-oxidized CNCs ultrathin film, made from a formulation that excludes the use of auxiliary compounds, to be used as a sensing platform. The physicochemical characterizations using UV–vis, Fourier transform infrared , and Raman spectroscopies, nuclear magnetic resonance, zeta potential, transmission electron and field emission scanning electron microscopies, X-ray diffraction, thermogravimetric analysis, and contact angle measurement showed that the adopted procedure led to (i) the modification of the CNC surface and (ii) the formation of smaller CNCs. The production of casting films from highly diluted CNC-modified aqueous suspensions showed that a very thin, transparent, self-supporting, and manipulable film could be obtained, which was not the case for diluted unmodified CNC suspension. Additionally, the CNC thin film has been demonstrated to be a suitable platform for hosting graphene quantum dots, based on which an optochemical sensor was successfully employed to detect iron-(III) in a dynamic range from 1 fM to 2 pM, yielding a limit of detection of 0.8 fM. [ABSTRACT FROM AUTHOR]

A disposable electrochemical immunosensor for on‐site detection of aflatoxin B1(AFB1), one of the most toxic mycotoxins in agri‐food products, was fabricated through a low‐cost cut‐printing method and then modified with zein/polypyrrole(PPy) electrospun nanofibers onto which anti‐AFB1 monoclonal antibodies were immobilized covalently. Fabrication was possible with an innovative and simple approach to adsorb nanofibers onto the working electrode during electrospinning. Electrochemical impedance spectroscopy was employed as the principle of detection, and the data collected with a portable potentiostat were treated with information visualization techniques. The nanostructured immunosensor showed a high sensitivity for AFB1 with a linear detection range from 0.25 to 10 ng mL−1 and a theoretical limit of detection of 0.092 ng mL−1, which is adequate to detect AFB1 in food, according to regulatory agencies. [ABSTRACT FROM AUTHOR]

Recently, strategies for developing colorimetric sensors relying on nanozymes for the detection of analytes of health, food, and environmental interest have gained significant importance. Herein, a rapid and sensitive colorimetric assay based on manganese dioxide/graphene quantum dot (MnO2/GQD) composites was developed for the detection of antioxidants in food. The composite, synthesized by a hydrothermal method, served as a nanozyme with outstanding oxidase-like catalytic activity to trigger the 3,3′,5,5′-tetramethybenzidine (TMB) chromogenic reaction. Then, an assay was performed to evaluate the reducing ability of antioxidants toward oxTMB by detecting color changes during the procedure. The colorimetric method achieved high selectivity and sensitivity toward the detection of gallic acid, tannic acid, and ascorbic acid with detection limits (S/N = 3) of 0.07, 0.28, and 0.69 μmol L–1, respectively. Moreover, the assay was used to accurately measure and discriminate the antioxidants in real food samples, revealing its great promise for portable and rapid food analysis. [ABSTRACT FROM AUTHOR]

Oxygen-generating biomaterials have the potential to improve tissue engineering and regenerative therapeutic strategies. However, the development of such materials capable of controlling the local partial pressure of oxygen (pO2) in the long term is still a major challenge. Here we report nanostructured composite membranes comprising electrospun fibers exhibiting a bead-on-string structure as a controlled oxygen-release system for periodontitis treatment. For this, calcium peroxide nanoparticles (CaO2 NPs) and manganese dioxide nanosheets (MnO2 NSs) were incorporated into the structure of hydrophobic electrospun poly (lactic acid) (PLA)-based nanofibers. We use CaO2 NPs as hydrogen peroxide (H2O2)-generating precursors when exposed to water, while MnO2 NSs were applied as a nanozyme to catalyze the decomposition of H2O2 to the final oxygen product. Our results revealed that the beads on the fibrous structure acted as reservoirs of CaO2 NPs and MnO2 NSs. Moreover, the composite membranes provided sustained oxygen release over 7 days, where levels were modulated by the CaO2 NP content. Such constructs exhibited suitable physicochemical properties and antimicrobial activities against some bacteria (e.g., Porphyromonas gingivalis and Treponema denticola) typically associated with aggressive and chronic periodontitis. In vitro studies also revealed that the membranes were not cytotoxic toward human oral keratinocyte (Nok-si) cells as well as enhanced the cell viability when high content of CaO2 NP and MnO2 NS were incorporated into the fiber's structure. Taken together, our results demonstrate that the nanostructured composite membranes show potential to be employed as oxygen-release platforms for periodontal tissue regeneration. [ABSTRACT FROM AUTHOR]

Ammonia (NH3) detection has gained considerable attention in agricultural and environmental monitoring, chemical and pharmaceutical processing, and disease diagnosis, which requires the development of sensors with high sensitivity. Herein, we propose a novel gas sensor based on nanocomposites of TiO2 hollow nanofibers and polyaniline (PANI) for the sensitive detection of ammonia at room temperature. TiO2 nanostructures in anatase phase were prepared by the combination of coaxial electrospinning and calcination treatment. The resulting material was mixed with PANI and deposited onto gold interdigitated electrodes (IDEs). The hybrid platforms exhibited superior sensing performance compared to the platform based on their individual phases, which is ascribed to a synergistic effect from p‐n heterojunction formation. Specifically, the platforms based on TiO2/PANI nanocomposite showed a fast response towards NH3 (e. g., 55 s at 10 ppm) at room temperature (25 °C). Additionally, the platform demonstrated the ability to detect NH3 at low concentrations (10–30 ppm) and a detection mechanism was proposed to explain the results. Overall, these results show the promise of electrospun TiO2 hollow nanofibers/PANI composites for the development of high‐performance room temperature ammonia sensors. [ABSTRACT FROM AUTHOR]