Immobilization of gold nanoclusters inside porous electrospun fibers for selective detection of Cu(II): A strategic approach to shielding pristine performance

Portable smartphone-integrated AuAg nanoclusters electrospun membranes for multivariate fluorescent sensing of Hg2+, Cu2+ and l-histidine in water and food samples

Detection of heavy metals have been pivotal due to their non-biodegradability and food chain accumulation. Herein, a multivariate ratiometric sensor was developed by in situ integrating AuAg nanoclusters (NCs) into electrospun cellulose acetate nanofibrous membranes (AuAg-ENM) for visual detection of Hg²⁺, Cu²⁺ and consecutive sensing of l-histidine (His), which was integrated into a smartphone platform for quantitative on-site detection. AuAg-ENM achieved multivariate detection of Hg²⁺ and Cu²⁺ by fluorescence quenching, and subsequent selective recovery of the Cu²⁺-quenched fluorescence by His, which distinguished Hg²⁺ and Cu²⁺ and fulfilled determination of His simultaneously. Notably, AuAg-ENM achieved selective monitoring of Hg²⁺, Cu²⁺ and His in water, food and serum samples with high accuracy comparable to ICP and HPLC tests. A logic gate circuit was devised to further explain and promote the application of AuAg-ENM detection by smartphone App. This portable AuAg-ENM provides a promising reference for fabricating intelligent visual sensors for multiple detection.

Advances in electrospun nanofibrous membrane sensors for ion detection

Harmful metal ions and toxic anions produced in industrial processes cause serious damage to the environment and human health. Chemical sensors are used as an efficient and convenient detection method for harmful ions. Electrospun fiber membranes are widely used in the field of solid-state chemical sensors due to high specific surface area, high porosity, and strong adsorption. This paper reviews the solid-state chemical sensors based on electrospinning technology for the detection of harmful heavy metal ions and toxic anions in water over the past decade. These electrospun fiber sensors have different preparation methods, sensing mechanisms, and sensing properties. The preparation method can be completed by physical doping, chemical modification, copolymerization, surface adsorption and self-assembly combined with electrospinning, and the material can also be combined with organic fluorescent molecules, biological matrix materials and precious metal materials. Sensing performance aspects can also be manifested as changes in color and fluorescence. By comparing the literature, we summarize the advantages and disadvantages of electrospinning technology in the field of ion sensing, and discuss the opportunities and challenges of electrospun fiber sensor research. We hope that this review can provide inspiration for the development of electrospun fiber sensors.

Thermoplasmonics Decontamination of Respirators Face Masks Using Silver Nanoparticles: A New Weapon in the Fight Against COVID-19 Pandemic

The current COVID-19 pandemic has resulted in an urgent need for methods to decontaminate respirators masks for reuse while keeping them intact and functional. The severe shortage of professional masks such as N95 and FFP2 has necessitated their reuse over long periods. A very promising method is the pasteurization of these masks by thermoplasmonic heat generated by plasmonics nanoparticles when they are irradiated by light. Under illumination at its plasmonic resonance, a metal nanoparticle features enhanced light absorption, turning it into an ideal nano-source of heat, remotely controllable using light. In this work, we propose a numerical study based on the finite element method (FEM) of the thermoplasmonic properties of silver nanoparticles (AgNPs) decorating polypropylene (PP) fibers which is a basic material for the manufacture of these masks. The surface plasmon resonance (SPR) of these nanostructures was investigated through the computation of the complex effective dielectric permittivity and the absorption cross section in the near UV-visible (NUV-Vis) range. First, the SPR characteristics of AgNPs for different morphologies are determined from the absorption spectra, including the SPR-peak position λ_max and the electric field enhancement. Second, we determine the power absorbed by an individual AgNP of different morphologies. From this, we calculate the internal temperature increase of the particle at the plasmonic resonance. The last step is devoted to the determination of the temperature profile in the surrounding medium in order to better understand and design the plasmon-assisted heating processes at the nanometric scale.

Nanotraps based on multifunctional materials for trapping and enrichment

Many biomarkers for early diagnosis of cancer and other diseases are difficult to detect because they often exist in body fluids in very low concentrations and are masked by high-abundance proteins such as albumin and immunoglobulins. At the same time, water pollution is one of the most serious environmental problems, but the existing adsorption materials have many shortcomings such as slow kinetics, small adsorption capacity and low adsorption efficiency. Nanotraps, mixed with gases or liquids, can capture and concentrate target substances, such as biomolecules, metal ions and oxoanions. Using nanotraps is a versatile sample pre-processing approach and it can improve the sensitivity of downstream analysis techniques. Herein, the preparations and applications of different types of nanotraps are mainly introduced. What's more, the shortcomings of using nanotraps in practical applications are also discussed. Using nanotraps is a promising sample pre-processing technology, which is of great significance for biomarkers discovery, diseases diagnosis, sewage purification and valuable ions recovery. STATEMENT OF SIGNIFICANCE: This review collates and summarizes the preparations and applications of different types of nanotraps, and discusses the shortcomings of using nanotraps in practical applications. Nanotraps, mixed with gases or liquids, can capture and concentrate target materials, such as biomolecules, metal ions and oxoanions. Using nanotraps is a versatile sample pre-processing approach and it can improve the sensitivity of downstream analysis techniques. During the COVID-19 pandemic, hydrogel nanotraps were successfully utilized for RT-PCR analysis with the FDA Emergency Used Authorization for COVID-19. Using nanotraps is a promising sample pre-processing technology, which is of great significance for biomarkers discovery, diseases diagnosis, sewage purification and valuable ions recovery.

Applications of nanomaterials in COVID-19 pandemic

The novel coronavirus 2019 (COVID-19) pandemic represents one of the biggest global health threats in the last two decades, so researchers around the world are searching for solutions and treatments for COVID-19. At the time of writing, there are no specific drugs that have demonstrated suitable effectiveness in treating COVID-19. The current challenge involves designing tools for the prevention, rapid and accurate diagnosis, drug delivery, and effective treatment of this novel coronavirus. In this short review, we discuss how nanotechnology offers new ways to combat COVID-19, and how nanomaterials can be applied to control the COVID-19 outbreak. We also summarize relevant studies regarding the use of nanomaterials for preventing viral spread, preparing vaccines, and diagnosing coronavirus, as well as studies that show how nanoparticles can be used as drug delivery systems for the treatment of viral infections. Research on nanotechnology-based diagnosis, drug delivery, and antiviral therapy is currently in the early stages. However, the unique chemical properties of some nanomaterials highlight the broad prospect of nanomaterials in the future, and we propose that they will play an important role in the fight against COVID-19.

Flexible electrospun nanofibrous film integrated with fluorescent carbon dots for smartphone-based detection and cellular imaging application

The dose of administered chemotherapy drugs is crucial to determine due to the potential for efficient or adverse outcomes for cancer patients. To date, no user-friendly and low-cost method of doxorubicin (DOX) detection using nontoxic and biodegradable materials has been reported. For this reason, in this work, we have developed for the first time a nanofiber-based sensing platform for sensitive and on-site DOX assay in just 10 min. This is obtained thanks to printable, porosity and embeddability features of electrospun nanofibrous films (ENFFs) combined with nitrogen and sulfur co-doped carbon dots (NS-CDs) as sensing probes. The assay was done by just pipetting analyte on the hydrophilic spots of the fabricated photoluminescence water-stable ENFFs where the color intensity was being darkened. DOX quenched NS-CDs fluorescence onto ENFFs through inner filter effect. The developed sensor was either coupled with smartphone technology to provide miniaturized, portable and easy-to-use device or an ordinary spectrofluorimeter for solid-state sensing applications (detection limit of 5.4 nM). Moreover, applicability of the designed sensor was evaluated in human serum with satisfactory recoveries. It is more interesting that the fabricated NS-CDs/ENF scaffolds have a high potential to detect the intracellular DOX to enhance cell proliferation leading to be considered as a multimodal tool in biomedical research and clinical diagnostics.

Encapsulation of gold nanoclusters: stabilization and more

Gold nanoparticles with only a few atoms, known as gold nanoclusters (AuNCs), have dimensions below 2 nm and feature singular properties such as size dependent luminescence. AuNCs are also highly photostable and have catalytic activity, low toxicity and good biocompatibility. With these properties, they are extremely promising candidates for application in bioimaging, sensing and catalysis. However, when stabilized only with small capping ligands, their use is hindered by lack of colloidal stability. Encapsulation of the AuNCs can contribute to provide a more robust protection and even to improve their properties. Here, we review the encapsulation of AuNCs in polymers, silica and metal organic frameworks (MOFs) for applications in bioimaging, sensing and catalysis.

Nanoparticle-based colorimetric sensors to detect neurodegenerative disease biomarkers

Neurodegenerative disorders (NDDs) are progressive, incurable health conditions that primarily affect brain cells, and result in loss of brain mass and impaired function. Current sensing technologies for NDD detection are limited by high cost, long sample preparation, and/or require skilled personnel. To overcome these limitations, optical sensors, specifically colorimetric sensors, have garnered increasing attention towards the development of a cost-effective, simple, and rapid alternative approach. In this review, we evaluate colorimetric sensing strategies of NDD biomarkers (e.g. proteins, neurotransmitters, bio-thiols, and sulfide), address the limitations and challenges of optical sensor technologies, and provide our outlook on the future of this field.

Gold Nanoparticles Synthesis and Antimicrobial Effect on Fibrous Materials

Depositing nanoparticles in textiles have been a promising strategy to achieve multifunctional materials. Particularly, antimicrobial properties are highly valuable due to the emergence of new pathogens and the spread of existing ones. Several methods have been used to functionalize textile materials with gold nanoparticles (AuNPs). Therefore, this review highlighted the most used methods for AuNPs preparation and the current studies on the topic in order to obtain AuNPs with suitable properties for antimicrobial applications and minimize the environmental concerns in their production. Reporting the detailed information on the functionalization of fabrics, yarns, and fibers with AuNPs by different methods to improve the antimicrobial properties was the central objective. The studies combining AuNPs and textile materials have opened valuable opportunities to develop antimicrobial materials for health and hygiene products, as infection control and barrier material, with improved properties. Future studies are needed to amplify the antimicrobial effect of AuNPs onto textiles and minimize the concerns related to the synthesis.

Single nozzle electrospinning promoted hierarchical shell wall structured zinc oxide hollow tubes for water remediation

HYPOTHESIS

Electrospun metal oxide hollow tubes are of great interest owing to their unique structural advantages compared to solid nanofibers. Although intensive research on preparation of hollow tubes have been devoted, formation of hierarchical shells remains a significant challenge.

EXPERIMENTS

Herein, we demonstrate the fabrication of highly uniform, reproducible and industrially feasible ZnO hollow tubes (ZHT) with two-level hierarchical shells via a simple and versatile single-nozzle electrospinning strategy coupled with subsequent controlled thermal treatment.

FINDINGS

The morphological investigation reveals that the hollow tubes built from nanostructures which has unique surface structure on their wall. The mechanism by which the composite fibers transferred to hollow tubes is primarily based on the evaporation rate of the polymeric template. Notably, tuning the heating rate from 5 °C to 50 °C/min possess adverse effect on formation of hollow tubes, thus subsequently produced ZnO nanoplates (ZNP). The comparative photocatalytic analysis emphasized that ZHT shows higher photocatalytic activity than ZNP. This finding has made an evident that the inherent abundant defects in the electrospun derived nanostructures are not only sufficient for improving the photocatalytic activity. Studies on bacterial growth inhibition showcased a superior bactericidal effect against Staphylococcus aureus and Escherichia coli implying its potentiality for disinfecting the bacteria from water.

Personalized Reusable Face Masks with Smart Nano-Assisted Destruction of Pathogens for COVID-19: A Visionary Road

The Coronavirus disease 2019 (COVID-19) emergency has demonstrated that the utilization of face masks plays a critical role in limiting the outbreak. Healthcare professionals utilize masks all day long without replacing them very frequently, thus representing a source of cross-infection for patients and themselves. Nanotechnology is a powerful tool with the capability to produce nanomaterials with unique physicochemical and antipathogen properties. Here, how to realize non-disposable and highly comfortable respirators with light-triggered self-disinfection ability by bridging bioactive nanofiber properties and stimuli-responsive nanomaterials is outlined. The visionary road highlighted in this Concept is based on the possibility of developing a new generation of masks based on multifunctional membranes where the presence of nanoclusters and plasmonic nanoparticles arranged in a hierarchical structure enables the realization of a chemically driven and on-demand antipathogen activities. Multilayer electrospun membranes have the ability to dissipate humidity present within the mask, enhancing the wearability and usability. The photothermal disinfected membrane is the core of these 3D printed and reusable masks with moisture pump capability. Personalized face masks with smart nano-assisted destruction of pathogens will bring enormous advantages to the entire global community, especially for front-line personnel, and will open up great opportunities for innovative medical applications.

Progress in the design and development of "fast-dissolving" electrospun nanofibers based drug delivery systems - A systematic review

Electrospinning has emerged as most viable approach for the fabrication of nanofibers with several beneficial features that are essential to various applications ranging from environment to biomedicine. The electrospun nanofiber based drug delivery systems have shown tremendous advancements over the controlled and sustained release complemented from their high surface area, tunable porosity, mechanical endurance, offer compatible environment for drug encapsulation, biocompatibility, high drug loading and tailorable release characteristics. The dosage formulation of poorly water-soluble drugs often faces several challenges including complete dissolution with maximum therapeutic efficiency over a short period of time especially through oral administration. In this context, challenges associated with the dosage formulation of poorly-water soluble drugs can be addressed through combining the beneficial features of electrospun nanofibers. This review describes major developments progressed in the preparation of electrospun nanofibers based "fast dissolving" drug delivery systems by employing variety of polymers, drug molecules and encapsulation approaches with primary focus on oral delivery. Furthermore, the review also highlights current scientific challenges and provide an outlook with regard to future prospectus.

Functionalized Electrospun Nanofibers as a Versatile Platform for Colorimetric Detection of Heavy Metal Ions in Water: A Review

The increasing heavy metal pollution in the aquatic ecosystem mainly driven by industrial activities has raised severe concerns over human and environmental health that apparently necessitate the design and development of ideal strategies for the effective monitoring of heavy metals. In this regard, colorimetric detection provides excellent opportunities for the easy monitoring of heavy metal ions, and especially, corresponding solid-state sensors enable potential opportunities for their applicability in real-world monitoring. As a result of the significant interest originating from their simplicity, exceptional characteristics, and applicability, the electrospun nanofiber-based colorimetric detection of heavy metal ions has undergone radical developments in the recent decade. This review illustrates the range of various approaches and functional molecules employed in the fabrication of electrospun nanofibers intended for the colorimetric detection of various metal ions in water. We highlight relevant investigations on the fabrication of functionalized electrospun nanofibers encompassing different approaches and functional molecules along with their sensing performance. Furthermore, we discuss upcoming prospectus and future opportunities in the exploration of designing electrospun nanofiber-based colorimetric sensors for real-world applications.

Atomic Layer Deposition of NiOOH/Ni(OH)2 on PIM-1-Based N-Doped Carbon Nanofibers for Electrochemical Water Splitting in Alkaline Medium

Portable and flexible energy devices demand lightweight and highly efficient catalytic materials for use in energy devices. An efficient water splitting electrocatalyst is considered an ideal future energy source. Well-aligned high-surface-area electrospun polymers of intrinsic microporosity (PIM-1)-based nitrogen-doped carbon nanofibers were prepared as a free-standing flexible electrode. A non-noble-metal catalyst NiOOH/Ni(OH)₂ was precisely deposited over flexible free-standing carbon nanofibers by using atomic layer deposition (ALD). The morphology, high surface area, nitrogen doping, and Ni states synergistically showed a low onset potential (η_HER =-40 and η_OER =290 mV vs. reversible hydrogen electrode), small overpotential at η₁₀ [oxygen evolution reaction (OER)=390.5 mV and hydrogen evolution reaction (HER)=-147 mV], excellent kinetics (Tafel slopes for OER=50 mV dec^-1 and HER=41 mV dec^-1 ), and high stability (>16 h) towards water splitting in an alkaline medium (0.1 m KOH). The performance was comparable with that of state-of-the-art noble-metal catalysts (e.g., Ir/C, Ru/C for OER, and Pt/C for HER). Post-catalytic characterization with X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy further proved the durability of the electrode. This study provides insight into the design of 1D-aligned N-doped PIM-1 electrospun carbon nanofibers as a flexible and free-standing NiOOH/Ni(OH)₂ decorated electrode as a highly stable nanocatalyst for water splitting in an alkaline medium.

Fluorescent and Colorimetric Electrospun Nanofibers for Heavy-Metal Sensing

The accumulation of heavy metals in the human body and/or in the environment can be highly deleterious for mankind, and currently, considerable efforts have been made to develop reliable and sensitive techniques for their detection. Among the detection methods, chemical sensors appear as a promising technology, with emphasis on systems employing optically active nanofibers. Such nanofibers can be obtained by the electrospinning technique, and further functionalized with optically active chromophores such as dyes, conjugated polymers, carbon-based nanomaterials and nanoparticles, in order to produce fluorescent and colorimetric nanofibers. In this review we survey recent investigations reporting the use of optically active electrospun nanofibers in sensors aiming at the specific detection of heavy metals using colorimetry and fluorescence methods. The examples given in this review article provide sufficient evidence of the potential of optically electrospun nanofibers as a valid approach to fabricate highly selective and sensitive optical sensors for fast and low-cost detection of heavy metals.

Removal of Retained Electrospinning Solvent Prolongs Drug Release from Electrospun PLLA Fibers

A major challenge in developing drug-releasing electrospun nanofibers is obtaining long-term drug release over many weeks with no burst release of drug. Here, we present new methods capable of prolonging the diffusive release of small molecule drugs from electrospun poly-L-lactic acid (PLLA) nanofibers. The methods focus on removal of retained electrospinning solvent through fiber heating, maintaining fibers in a laboratory setting, or a combination of these methods. These post-fabrication methods altered the release characteristics of a model small molecule drug, 6-aminonicotinamide (6AN), from PLLA fibers. Specifically, untreated fibers released 6AN over 9 days, and fibers that underwent a combined treatment of maintenance in a laboratory setting and heating released 6AN over 44 days. The unique and simple method presented here prolongs diffusive release of a small molecule drug from electrospun fibers and has potential to assist in lengthening small molecule drug release from a variety of polymeric nanomaterials.

Recent Advances of Electrospun Nanofibrous Membranes in the Development of Chemosensors for Heavy Metal Detection

It is critical to detect and analyze the heavy metal pollutions in environments and foods. Chemosensors have been widely investigated for fast detection of analytes such as heavy metals due to their unique advantages. In order to improve the detection sensitivity of chemosensors, recently electrospun nanofibrous membranes (ENMs) have been explored for the immobilization of chemosensors or receptors due to their high surface-to-volume ratio, high porosity, easiness of fabrication and functionalization, controllability of nanofiber properties, low cost, easy detection, no obvious pollution to the detection solution, and easy post-treatment after the detection process. The purpose of this review is to summarize and guide the development and application of ENMs in the field of chemosensors for the detection of analytes, especially heavy metals. First, heavy metals, chemosensors, and four types of preparation methods for ENM-immobilized chemosensors/receptors are briefly introduced. And then, ENM-immobilized chemosensors/receptors and their application progresses for optical, electro, and mass detections of heavy metals are reviewed according to the four types of preparation methods. Finally, the application of ENM-immobilized chemosensors/receptors is summarized and an outlook is provided. The review will provide an instruction to the research and development of ENM-immobilized chemosensors/receptors for the detection of analytes.

Recent advances in nanomaterials for water protection and monitoring

Nanomaterials (NMs) for adsorption, catalysis, separation, and disinfection are scrutinized. NMs-based sensor technologies and environmental transformations of NMs are highlighted.

Size-tunable copper nanocluster aggregates and their application in hydrogen sulfide sensing on paper-based devices

Polystyrene sulfonate (PSS), a strong polyelectrolyte, was used to prepare red photoluminescent PSS-penicillamine (PA) copper (Cu) nanoclusters (NC) aggregates, which displayed high selectivity and sensitivity to the detection of hydrogen sulfide (H₂S). The size of the PSS-PA-Cu NC aggregates could be readily controlled from 5.5 μm to 173 nm using different concentrations of PSS, which enabled better dispersity and higher sensitivity towards H₂S. PSS-PA-Cu NC aggregates provided rapid H₂S detection by using the strong Cu-S interaction to quench NC photoluminescence as a sensing mechanism. As a result, a detection limit of 650 nM, which is lower than the maximum level permitted in drinking water by the World Health Organization, was achieved for the analysis of H₂S in spring-water samples. Moreover, highly dispersed PSS-PA-Cu NC aggregates could be incorporated into a plate-format paper-based analytical device which enables ultra-low sample volumes (5 μL) and feature shorter analysis times (30 min) compared to conventional solution-based methods. The advantages of low reagent consumption, rapid result readout, limited equipment, and long-term storage make this platform sensitive and simple enough to use without specialized training in resource constrained settings.