Electrospun Nanofiber Mats as “Smart Surfaces” for Desorption Electrospray Ionization Mass Spectrometry (DESI MS)-Based Analysis and Imprint Imaging

In this paper, desorption electrospray ionization mass spectrometry (DESI MS)-based molecular analysis and imprint imaging using electrospun nylon-6 nanofiber mats are demonstrated for various analytical contexts. Uniform mats of varying thicknesses composed of ∼200 nm diameter fibers were prepared using needleless electrospinning. Analytical applications requiring rapid understanding of the analytes in single drops, dyes, inks, and/or plant extracts incorporated directly into the nanofibers are discussed with illustrations. The possibility to imprint patterns made of printing inks, plant parts (such as petals, leaves, and slices of rhizomes), and fungal growth on fruits with their faithful reproductions on the nanofiber mats is illustrated with suitable examples. Metabolites were identified by tandem mass spectrometry data available in the literature and in databases. The results highlight the significance of electrospun nanofiber mats as smart surfaces to capture diverse classes of compounds for rapid detection or to imprint imaging under ambient conditions. Large surface area, appropriate chemical functionalities exposed, and easiness of desorption due to weaker interactions of the analyte species are the specific advantages of nanofibers for this application

A Critical Review on Materials for Solid Oxide Fuel Cell Components

Solid-oxide fuel cells are efficient devices for the conversion of chemical to electrical energy and a typical solid-oxide fuel cell consists of a solid electrolyte, cathode, and anode. In the last few decades, researchers have been working extensively on materials development for different components of these devices. In this review article, we briefly discuss the requirements for different components and review prominent materials families explored by the scientific community. As the search for greener energy alternatives such as solid-oxide fuel cells have intensified manifold due to the climate change emergency, a substantial literature was produced on the materials development of these devices and, therefore, we believe a brief review article dedicated to the same will be valuable for the scientific community, particularly new young entrant researchers in the field

Organic Solvent-Free Fabrication of Durable and Multifunctional Superhydrophobic Paper from Waterborne Fluorinated Cellulose Nanofiber Building Blocks

In view of a great demand for paper-based technologies, nonwettable fibrous substrates with excellent durability have drawn much attention in recent years. In this context, the use of cellulose nanofibers (CNFs), the smallest unit of cellulosic substrates (5-20 nm wide and 500 nm to several microns in length), to design waterproof paper can be an economical and smart approach. In this study, an eco-friendly and facile methodology to develop a multifunctional waterproof paper via the fabrication of fluoroalkyl functionalized CNFs in the aqueous medium is presented. This strategy avoids the need for organic solvents, thereby minimizing cost as well as reducing safety and environmental concerns. Besides, it widens the applicability of such materials as nanocellulose-based aqueous coatings on hard and soft substrates including paper, in large areas. Water droplets showed a contact angle of 160° (±2°) over these surfaces and rolled off easily. While native CNFs are extremely hydrophilic and can be dispersed in water easily, these waterborne fluorinated CNFs allow the fabrication of a superhydrophobic film that does not redisperse upon submersion in water. Incorporated chemical functionalities provide excellent durability toward mechanochemical damages of relevance to daily use such as knife scratch, sand abrasion, spillage of organic solvents, etc. Mechanical flexibility of the chemically modified CNF composed paper remains intact despite its enhanced mechanical strength, without additives. Superhydrophobicity induced excellent microbial resistance of the waterproof paper which expands its utility in various paper-based technologies. This includes waterproof electronics, currency, books, etc., where the integrity of the fibers, as demonstrated here, is a much-needed criterion.Peer reviewe

Electrohydrodynamic Assembly of Ambient Ion-Derived Nanoparticles to Nanosheets at Liquid Surfaces

We describe an ambient ion-based method to create free-standing metal nanosheets, which in turn are composed of nanoparticles of the corresponding metal. These nanoparticle-nanosheets (NP-NSs) were formed by the electrospray deposition (ESD) of metal ions on a liquid–air interface leading to nanoparticles that self-organize under the influence of electrohydrodynamic flows, driven by the electric field induced by the applied potential. Such a two-dimensional organization of noble metals is similar to the assembly of molecules at liquid–air interface and has the possibility of creating a category of new materials useful for diverse applications. Enhanced catalytic activity of the formed NP-NSs for Suzuki–Miyaura coupling reaction was demonstrated, which was attributed to their large surface-to-volume ratios

Synthesis of Silicon Nanoparticles from Rice Husk and their Use as Sustainable Fluorophores for White Light Emission

Silicon nanoparticles (Si NPs) exhibiting observable luminescence have many electronic, optical, and biological applications. Owing to reduced toxicity, they can be used as cheap and environmentally friendly alternatives for cadmium containing quantum dots, organic dyes, and rare earth-based expensive phosphors. Here, we report an inexpensive silicon precursor, namely rice husk, which has been employed for the synthesis of Si NPs by rapid microwave heating. The Si NPs of ∼4.9 nm diameter exhibit observable green luminescence with a quantum yield of ∼60%. They show robust storage stability and photostability and have constant luminescence during long-term UV irradiation extending over 48 h, in contrast to other luminescent materials such as quantum dots and organic dyes which quenched their emission over this time window. Green luminescent Si NPs upon mixing with synthesized red and blue luminescent Si NP species are shown to be useful for energy-efficient white light production. The resulting white light has a color coordinate of (0.31, 0.27) which is close to that of pure white light (0.33, 0.33). The performance of our white light emitting material is comparable to that of a commercial white light emitting diode (WLED) bulb and is shown to be better than that of a commercial compact fluorescent lamp (CFL)

Electrohydrodynamic Assembly of Ambient Ion-Derived Nanoparticles to Nanosheets at Liquid Surfaces

We describe an ambient ion-based method to create free-standing metal nanosheets, which in turn are composed of nanoparticles of the corresponding metal. These nanoparticle-nanosheets (NP-NSs) were formed by the electrospray deposition (ESD) of metal ions on a liquid–air interface leading to nanoparticles that self-organize under the influence of electrohydrodynamic flows, driven by the electric field induced by the applied potential. Such a two-dimensional organization of noble metals is similar to the assembly of molecules at liquid–air interface and has the possibility of creating a category of new materials useful for diverse applications. Enhanced catalytic activity of the formed NP-NSs for Suzuki–Miyaura coupling reaction was demonstrated, which was attributed to their large surface-to-volume ratios

Approaching Sensitivity of Tens of Ions Using Atomically Precise Cluster–Nanofiber Composites

A new methodology has been demonstrated for ultratrace detection of Hg²⁺, working at the limit of a few tens of metal ions. Bright, red luminescent atomically precise gold clusters, Au@BSA (BSA, bovine serum albumin), coated on Nylon-6 nanofibers were used for these measurements. A green emitting fluorophore, FITC (fluorescein isothiocyanate), whose luminescence is insensitive to Hg²⁺ was precoated on the fiber. Exposure to mercury quenched the red emission completely, and the green emission of the fiber appeared which was observed under dark field fluorescence microscopy. For the sensing experiment at the limit of sensitivity, we have used individual nanofibers. Quenching due to Hg²⁺ ions was fast and uniform. Adaptation of such sensors to pH paper-like test-strips would make affordable water quality sensors at ultralow concentrations a reality

Electrohydrodynamic Assembly of Ambient Ion-Derived Nanoparticles to Nanosheets at Liquid Surfaces

We describe an ambient ion-based method to create free-standing metal nanosheets, which in turn are composed of nanoparticles of the corresponding metal. These nanoparticle-nanosheets (NP-NSs) were formed by the electrospray deposition (ESD) of metal ions on a liquid–air interface leading to nanoparticles that self-organize under the influence of electrohydrodynamic flows, driven by the electric field induced by the applied potential. Such a two-dimensional organization of noble metals is similar to the assembly of molecules at liquid–air interface and has the possibility of creating a category of new materials useful for diverse applications. Enhanced catalytic activity of the formed NP-NSs for Suzuki–Miyaura coupling reaction was demonstrated, which was attributed to their large surface-to-volume ratios

Gold-Induced Unfolding of Lysozyme: Toward the Formation of Luminescent Clusters

Ion mobility mass spectrometry studies on Au_<i>n</i>-Lyz adducts showed gradual unfolding of the protein structure during binding of Au⁺ to the protein. The change of the charge state envelope in Au_<i>n</i>-Lyz from that of Lyz in ESI MS data confirmed the relaxation of the protein structure. This Au⁺ binding occurs at cysteine sites through the breakage of disulfide bonds and this ruptures the H-bonded folded network structure of the protein leading to ∼30% change in helicity. Nearly 15% loss in the total H-bonding occurred during the attachment of 8 Au to the protein as calculated by a molecular dynamics simulation. Different Au_<i>n</i>-Lyz structures were simulated, which confirmed significant unfolding of the protein. The structural insights were used to understand similar unfolding in the solution state as seen via circular dichroism (CD) and Fourier transform infrared (FTIR) spectroscopy. This open structure is indeed necessary to accommodate a cluster core inside a protein cavity during luminescent cluster synthesis. These studies unambiguously establish noble metal binding-induced conformational changes of protein structures to accommodate the clusters