The discovery of graphene has led to a rising interest in seeking quasi two-dimensional allotropes of several elements and inorganic compounds. Boron, carbon’s neighbour in the periodic table, presents a curious case in its ability to be structured as graphene. Although it cannot independently constitute a honeycomb planar structure, it forms a graphenic arrangement in association with electron-donor elements. This is exemplified in magnesium diboride (MgB2): an inorganic layered compound comprising boron honeycomb planes alternated by Mg atoms. Till date, MgB2 has been primarily researched for its superconducting properties; it hasn’t been explored for the possibility of its exfoliation. Here we show that ultrasonication of MgB2 in water results in its exfoliation to yield few-layer-thick Mg-deficient hydroxyl-functionalized nanosheets. The hydroxyl groups enable an electrostatically stabilized aqueous dispersion and create a heterogeneity leading to an excitation wavelength dependent photoluminescence. These chemically modified MgB2 nanosheets exhibit an extremely small absorption coefficient of 2.9 ml mg−1 cm−1 compared to graphene and its analogs. This ability to exfoliate MgB2 to yield nanosheets with a chemically modified lattice and properties distinct from the parent material presents a fundamentally new perspective to the science of MgB2 and forms a first foundational step towards exfoliating metal borides.

Layered metal diborides that contain metal atoms sandwiched between boron honeycomb planes offer a rich opportunity to access graphenic forms of boron. We recently demonstrated that magnesium diboride (MgB ) could be exfoliated by ultrasonication in water to yield boron-based nanosheets. However, knowledge of the fate of metal boride crystals in aqueous phases is still in its incipient stages. This work presents our preliminary findings on the discovery that MgB crystals can undergo dissolution in water under ambient conditions to result in precursors (prenucleation clusters) that, upon aging, undergo nonclassical crystallization preferentially growing in lateral directions by two-dimensional (2D) oriented attachment. We show that this recrystallization can be utilized as an avenue to obtain a high yield (≈92 %) of boron-based nanostructures, including nanodots, nanograins, nanoflakes, and nanosheets. These nanostructures comprise boron honeycomb planes chemically modified with hydride and oxy functional groups, which results in an overall negative charge on their surfaces. This ability of MgB crystals to yield prenucleation clusters that can self-seed to form nanostructures comprising chemically modified boron honeycomb planes presents a new facet to the physicochemical interaction of MgB with water. These findings also open newer avenues to obtain boron-based nanostructures with tunable morphologies by varying the chemical milieu during recrystallization.

Diabetes leads to chronic microvascular complications for the heart, kidney, and eyes due to uncontrolled glycemic fluctuations. Self-monitoring blood glucose meters can only provide a snapshot of glucose level and are incapable of capturing the granular glucose fluctuations over a 24 hour period. Clinical research has indicated that random blood glucose fluctuations can lead to organ damage. In pursuit of better glucose management, continuous glucose monitoring (CGM) is emerging as a popular alternative owing to its ability to detect instantaneous changes in glucose levels and to alert the users of impending hypo- or hyper-glycemic events. In the last decade, several CGM devices have been launched in the market based on different glucose sensing chemistries and techniques. More research is still needed to come up with novel bio sensing concepts to make CGM low cost and highly accurate. Here, we elaborate the CGM techniques such as electrochemical, optical, reverse iontophoresis, microdialysis, and impedance spectroscopy. We emphasize on the widely used electrochemical CGMs with a focus on sensor design and bio-compatibility. We also provide an outlook for the future technologies, highlighting the need for innovative materials, possibility of integrating with the Internet of Things (IoT) for real-time e-health monitoring.

Metal borides are known for their extraordinarily rich chemistry and extensive range of properties. Although their diversity and chemically tunable properties create abundant possibilities for several applications, their potential has not been fully realized. This is because metal borides have been primarily investigated in their bulk form. In this work, we present a chemical method to nanoscale MgB 2 a representative from the family of layered metal diborides that comprise metal atoms sandwiched in between boron honeycomb planes. Their lattice structure offers a unique opportunity to obtain access to graphenic planes of boron upon exfoliation. We show that a treatment of MgB 2 with acid followed by intercalation with organoammonium ions swells the crystals and partly delaminates these to multilayer thick (∼300−400 nm) lamellas, which resemble the shape of accordions. These nanoaccordions can be sonicated in water to yield few-layer-thick (∼3−5 nm) nanosheets. These nanostructures are found to be Mg-deficient and functionalized with oxygen-based moieties. We also present a preliminary study to demonstrate that these oxy-functionalized nanostructures have the potential to be utilized as flame retardant nanofillers. The thermogravimetric analysis reveals that a composite of epoxy resin with sonicated nanoaccordions exhibits an effective char residue gain of 6.0%. Furthermore, by adding only 2% sonicated nanoaccordions, the LOI value of epoxy was found to increase from 20.1 to 22.5, while the burning rate (determined by UL-94 horizontal burning test) decreased significantly from 31.7 to 15.1 mm/min. These flame retardant enhancement metrics are not only superior when compared with graphene and its analogues but also at the extremes of other flame retardant nanofillers at similar loadings. The ability to exfoliate a layered metal boride to obtain chemically functionalized nanoaccordions with flame retardant properties presents an unprecedented perspective to utilize MgB 2 and showcases the rich prospects offered by the family of layered metal diborides.

Protein based nanoparticles are functionally efficient for drug or gene delivery due to their biodegradable nature and easy elimination from the body. Silk, a natural biomaterial, is being used extensively as drug/ biomolecule delivery system. Silk protein sericin (glue protein) coates the silk fibers and is discarded as a waste product in the textile industry. As a potential biomaterial, sericin has multiple advantages due to its hydrophilic and cytocompatible nature. In this study, sericin based nanoparticles were prepared by a protein de-solvation method with a diameter of 100-150 nm. The structural morphology, surface charge and cytocompatibility were measured against mouse fibroblast. Modification of the surface charge (from anionic to cationic) was done to achieve optimum DNA binding. The cellular uptake of the FITC conjugated nanoparticles is analyzed and followed up by the delivery of extracellular genes within the fibroblasts. The successful expression of the green fluorescence protein confirms the prospective use of natural silk protein sericin based nanoparticles as a therapeutic DNA delivery system.