Titanium diboride (TiB2), a layered ceramic material, comprised of titanium atoms sandwiched in between honeycomb planes of boron atoms, exhibits a promising structure to utilize the rich chemistry offered by the synergy of titanium and boron.

The present work reports green route-waste recycled carbon nanolights, i.e., carbon dots (GCDs), synthesized via a facile one-step pyrolysis method from Citrus limetta waste pulp. The size of these obtained pristine GCDs is ∼4−7 nm (HR-TEM), with high optical and structural quality as revealed by FT-IR and Raman spectroscopic analysis. They exhibit the highest quantum yield of 63.3% over other similar green synthesized GCDs, favorable for many applications. Further, we demonstrate the multifunctional aspects of these synthesized GCDs for photoelectrochemical water splitting, photocatalytic methylene blue degradation, Fe(III) ions sensing, bactericidal activity (against E. coli and S. aureus), and bioimaging with excellent performance. The visible light active characteristic of GCDs is observed to achieve an efficient current density of ∼6 mA/cm 2 toward water splitting. This study demonstrates the waste to wealth potential of recycled waste derived GCDs in a wide range of application domains.

Transition-metal diborides are a class of abundantly available ceramic materials that exhibit a landscape of rich properties such as extraordinary high strength, exceptional hardness, and high-melting points. To date, these materials have been investigated primarily for their bulk scale properties. Many of these transition-metal diborides adopt an AlB2-type structure. In this type of structure, the metal atoms are sandwiched between alternating layers of boron atoms. Examples of these types of borides include, magnesium diboride (MgB2), titanium diboride (TiB2), chromium diboride (CrB2), etc. The AlB2-type structure is appealing for a plethora of reasons, primary among them is the inherent presence of boron atoms arranged in a honeycomb pattern reminiscent of the graphenic arrangement. This provides an opportunity to access two-dimensional (2D) boron. Recent research trends indicate a rising interest in nanoscaling these borides to yield 2D nanostructures. Research groups across the globe are currently pursuing this very objective, and multiple reports have already emerged showing that it is possible to nanoscale these bulk AlB2-type borides into nanosheets. One of the routes that researchers have adopted to this end is the well-recognized, top-down exfoliation. This involves methods such as liquid-phase exfoliation, mechanical exfoliation, and chemically induced selective extraction. This review will chronicle the research evolution of top-down exfoliation of metal borides from a physicochemical context and present the reader with a summary of these methods and the associated findings. We will also briefly discuss the various areas where these nanoscaled metal borides have just started finding applications toward sustainable technologies and present our perspective on where the field is headed. We hope that this review will be a timely addition to the fast-evolving literature on nanoscaling metal borides.

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