We discuss the synthesis and properties of plasmonic zirconium nitride nanocrystals produced using a nonthermal plasma reactor. The process enables the continuous conversion of chemical precursors into free-standing ∼10 nm diameter nanoparticles. Oxidation limits the resonant plasmon energy from ∼2.6 eV for ideal unoxidized particles to ∼2.1 eV for particles exposed to air at room temperature. A simple modification to the plasma process allows the inflight growth of a conformal silicon oxynitride shell onto the zirconium nitride core. The shell inhibits the oxidation of the core, resulting in particles with a plasmon energy of 2.35 eV. These particles show good plasmonic behavior even after annealing in air at 300 °C, largely improved when compared to unprotected particles that oxidize and lose plasmonic activity at the same temperature. This work represents a step toward the development of earth-abundant, thermally and chemically resistant nanoparticles that can offer an inexpensive alternative to gold and silver and extended applicability in harsh environments.

Plasmas interacting with liquids enable the generation of a highly reactive interfacial liquid layer due to a variety of processes driven by plasma-produced electrons, ions, photons, and radicals. These processes show promise to enable selective, efficient, and green chemical transformations and new material synthesis approaches. While many differences are to be expected between conventional electrolysis and plasma–liquid interactions, plasma–liquid interactions can be viewed, to a first approximation, as replacing a metal electrode in an electrolytic cell with a gas phase plasma. For this reason, we refer to this method as plasma-driven solution electrochemistry (PDSE). In this Perspective, we address two fundamental questions that should be answered to enable researchers to make transformational advances in PDSE: How far from equilibrium can plasma-induced solution processes be driven? and What are the fundamental differences between PDSE and other more traditional electrochemical processes? Different aspects of both questions are discussed in five sub-questions for which we review the current state-of-the art and we provide a motivation and research vision.

We discuss the synthesis and properties of nanoparticles and thin films for refractory plasmonic applications. The approach focuses on titanium nitride (TiN), which overcomes the limitations of more common plasmonic materials like silver and gold with respect to temperature stability. Freestanding TiN-based nanoparticles are produced in two serially connected plasma reactors, where TiN nanocrystals are nucleated in a first plasma stage, then aerodynamically dragged in a second stage, and conformally coated with a silicon nitride layer. An in-depth comparison between bare and coated TiN nanoparticles is presented in terms of the structural, chemical, and optical properties. Coating of the titanium nitride core reduces its oxidation upon exposure to air, drastically improving the plasmonic response. Thin films realized using the core–shell structure show practically no change in reflectivity, even when the thin films are heated to 900 °C in an inert atmosphere. This study introduces a simple surface passivation scheme that enhances the functionality of the material, providing further confirmation of the potential of nitride-based plasmonic materials as high-quality refractory optical compounds for a broad range of applications.

We demonstrate that copper-zinc-tin-sulphide nanoplatelets can be directly grown onto a molybdenum-coated substrate using spray pyrolysis starting from a mixture of metal thiocarbamates precursors. The structure and phase purity of the nanoplatelets is discussed in detail.

Transparent cranial window to the brain is highly desirable for brain therapies because such cranial implant would allow for continuous monitoring of brain disorders and long‐term delivery of photodynamic therapy into the brain without repeated surgeries for opening skull. Nanostructured yttria‐stabilized zirconia (YSZ) is a potential candidate for the window to the brain application because of its promising mechanical and optical properties. In this study, a new process using aerosol spray pyrolysis was established for synthesizing 6–7 nm YSZ nanopowders with precisely controlled compositions. YSZ nanopowders with 3 M ratios of yttria to zirconia, specifically 3, 6, and 8% yttria in zirconia (referred to as 3YSZ, 6YSZ, and 8YSZ, respectively) were synthesized and characterized. The size, structure, and composition of the produced YSZ nanoparticles are highly controllable and scalable. The in vitro cytocompatibility of the YSZ nanoparticles with bone marrow mesenchymal stem cells (BMSCs) was investigated using a direct exposure culture method for cranial implant applications. Nondoped ZrO2 and commercially available 8YSZ (named as C_8YSZ) served as controls for the in vitro cell studies. BMSCs exhibited normal morphology when cultured with the YSZs of 3 M ratios in the concentrations of 10 mM, 30 mM, and 60 mM, as well as ZrO2 and C_8YSZ controls. The BMSCs cultured with 3YSZ and 6YSZ showed no statistical differences in cell adhesion density when compared with the ZrO2 and C_8YSZ controls at respective concentrations of 10–60 mM. The possible release of YSZ nanoparticles from cranial window implants should be carefully considered and further studied.