Highly stable sub-5 nm Sn₆O₄(OH)₄ nanocrystals with ultrahigh activity as advanced photocatalytic materials for photodegradation of methyl orange

Beneficial Impurities and Phase Control in Colloidal Synthesis of Tin Monoselenide

The effect of impurities in colloidal synthesis of SnSe in oleylamine surfactant was investigated. Specifically, it was found that impurities such as water, hydrochloric acid, and carbon dioxide stabilize the recently discovered cubic phase of tin monoselenide, π-SnSe. We describe the reaction that releases HCl to the reaction medium through reaction of SnCl₂ with moisture and its subsequent reaction with oleylamine, transforming it from neutral to charged surfactant. A similar path occurs in the case of CO₂, which reacts with oleylamine to give charged oleylammonium-oleylcarbamate molecular pairs. By exposing the reaction to controlled concentrations of "beneficial contaminants", hitherto a major source of irreproducibility in this synthesis, we demonstrate phase and shape control from π-SnSe cubes to α-SnSe rods.

Laser-Ablated ZnO Nanoparticles and Their Photocatalytic Activity toward Organic Pollutants

This work aimed to prepare nanostructures of ZnO with various lasers, testing them as photocatalysts, and comparing their morphology and activity in the degradation of organic pollutants in aqueous media. ZnO nanospheres (ns-ZnO) and ZnO nanorods (ms-ZnO) were prepared via the laser ablation of a Zn metal plate in water using nanosecond- and millisecond-pulsed lasers, respectively. The obtained materials were characterized using a set of optical, structural, and surface-science techniques, such as UV-vis spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Under visible-light irradiation, both nanostructures were found to be catalytically active toward the oxidation of methylene blue, which was used as a model compound. The ZnO nanorods fabricated with the millisecond laser showed better photocatalytic performance than their spherically shaped counterparts obtained by means of the nanosecond laser, which could be assigned to a larger number of defects on the ms-ZnO surface.

Laser Synthesis and Processing of Colloids: Fundamentals and Applications

Driven by functionality and purity demand for applications of inorganic nanoparticle colloids in optics, biology, and energy, their surface chemistry has become a topic of intensive research interest. Consequently, ligand-free colloids are ideal reference materials for evaluating the effects of surface adsorbates from the initial state for application-oriented nanointegration purposes. After two decades of development, laser synthesis and processing of colloids (LSPC) has emerged as a convenient and scalable technique for the synthesis of ligand-free nanomaterials in sealed environments. In addition to the high-purity surface of LSPC-generated nanoparticles, other strengths of LSPC include its high throughput, convenience for preparing alloys or series of doped nanomaterials, and its continuous operation mode, suitable for downstream processing. Unscreened surface charge of LSPC-synthesized colloids is the key to achieving colloidal stability and high affinity to biomolecules as well as support materials, thereby enabling the fabrication of bioconjugates and heterogeneous catalysts. Accurate size control of LSPC-synthesized materials ranging from quantum dots to submicrometer spheres and recent upscaling advancement toward the multiple-gram scale are helpful for extending the applicability of LSPC-synthesized nanomaterials to various fields. By discussing key reports on both the fundamentals and the applications related to laser ablation, fragmentation, and melting in liquids, this Article presents a timely and critical review of this emerging topic.

Nanostructures prepared via laser ablation of tin in water

Ablation of Sn in water with millisecond and nanosecond pulsed lasers produces different core@shell nanostructures.

Electronic Reconstruction of α-Ag2WO4 Nanorods for Visible-Light Photocatalysis

α-Ag2WO4 (AWO) has been studied extensively due to its H2 evolution and organic pollution degradation ability under the irradiation of UV light. However, the band gap of AWO is theoretically calculated to be 3.55 eV, resulting in its sluggish reaction to visible light. Herein, we demonstrated that, by using the electronic reconstruction of AWO nanorods upon a unique process of laser irradiation in liquid, these nanorods performed good visible-light photocatalytic organics degradation and H2 evolution. Using commercial AWO powders as the starting materials, we achieved the electronic reconstruction of AWO by a recrystallization of the starting powders upon laser irradiation in liquid and synthesized AWO nanorods. Due to the weak bond energy of AWO and the far from thermodynamic equilibrium process created by laser irradiation in liquid, abundant cluster distortions, especially [WO6] cluster distortions, are introduced into the crystal lattice, the defect density increases by a factor of 2.75, and uneven intermediate energy levels are inset into the band gap, resulting in a 0.44 eV decrease of the band gap, which modified the AWO itself by electronic reconstruction to be sensitive to visible light without the addition of others. Further, the first-principles calculation was carried out to clarify the electronic reconstruction of AWO, and the theoretical results confirmed the deduction based on the experimental measurements.