An official website of the United States government
Understanding of structural and morphological evolution in nanomaterials is critical in tailoring their functionality for applications such as energy conversion and storage. Here, we examine irradiation effects on the morphology and structure of amorphous TiO2 nanotubes in comparison with their crystalline counterpart, anatase TiO2 nanotubes, using high-resolution transmission electron microscopy (TEM), in situ ion irradiation TEM, and molecular dynamics (MD) simulations. Anatase TiO2 nanotubes exhibit morphological and structural stability under irradiation due to their high concentration of grain boundaries and surfaces as defect sinks. On the other hand, amorphous TiO2 nanotubes undergo irradiation-induced crystallization, with some tubes remaining only partially crystallized. The partially crystalline tubes bend due to internal stresses associated with densification during crystallization as suggested by MD calculations. These results present a novel irradiation-based pathway for potentially tuning structure and morphology of energy storage materials.
more »
« less
Microwave Synthetic Routes for Shape-Controlled Catalyst Nanoparticles and Nanocomposites
The use of microwave irradiation for the synthesis of inorganic nanomaterials has recently become a widespread area of research that continues to expand in scope and specialization. The growing demand for nanoscale materials with composition and morphology tailored to specific applications requires the development of facile, repeatable, and scalable synthetic routes that offer a high degree of control over the reaction environment. Microwave irradiation provides unique advantages for developing such routes through its direct interaction with active reaction species, which promotes homogeneous heat distribution, increased reaction rates, greater product quality and yield, and use of mild reaction conditions. Many catalytic nanomaterials such as noble metal nanoparticles and intricate nanocomposites have very limited synthetic routes due to their extreme temperature sensitivity and difficulty achieving homogeneous growth. This work presents recent advances in the use of MW irradiation methods to produce high-quality nanoscale composites with controlled size, morphology, and architecture.
more »
« less
- Award ID(s):
- 2004187
- PAR ID:
- 10283802
- Date Published:
- Journal Name:
- Molecules
- Volume:
- 26
- Issue:
- 12
- ISSN:
- 1420-3049
- Page Range / eLocation ID:
- 3647
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
The versatility of early transition metal chalcogenide nanomaterials, including chalcogenide perovskites, has attracted enormous attention for a variety of applications, such as photovoltaics, photocatalysis, and optoelectronic devices. These nanomaterials exhibit unique electronic and optical properties, allowing for a broad range of applications, depending on their chemical composition and crystal structure. However, solution-phase synthesis of early transition metal chalcogenide nanocrystals is challenging due, in part, to their high crystallization energy and oxophilicity. In this feature article, we explore various synthetic routes reported for inorganic ternary and binary sulfide and selenide nanomaterials that include transition metals from groups 3, 4, and 5. By systematically comparing different synthetic approaches, we identify trends and insights into the chemistry of these chalcogenide nanomaterials.more » « less
-
Abstract Demand for fast, energy‐dense storage drives the research into nanoscale intercalation materials. Nanomaterials accelerate kinetics and can modify reaction path thermodynamics, intercalant solubility, and reversibility. The discovery of intercalation pseudocapacitance has opened questions about their fundamental operating principles. For example, are their capacitor‐like current responses caused by storing energy in special near‐surface regions or rather is this response due to normal intercalation limited by a slower faradaic surface‐reaction? This review highlights emerging methods combining tailored nanomaterials with the process of elimination to disambiguate cause‐and‐effect at the nanoscale. This method is applied to multiple intercalation pseudocapacitive materials showing that the timescales exhibiting surface‐limited kinetics depended on the total intercalation length scale. These trends are inconsistent with the near‐surface perspective. A revised current‐model without assuming special near‐surface storage fits experimental data better across wide timescales. This model, combined with tailored nanomaterials and the process of elimination, can isolate material‐specific effects such as how amorphization/defect‐tailoring modifies both insertion and diffusion kinetics. Avenues for both faster intercalation pseudocapacitance and increased energy density are discussed. A relaxation time argument is suggested to explain the continuum between battery‐like and pseudocapacitive behaviors. Future directions include synthetic methods emphasizing tailored defects and analytical methods that minimize assumptions.more » « less
-
Abstract The Newman Kwart Rearrangement (NKR) offers an efficient and high‐yielding method for producing substituted thiophenols from phenols. While an industrially important protocol, it suffers from high activation energy barriers (35–43 kcal/mol), requiring the use of extreme temperatures (>200 °C) and specialty equipment. This report details a highly efficient and straightforward method for facilitating the NKR using photothermal conversion. This underused, unique reactivity pathway arises from the irradiation of nanomaterials that relax via a non‐radiative decay pathway to generate intense thermal gradients. We show carbon black (CB) can be an inexpensive and abundant photothermal agent under visible light irradiation to achieve a facile NKR under mild conditions. The scope includes a wide array of stereo‐ and electronically diverse substrates with increasing difficulty of rearrangement, including BHT and BINOL as effective substrates. Furthermore, we demonstrate the unique application for temporal control in a thermal reaction and tunability of thermal gradients by modulating light intensity. Ultimately, photothermal conversion enables high‐temperature reactions with simple, visible light irradiation.more » « less
-
Abstract Among many biomass‐derived intermediate compounds, 5‐hydroxymethylfurfural (HMF) has been regarded as a platform chemical because it can be used to produce numerous valuable products. However, the difficulty of HMF isolation from reaction media coupled with its poor stability have significantly inhibited its large‐scale production and application. In this work, we report a single‐step process for the direct production of HMF from glucose using green chemical methods. Optimized glucose isomerization and dehydration under microwave irradiation achieved a respectable HMF yield (70 %) using a biphasic solvent mixture (water/THF), high glucose concentration (30 % w/v), catalytic amounts of AlCl3(5 mol%) and HCl (15 mol%). The reaction can be completed within minutes at 165 °C. Overall, our microwave‐assisted strategy enables the direct conversion of commercially available glucose to the highly valuable platform chemical HMF without the use of expensive solvents or catalysts, suggesting an economically attractive approach for upgrading carbohydrates.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/molecules26123647
