Esther H. Lan

Bio: Esther H. Lan is an academic researcher from University of California, Los Angeles. The author has contributed to research in topics: Mesoporous silica & Silica gel. The author has an hindex of 13, co-authored 35 publications receiving 1370 citations. Previous affiliations of Esther H. Lan include University of California, Berkeley.

Porous One-Dimensional Nanomaterials: Design, Fabrication and Applications in Electrochemical Energy Storage.

Abstract: Electrochemical energy storage technology is of critical importance for portable electronics, transportation and large-scale energy storage systems. There is a growing demand for energy storage devices with high energy and high power densities, long-term stability, safety and low cost. To achieve these requirements, novel design structures and high performance electrode materials are needed. Porous 1D nanomaterials which combine the advantages of 1D nanoarchitectures and porous structures have had a significant impact in the field of electrochemical energy storage. This review presents an overview of porous 1D nanostructure research, from the synthesis by bottom-up and top-down approaches with rational and controllable structures, to several important electrochemical energy storage applications including lithium-ion batteries, sodium-ion batteries, lithium-sulfur batteries, lithium-oxygen batteries and supercapacitors. Highlights of porous 1D nanostructures are described throughout the review and directions for future research in the field are discussed at the end.

Photo-induced proton gradients and ATP biosynthesis produced by vesicles encapsulated in a silica matrix

Abstract: Sol-gel immobilization of soluble proteins has proven to be a viable method for stabilizing a wide variety of proteins in transparent inorganic matrices. The encapsulation of membrane-bound proteins has received much less attention, although work in this area suggests potential opportunities in microarray technology and high-throughput drug screening. The present paper describes a liposome/sol-gel architecture in which the liposome provides membrane structure and protein orientation to two transmembrane proteins, bacteriorhodopsin (bR) and F(0)F(1)-ATP synthase; the sol-gel encapsulation converts the liposomal solution into a robust material without compromising the intrinsic activity of the incorporated proteins. Here we report on two different proteoliposome-doped gels (proteogels) whose properties are determined by the transmembrane proteins. Proteogels containing bR proteoliposomes exhibit a stable proton gradient when irradiated with visible light, whereas proteogels containing proteoliposomes with both bR and F(0)F(1)-ATP synthase couple the photo-induced proton gradient to the production of ATP. These results demonstrate that materials based on the liposome/sol-gel architecture are able to harness the properties of transmembrane proteins and enable a variety of applications, from power generation and energy storage to the powering of molecular motors, and represent a new technology for performing complex chemical synthesis in a solid-state matrix.

Synthesis of sol-gel encapsulated heme proteins with chemical sensing properties

Abstract: Heme proteins such as cytochrome-c (cyt-c), hemoglobin (Hb), and myoglobin (Mb) have been successfully encapsulated in sol-gel derived silica matrices, retaining their spectroscopic properties and chemical function. The thermal stability of cyt-c was significantly improved by immobilization in a porous silica network. Results from optical absorption, resonance Raman, and thermal denaturation studies suggest that biomolecules such as cyt-c design self-specific pores in the silica network according to the size and shape requirements of the biomolecule. Hb and Mb, immobilized using the sol-gel process, bound ligands similar to the proteins in aqueous buffer, and silica-encapsulated manganese myoglobin (MnMb) was a viable detector for nitric oxide (NO).

Measurement of Dissolved Oxygen in Water Using Glass-Encapsulated Myoglobin

Abstract: Myoglobin (Mb) encapsulated in a glasss matrix by the sol-gel method was examined as a sensing element for measurement of dissolved oxygen (DO) in water using electronic absorption spectroscopy in the visible region. The Mb-containing gel was porous and transparent, and the encapsulated Mb exhibited the same chemical and spectroscopic properties in the gel as in solution upon reduction of metMb with dithionite to give deoxyMb or absorption of DO to the oxyMb. The absorbance of a deoxyMb-containing gel changed linearly with time upon exposure to DO for the first 8 min, or longer, at three selected wavelengths, 418, 431.5, and 436 nm. The linear absorbance change rate was established in a few minutes, <5 min, and was directly proportional to the concentration of DO, itch is found to be a unique property of the sol-gel glass-encapsulated Mb. The overall changes in absorbance at 431.5 and 436 nm were substantially larger than at 418 nm for a given DO concentration, and thus the correlation index was significantly higher at those wavelengths. The DO concentrations examined in this study ranged from 2 (25% air-saturated water) to 8 ppm (100% air-saturated water).These results indicate that the DO concentration can be determined quantitatively by observed the rate of change of the visible absorption spectrum of glass-encapsulated deoxyMb. This method does not require stirring of the water sample. Moreover, this method does not require the water sample to be used to a gaseous environment during the measurement, unlike the membrane polarographic often detector method. Thus a glass-encapsulated Mb gel prepared by the sol-gel method is a pratical sensing element for accurate and reproducible measurement of DO concentrations in water

Crystallinity of inorganic films grown by atomic layer deposition: Overview and general trends

Abstract: Atomic layer deposition (ALD) is gaining attention as a thin film deposition method, uniquely suitable for depositing uniform and conformal films on complex three-dimensional topographies. The deposition of a film of a given material by ALD relies on the successive, separated, and self-terminating gas–solid reactions of typically two gaseous reactants. Hundreds of ALD chemistries have been found for depositing a variety of materials during the past decades, mostly for inorganic materials but lately also for organic and inorganic–organic hybrid compounds. One factor that often dictates the properties of ALD films in actual applications is the crystallinity of the grown film: Is the material amorphous or, if it is crystalline, which phase(s) is (are) present. In this thematic review, we first describe the basics of ALD, summarize the two-reactant ALD processes to grow inorganic materials developed to-date, updating the information of an earlier review on ALD [R. L. Puurunen, J. Appl. Phys. 97, 121301 (2005)], and give an overview of the status of processing ternary compounds by ALD. We then proceed to analyze the published experimental data for information on the crystallinity and phase of inorganic materials deposited by ALD from different reactants at different temperatures. The data are collected for films in their as-deposited state and tabulated for easy reference. Case studies are presented to illustrate the effect of different process parameters on crystallinity for representative materials: aluminium oxide, zirconium oxide, zinc oxide, titanium nitride, zinc zulfide, and ruthenium. Finally, we discuss the general trends in the development of film crystallinity as function of ALD process parameters. The authors hope that this review will help newcomers to ALD to familiarize themselves with the complex world of crystalline ALD films and, at the same time, serve for the expert as a handbook-type reference source on ALD processes and film crystallinity.

Applications of advanced hybrid organic–inorganic nanomaterials: from laboratory to market

Abstract: Today cross-cutting approaches, where molecular engineering and clever processing are synergistically coupled, allow the chemist to tailor complex hybrid systems of various shapes with perfect mastery at different size scales, composition, functionality, and morphology. Hybrid materials with organic–inorganic or bio–inorganic character represent not only a new field of basic research but also, via their remarkable new properties and multifunctional nature, hybrids offer prospects for many new applications in extremely diverse fields. The description and discussion of the major applications of hybrid inorganic–organic (or biologic) materials are the major topic of this critical review. Indeed, today the very large set of accessible hybrid materials span a wide spectrum of properties which yield the emergence of innovative industrial applications in various domains such as optics, micro-electronics, transportation, health, energy, housing, and the environment among others (526 references).

Food protein-based materials as nutraceutical delivery systems

Abstract: Incorporation of bioactive compounds–such as vitamins, probiotics, bioactive peptides, and antioxidants etc.–into food systems provide a simple way to develop novel functional foods that may have physiological benefits or reduce the risks of diseases. As a vital macronutrient in food, proteins possess unique functional properties including their ability to form gels and emulsions, which allow them to be an ideal material for the encapsulation of bioactive compounds. Based on the knowledge of protein physical–chemistry properties, this review describes the potential role of food proteins as substrate for the development of nutraceutical delivery systems in the form of hydrogel, micro-, or nano- particles. Applications of these food protein matrices to protect and delivery-sensitive nutraceutical compounds are illustrated, and the impacts of particle size on release properties are emphasized.