Challenges and approaches for high-voltage spinel lithium-ion batteries.

Lithium-ion (Li-ion) batteries have been developed for electric vehicle (EV) applications, owing to their high energy density. Recent research and development efforts have been devoted to finding the next generation of cathode materials for Li-ion batteries to extend the driving distance of EVs and lower their cost. LiNi(0.5)Mn(1.5)O(4) (LNMO) high-voltage spinel is a promising candidate for a next-generation cathode material based on its high operating voltage (4.75 V vs. Li), potentially low material cost, and excellent rate capability. Over the last decade, much research effort has focused on achieving a fundamental understanding of the structure-property relationship in LNMO materials. Recent studies, however, demonstrated that the most critical barrier for the commercialization of high-voltage spinel Li-ion batteries is electrolyte decomposition and concurrent degradative reactions at electrode/electrolyte interfaces, which results in poor cycle life for LNMO/graphite full cells. Despite scattered reports addressing these processes in high-voltage spinel full cells, they have not been consolidated into a systematic review article. With this perspective, emphasis is placed herein on describing the challenges and the various approaches to mitigate electrolyte decomposition and other degradative reactions in high-voltage spinel cathodes in full cells.

Chromic materials for responsive surface-enhanced resonance Raman scattering systems: a nanometric pH sensor.

The use of chromic materials for responsive surface-enhanced resonance Raman scattering (SERRS) based nanosensors is reported. The potential of nano-chromic SERRS is demonstrated with the use of the halochrome methyl yellow to fabricate an ultrasensitive pH optical sensor. Some of the challenges of the incorporation of chromic materials with metal nanostructures are addressed through the use of computational calculations and a comparison to measured SERRS and surface-enhanced Raman scattering (SERS) spectra is presented. A strong correlation between the measured SERRS and the medium's proton concentration is demonstrated for the pH range 2-6. The high sensitivity achieved by the use of resonance Raman conditions is shown through responsive SERRS measurements from only femtolitres of volume and with the concentration of the reporting molecules approaching the single molecule regime.

Single molecule analysis by surfaced-enhanced Raman scattering.

Our main objective in this tutorial review is to provide insight into some of the questions surrounding single molecule detection (SMD) using surface-enhanced Raman scattering (SERS) and surface-enhanced resonance Raman scattering (SERRS). Discovered thirty years ago, SERS is now a powerful analytical tool, strongly tied to plasmonics, a field that encompasses and profits from the optical enhancement found in nanostructures that support localized plasmon excitations. The spectrum of the single molecule carries the quantum fingerprints of the system modulated by the molecule-nanostructure interactions and the electronic resonances that may result under laser excitation. This information is embedded in vibrational band parameters. The dynamics and the molecular environment will affect the bandwidth of the observed Raman bands. In addition, the localized surface plasmon resonances (LSPR) empower the nanostructure with a number of optical properties that will also leave their mark on the observed inelastic scattering process. Therefore, controlling size, shape and the formation of the aggregation state (or fractality) of certain metallic nanostructures becomes a main task for experimental SERS/SERRS. This molecule-nanostructure coupling may, inevitably, lead to spectral fluctuations, increase photobleaching or photochemistry. An attempt is made here to guide the interpretation of this wealth of information when approaching the single molecule regime.

Chemically selective sensing through layer-by-layer incorporation of biorecognition into thin film substrates for surface-enhanced resonance Raman scattering.

In this work, the fabrication, characterization, and application of avidin/Ag nanoparticle layer-by-layer (LbL) films as chemically selective substrates for surface-enhanced resonance Raman scattering (SERRS) is demonstrated. The biospecific interaction between avidin and the small molecule biotin, one of the strongest known to exist in nature, is exploited to preferentially capture biotinylated species from solution. This highly favored adsorption is shown to yield SERRS concentration enhancements and improved detection sensitivities of ca. 102 for commercially available and in situ prepared biotinylated species over their nontagged counterparts.

Inherent complexities of trace detection by surface-enhanced Raman scattering.

Surface-enhanced Raman scattering (SERS) and surface-enhanced resonance Raman scattering (SERRS) are powerful optical scattering techniques used in such frontier areas of research as ultrasensitive chemical analysis, the characterization of nanostructures, and the detection of single molecules. However, measuring and, most importantly, interpreting SERS/SERRS spectra can be incredibly challenging. This is the result of modifications to the measured spectra that are due to of a variety of instabilities and contributions. These interferences and modifications arise from the nature of the enhancement itself, as well as the conditions used to attain SERS spectra. The present report is an attempt to collect in one place the analytical interferences that are most commonly found during the collection of SERS/SERRS spectra.

Gold nanoparticle embedded, self-sustained chitosan films as substrates for surface-enhanced Raman scattering.

In this work, self-sustained, biocompatible, biodegradable films containing gold nanostructures have been fabricated for potential application in nanobioscience and ultrasensitive chemical and biochemical analysis. We report a novel synthesis of gold nanoparticles mediated by the biopolymer chitosan. Self-supporting thin films are formed from the resultant gold-chitosan nanocomposite solutions and characterized by UV-visible surface plasmon absorption, transmission electron microscopy, atomic force microscopy, infrared absorption, and Raman scattering measurements. Results demonstrate control over the size and distribution of the nanoparticles produced, which is promising for several applications, including the development of biosensors. As a proof of principle, we demonstrate that gold-chitosan films can be employed in trace analysis using surface-enhanced Raman scattering.

Overtones and combinations in single-molecule surface-enhanced resonance Raman scattering spectra.

The observation of overtones and combinations in the SERRS spectra of single molecules dispersed in Langmuir-Blodgett monolayers is confirmed for a family of molecules. The detection of fundamentals, combinations, and overtones in single-molecule spectra of a series of perylenetetracarboxylic diimides (PTCD) is achieved with spatially resolved surface-enhanced resonance Raman scattering (SERRS). The Langmuir-Blodgett technique is used to create monomolecular thick films on metal islands containing on average one probed molecule within the field of view of the Raman microscope. The enhancement needed for single-molecule detection is achieved through the multiplicative effects of electromagnetic enhancement by metal nanostructures and resonance Raman enhancement by excitation into molecular electronic absorption bands. Overtone and combination progressions are well resolved in the average SERRS spectra of all three PTCD molecules.