As recent years have shown an increasing use of polymers for the fabrication of firearms, it is necessary to develop techniques for the reconstruction of obliterated serial numbers that are stamped in these materials. Hyperspectral Raman imaging has proven to be a suitable technique for this purpose, as it is sensitive to residual strain. The extraction of relevant information however requires an advanced two-step fitting procedure (i.e., the identification of strain-sensitive peaks followed by the fitting itself) that may be somewhat time consuming. In this study, principal component analysis (PCA), an exploratory method of the Raman data, is proposed to overcome this deficit. The results show that PCA offers better visual contrast in comparison to the previously reported mathematical modeling technique, as it is able to highlight pertinent variance in the original dataset, for multiple polymers, such as polycarbonate, polyethylene, nylon, and nylatron. Results obtained by limiting acquisition
archetypical" hybrid 3D perovskites, a vivid interest has emerged for their derivatives with reduced dimensionality.The general formula of 2D perovskites is A 2 BX 4 , where A is a monovalent organic cation, B is a divalent metallic cation (for example Pb), and X is a halide anion (Cl, Br, or I). 2D perovskites consist of alternating organic (A) and inorganic layers ([BX 6 ] 4octahedra), where A acts as an electronically insulating spacer that strongly confine excitons in the inorganic part, forming a natural multiple quantum well.In particular, layered 2D Ruddlesden-Popper perovskites combine some of the outstanding physical properties of hybrid 3D perovskites with the unique tunability of low-dimensional materials. [3][4][5] As a result of dielectric confinement, the excitons in 2D perovskites are stable and show strong photoluminescence up to room temperature, unlike the artificially constructed quantum well structures of the classical III−V semiconductors (for example, the GaAs-based heterostructures). For these reasons 2D perovskites have become one of the forefronts Combining the characteristics of hybrid perovskites and layered materials, 2D Ruddlesden-Popper perovskites exhibit unique properties, some of which still require to be deeply understood. In this study, the vibrational signatures of such materials are analyzed by collecting experimental Raman spectra of four distinct compounds. Supported by density functional theory simulations, the role of the phenyl spacer single fluorination on the phonon modes of two similar yet different compounds, i.e., phenethylammonium lead iodide (PEAI) and 4-fluorophenethylammonium lead iodide (PEAI-F), is explained. In addition, this work analyzes some so-far unreported experimental Raman peaks in the 600-1100 cm −1 range and discusses their origin in this class of 2D compounds. This work paves the way for a better design of novel compounds as well as for their exploitation in (opto)electronic applications.
Metal nanoparticles (NP) supported on TiO 2 are known to be efficient photocatalysts for solar-to-chemical energy conversion. While TiO 2 decorated with copper NPs has the potential to become an attractive system, the poor oxidative stability of Cu severely limits its applicability. In this work, we demonstrate that, when Cu NPs supported on TiO 2 nanobelts (NBs) are engaged in the photocatalytic generation of H 2 from water under light illumination, Cu is not only oxidized in CuO but also dissolved under the form of Cu + /Cu 2+ ions, leading to a continuous reconstruction of nanoparticles via Ostwald ripening. By nanoencapsulating the CuO x (Cu/CuO/Cu 2 O) NPs by a few layers of carbon supported on TiO 2 (TC@C), Ostwald ripening can be suppressed. Simultaneously, the resulting CuO x @C NPs are photoreduced under light illumination to generate Cu@C NPs. This photoswitching strategy allows the preparation of a Cu plasmonic photocatalyst with enhanced activity for H 2 production. Remarkably, the photocatalyst is even active when illuminated with visible light, indicating a clear plasmonic enhancement of photocatalytic activity from the surface plasmonic resonance (SPR) effect of Cu NPs. Three-dimensional electromagnetic wavefrequency domain (3D-EWFD) simulations were conducted to confirm the SPR enhancement. This advance bodes for the development of scalable multifunctional Cu-based plasmonic photocatalysts for solar energy transfer.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.