Impact of Composition on the Optical Properties of Colloidal Ternary Spinel Oxide Nanocrystals: Spinel Ferrites versus Spinel Gallates.

Facile synthesis of ternary spinel Co–Mn–Ni nanorods as efficient bi-functional oxygen catalysts for rechargeable zinc-air batteries

Ternary spinel oxides of formula AB2O4 are semiconductors that possess compositionally and structurally tunable magnetic and optoelectronic properties that, when coupled with their extraordinary chemical and thermal stability, offer functional materials with applications in the fields of photocatalysis, solar energy conversion, gas sensing, and photoelectrochemistry. Nanocrystals of these materials offer the additional advantages of high surface area-to-volume ratios and the ability to use surface functionalization as a plausible strategy for tailoring their optoelectronic properties to improve their function in a specific application. Here, we demonstrate that surface-bound species can dominate the absorption spectra of colloidal ternary spinel oxide nanocrystals. We show that the surface functionalization of cobalt-containing systems with thiol ligands leads to the growth of an intense peak centered at 2.4 eV (518 nm) in their absorption spectra, which arises due to the formation of cobalt-thiolate linkages on the nanocrystal surface. We demonstrate that the observed optical change can be used to track ligand exchange reactions and assess the relative binding affinity of thiol, amine, and carboxylate ligands to the nanocrystal surface. This work highlights the significant role that surface chemistry can play in determining the optical properties of ternary spinel oxide nanocrystals.

Investigation on structural, morphological and optical properties of Co-doped ZnO thin films

The electronic, optical, thermodynamic stability, and hydrogen storage properties of the metal hydride halides Ca 2 H 3 Br and Ba 2 H 3 I were systematically analyzed using density functional theory (DFT). The optimized crystal structures demonstrate that both compounds crystallize in a monoclinic lattice with distinct atomic arrangements. Electronic band structure calculations reveal that both materials are indirect semiconductors, with Ca 2 H 3 Br exhibiting a smaller band gap (1.580 eV) than Ba 2 H 3 I (2.185 eV), indicating stronger visible-light absorption potential. Density of states analysis shows that Ba 2 H 3 I has a higher valence band density, favoring hole transport, while Ca 2 H 3 Br has a larger conduction band density, enhancing electron mobility. Optical properties, including the real and imaginary parts of the dielectric function, refractive index, extinction coefficient, absorption coefficient, and optical conductivity, indicate strong photon–material interactions in both the visible and UV regions. Ca 2 H 3 Br exhibits higher absorption in the visible range, whereas Ba 2 H 3 I is more efficient in the UV region. The calculated formation energies of −1.104 eV/atom for Ca 2 H 3 Br and −1.014 eV/atom for Ba 2 H 3 I confirm their thermodynamic stability. Moreover, hydrogen storage analysis shows gravimetric capacities of 1.86 wt% for Ca 2 H 3 Br and 0.75 wt% for Ba 2 H 3 I, highlighting Ca 2 H 3 Br as the more promising candidate for hydrogen-based energy applications. These results demonstrate that both materials are multifunctional, combining optoelectronic performance with stability and hydrogen storage potential, making them suitable for next-generation energy and photonic devices.

ZrO2 exhibits low optical absorption in the near- UV range and is one of the highest laser-induced damage threshold (LIDT) materials; it is, therefore, very attractive for laser optics applications. This paper reports explorations of reactive sputtering technology for deposition of ZrO2 films with low extinction coefficient k values in the UV spectrum region at low substrate temperature. A high deposition rate (64 % of the pure metal rate) process is obtained by employing active feedback reactive gas control which creates a stable and repeatable deposition processes in the transition region. Substrate heating at 200 C was found to have no significant effect on the optical ZrO2 film prop- erties. The addition of nitrogen to a closed-loop controlled process was found to have mostly negative effects in terms of deposition rate and optical properties. Open-loop O2 gas- regulated ZrO2 film deposition is slow and requires elevated (200 C) substrate temperature or post-deposition annealing to reduce absorption losses. Refractive indices of the films were distributed in the range n = 2.05-2.20 at 1,000 nm and extinction coefficients were in the range k = 0.6 9 10 -4 and 4.8 9 10 -3 at 350 nm. X-ray diffraction analysis showed crystalline ZrO2 films consisted of mono- clinic ? tetragonal phases when produced in Ar/O2 atmosphere and monoclinic ? rhombohedral or a single rhombohedral phase when produced in Ar/O2 ? N2. Optical and physical properties of the ZrO2 layers produced in this study are suitable for high-power laser applications in the near-UV range.

Nd3+ Doping effect on the optical and electrical properties of SnO2 thin films prepared by nebulizer spray pyrolysis for opto-electronic application

Influence of plasma ion-beam assistance on TiO 2 and MgF 2 thin films deposited by plasma ion-assisted deposition

Envisioning the attachment of CdS nanoparticles on the surface of MFe2O4 (M = Zn, Co and Ni) nanocubes: Analysis of structural, optical, magnetic and photocatalytic properties

The micro-properties (structure and composition) and macro-properties (electrical and optical properties) of zinc oxide thin films deposited on glass substrates using a filtered vacuum arc deposition system were investigated as a function of oxygen pressure (0.37–0.5 Pa) and arc current (100–300 A). The films were polycrystalline and the crystal plane orientation varied with the oxygen pressure and arc current, tending to be aligned parallel to the c-axis. The sizes of the crystallite grains were 10–35 nm. The films were found to be compressively stressed, with stress in the range of −2.5–0 GPa. The stress in any sample decreased as a function of arc current; however, its dependence on the pressure also depended on the applied arc current. The compressive stress in samples deposited with arc current in the range 100–150 A, decreased with the pressure from −2.5 to −1.5 GPa (0.37–0.5 Pa), whereas it increased with the oxygen pressure in samples deposited with arc current ranging from 200–300 A. The compressive stress in all samples deposited with the highest oxygen pressure (0.51 Pa) was in a relatively narrow range of −2.1 to −1.7 GPa.Film composition, determined by x-ray photoelectron spectroscopy, depended weakly on the deposition parameters. All samples had zinc excess, with a typical oxygen to zinc atomic concentration ratio of 0.7–0.8. Film thickness, in the range of 80–780 nm, depended linearly on both the deposition parameters.The electrical resistivity (ρ) of the films was in the range of (1–5) × 10−4 Ωm, depending weakly on the deposition parameters. The electrical resistivity of the films with larger grain size was higher than that of films with smaller grains, whereas it increased with film stress. The optical transmission of the films, expressed by the extinction coefficient, depended strongly on both the deposition parameters (arc current and oxygen pressure). The lowest extinction was obtained with films deposited with higher pressure (P ⩽ 0.5 Pa) and lower arc current (I ⩾ 200 A). The lowest extinction coefficient was ∼4 × 10−4 nm−1 in the visible and the near-IR range of the spectrum. Films with larger grain size and lower stress had a relatively larger extinction coefficient (∼8 × 10−3 nm−1).

Collocated aircraft observations of microstructure and radiative properties of winter boundary layer clouds over the East China Sea and the Japan Sea have been carried out in January 1999 within the Japanese Cloud and Climate Study (JACCS) program. The first part of the paper describes the in situ measured microphysical and optical properties for two cases of boundary layer winter stratocumulus clouds, which concern, first, a rather uniform, supercooled water cloud contaminated by aerosols and, second, a highly heterogeneous, mixed‐phase stratiform cloud. Using the Polar Nephelometer, a new instrument for measuring, in situ, the scattering phase function of cloud droplets and ice particles, the polluted, continental‐type stratocumulus cloud can be optically regarded as a liquid water cloud because the measured scattering phase functions fitted very well with those calculated from Mie theory for the directly measured FSSP size distributions. In mixed‐phase cloud, the measured scattering phase function shows that ice particles strongly affect optical properties of the cloud, where large number of liquid water droplets with higher extinction coefficient and asymmetry factor values were converted into a much smaller number of large ice crystals with lower extinction coefficient and asymmetry factor. Furthermore, a quasi‐stable liquid‐topped cloud layer with precipitating ice particles was noticed; the layer may, first, affect the cloud radiative properties and, second, seriously restrict the interpretation of satellite cloud composition retrievals.

Spectral extinction coefficients of background aerosols in Europe, North and South America: A comparison

AIN material is well known with its high band gap, electroinsulating and piezoelectric properties, chemical stability, hardness and high decompoition temperature [1]. AIN thin films find large application in microelectronics and optoelectronics. They are good thermal conductors and resistant to thermal shocks [2], So far they do not find large application in optical coatings due to the technological difficulties in their production and large compressive stress. The films are subjected to oxidizing during heating under ambient air, which leads to reducing their refractive index and change of their mechanical and other physical properties [3], Additional big problem so far is the higher extinction coefficient of AIN, which normally exceeds 10-3 and make it unacceptable for many optical applications. Nevertheless, AIN is a prospective material for deposition of multilayer stacks of type Al2O3/AlN or index profile coatings from evaporation or sputtering of metal Al and alternative changing the reactive gases in the vacuum chamber. Deposition of AIN thin films with high refraction index, low extinction coefficient and small mechanical stress still seems a challenging task.

The properties of the l‐μm volume extinction coefficient of two geographically different high‐altitude cloud systems have been examined for the posteruption period (1985–1990) of the April 1982 El Chichón volcanic event with emphasis on the effect of volcanic aerosols on clouds. These two high‐altitude cloud systems are the tropical clouds in the tropopause region observed by the Stratospheric Aerosol and Gas Experiment (SAGE) II and the polar stratospheric clouds (PSCs) sighted by the Stratospheric Aerosol Measurement (SAM) II. The results indicate that volcanic aerosols alter the frequency distributions of these high‐altitude clouds in such a manner that the occurrence of clouds having high extinction coefficients (6×10−3– 2×10−2km−1) is suppressed, while that of clouds having low extinction coefficients (2×10−3– 6×10−2km−1) is enhanced. This influence of the volcanic aerosols appears to be opposite to the increase in the extinction coefficient of optically thick clouds observed by the Earth Radiation Budget Experiment (ERBE) during the initial posteruption period of the June 1991 Pinatubo eruption. A plausible explanation of this difference, based on the Mie theory, is presented. The Mie calculation indicates that there are two possible types of response of cloud extinction coefficient to changes in aerosol concentration depending on the primary effective radius (re) of cloud systems observed by the instrument. These two types of response are separated by the cloud particle effective radius of about 0.8 μm. Whenreis smaller than 0.8 μm, the cloud extinction coefficient decreases in response to increases of aerosol concentration, and whenreis greater than 0.8 μm, the opposite happens. As a consequence, the effective radius of most, if not all, of the high‐altitude clouds, measured by the SAGE series of satellite instruments must be less than about 0.8 μm. This mean cloud particle size implied by the satellite extinction‐coefficient data at a single wavelength (1 μm) is further substantiated by the particle size analysis based on cloud extinction coefficient at two wavelengths (0.525 and 1.02 μm) obtained by the SAGE II observations. Most of the radiation measured by ERBE is reflected by cloud systems comprised of particles having effective radii much greater than 1 μm. A reduction in the effective radius of these clouds due to volcanic aerosols is expected to increase their extinction‐coefficient values, opposite the effect observed by SAGE II and SAM II. This work further illustrates the capability of the solar occultation satellite sensor to provide particulate extinction‐coefficient measurements important to the study of the aerosol‐cloud interactions. Finally, the June 1991 Mount Pinatubo major eruption put 3 times more material into the stratosphere than that of the 1982 El Chichón volcanic event. It is important to examine the variations of the extinction coefficient of these two high‐altitude cloud systems for the posteruption years of the Pinatubo volcanic event for further evidence of the impact of volcanic aerosols on high‐altitude clouds.

While certain ternary spinel oxides have been well-explored with colloidal nanochemistry, notably the ferrite spinel family, ternary manganese (Mn)-based spinel oxides have not been tamed. A key composition is cobalt (Co)-Mn oxide (CMO) spinel, CoxMn3-xO4, that, despite exemplary performance in multiple electrochemical applications, has few reports in the colloidal literature. Of these reports, most show aggregated and polydisperse products. Here, we describe a synthetic method for small, colloidally stable CMO spinel nanocrystals with tunable composition and low dispersity. By reacting 2+ metal-acetylacetonate (M(acac)2) precursors in an amine solvent under an oxidizing environment, we developed a pathway that avoids the highly reducing conditions of typical colloidal synthesis reactions; these reducing conditions typically push the system toward a monoxide impurity phase. Through surface chemistry studies, we identify organic byproducts and their formation mechanism, enabling us to engineer the surface and obtain colloidally stable nanocrystals with low organic loading. We report a CMO/carbon composite with low organic contents that performs the oxygen reduction reaction (ORR) with a half-wave potential (E1/2) of 0.87 V vs RHE in 1.0 M potassium hydroxide at 1600 rpm, rivaling previous reports for the highest activity of this material in ORR electrocatalysis. We extend the general applicability of this procedure to other Mn-based spinel nanocrystals such as Zn-Mn-O, Fe-Mn-O, Ni-Mn-O, and Cu-Mn-O. Finally, we show the scalability of this method by producing inorganic nanocrystals at the gram scale.

A study of the optical properties of titanium oxide films prepared by dc reactive magnetron sputtering