Engineering of Solar Energy Harvesting Tb3+-Ion-Doped CdS Quantum Dot Glasses for Photodissociation of Hydrogen Sulfide.

The photocatalytic properties of CdS quantum dots (Q-dots) and Tb3+-doped CdS Q-dots dispersed in a borosilicate glass matrix were investigated for the photodissociation of hydrogen sulfide (H2S) into hydrogen (H2) gas and elemental sulfur (S). The Q-dot-containing glass samples were fabricated using the conventional melt-quench method and isothermal annealing between 550 and 600 °C for 6 h for controlling the growth of CdS and Tb3+-ion-doped CdS Q-dots. The structure, electronic band gap, and spectroscopic properties of the Q-dots formed in the glass matrix after annealing were analyzed using Raman and UV-visible spectroscopies, X-ray powder diffraction, and transmission electron microscopy. With increasing annealing temperature, the average size range of the Q-dots increased, corresponding to the decrease of electronic band gap from 3.32 to 2.24 eV. For developing the model for photocatalytic energy exchange, the excited state lifetime and photoluminescence emission were investigated by exciting the CdS and Tb3+-doped CdS quantum states with a 450 nm source. The results from the photoluminescence and lifetime demonstrated that the Tb3+-CdS photodissociation energy exchange is more efficient from the excited Q-dot states compared to the CdS Q-dot glasses. Under natural sunlight, the hydrogen production experiment was conducted, and an increase of 26.2% in hydrogen evolution rate was observed from 0.02 wt % Tb3+-doped CdS (3867 µmol/h/0.5 g) heat-treated at 550 °C when compared to CdS Q-dot glass with a similar heat treatment temperature (3064 µmol/h/0.5 g). Furthermore, the photodegradation stability of 0.02 wt % Tb3+-CdS was analyzed by reusing the catalyst glass powders four times with little evidence of degradation.

Fabrication and Characterisation of the Cytotoxic and Antibacterial Properties of Chitosan-Cerium Oxide Porous Scaffolds.

Bone damage arising from fractures or trauma frequently results in infection, impeding the healing process and leading to complications. To overcome this challenge, we engineered highly porous chitosan scaffolds (S1, S2, and S3) by incorporating 30 (wt)% iron-doped dicalcium phosphate dihydrate (Fe-DCPD) minerals and different concentrations of cerium oxide nanoparticles (CeO2) (10 (wt)%, 20 (wt)%, and 30 (wt)%) using the lyophilisation technique. The scaffolds were specifically designed for the controlled release of antibacterial agents and were systematically characterised by utilising Raman spectroscopy, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy methodologies. Alterations in the physicochemical properties, encompassing pore size, swelling behaviour, degradation kinetics, and antibacterial characteristics, were observed with the escalating CeO2 concentrations. Scaffold cytotoxicity and its impact on human bone marrow mesenchymal stem cell (BM-MSCs) proliferation were assessed employing the 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) assay. The synthesised scaffolds represent a promising approach for addressing complications associated with bone damage by fostering tissue regeneration and mitigating infection risks. All scaffold variants exhibited inhibitory effects on bacterial growth against Staphylococcus aureus and Escherichia coli strains. The scaffolds manifested negligible cytotoxic effects while enhancing antibacterial properties, indicating their potential for reducing infection risks in the context of bone injuries.

Femtosecond Laser Deposition of Germanium Selenide onto Silicon Platform at Different Substrate Temperatures.

Germanium selenide (GeSe) thin films were fabricated by employing femtosecond pulsed-laser deposition (fs-PLD) on silicon (100) substrates at various substrate temperatures, ranging from 25 °C to 600 °C. The thin films' surface morphology qualities and optical properties were studied by utilising transmission electron microscopy (TEM) and X-ray diffraction (XRD). The X-ray diffraction result signifies that the thin films deposited on the silicon at a substrate temperature below 400 °C were amorphous Ge-Se. In contrast, those grown at 400 °C and above exhibited crystallised peaks of Ge-Se orthorhombic and tetragonal structures. The deposition growth rate of the thin films was also found to decrease substantially with increasing substrate temperature. These results show that the fs-PLD process has great potential for fabricating good quality Ge-Se thin film. This technique could enable the manufacture of modern optoelectronic devices for applications in optical communication, sensing, and ovonic threshold switching for the high-density crossbar memory array.

Effect of Yb3+ on the Structural and Visible to Near-Infrared Wavelength Photoluminescence Properties in Sm3+-Yb3+-Codoped Barium Fluorotellurite Glasses.

We report on the Sm3+ and Sm3+:Yb3+-doped barium fluorotellurite glasses prepared using the conventional melting and quenching method. The spectroscopic characterisations were investigated with Raman and FTIR to evaluate the glasses' structural and hydroxyl (-OH) content. The Raman analysis revealed a structural modification in the glass network upon adding and increasing the Yb3+ concentration from a TeO3 trigonal pyramid to a TeO4 trigonal bi-pyramid polyhedral. At the same time, the FTIR measurements showed the existence of -OH groups in the glass. Thus, under the current experimental conditions and nominal composition, the -OH group contents are too large to enable an effective removal. The near-infrared region of the absorption spectra is employed to determine the nephelauxetic ratio and bonding parameters. The average nephelauxetic ratio decreases, and the bonding parameter increases with the increasing Yb3+ content in the glasses. A room temperature visible and near-infrared photoluminescence ranging from 500 to 1500 nm in wavelength and decay properties were investigated for glasses doped with Sm3+ and Sm3+-Yb3+ by exciting them with 450 and 980 nm laser sources. Exciting the Sm3+- and Sm3+-Yb3+-doped glasses by 450 nm excitation reveals a new series of photoluminescence emissions at 1200, 1293, and 1418 nm, corresponding to the 6F11/2 state to the 6HJ (J = 7/2, 9/2, 11/2) transitions. Under the 976 nm laser excitation, a broad photoluminescence emission from 980 to 1200 nm was detected. A decay lifetime decreased from ~244 to ~43 µs by increasing the Yb3+ content, ascribing to concentration quenching and the OH content.

Erbium-Doped Nanoparticle-Polymer Composite Thin Films for Photonic Applications: Structural and Optical Properties.

Erbium-doped nanocrystal (NC)-dispersed polymer thin films are attractive core materials for use in optical waveguides as they can provide high optical gain and enable the formation of compact waveguide amplifiers. Nonetheless, there are significant challenges associated with obtaining good dispersibility of NCs into a polymer matrix and favorable optical properties. Therefore, in this paper, we report the fabrication of Er3+-doped ceria (EGC) NCs employing the Leeds alginate process (LAP) and their incorporation into a siloxane polymer matrix. The surface morphology and compositional, structural, and optical properties of the fabricated films are evaluated to assess the NC dispersion and their suitability for the waveguide amplifier. The photoluminescence (PL) and lifetime measurements of the NCs-polymer nanocomposite thin film samples show intense, broadband PL emission of the Er3+ ions at 1534 nm (4I13/2 → 4I15/3 transition) with a full width at half-maximum (fwhm) of ∼64 nm and lifetime in the range of 2.6-3.0 ms. The inhomogeneously broadened PL spectra and improvement in lifetime of NCs in the polymer are important results that we report. The EGC NCs-polymer nanocomposite thin films also exhibit excellent transparency in the NIR wavelength range and a refractive index in the range of 1.53-1.58 in the visible wavelength. The work presented here clearly demonstrates the potential of using high-quality Er-doped nanocomposite polymer thin films for interesting applications such as compact low-cost waveguide amplifiers and lasers.

Photoluminescence intensity ratio of Eu-conjugated lactates-A simple optical imaging technique for biomarker analysis for critical diseases.

Instant measurement of elevated biomarkers such as lactic acid offers the most promising approaches for early treatment and prevention of many critical diseases including cardiac arrest, stroke, septic shock, trauma, liver dysfunction, as well as for monitoring lactic acid level during intense exercise. In the present study, a unique dependence of visible photoluminescence of Eu3+ ions resulting from 5 D0 to 7 FJ(J = 0,1,2,3,4) transitions, which can be exploited for rapid detection of biomarkers, both in vitro and ex vivo, has been reported. It is observed that the integrated intensity ratio of photoluminescence signals dominating at 591 and 616 nm originating from 5 D0 to 7 F2 and 5 D0 to 7 F1 transitions in Eu3+ ions can be used as a biosensing and bioimaging tool for detection of biomarkers released at disease states. The Eu3+ integrated photoluminescence intensity ratio approach reported herein for optical detection of lactates in blood serum, plasma and confocal imaging of brain tissues has very high potential for exploitation of this technique in both in vitro monitoring and in vivo bioimaging applications for the detection of biomarkers in various diseases states.

Rapid long-wave infrared laser-induced breakdown spectroscopy measurements using a mercury-cadmium-telluride linear array detection system.

In this work, we develop a mercury-cadmium-telluride linear array detection system that is capable of rapidly capturing (∼1-5 s) a broad spectrum of atomic and molecular laser-induced breakdown spectroscopy (LIBS) emissions in the long-wave infrared (LWIR) region (∼5.6-10 µm). Similar to the conventional UV-Vis LIBS, a broadband emission spectrum of condensed phase samples covering the whole 5.6-10 µm region can be acquired from just a single laser-induced microplasma or averaging a few single laser-induced microplasmas. Atomic and molecular signature emission spectra of solid inorganic and organic tablets and thin liquid films deposited on a rough asphalt surface are observed. This setup is capable of rapidly probing samples "as is" without the need of elaborate sample preparation and also offers the possibility of a simultaneous UV-Vis and LWIR LIBS measurement.

Mid-infrared, long wave infrared (4-12 µm) molecular emission signatures from pharmaceuticals using laser-induced breakdown spectroscopy (LIBS).

In an effort to augment the atomic emission spectra of conventional laser-induced breakdown spectroscopy (LIBS) and to provide an increase in selectivity, mid-wave to long-wave infrared (IR), LIBS studies were performed on several organic pharmaceuticals. Laser-induced breakdown spectroscopy signature molecular emissions of target organic compounds are observed for the first time in the IR fingerprint spectral region between 4-12 µm. The IR emission spectra of select organic pharmaceuticals closely correlate with their respective standard Fourier transform infrared spectra. Intact and/or fragment sample molecular species evidently survive the LIBS event. The combination of atomic emission signatures derived from conventional ultraviolet-visible-near-infrared LIBS with fingerprints of intact molecular entities determined from IR LIBS promises to be a powerful tool for chemical detection.