UV-visible Range Research Articles

Peculiar nonlinear optical absorption and optical limiting behaviors of bismuth-based binary and ternary nanostructures

A single-beam Z-Scan experiment was used to investigate the nonlinear optical absorption and optical limiting properties of pristine Bi2O3, binary rGO/Bi2O3, Bi2O3/WO3 and ternary rGO/Bi2O3/WO3 nanostructures. These nanostructures were synthesized using a facile hydrothermal method. The crystallite size, interplanar spacing, allotropes of carbon and functional groups were characterized using XRD, Raman and FTIR. The morphology of the synthesized compounds was confirmed by SEM and TEM analyses. EDS analysis confirmed the existence of elements such as C, O, Bi and W. A linear optical study illustrates that the pristine Bi2O3 exhibited absorption within the UV range of 200 nm and 400 nm, whereas the binary and ternary nanostructures displayed absorption in the UV–Visible range from 200 nm to 800 nm. The synthesized nanostructures shows exciting nonlinear absorption such as genuine 2PA (pristine Bi2O3), W-type SA to RSA (binary rGO/Bi2O3, Bi2O3/WO3) and sequential 2PA (ternary rGO/Bi2O3/WO3). Bismuth-based nanostructures exhibit the lowest optical limiting (OL) threshold and a greater two-photon absorption coefficient. The extended conjugation for charge transfer and the presence of high defect-induced states in rGO, along with the strong UV–Visible absorption of Bi2O3 and WO3 which leads to a unique nonlinear optical response. This response holds promise for potential applications in energy stabilizers and laser safety devices operating at 532 nm and 9 ns laser domain.

Role of CeO₂ and calcination temperature on the structural and optical properties of (ZnO) ₁-x/ (CeO₂)ₓ nanocomposites in the UV–visible region

This study explores the optical properties of (ZnO)1-x/(CeO2)x nanocomposites within the UV–visible range (250–1000 nm). Two sets of samples were synthesized using a gelatin-based sol-gel method. The first set comprises (ZnO)1-x/(CeO2)x, where x values are 0.0 (pure ZnO), 0.03 (ZCe3), 0.05 (ZCe5), and 0.01 (ZCe10) that calcined at 600 °C for 2 h. The second set consists of (ZnO)0·97/(CeO2)0.03 samples, which were obtained at varying temperatures denoted as ZCe3-700, ZCe3-800, ZCe3-900, and ZCe3-1000 °C. X-ray diffraction (XRD) analysis was employed to investigate the structure of the prepared nanocomposites under different conditions. The XRD patterns revealed a hexagonal lattice structure for ZnO and a cubic lattice structure for CeO₂, confirming that ZnO and CeO₂ nanocrystals grew independently. The crystalline size of the samples was determined using the Size Strain Plot (SSP) method. Reflectance data acquired through UV–visible spectroscopy were utilized to calculate the band-gap value, which was subsequently analyzed using the Kramer-Kronig method. The results indicate that, although there is negligible variation in the band gap values among samples prepared with different combinations and temperatures, these parameters influence n(ω) and k(ω). These findings suggest that ZnO/CeO₂ nanocomposites hold promise for optoelectronic applications, and the optical properties can be fine-tuned by controlling the aspect ratio of ZnO and CeO₂.

Improving the UV–Vis light-harvesting of Er3+ using Mn4+ as a sensitizer in Li2TiO3 host

A series of Li2TiO3 phosphors, both singly doped with Mn4+ and codoped with Mn4+ and Er3+, were synthesized using a solid-state reaction at high temperatures. In the Li2TiO3:Mn4+/Er3+ system, Mn4+ ions have the ability to absorb UV–Vis photons within the range of 250–600 nm. Subsequently, an energy transfer process occurs between Mn4+ and Er3+ ions, resulting in the emission of near-infrared light originating from Er3+ ions. When excited by light at 365 nm, the Li2TiO3:Mn4+-Er3+ phosphors demonstrated a strong emission in the far-red region, peaking at 682 nm, which corresponds to the 2E→4A2 transition of Mn4+ ions. Additionally, an emission at 1555 nm was observed, associated with the 4I13/2→4I15/2 transition of Er3+ ions. The discussion of the energy transfer from Mn4+ to Er3+ involves the investigation of variations in Er3+ doping and the lifetime values of Mn4+. The absorption of Mn4+ in the UV–Vis range and the subsequent energy transfer to Er3+ ions suggest that these materials could be utilized as spectral converters, enhancing the UV–Vis absorption efficiency of luminescent materials based on Er3+.

Synergic versus Antagonist Effects of Rutin on Gallic Acid or Coumarin Incorporated into Chitosan Active Films: Impacts on Their Release Kinetics and Antioxidant Activity.

This work deals with the study of the release and antioxidant activity kinetics of three natural antioxidants associated as binary mixture (coumarin, and/or gallic acid and rutin) from chitosan films. Antioxidants were incorporated into film alone or in binary mixture. The aim was to determine the influence of rutin on the phenolic acid and benzopyrone. The UV-visible light transmission spectra of the films were also investigated. Neat chitosan films and chitosan incorporated coumarin exhibited high transmittance in the UV-visible light range, while GA-added chitosan films showed excellent UV light barrier properties. The molecular interactions between chitosan network and antioxidants were confirmed by FTIR where spectra displayed a shift of the amide-III peak. Rutin has a complex structure that can undergo ionization. The chitosan network structure induced change was found to influence the release behavior. The film containing rutin showed the highest antioxidant activity (65.58 ± 0.26%), followed by gallic acid (44.82 ± 3.73%), while coumarin displayed the lowest activity (27.27 ± 4.04%). The kinetic rate against DPPH-free radical of rutin is three times higher than coumarin. The kinetic rates were influenced by the structure and interactions of the antioxidants with chitosan. Rutin exhibited a slow release due to its molecular interactions with chitosan, while coumarin and gallic acid showed faster release. The diffusion coefficient of coumarin is 900 times higher than that of rutin. The rutin presence significantly delayed the release of the gallic acid and coumarin, suggesting an antagonistic effect. However, their presence weakly affects the release behavior of rutin.

Degradation of sertraline using a continuous-flow filtration/photocatalysis system based on carbon fiber (PWB-3) modified with WO3 under LED chip irradiation

This work describes a filtration/photocatalytic system based on carbon fiber (CF) PWB-3 modified with WO3, to obtain a system capable of simultaneously filtering and degrading sertraline (SER) in simulated and real effluents. The CF was prepared by chemical electrodeposition and subsequent thermal treatment at 450 °C. X-ray diffraction patterns of CF/WO3/450 showed characteristic peaks for C and WO3 in monoclinic phase (more photoactive). The material presented broad absorption in UV–Vis range (300–700 nm), and a band gap of 3.6 eV. Scanning electron micrographs showed a thin film (WO3) formation on the CF surface. XPS analysis assigned the species C 1s, O 1s, W (4f, 4f7/2, 4d5/2 4d3/2), in addition to an intense peak at 530 eV attributed to metallic bonding (W-O). Modification with WO3 increased BET surface area from 0.20 to 3.1 m2 g−1, indicative of mesoporous-type material. Evaluation of the filtration/photocatalysis system under experimental conditions (100 mL, 2.0 mg L-1 SER, pH 5.6, and UV LED irradiation) enabled the optimization of reactor operating parameters. Use of an ideal flow rate of 180 mL min−1 and a membrane stabilization time of 30 min provided adequate contact between the solid and liquid phases and good mass transfer, achieving concentrations below the limit of detection for simulated and real effluent samples, at 90 and 30 min, respectively. It was shown that HO•, 1O2, O2•-, H2O2, and h+ played an important role in SER degradation, with some degradation products being identified and the main route being hydroxylation, demethylation, and dechlorination reactions. The combined system showed excellent potential for filtration applications, reducing problems associated with encrustation, providing rapid retention, and simplifying the treatment of contaminated water.

Poly(tetrasubstituted-aryl imidazole)s: A Way to Obtain Multi-Chromophore Materials with a Tunable Absorption/Emission Wavelength

Some original poly(tetrasubstituted imidazole)s incorporating different units were synthesized and characterized. These materials were obtained via a cascade polycondensation process assisted by microwave irradiation that was developed by our team. This time, we integrated two well-known chromophore structures into the macromolecular backbone, which were benzothiadiazole (BTD) and diketopyrrolopyrrole (DKPP). These new polymers were fully characterized: their chemical structures were confirmed using NMR spectroscopy and their thermal, optical and electrochemical properties were investigated and compared with a reference polymer containing a phenyl spacer instead of the mentioned chromophore units. These materials were found to exhibit a large Stokes shift of up to 350 nm. Furthermore, a polymer presenting large absorption on the UV–visible range and an emission close to the near-infrared region was obtained by coupling the mentioned moieties. According to the established properties of this latter polymer, it presents a potential for applications in biological imaging or optoelectronic devices.

Antibactericidal Ir(III) and Ru(II) Complexes with Phosphine-Alkaloid Conjugate and Their Interactions with Biomolecules: A Case of N-Methylphenethylamine.

The phosphine ligand (Ph2 PCH2 N(CH3 )(CH2 )2 Ph, PNMPEA) obtained by the reaction of the (hydroxymethyl)diphenylphosphine with naturally occurring alkaloid N-methylphenethylamine, was used to synthesize the half-sandwich iridium(III) (Ir(η5 -Cp*)Cl2 Ph2 PCH2 N(CH3 )(CH2 )2 Ph, IrPNMPEA) and ruthenium(II) (Ru(η6 -p-cymene)Cl2 Ph2 PCH2 N(CH3 )(CH2 )2 Ph, RuPNMPEA) complexes. They were characterized using a vast array of methods, including 1D and 2D NMR, ESI(+)MS spectrometry, elemental analysis, cyclic voltammetry (CV), electron spectroscopy in the UV-Vis range (absorption, fluorescence) and density functional theory (DFT). The initial antimicrobial activity in vitro toward Gram-positive and Gram-negative bacterial strains was examined, indicating that both complexes are selective towards Gram-positive bacteria, e. g., Staphylococcus aureus, where the IrPNMPEA has been more bactericidal compared to RuPNMPEA. Additionally, the interactions of these compounds with various biomolecules, such as DNA (ctDNA, plasmid DNA, 9-ethylguanine (9-EtG), and 9-methyladenine (9-MeA)), nicotinamide adenine dinucleotide (NADH), glutathione (GSH), and ascorbic acid (Asc) were described. The results showed that both Ir(III) and Ru(II) complexes accelerate the oxidation process of NADH, GSH and Asc that appeared to occur by an electron transfer mechanism. Interestingly, only IrPNMPEA leads to the formation of various biomolecule adducts, which can explain its higher activity. Furthermore, RuPNMPEA and IrPNMPEA have been interacting with the DNA through weak noncovalent interactions.

Optical Asymmetry and Structural Complexity in Hierarchically Organized Chiral CuO Nanostructures: Insight into the Geometric and Crystallographic Effects on Cooperative Chirality.

Optical asymmetry and structural complexity across different length scales were realized in flower-shaped CuO nanostructures, prepared through refluxing an aqueous solution of copper acetate, sodium hydroxide, and D-tartaric acid, as well as in their toroid-like forms obtained on calcination at 600 °C. Atomic scale chirality in the flower morphology could be visualized as putative Boerdijk-Coexter-Bernal like tetrahelical fragments, while that in the toroid form could be identified as screw dislocation-driven helicity. The fraction of asymmetry in the nanostructures has been evaluated from their chiroptical responses based on Kuhn asymmetry factor (g) from circular dichroism (CD) spectroscopy in the entire UV-vis range. The origin of chirality in the two CuO nanostructures has been assigned to the helical arrangement of the Cu-O-Cu network in accordance with their microscopic and spectroscopic observations. Attempts have been made to interpret the crystallographic and geometric chiralities in the two CuO nanostructures based on the redshift and augmented intensity of the CD signal along with an increase in their corresponding anisotropic factor on calcination. Further, the diverse interaction of the toroid-shaped CuO nanostructures with enantiomeric tryptophan moieties has been illustrated from the measurement of their corresponding thermodynamic parameters.

Efficiency of cathodic arc-grown N-doped TiO2 films for the photocatalytic reduction of Cr(VI) under UV-Vis irradiation

The photocatalytic activity of undoped and N-doped TiO2 anatase films with different thicknesses prepared by cathodic arc deposition on glass substrates is reported. After TiO2 deposition, the doping of the films was carried out by plasma immersion ion implantation in a nitrogen environment. The composition of the films was studied by x-ray photoelectron spectroscopy, the surface morphology was analyzed by atomic force microscopy and the crystalline structure was examined by x-ray diffraction. The thickness was determined by observing the film cross section with scanning electron microscopy. The transmittance of the films in the UV-Vis range was studied as well. The photocatalytic activity of the films was evaluated through the efficiency in the reduction of Cr(VI) in the presence of ethylenediaminetetraacetic acid under UV-Vis irradiation. N-doped films presented a higher photocatalytic efficiency than undoped films: Cr(VI) reduction after 5 h irradiation augmented from 58% (pure TiO2) to 85% (N-doped TiO2) for films of 300 nm thickness, and from 69% to 85% for films with a thickness of 440 nm. On the other hand, pure TiO2 films of 790 nm thickness were more efficient (99% of Cr(VI) reduction) but the effect of doping on the photocatalytic activity was negligible.

Bimetallic oxide Mg-Cu nanoparticles synthesis and application in photometric sensing of trypsin in the presence of tap water, ammonia, and glutamine

The concentration of biomolecules such as trypsin and ammonia in bodily fluids are indicators of health conditions including pancreatic diseases and acute liver failure respectively. The maximum UV-Visible intensity and wavelength shifts of Mg-Cu bimetallic oxide nanoparticles (BNPs) were found to be proportional to changes in trypsin and ammonia concentration. The BNPs could selectively detect trypsin in tap water containing ions, ammonia, and glutamine at concentrations as low as 0.0003%v/v. The synthesis of Mg-Cu BNPs was accomplished by ablating a mixture of Mg and Cu powders and Mg and Cu colloids using a Nd:YAG 1064 nm laser in isopropanol alcohol and HCl. The BNPs demonstrated higher optical absorbance intensity in the UV-Visible range compared to their monometallic constituents, making them more suitable for use in biochemical sensing of trypsin and ammonia. The BNPs exhibited a massive 730-fold increase in electrical conductivity compared to monometallic Mg nanoparticles (0.001 mS/cm vs. 0.73 mS/cm). Field emission scanning electron microscopy was used to visualize the NP morphologies, revealing pyramidal and quasi-spherical BNPs with diameters as small as 5 nm.

Green synthesized silver nanoparticles mediated by Fusarium nygamai isolate AJTYC1: characterizations, antioxidant, antimicrobial, anticancer, and photocatalytic activities and cytogenetic effects

Green biosynthesized nanoparticles have a bright future because they can be produced using a method that is more energy-efficient, cost-effective, repeatable, and environmentally friendly than physical or chemical synthesis. In this study, silver nanoparticles (AgNPs) were produced using the Fusarium nygamai isolate AJTYC1. Several techniques were used to characterize the synthesized AgNPs, including UV–Vis spectroscopy, transmission electron microscope, zeta potential analysis, X-ray diffraction analysis, energy dispersive X-ray, and Fourier transform-infrared spectroscopy. AgNPs showed a distinctive surface plasmon resonance (SPR) peak in the UV–visible range at 310 nm. The morphology of the biosynthesized AgNPs was spherical, and the TEM image shows that they ranged in size from 27.3 to 53.1 nm. The notable peaks of the FT-IR results show the different groups for the alkane, alkynes, cyclic alkenes, carboxylic, aromatic amine, esters, and phenolics. Additionally, the results showed that AgNPs had superior antioxidant activity when compared to ascorbic acid and butylated hydroxytoluene, which is a powerful antioxidant. Additionally, AgNPs have antibacterial action utilizing agar diffusion against gram-positive bacteria, gram-negative bacteria, and antifungal activity. AgNPs’ anticancer activity varied depending on the type of cancer it was used to treat, including hepatocellular cancer (HepG2), colorectal carcinoma (HCT116), and breast cancer of the mammary gland (MCF7). The viability of the cancer cell lines was reduced with increasing AgNP concentration. AgNPs also demonstrated promising photocatalytic activity by reducing methylene blue, safranin, crystal violet, and green malachite by 88.3%, 81.5%, 76.4%, and 78.2%, respectively. In addition, AgNPs significantly affected the Allium cepa plant’s mitotic index and resulted in chromosomal abnormalities as compared to the control. Thus, the synthesized AgNPs demonstrated an efficient, eco-friendly, and sustainable method for decolorizing dyes as well as antioxidant, antibacterial, antifungal, and anticancer activities. This could be a huge victory in the fight against numerous dynamic diseases and lessen wastewater dye contamination.

RETRACTED: Optoelectronic properties of copper-fused Zn(1-x) SCux grown nanofilms for solar cell devices

On glass substrates in a basic medium, Zn(1-x)SCux nanostructures were produced using a chemical bath approach for an adjusted dopant concentration (DC) (0.01–0.05 M) at 80 °C, and annealed at 300 °C for 2.5 h. The X-ray diffraction pattern revealed a α-ZnS phase in the produced films with a stronger diffraction peak at 31.775°. The creation of a high crystalline structure in the α-ZnS phase is confirmed by Raman spectral analysis. SEM images revealed a uniform and dense surface morphology with modest grain size sharing and no fractures. The existence of anticipated Zn, S, and Cu was detected by energy-dispersive X-ray spectroscopy. Spectrophotometry in the UV–visible range showed a redshift. Additionally, as DC is increased, the optical band gaps (3.82–3.99 eV) and transmittance were observed to increased. The projected crystallite sizes (3.58–2.45 nm) based on energy band gaps shrank as DC increased. Infrared spectroscopy using the Fourier transform did not reveal any contaminant signals. The electrical conductivity was p-type, according to the Hall Effect investigation.

Binding of Mammea A/AA (MA) to calf thymus DNA revealed by the ratiometric absorbance of MA in the UV-visible range molecular dynamic simulations and TD-DFT calculations

The in vitro anti-proliferative activity of MA ( 5,7-dihydroxy-8-(3-methylbut-2-enyl)-6-(3-methyl-1-oxobutyl)-4-phenyl[1]2H-[1]benzopyran-2-one)on a variety of cancer cells was previously demonstrated. This work strives to understand the mechanisms by which MA exerts this biological activity. Thereafter, the binding of MA to calf thymus DNA was studied by monitoring the change in the UV-visible absorbance of MA. It was found that, the response of MA to binding with calf thymus DNA is characterised by an increase in the AS/AL ratio of the absorbance of the longest wavelength absorption band to the shortest one, and the appearance of a new band at about 377 nm assigned to S0→S1 transition, which is red shifted as compared to free MA. From the bands ratio, the binding constant is found to be 4.3x105 M−1, indicating strong binding. The deduced binding free energy, enthalpy and entropy are −7.7 kcal/mol, −10.89 ± 0.28 kcal/mol and −54.46 ± 4 J/K, respectively, indicating that MA binds to DNA by a non-bonding Van der Waals type interactions and hydrogen bonds. Further study with classical molecular dynamics shows that MA binds to DNA by intercalation, where it is positioned between two AT base pairs. Unlike isolated MA, TDDFT calculations on ten images extracted from the MD trajectory show that, the frontier molecular orbitals of the complex are distributed over the DNA and MA. This indicates a strong stacking interaction and then explains the hypochromism and the red shift of the S0→S1 transition. The present work demonstrates the potency of MA as antitumor compound and as absorbance-based molecular probe. Communicated by Ramaswamy H. Sarma

Liquid Crystalline Magneto-Optically Active Peralkylated Azacoronene.

Organic Faraday rotators have gained significant attention in recent years as a promising alternative to traditional inorganic magneto-optical (MO) materials as a result of their lower cost, superior mechanical properties, and potential for large-scale deployment. This interest is peaked by the fact that a number of high symmetry, rigid, strongly optically absorbing organic chromophores display Verdet constants an order of magnitude higher than commercial inorganic Faraday rotators. Critical to the development of new generations of organic materials is the ability to organize them in optimal structures for optical coupling/measurements. We report herein the synthesis of a dodecyl-substituted hexapyrrolohexaazacoronene (C12-HPHAC) displaying discotic liquid crystalline (LC) properties and large Faraday rotation. Thin films with a redox mixed C12-HPHAC/C12-HPHAC+2 composition display a discotic columnar LC phase, are stable to air and moisture in the solid and solution states, and achieve a maximum Verdet constant of 3.36 × 105 deg T-1 m-1 at 700 nm. This result is consistent with Serber's model of magnetic circular birefringence and displays one of the largest reported Verdet constants for organic materials in the UV-Vis range. The LC phase aligns the molecules and leads to gains in Verdet constants of up to 105% through the favorable orientation of the molecules' magnetic and electric transition dipole moments with respect to the applied magnetic field.

Exploring the Nature of Anion-π Interactions: Complexes of π-Acceptors with Fluoro- or Oxoanions Compared to the Associations with Halides.

The variations in the nature and properties of the anion-π complexes with different types of anions are identified via experimental (UV-vis and X-ray crystallographic) measurements and computational analysis of the associations of tetracyanopyrazine, tetrafluoro-, or dichlorodicyano-p-benzoquinone. Co-crystals of these π-acceptors with the salts of fluoro- and oxoanions (PF6-, BF4-, CF3SO3-, or ClO4-) comprised anion-π bonded alternating chains or 1:2 complexes showing interatomic contacts of up to 15% shorter than the van der Waals separations. DFT computations confirmed that binding energies between the neutral π-acceptors and polyatomic noncoordinating oxo- and fluoroanions are comparable to those in the previously reported anion-π complexes with more nucleophilic halides. Yet, while the latter show distinct charge-transfer bands in the UV-vis range, the absorption spectra of the solutions containing oxo- and fluoroanions and the π-acceptors were close to those of the individual reactants. The natural bond orbital (NBO) analysis revealed a very small charge transfer of Δq = 0.01-0.02 e in the complexes with oxo- or fluoroanions as compared to the Δq = 0.05-0.22 e found for analogous complexes with halides. These distinctions were related to the smaller frontier orbital energy gap and better overlap in the complexes with halides (since the highest occupied orbitals of these monoatomic anions are closer in energy to the lowest unoccupied orbitals of the π-acceptors) as compared to that in the multicenter-bonded associations with polyatomic oxo- and fluoroanions. In accordance with these data, the energy decomposition analysis showed that while the complexes of neutral π-acceptors with the fluoro- and oxoanions are formed predominantly via electrostatic interaction, the associations with halides comprised significant orbital (charge-transfer) interactions and they explain their spectral and structural features.

Synthesis and optical properties of the glassy compound As0.63S2.70Sb1.37Te0.30

The amorphous calcogenide semiconductor As0.63S2.70Sb1.37Te0.30 was synthesized and thin films based on it were obtained. XRD and optical images investigations showed the amorphous and homogeneous nature of the samples. The optical transmission spectrum in the UV-Vis range of As0.63S2.70Sb1.37Te0.30 thin films shows good transparency in the spectral range 0.7-3.5 µm with a single absorption threshold at 2.05 eV and with refractive index in infrared 2.3. The irradiation of films with light leads to a parallel shift of the transmission spectrum to the IR range. The materials with As0.63S2.70Sb1.37Te0.30 composition have high optical transparency have high optical transparency that make they promises for applications in holographic memory devices, optical amplitude and phase recorder, optical processing units and others.

Judd–Ofelt and photoluminescence analysis of Nd2O3-doped within host fluoroborate glass from the system B2O3–NaF–La2O3

Undoped glass of chemical composition 70B2O3–25NaF–5La2O3 together with Nd2O3-doped samples were prepared via conventional melt and annealing procedure. The prepared glasses were investigated through photoluminescence measurements to find out their extent for the lasing application. The undoped sample reveals two UV absorption peaks while Nd2O3-doped samples show 10 well-characterized peaks in the UV–Visible range that are correlated to different transition states of Nd3+ ions. Three different bands are detected in the emission spectra at 875 nm (4F3/2 → 4I9/2), 1056 nm (4F3/2 → 4I11/2), and 1326 nm (4F3/2 → 4I13/2). The Judd–Ofelt parameters (Ω2, Ω4, Ω6) and radiative properties were estimated using the Judd–Ofelt theory. The represented data indicated that the transition line 4F3/2 → 4I11/2 is the sharpest and lowest bandwidth value than other detected transitions. The structural analysis by FTIR vibrational modes suggested that the IR absorption bands within the range 800–1200 cm−1 originate from both combined vibrations of tetrahedral (BO4) and (BO3F) groups together with (NaF4) groups beside triangular BO3 groups which are vibrating within the range 1200–1600 cm−1. The addition of Nd2O3 is assumed to cause the possible transformation of some structural B–O bonds within the range of triangular borate units referring to the possible formation of pyroborate units or similar structural groups.

Plasma-Assisted N-Doped TiO2 Nanotube Array as an Active UV–vis Photoanode

This work shows the possibility of using plasma nitriding under ultra-high-vacuum conditions to introduce nitrogen into a titanium dioxide structure in the form of nanotubes with a diameter of about 110 nm. Nanotubes were produced by the anodic oxidation of Ti foil in a solution based on glycerine and water with the addition of ammonium fluoride at a voltage of 25 V. Based on experimental evidence obtained by X-ray photoelectron spectroscopy (XPS, in situ), it has been shown that alternating nitriding and annealing processes at 450 °C leads to formation of Ti-N-O, Ti-N, and Ti-O-N chemical bonds in the TiO2 crystal structure (anatase). The observed changes were identified as interstitial or substitutional admixtures or variations of these. The spectrophotometric and spectrophotoelectrochemical tests performed showed that the photoactivity of the photoanodes doped with nitrogen and annealed at 450 °C in the UV–vis range was significantly greater than that of the photoanodes without nitrogen. The highest maximum photocurrent density, of about 30.0 μA·cm–2 at a wavelength of λ = 350 nm, was obtained for the double-nitrided and once-annealed sample, where nitrogen was mainly incorporated in the interstitial positions in the TiO2 lattice. For the materials not nitrided as well as annealed only at 450 °C and pristine, the worse photoresponse was received at the levels of ∼16 and ∼0.2 μA·cm–2, respectively. The thermo-chemical treatment applied also effectively extended the operational range of the photoanodes toward visible light, where a wide maximum of light absorption was observed from ∼400 to ∼700 nm, with a maximum wavelength of 550 nm and an estimated bandgap energy of 2.5 eV. Our investigations confirmed that photoelectrochemical (PEC) performance for TiO2 NT-based photoanodes was achieved by the optimum annealing condition and concentration of nitrogen, where the narrowed bandgap was observed by generating a new N 2p energy level above the O 2p valence band. The following research techniques were used to identify the changes taking place in the materials produced: XPS spectroscopy, UV–vis spectroscopy, PEC measurements, X-ray diffraction structural measurements, and scanning electron microscopic observations.

Real-Time Intraoperative Detection of Margins for Oral Cavity Squamous Cell Carcinoma.

Obtaining negative surgical cancer margins is the strongest predictor for the long-term survival of oral cavity squamous cell carcinoma patients. To verify that the tumor has been completely removed, surgeons rely on pathologic evaluation of frozen sections to determine surgical margins, which can be time-consuming and subjective. Herein, we detail the real-time intraoperative use of dynamic optical contrast imaging (DOCI), a novel imaging modality that rapidly distinguishes head and neck cancer from healthy adjacent tissues based on fluorescence decay information from spectral bands in the UV-VIS range. Analysis of DOCI revealed microscopic characterization sufficient for tissue type identification consistent with histology (p < .05). DOCI delivers a clinically relevant tool that may better inform and drive precision surgery, directly impacting surgical outcomes and improving overall survival for our patients.

Good optical transparency is not an essential requirement for effective solar water disinfection (SODIS) containers

The efficacy of 10 L polypropylene (PP) transparent jerry cans (TJCs) to inactivate E. coli, MS2-phage and Cryptosporidium parvum via solar water disinfection (SODIS) was tested in well water or general test water under natural sunlight. Food-safe PP was used to manufacture the TJCs and a clarifying agent was added to improve optical transparency in the UV–visible range. 10 L PP TJCs and 2 L polyethylene terephthalate (PET) bottles were filled with well water, spiked separately with (∼106 CFU/mL of E. coli, ∼106 PFU/mL of MS2 phage and 5 ×105C. parvum oocysts per litre) and exposed to natural sunlight for 6 h. While the 10 L PP TJC prototype had poorer transparency (UV-B 0.001%, UV-A 4.29%, and visible 92% for TJCs without clarifier and UV-B 1.36%, UV-A 8.01%, and visible 90.01% for TJCs with clarifier) than standard 2 L PET (UV-B 0.72%, UV-A 10–85%, and visible 80–90%); log reduction values (LRVs) > 5, 2 and 0.8 for E. coli, MS2-phage, and C. parvum, respectively, were observed for the TJCs within six hours respectively, which is a minimum standard for drinking water established by the World Health Organisation (WHO). We observed similar inactivation kinetics for all three organisms in PP TJCs and PET bottles despite the poorer optical transparency properties of the SODIS jerry cans. Therefore, for effective SODIS, container optical transparency is not as important as previously believed. We conclude that good visible transparency is not a necessary requirement for containers intended for SODIS use.