Ultraviolet-visible Range Research Articles

Construction of g-C3N4/SnSe2/H-TiO2 Ternary Heterojunction for High-Performance Photodetectors

Two-dimensional layered materials have been widely used in the field of photodetectors because of their unique photoelectric properties. Among them, the multi-heterojunction based on two-dimensional materials with high carrier separation efficiency is expected to be designed as a high-performance photodetector (PD). This work focuses on the fabrication of g-C3N4/SnSe2/H-TiO2 ternary heterojunctions for photodetectors, obtained by depositing SnSe2 and g-C3N4 nanosheets onto TiO2 nanotube arrays using chemical vapor deposition and impregnation methods, respectively. The formation of the g-C3N4/SnSe2/H-TiO2 ternary heterojunction enhances and broadens absorption in the ultraviolet-visible range. Photoelectrochemical measurements have confirmed that the fabricated g-C3N4/SnSe2/H-TiO2 ternary heterojunction photodetector exhibits remarkable light detection capabilities at 370, 450, and 520 nm, meaning broadband photodetection behavior. Notably, under light illumination of 370 nm wavelength, it demonstrates a high responsivity of 2.742 A W−1, an impressive detectivity of 5.84 × 1010 Jones, an external quantum efficiency of 9.21 × 102 %, and excellent stability. This high performance can be attributed to the effective separation and transfer of photogenerated carriers within the ternary heterojunction, significantly enhancing the photoresponse. The construction of the novel broadband-responsive ternary g-C3N4/SnSe2/TiO2 heterojunction holds promise for driving the future development of wideband, high-performance, and highly integrated photodetectors.

Solvatochromism and preferential solvation of 2,6-dichloro-4-nitroaniline in pure and binary aqueous mixtures

In this study, the solvatochromic behavior of 2,6-dichloro para-nitroaniline (DCPNA) was investigated in a wide range of pure solvents, and binary solvent mixtures of water with ethanol, dimethyl sulfoxide, and dimethyl formamide at 298.15 K. The absorption spectrum of DCPNA in the ultraviolet–visible range exhibits a characteristic peak that shifts with changes in the solvent along the absorption wavelength. The influential factors and their roles in solvatochromism were determined through KAT-LSER analysis in pure solvents. Solvatochromism in binary solvent mixtures showed a completely non-linear trend with respect to the composition of the solution. The recently introduced preferential solvation model was utilized to model the absorbed light wavenumber in aqueous solvent mixtures. This model elucidates the separate effects of preferential solvation of DCPNA and the non-ideal behavior of aqueous solvent mixtures in the non-linearity of solvatochromism.

Effect of Hot Pressing on the Optical, Thermal, and Dielectric Properties of Solution Cast Prepared Nanocomposite Films Based on a Poly(Vinylidene Fluoride-co-Hexafluoropropylene) and Poly(Ethylene Oxide) Blend Matrix with Dispersed Zinc Oxide Nanoparticles

In our research described herein, the hot pressing treatment at 90 °C under 2 tons of pressure on solution cast polymer nanocomposite (PNC) films based on a host matrix of poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) and poly(ethylene oxide) (PEO) with varying polymer blend compositions (20, 50, and 80 wt% P(VDF-HFP) or PEO) and 2 wt% zinc oxide (ZnO) nanofiller, was performed; the effects of this treatment and the composition variations on the optical, thermal, and dielectric properties was explored. The ultraviolet-visible wavelength range study revealed slightly reduced absorbance and a little increased energy band gap after the hot pressing of the nanocomposite films. Differential scanning calorimetry of the solution cast-hot pressed (SC-HP) PNC films explained the reduced thermal stability of the poly(ethylene oxide) crystallites and also the degree of crystallinity. The broadband dielectric measurements of these materials, at 27 °C, confirmed significant changes in various dielectric polarization processes, demonstrating a large redistribution of constituent interfaces by the hot press treatment. Additionally, the 90 °C hot pressed PNC film of equal polymer compositional ratio was further hot pressed at 130 °C and 160 °C, step by step, and characterized to examine the variations in dielectric properties. The properties of these thermally treated composite films are discussed concerning their use for flexible device applications.

Influence of Congored on the Optical, Dielectric and Thermal Behavior of Polymethyl Methacrylate and Polyvinyl Chloride

Polymethyl methacrylate (PMMA)/Congo Red (CR) and polyvinyl chloride (PVC)/CR composite films were prepared on optical glass by the drop method for optical measurements and also prepared as tablets under pressure for dielectrical measurements. The optical transmission spectra measurements for PMMA and PVC film doped with CR showed a highly absorption in the ultraviolet-visible (UV-Vis) optical range (at 353 nm and 518 nm) and considerably blocking in broad visible range (190 nm–640 nm). PMMA/CR and PVC/CR composite films containing congo red at a concentration of 1 wt% showed maximum absorption bands at 290 nm and 416 nm, but their transmittance percentages were reasonably reduced compared to those of pure PMMA and PVC. Both of composites indicated high transmittances between 640 nm and 800 nm. The optical constants of the PMMA/CR and PVC/CR composite films such as optical band energy gaps (Eg) estimated using Tauc’s model, refractive index and reflectance (%) were calculated. UV–Vis, Fourier transform infrared spectroscopy (FTIR) and Thermogravimetry Analysis (TGA) measurements were used to confirm the breakdown of the -N = N- azo group bonds attached to the aromatic ring as a result of thermal decomposition of CR at 500 °C, and it was suggested that N2 gas was eliminated from the CR above 360 °C. The dielectric plots showed that the dielectric constant increased when the CR is doped up to 70 wt% in the polymer matrices. A further increase in the doping concentration of CR resulted in an increase of the dielectric constant. The dielectric constant decreased with an increase in the frequency for all of the samples. The ac (alternating current) conductivity values of PMMA and PVC showed an increase with increasing CR dopant in the polymer composites, while the ac conductivity values were found to be values between those of the pure polymers and CR.

Investigating Ultraviolet-Visible Absorption of Pure Water and Normal Saline under the Treatment of Taheri Consciousness Fields

UV-Vis spectroscopy is a spectrophotometric technique that relies on the absorption of light by species within the ultraviolet to visible range (200 to 700 nanometers). The study of water absorption has been conducted over the decades from the 1930s to the 1980s to investigate electron transfer levels in various studies. The investigation of the absorptive properties of solutions provides significant information about changes in their internal environment, reactions, and molecular interactions. In this study, with the aim of investigating the effectiveness of T-Consciousness Fields on water molecules and examining the potential changes in the physical properties of water, we have focused on the changes in light absorption in the ultraviolet-visible range by water molecules in the presence of T-Consciousness Fields 1, 2, and 3. Additionally, alongside observing the effects of T-Consciousness Fields on the absorptive properties of pure water, the absorptive properties of normal saline are investigated to provide a valuable basis for comparison. In this study, absorptive properties of normal saline are also examined using UV-Vis absorption spectroscopy. Changes in absorption between the control and samples subjected to T-Consciousness Fields 1, 2, and 3 are obtained compared to the standard deviations of changes caused by the control for each wavelength. According to the results obtained for pure water, T-Consciousness Field 1 has led to significant changes in the visible region, exceeding the standard deviation. In the case of normal saline samples, the absorption resulting from the samples in the visible region in the case of T-Consciousness Field 1 shows a decreasing trend, and in the case of T-Consciousness Field 2, it exhibits an increasing trend. Furthermore, the changes in absorption in the sample treated with T-Consciousness Field 3 fall within the range of the average standard deviation of absorption values for the sample and control. A detailed analysis of absorption regions and a comparison of the effectiveness of the three applied T-Consciousness Fields on pure water and normal saline are in the authors' agenda.

Use of photosensitive molecules in the crosslinking of biopolymers: applications and considerations in biomaterials development.

The development of diverse types of biomaterials has significantly contributed to bringing new biomedical strategies to treat clinical conditions. Applications of these biomaterials can range from mechanical support and protection of injured tissues to joint replacement, tissue implants, and drug delivery systems. Among the strategies commonly used to prepare biomaterials, the use of electromagnetic radiation to initiate crosslinking stands out. The predominance of photo-induced polymerization methods relies on a fast, efficient, and straightforward process that can be easily adjusted to clinical needs. This strategy consists of irradiating the components that form the material with photons in the near ultraviolet-visible wavelength range (i.e., ∼310 to 750 nm) in the presence of a photoactive molecule. Upon photon absorption, photosensitive molecules can generate excited species that initiate photopolymerization through different reaction mechanisms. However, this process could promote undesired side reactions depending on the target zone or treatment type (e.g., oxidative stress and modification of biomolecules such as proteins and lipids). This review explores the basic concepts behind the photopolymerization process of ex situ and in situ biomaterials. Particular emphasis was put on the photosensitization initiated by the most employed photosensitizers and the photoreactions that they mediate in aqueous media. Finally, the undesired oxidation reactions at the bio-interface and potential solutions are presented.

A theoretical study of ferrocene based on combined configuration interaction singles (CIS) and time-dependent density functional theory (TDDFT) approach

The state-of-the art density functional theory (DFT) is used to clearly resolve the two parallel cyclopentadienyl rings of ferrocene, which are either staggered (D5d symmetry) or eclipsed (D5h symmetry), in their ground-state conformation. Present result revealed that the eclipsed conformer with D5h point group represents the true minimum ground state structure of ferrocene. Natural population analysis is used to determine how atomic charge is distributed across different atoms of ferrocene D5h conformer and also the distribution of electrons in the core, valence, and Rydberg sub-shells. It is further investigated in potential energy scan that the rotation of the dihedral angle δ from 0° to 3π/5 will reproduce three times D5h or D5d conformers periodically as the period of 2π/5 due to the pentagonal structure of the CP ring. Further to examine optical spectra in the ultraviolet-visible (UV–vis) range, configuration interaction single (CIS) and time-dependent density functional theory (TDDFT) have conducted which help in locating the significant electronic shifts between different energy levels. Absorption spectra for high spin states were also generated in order to comprehend the characteristics of low-lying spin excitation. According to our estimates, the greatest absorption intensity is restricted to an energy range of 4–6 eV. Knowledge of ferrocene conformers will improve the research on other metallocenes and their derivatives, which have applications in biotechnology, nanotechnology, and solar technology.

First-principles calculations investigating structural, electronic optical and elastic properties of ABSe3 (A = Rb, Cs) compounds explored for photovoltaic and optoelectronics applications

In few recent years, great and significant efforts are devoted from researcher all over the world to pursue the revolution of photovoltaic’s materials and their uses in various applications. In the present work, a series of ab-initio simulations based on the density functional theory DFT plane wave pseudo-potential (PW-PP) method and hence performed towards the perselenoborate materials ABSe3 (A = Rb,Cs) for the first time along the three main polarizations of the incident wave directions [100], [010] and [001] with the aim of exploring their structural, electronic, optical and elastic properties. The generalized gradient approximation Perdew–Burke–Ernzerhof (GGA-PBE) carried out with CASTEP code is used for the exchange–correlation potential. The computed results showed that the structural properties of investigated compounds are very good agreement to the available experimental data, showing that the current calculations are quite accurate. Moreover, the density of states and electronic band structure calculations reveal that RbBSe3 (CsBSe3) compounds exhibit direct band gap semiconductor nature 1.66 eV (1,82 eV) respectively within the optimal range band gap 1eV–2eV required for photovoltaic’s applications makes them having great potential to obtain efficient Perovskite solar cell PSC. Additionally, our finding optical properties calculations reveal that the two investigated compounds exhibit strong absorption (prominent absorption peaks up 2,4 × 105cm−1) in UV range, while the real part of the refractive index for RbBSe3 (CsBSe3) was 2.62 (2.60) respectively which might be beneficial for photovoltaic application (top cell in solar cell) and optical applications. Also, high optical conductivity (∼1015sec−1) is found to be observed in visible ultraviolet range (1.7 eV to 30 eV). The lower reflectivity seen by RbBSe3 compared to CsBSe3 in the larger energy spectrum of electromagnetic radiation suggests that RbBSe3 compound is more suitable for electronic applications. Further, once the elastic constants are obtained, the calculated mechanical properties, bulk modulus (B), shear modulus (G), the ratio B/G, Young’s modulus (E), Poisson’s ratio (ν), anisotropy universal (AU) are calculated. Our calculated Young’s modulus indicate that the CsBSe3 is less hardness compared to RbBSe3, while Poisson’s ratio calculated leads them to have a character ionic and RbBSe3 is more ductile than CsBSe3. The calculation value of θ D predicted from elastic constants appears low which is closely related to many physical properties such as specific heat and melting temperature. Finally, the finding results reveal another way of investigating mechanical stability, where both compounds are mechanically stable since all elastic constant computed are perfectly satisfied the Born stability criteria, flexible and brittle. Finally, we hope that all these results will be helpful for designing photovoltaic and optoelectronic devices.

Insights into structural, electronic, optical properties, and impedance spectroscopy of semi-doped perovskite Nd0.5Ba0.5CoO3: A theoretical and experimental study

In this study, the electronic, structural, and optical properties of semi-doped perovskite Nd0.5Ba0.5CoO3 (NBCO) were investigate using the CASTEP software, which relies on density functional theory (DFT) along with the correlation function of generalized gradient approximation (GGA) and Perdew-Burke-Ernzerhof (PBE). The mesh parameters of the (super) cell indicate that NBCO adopts an orthorhombic structure in the Pmmm space group, featuring a Coulomb Energy (EC) of approximately −244 eV. DFT and total density of states (DOS) analyses reveal that the as-prepared perovskite manifests metallic characteristics, and a notable covalent interaction is observed between the O-p and Co-d spin states, indicating strong hybridization between these orbitals. Remarkably, NBCO demonstrates 100 % spin polarization (P) at the Fermi level, with a calculated total magnetic moment of approximately 3.44 μB. Moreover, low dielectric loss (tgδ) values suggest facile electron movement, and impedance spectroscopy illustrates a dielectric relaxation phenomenon. DFT calculations predict an orthorhombic crystal structure with higher electron density at cobalt atom positions. Band structure and DOS analyses affirm metallic behavior owing to the robust hybridization between oxygen-p and cobalt-d orbitals. Optical property assessments reveal potential applications in spintronics and optoelectronics, with notable absorption in the ultraviolet–visible range. The conductivity spectra from impedance spectroscopy contribute to understanding temperature-dependent charge transport mechanisms. Dielectric constants decrease with increasing frequency and temperature, while dielectric losses remain low, indicating efficient electron movement. The material adheres to a metallic conduction mechanism as described by Drude's law, and the material's 100 % spin polarization at the Fermi level and a total magnetic moment of 3.44 μB are significant findings. Negative dielectric constants observed at specific frequencies suggest potential applications in metamaterials. Overall, the determined properties position NBCO cobaltite as a promising candidate for high-frequency devices, spintronic components, and sensors.

Synthesis, photoluminescence and gamma attenuation properties of europium-doped borate glasses

In this research, we investigate in detail the physical, thermal, photoluminescence, and gamma radiation-shielding properties of a new borate glass system doped with Eu3+ ions identified as: 50B2O3–15Na2O – (20-x)PbO–15ZnO – xEu2O3. In particular, the study evaluates the changes in the optical, physical, gamma shielding, and dosimetry properties of the borate glass as functions of the chemical composition. The Eu³⁺-doped borate glassy specimens were prepared using melting-quenching technique. The density of the glasses increased from 3.99 g/cm3 to 4.27 g/cm3 as the Eu2O3 concentration increased from 0 to 3 mol%. A decrease in the concentration of lead oxide led to a decrease in optical absorption in the ultraviolet–visible range. XRD spectra analysis showed that the glasses were purely amorphous. The melting and glass-transition temperatures of the glasses decreased and increased with Eu ion concentration, respectively. The samples doped with Eu3+ showed bright emission photoluminescence under UV excitation. The values of the mass attenuation coefficient (μρ) obtained from XCOM and FLUKA agreed within 1.07%. The values of μρ fluctuated between 0.0329 cm2/g and 54.1851 cm2/g, 0.0329 cm2/g and 53.7354 cm2/g, and 0.0328 cm2/g and 53.6232 cm2/g for Eu2O3 concentrations of 0, 2, and 3 mol%, respectively. The glasses became more effective at absorbing photons when the Eu2O3 content was increased. For 10 mm thick glass, the dose rate for 15 keV photons was about 43.5 μR/h, 43.7 μR/h, and 43.8 μR/h for Eu2O3 concentrations of 0, 2, and 3 mol%, respectively. In addition, Eu2O3 suppressed photon scattering in the glasses. The glass with the highest Eu2O3 concentration displayed better gamma-ray absorption compared to a broad spectrum of shielding materials.

Demonstrating the high sensitivity of MoS2 monolayers in direct x-ray detectors

Two-dimensional transition metal dichalcogenides (TMDCs) are demonstrated to be appealing semiconductors for optoelectronic applications, thanks to their remarkable properties in the ultraviolet-visible spectral range. Interestingly, TMDCs have not yet been characterized when exposed to x rays, although they would be ideal candidates for optoelectronic applications in this spectral range. They benefit from the high cross section of the constituent heavy atoms, while keeping the absorption very low, due to the ultrathin structure of the film. This encourages the development of photodetectors based on TMDCs for several applications dealing with x rays, such as radioprotection, medical treatments, and diagnosis. Given the atomic thickness of TMDCs, they can be expected to perform well at low dose measurements with minimal perturbation of the radiation beam, which is required for in vivo applications. In this paper, the use of TMDCs as active materials for direct x-ray detection is demonstrated, using a photodetector based on a MoS2 monolayer (1L-MoS2). The detector shows a response to x rays in the range of 101–102 keV, at dose rates as low as fractions of mGy/s. The sensitivity of 1L-MoS2 reaches values in the range of 108–109µC Gy−1 cm−3, overcoming the values reported for most of the organic and inorganic materials. To improve the x-ray photoresponse even further, the 1L-MoS2 was coupled with a polymeric film integrating a scintillator based on terbium-doped gadolinium oxysulfide (Gd2O2S:Tb). The resulting signal was three times larger, enabled by the indirect x ray to visible photoconversion mechanism. This paper might pave the way toward the production of ultrathin real-time dosimeters for in vivo applications.

Water brownness regulates the bioavailability of a fluoroquinolone antibiotic: UV-absorbance as a predictor of ciprofloxacin ecotoxicity

Dissolved organic carbon (DOC) is a powerful regulator of the ecotoxicity of ciprofloxacin (CIP), a widely applied fluoroquinolone antibiotic. In this study, we investigated the impact of DOC from a variety of sources on CIP bioavailability, using a cyanobacteria growth inhibition test with Microcystis aeruginosa. We analyzed the impact from two perspectives: (1) DOC concentration, and (2) water brownness, defined in this work as the light absorbance of DOC solutions. The toxicity tests were conducted with (1) unprocessed freshwater DOC in the naturally occurring state, (2) DOC extracted from a freshwater stream (Schwarzbach stream, Küchelscheid, Belgium), and (3) the commercial DOC product Suwannee River organic matter. Across all DOC sources investigated, a strong negative correlation was observed between CIP ecotoxicity and light absorbance at four wavelengths across the ultraviolet–visible range (e.g., A350), whereas CIP ecotoxicity correlated poorly with the DOC concentration. In addition, the interactions between CIP and DOC were modelled as a CIP-DOC binding process to allow the quantification of the inhibitory effects of DOC on CIP toxicity via binding constants (Kd,CIPx, with x being the ionic charge + or +/−, L g−1). Processed DOC sources showed higher binding potency than most of the unprocessed DOC sources, suggesting that toxicity tests employing only processed DOC potentially overestimates the impact of DOC in natural environments. Nonetheless, the light absorption coefficient (i.e., ε350) appeared a reliable predictor of the Kd,CIP+/− (and thus of the potential of the DOC source to reduce ecotoxicity of CIP) of both processed and unprocessed DOC. The relationship can be further incorporated into model simulations to estimate CIP bioavailability in dynamic environments. It is concluded that the brownness of water is a better predictor of the impact of DOC on CIP bioavailability than the DOC concentration itself.

Lithography-Free Bismuth Metamaterials for Advanced Light Manipulation

Bismuth shows outstanding optical properties, including a metal-like response in the ultraviolet-visible range and a dielectric character with a giant refractive index in the infrared range. In recent years, such unique properties have been employed to construct bismuth-based metamaterials with remarkable optical responses in these spectral regions, especially with cost-effective lithography-free methods. Such responses can be manipulated, both in an astatic way by suitable metamaterial design and in a dynamic way by harnessing the solid–liquid transition of bismuth. In this paper, we review the advances in this field and highlight the applications of such metamaterials to information technology production, energy harvesting and sensing.

The Ultraviolet-Visible Luminescence of Ce3+ in Ca2Mg(BO3)2 Phosphors with Potential Applications

New phosphors Ca2Mg(BO3)2: Ce3+ were synthesized by the solid-state reaction method at a high temperature. The phase purity was characterized by powder X-ray diffraction (XRD). The ultraviolet-visible (UV-Vis) optical properties of Ce3+ have been investigated, and the lowest 5d levels, the emission, and the Stokes shifts of Ce3+ in the host lattice were identified. In addition, its concentration quenching process was also studied. The results show that Ce3+ ions enter Ca2+ sites with only one emission in a UV-Vis range and that the optimum doping concentration is x = 0.05. The excitation and emission spectra were evaluated to clearly reveal luminescence features.

Growth of CuO nanoparticles using one step chemical bath deposition under microwave heating and their characterizations

Abstract Varied morphologies of crystalline copper oxide nanoparticles were synthesized using one step chemical bath deposition under microwave heating of prepared growth solution at 1200 W microwave power for a very short duration of 2–8 min. The structure and crystallinity of the as grown copper oxide nanoparticles were studied by wide angle X-ray diffractometer analysis. The particle size values obtained from Scherrer’s relation and the Williamson–Hall plot methods are in the 16–18 nm range. The approximate size of as grown copper oxide nanoparticles evaluated from field emission scanning electron microscopic images are in the range of approximately 15–20 nm. The presence of copper and oxygen was verified by energy dispersive X-ray spectroscopy analysis. Their weight % and atomic % exhibits the rich amount of development of copper oxide nanoparticles in a 1:1 stoichiometric ratio. The optical properties of as grown copper oxide nanoparticles were examined by assessing absorption spectra of the sample in ultraviolet–visible range. The significant peak of absorption spectra is seen near 340 nm wavelength which explains the mono-dispersion behaviour of nanoparticles. Evaluation of Urbach energy of copper oxide nanoparticles reveals that the nanomaterial has microstructural lattice disorder. These characterizations of as synthesized copper oxide nanoparticles explain the feasibility and potential of such nanomaterial to be incorporated in a wide range of utilities.

Development of Methods for Determining Near-Surface Plasma Parameters During Tests of Fusion Reactor First-Wall Prototypes Using the PLM Device

Plasma-surface interaction and high heat flux on plasma-facing materials in magnetic fusion devices cause surface ablation and degradation, while the influx of eroded materials into plasma can have a shielding effect. The reduction of the power load due to the plasma detachment effect over tungsten fuzz is an important phenomenon to be investigated for the ITER divertor problem. Measuring near-wall plasma parameters is a challenging task, requiring the development of improved and advanced techniques, including high-resolution spectroscopic methods. In this paper, we present study results of steady-state plasma over tungsten fuzz formed in plasma linear multicusp (PLM). The PLM device is a linear plasma trap composed of an eight-pole multicusp magnetic field with steady-state plasma discharge with parameters similar to the scrape-off layer and divertor plasma in a tokamak. We used spectroscopic measurements to estimate spatial distributions of plasma radiation in the vicinity of the sample surface exposed to the plasma column. Thus, we obtained information on the temperature and composition of the boundary layer plasma and the temperature of the sample surface. Helium plasma exhibits ionization-type nonequilibrium even at atmospheric pressure, necessitating the use of specific methods to estimate its electron temperature Te. When the helium ion spectral line He II 468.5 nm is present in the spectra, its intensity ratio to one of the atomic lines He I can be described by using coronal approximation. Spectrum analysis has shown that emitting helium ions are highly sensitive indicators of average electron energy = 3kTe/2. Therefore, utilizing intensity ratios of the strongest emitting lines in the ultraviolet-visible near-infrared range, He II 468.6 nm and several He I lines with well-known electron excitation functions were found to be a reliable Te measurement method in the case of magnetized low-pressure helium plasma. We also propose a method for determining the concentrations of the metallic admixture in the plasma on the data on relative intensities of its spectral lines.

Exploring thermoplasmonic profiles of some noble metallic nanospheres

In the current study, we have described the photothermal effect of noble metal (Au, Ag, or Cu) nanospheres immersed in water (at ambient conditions) with the radius of nanospheres ranging from 10 nm to 50 nm. The theoretical simulation software MiePlot based on Mie’s theory is used to calculate the optical properties like absorption and scattering of light energy. In order to determine the heat generation by light energy absorption of nanospheres and temperature distribution by plasmonic nanospheres, we computed the steady using state heat transfer equation. The plasmonic nanoparticle have a property of surface plasmon resonance (SPR) that can be used to heat up the surrounding by absorbing maximum light from irradiated beam. Based on this, we calculated the absorption cross-section of noble metal nanosphere with various sizes. The surface plasmon resonance have been tuned from ultraviolet-visible (UV-vis) range by varying the size of these nanosphere. Since, the radius of the nanosphere had a significant impact on the temperature and the maximum temperature increase inside the nanoparticle is associated with its absorption cross-section. These theoretical studies seek to advance our fundamental knowledge of the heating process by plasmonic nano-heaters in UV-vis region, which has numerous practical uses. • The SPR for noble metals is tuned from Ultraviolet-visible range by varying the size of nanosphere. • The maximum absorption for Au, Ag, and Cu noble metals nanospheres is perceived at the wavelength of 543 nm, 390 nm, and 582 nm, respectively. • The temperature profiles of noble metal nanospheres with varying wavelength are reported. • The maximum temperature increase is found inside the nanosphere for different radii in the presence of water (n = 1.33) as surrounding medium.

Optical properties of graphene/ZnO spheres/Au heterostructure for enhanced van der Waals saturable absorbers

Van der Waals (vdW) heterostructures offer a promising platform for optimizing and controlling physical properties of a variety of materials and devices, which has attracted extensive attentions in ultrafast photonic applications. Here, a hybrid vdW saturable absorber (SA) based on ZnO sphere heterostructures has been fabricated by transferring the low-temperature hydrothermal method ZnO spheres onto gold mirrors and covering with Au nanoparticles and the graphene layer. In comparison with the ZnO sphere SA, the vdW SA exhibits the stronger emission intensity in the ultraviolet-visible range and the higher optical absorption in the near-infrared range, respectively. Meanwhile, by using the balanced twin-detector technology, a modulation depth of 6.6% has been obtained from vdW SA, which is 2.8 times greater than that of the solo ZnO SA due to the harvest of photons and the transfer of photon-generated carriers in the vdW heterostructure. Based on the hybrid vdW SA, a quite stable Q-switched laser and a mode-locked laser operation with a tunable wavelength range from 1531.4 to 1560.4 nm have been achieved. These results demonstrate a effective strategy for enhancing nonlinear optical properties of SAs and pave a way for developing novel types of SAs for the application of ultrafast lasers.

Type-I SnSe2/ZnS heterostructure improving photoelectrochemical photodetection and water splitting

Two-dimensional van der Waals heterostructures have been widely designed and applied to numerous optoelectronic devices such as photoelectrochemical (PEC)-type photodetectors, water splitting, and solar cells. The understanding of the influence of band alignment in type-I heterostructures on the photoelectric response remains incomplete yet essential for designing new optoelectronic devices. Herein, two-step physical vapor deposition is used to construct a type-I SnSe2/ZnS heterostructure, which is confirmed by ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy. The type-I heterostructure-based PEC-type photodetector exhibits excellent photoresponse, high stability, and high sensitivity in the ultraviolet-visible range. Furthermore, the photoresponsivity of SnSe2/ZnS is up to 172.60 µA W−1, which is 7.4- and 2.0-fold larger than that of pure ZnS and SnSe2, respectively. Moreover, the SnSe2/ZnS heterostructure possesses high photoelectrocatalytic activity in water splitting, and the total hydrogen production within 2 h is up to 81.25 µmol cm−2. The high PEC-type photodetector and water splitting performances in SnSe2/ZnS are due to the synergistic effect of high light utilization and efficient charge transport. Our work provides a new method for improving photoelectric response by forming type-I heterostructures and for designing high-performance optoelectronic devices for photodetectors and water splitting.

Novel fluorescent nanofibrous polyether template developed by SNAr polymerization of fluoroaryl-containing 1, 3, 4-oxadiazole: Photophysical properties, mesogenic phases and self-assembly

Supramolecular organogels that respond to external stimuli have been extensively investigated; however, assembling a liquid crystal-based fluorescent gel with an efficient thermoreversible activity is a difficult challenge. Various pentafluorobenzene-containing aromatic adducts have been synthesized via nucleophilic aromatic substitution (SNAr), which is highly regio-selective to para positions. In order to prepare calamitic liquid crystals, those pentafluorobenzene-functionalized 1, 3, 4-oxadiazole aromatic adducts are a perfect choice. Novel fluoroaryl(FA)-containing 1, 3, 4-oxadiazole (Ox) main-chain polyether (PE) (FAOx@PE) were synthesized employing in situ SNAr as a practical technique for the synthesis of fluorescent liquid crystals with perfluoroaryl groups and ether bonds. The perfluoroaryl group was inserted into the 1, 3, 4-oxadiazole compound by the reaction of potassium pentafluorobenzoate and tetrazole-containing biphenyl using a DCC-assisted decarboxylating coupling. Using 1H/13C/19F NMR and FTIR spectroscopic techniques, the chemical structure of FAOx@PE was determined. Differential scan calorimeter (DSC), X-ray diffraction (XRD) and polarization microscope (POM) were utilized to examine the liquid crystal mesophases. The absorption and emission spectral patterns were detected in the ultraviolet–visible range demonstrating solvatochromic activity. Scanning electron microscope (SEM) was employed to inspect the nanofibrous morphology of FAOx@PE organogel.