Visible Light Range Research Articles

Visible-light photocatalytic activity of rutile (TiO2) annealed with melamine under an argon atmosphere.

Visible-light active photocatalysts were obtained by rutile (TiO2) high-temperature treatment in an inert argon atmosphere with addition of different amounts of melamine. The samples were characterized using X-ray diffraction, transmission and scanning electron microscopy, Fourier-transform infrared and Raman spectroscopy, UV-Vis diffuse reflectance, photoluminescence and X-ray photoelectron spectroscopy, temperature-programmed desorption of NH3 and CO2, and Brunauer-Emmett-Teller and thermogravimetric analysis. The effect of varying melamine amount on the crystal phase, crystallite size, and morphological and optical properties of the prepared materials was investigated. The photocatalytic activity was tested in the two types of reactions: photooxidation of dyes and photoreduction of Cr2O7-2 under UV and visible-light irradiation. Rutile with the addition of melamine, annealed in an argon atmosphere, exhibited photocatalytic activity when irradiated with visible light in all the reactions studied. We explain this by a change in its morphological and optical properties, such as the formation of new surface-active centers and increased absorption in the visible range of light.

Design of Perovskite Nanowire Solar Cells with an Adjustable Transmission Visible Light Spectrum.

Translucent film solar cells have significant applications in various scenarios, indicating strong potential for application. However, translucent film solar cells typically only regulate the transmitted light intensity and cannot flexibly adjust the transmission wavelength. Here, a perovskite nanowire (PNW) solar cell that utilizes the light capture performance of a single nanowire to achieve flexible wavelength adjustment in the visible light range was designed. The characteristic scale of a PNW enables the adjustment of absorption coefficients (Qabs) at different wavelengths, combined with the constraint relationship among reflectivity, absorptivity, and transmissivity, to adjust the wavelength of the transmittance spectrum of the solar cell. In addition, the PNW light capture effect increases the open circuit voltage (VOC) by about 5%. Finally, the light transmitted by PNW solar cells can vary among yellow, red, and purple, and the highest PCE can be maintained at around 20%, which enhances the application of transparent solar cells.

Correction of emissivity in thermograms with neural networks

ABSTRACT Infrared thermography, a non-destructive testing technique, enables the measurement and visualisation of surface temperatures by capturing images of emitted infrared radiation. To achieve accurate results, it is essential to correct for emissivity, a material-dependent property that affects the amount of emitted infrared radiation and distorts apparent temperatures across different materials. This study proposes a new approach for correcting thermograms by segmenting an image of the same object captured in the visible light range into material classes using a convolutional neural network. For each material class, the emissivity is determined and used for the correction. The methodology includes setting up experiments for image acquisition, determining emissivity through controlled experiments, and registering the infrared images and visible light images. Unlike previous methods, this approach can be designed to be fully automated in the future and is robust to heterogeneous temperature distributions. Two experiments are conducted in this study: a proof of concept study involving specimens made of different materials and a study focusing on a printed circuit board. It was found that the correction procedure worked for both case studies. However, the quality of the correction is highly depended on the accuracy of the individual steps in the correction procedure.

Effects of Zn Doping on Optical Properties of Polycrystalline β-Ga2O3

In this study, Zn-doped Ga2O3 polycrystalline samples were prepared by solid-phase sintering, and the effects of Zn doping on the optical properties of Ga2O3 were investigated. It is found that the introduced Zn ions disrupted the Ga-O bonds and formed ZnGa, altering the Ga-O vibration modes and causing a blue shift in the related Raman mode. From near-infrared to visible light-range was a transparent region for Zn-doped Ga2O3. The fundamental optical bandgap underwent a decrease with increasing Zn doping content, primarily due to the p-d orbital hybridization of the O 2p and Zn 3d orbitals causing an upward shift valence band maximum and band renormalization effect-induced band-tails. The recombination of electrons at donor levels (VO) and holes at acceptor levels (VGa or VO-VGa) gave rise to blue-green luminescence. Zn doping increased the concentration oxygen vacancies (VO), resulting in significant blue-green luminescence enhancement in Zn-doped Ga2O3. Additionally, Zn doping resulted in a noticeable reduction in the red luminescence of Ga2O3, which may be attributed to Zn doping suppressing nitrogen incorporation from the air during high-temperature preparation processes.

Contributions from light level and spectral content on refractive development in young rabbits.

To compare the effects of manipulating light levels versus manipulating the spectral content of short wavelengths (blue light) of ambient lighting on refractive development in young rabbits. A total of 32 healthy 3-week-old rabbits were randomly assigned to one of the four groups with 8 in each group for 12wk: Control group (NC) under low blue light (output ratio of blue light 1.8%) at low illuminance (341 lx), HI group under low blue light (output ratio of blue light 1.6%) at high illuminance (5057 lx), simulating natural light (S-NL) group under high blue light (output ratio of blue light 4.9%) at high illuminance (5052 lx), and MB group under high blue light (output ratio of blue light 5.2%) at low illuminance (342 lx). The lighting in each group were provided by light emitting diode (LED) lamps emitting visible light (range 380-780 nm) in addition to (or not) LED lamps only emitting short wavelength (range 380-500 nm). Refraction, axial length, and corneal curvature radius were assessed by retinoscopy, ultrasonography and keratometry, respectively. Average data of both eyes for each animal were used as single values and compared among groups. During the 12-week intervention, all animals had an emmetropization period. The decrease of refraction in rabbits in HI group was similar to S-NL group, both slower than that of NC group (P<0.001). At the 12th week, the refraction (3.000±0.267 D) and vitreous cavity depth (7.421±0.168 mm) of S-NL was similar to HI group (3.250±0.267 D, 7.264±0.256 mm), significantly different from NC group (1.937±0.291 D, 7.825±0.313 mm; P<0.001 for both). High blue light at low illuminance had little effect on refraction change. At the end of intervention, the difference of refraction (2.219±0.281 D) and vitreous cavity depth (7.785±0.229 mm) in MB group were not statistically significant (P=0.311, P=0.749) compared with NC group. The other components were less affected by lighting conditions (P>0.05). The light levels per se but not the rich in spectral content of short wavelengths determine the inhibitory effect of ambient lighting on myopia development in rabbits.

Low-Coordination Triangular Cu3 Motif Steers CO2 Photoreduction to Ethanol.

Photoreduction of CO2 using copper-based multi-atom catalysts (MACs) offers a potential approach to achieve value-added C2+ products. However, achieving MACs with high metal contents and suppressing the thermodynamically favored competing ethylene production pathway remain challenging, thus leading to unsatisfactory performance in ethanol production. Herein, we developed a "pre-locking and nanoconfined polymerization" strategy for synthesis of an ultra-high-density Cu MAC with low-coordination triangular Cu3 motifs (Cu3 MAC) on polymeric carbon nitride mesoporous nanofibers. The Cu3 MAC with Cu contents of 36 wt% achieves a high reactivity of 117 µmol g-1 h-1 for ethanol production from CO2 and H2O, with a remarkable selectivity of 98% under simulated sunlight irradiation, representing one of the highest performances in ambient conditions without sacrificial reagents. The superior catalytic efficiency is attributed to the triangular Cu3 configuration, in which both Cu(I) and Cu(II) coexist, predominantly as Cu(I). Such Cu3 motifs act as strong alkaline sites that effectively chemisorb and activate CO2, extend visible-light absorption range, while accumulating high-density electrons and favoring 12-electron-transfer products. An accelerated asymmetric C─C coupling with adsorption configuration of the bridge-adsorbed *CO at paired Cu sites and atop-adsorbed *CO at adjacent single Cu atom was observed, enabling preferential formation of *CHCHOH intermediates to produce ethanol.

Design, synthesis, and optimization of a novel ternary photocatalyst for degradation of cephalexin antibiotic in aqueous solutions

The widespread use of antibiotics in veterinary and medical applications has increased the possibility of water contamination, which causes adverse effects such as increased bacterial resistance in humans and other organisms. This study, investigates the efficient removal of cephalexin (CPX) using Fe doped TiO2–Bi2O3 nanocomposite, synthesized via the simple sol–gel method as a visible active photocatalyst. The weight fraction of Fe (3–7 wt%), and Bi2O3 (7–11 wt%) was optimized. The Fe–TiO2–Bi2O3 nanocomposite with a weight fraction of 3 and 11% for Fe and Bi2O3 has the best photocatalytic activity for Cephalexin degradation. The characteristics of photocatalyst with optimum composite (3 wt% of Fe and 11 wt% Bi2O3) were also investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), diffuse reflectance spectra (DRS) and FTIR. The DRS spectra approved that the adsorption wavelength of Fe-doped TiO2–Bi2O3 is in the visible light range. The influence of amount of catalyst (0.5–1.5 g/L), Cephalexin concentration (5–15 mg/L) and initial pH of the solution (3–9) in on CPX photodegradation was modeled and optimized using central composite design based on response surface methodology. Maximum cephalexin degradation Under visible light irradiation (50 W LED, 395–400 nm) was achieved about 74% at 5 mg/L of CPX, 1.5 g/L catalyst loading and pH of 9 in 240 min. Moreover, using a 15W UV lamp under the same conditions increased the degradation efficiency to 96% at 120 min. Considering the high potential of Fe–TiO2/Bi2O3 nanocomposite in removing Cephalexin antibiotics, it can be considered a suitable candidate for removing antibiotics from contaminated water sources.

Vapor deposition assisted in-situ construction of graphitic carbon nitride homojunction capable of enhanced visible-light-driven hydrogen generation.

Graphitic carbon nitride (g-C3N4) has garnered considerable attention in the field of photocatalysis due to its suitable bandgap (~2.7 eV), abundant elemental composition, high chemical stability, and environmentally friendly synthesis process. In this study, a novel g-C3N4 homojunction material with controllable morphology was successfully fabricated via a simple and efficient vapor deposition method. Under visible light irradiation, this material demonstrated exceptional photocatalytic hydrogen evolution performance, achieving a hydrogen production rate of 334 μmol g-1 h-1, approximately 24 times higher than that of conventional bulk g-C3N4. This remarkable enhancement in performance can be attributed to the synergistic effects of several factors, including a significant increase in specific surface area, expanded visible-light absorption range, efficient separation and migration of photogenerated charge carriers, and the coupling effect of optimized band structure and crystal morphology. This study not only provides new insights for further enhancing the photocatalytic performance of CN-based materials but also lays a solid foundation for their practical applications in sustainable energy and environmental remediation.

Supramolecular Engineering of Narrow Absorption Bands by Exciton Coupling in Pristine and Mixed Solid-State Dye Aggregates.

Tunability of functional properties in a continuous manner is desired but challenging to accomplish for organic solid-state materials. Herein, we describe a method for tuning optoelectronic properties of solid-state aggregates with narrow absorption bands. First, we systematically shift the absorption maxima of highly dipolar merocyanine dyes in solution by chemical alterations of their chromophore cores. This leaves their solid-state packing arrangements unchanged, affording similar J- and H-coupled aggregate absorption bands at different wavelengths. Next, mixing these isostructural dyes leads to a spectral fine-tuning of the mixed layers, which could be characterized as crystalline organic solid solutions and utilized in narrowband color-selective organic photodiodes. Finally, we devise a semiempirical model, which explains the observed spectral tuning in terms of the molecular exciton theory. Thus, we demonstrate narrowband absorbing solid-state aggregates spanning the wavelength range of 437-760 nm, whose absorption can be fine-tuned over 40% of the visible light range.

The electronic structure, optical and magnetic properties of Cu, Fe, Mn, Ni, and V Doped Bi2WO6 in the visible light region

Abstract The elastic and mechanical properties of intrinsic Bi2WO6 semiconductors, along with the electronic, optical, and magnetic properties of Cu-, Fe-, Mn-, Ni-, and V-doped Bi2WO6 at a uniform doping concentration of 6.25%, are studied using density functional theory (GGA+U). The study shows that intrinsic Bi2WO6 semiconductors exhibit good mechanical stability, anisotropy, and mixed ionic-covalent characteristics (Poisson’s ratio ν = 0.17), classifying them as brittle oxide materials (B/G ≈ 0.8). Compared to intrinsic Bi2WO6, the doped Bi2WO6 exhibits a narrower bandgap, a broader absorption spectrum, and higher optical sensitivity. Their optical properties in the visible light range surpass those of intrinsic Bi2WO6, making them more promising for use as semiconductor catalysts. Notably, Cu- and V-doped Bi2WO6 exhibit higher absorption coefficients in the visible light region compared to other element-doped Bi2WO6, with a broader absorption spectrum and more pronounced photocatalytic effects. Furthermore, Cu-, Fe-, Mn-, Ni-, and V-doped Bi2WO6materials exhibit characteristics of diluted magnetic semiconductors, The total magnetic moments are 1.793 μ B (Bi1.9375Cu0.0625WO6), 3.086 μ B (Bi1.9375Fe0.0625WO6), 3.823 μ B (Bi1.9375Mn0.0625WO6), 1.257 μ B (Bi1.9375Ni0.0625WO6), and 1.859 μ B (Bi1.9375V0.0625WO6). Bi1.9375Mn0.0625WO6 exhibits ferromagnetic ordering, while Bi1.9375Cu0.0625WO6, Bi1.9375Fe0.0625WO6, Bi1.9375Ni0.0625WO6, and Bi1.9375V0.0625WO6 exhibit Ferrimagnetic ordering. Compared to other element-doped Bi2WO6, Bi1.9375Mn0.0625WO6 shows a larger energy difference between the FM and NM ordering states(ΔE = 18.510 eV), demonstrating stronger magnetic ordering than Cu-, Fe-, Ni-, and V-doped Bi2WO6, and these materials hold potential for application in electronic spin-polarized devices.

First-Principles Calculations of the Optical Properties of Bi4Si3O12: RE (RE = Ho3+, Tb3+, Eu3+, Gd3+, Sm3+, Tm3+) Crystals

This study employs the first-principles calculation method based on density functional theory to investigate and analyze the effects of doping various rare earthions on the optical properties of bismuth silicate (Bi4Si3O12, BSO) crystals. The results indicate that the electronic structure variations of rare earth ions significantly influence the electronic structure and transition characteristics of BSO crystals, thereby altering their optical properties. Specifically, Tm3+ doping notably enhances the polarization capability and infrared responsiveness of BSO crystals, Ho3+ doping improves their absorption and scattering abilities in the visible light range, while Eu3+ doping enhances their ultraviolet absorption. Overall, Tm3+ doping and Ho3+ doping exhibit the most prominent effects on the optical performance of BSO crystals, providing theoretical guidance for designing and optimizing BSO crystals with specific optical properties.

Broadband spectropolarimetry based on single-shot intensity images of polychromatic structured vector beams

Broadband polarization measurement plays a crucial role in numerous fields, spanning from fundamental physics to a wide range of practical applications. However, traditional approaches typically rely on combinations of various dispersive optical elements, requiring bulky systems and complicated time-consuming multiple procedures. Here we have achieved broadband spectropolarimetry based on single-shot images for spatial intensity distributions of polychromatic vector beams. A custom-designed diffractive optical element and a vortex retarder convert the incident polychromatic waves into structured vector beams: the former diffracts light of different wavelengths into concentric circles of different radii, while the latter codes their polarization information into intensity distributions along the azimuthal direction. The validation experiments verify our exceptional measurement accuracy (RMS errors&lt;1%) for each Stokes component in the visible light range (400–700 nm), with good spectral (&lt;0.8 nm) and temporal (an output rate of 100 Hz) resolutions. We have further employed our broadband polarimeter to study the mutarotation of glucose, making direct observations of temporal evolutions of chemical reactions accessible. Our work has significantly broadened the toolboxes of spectropolarimetry, which can potentially incubate various disruptive applications that depend on broadband polarization measurements.

Effects of Cu, Ag, and Au Elements Doping on the Electronic and Optical Properties of β-Ga2O3 via First-Principles Calculations.

β-Ga2O3, as a semiconductor material with an ultrawide band gap (Eg > 4.8 eV), emerges as a promising candidate for ultraviolet (UV)-transparent semiconductors. Its distinctive property of high transparency from visible light to the ultraviolet region gives it broad application prospects in the fields of deep UV light-emitting diodes (LEDs), UV lasers, and electronic devices. This study employed first-principles calculations utilizing the generalized gradient approximation+ U (GGA+U) method to investigate the impact of doping β-Ga2O3 with transition metals including copper (Cu), silver (Ag), and gold (Au) on its electronic structure and optical properties. The findings reveal that under oxygen (O)-rich conditions, the formation energy of the doped system is lower compared to gallium (Ga)-rich conditions. And the Cu-doped β-Ga2O3 is demonstrated to possess the lowest formation energy, indicating an enhanced stability of the β-Ga2O3. Additionally, the intrinsic band gap of β-Ga2O3 is calculated to be 4.853 eV, whereas the band gaps of transition metal (TM)-doped β-Ga2O3 are significantly reduced. Specifically, the band gaps of Cu-doped, Ag-doped, and Au-doped β-Ga2O3 are 1.228, 0.982, and 1.648 eV, respectively. This reduction can be attributed to the introduction of impurity levels by the transition metals, which modify the electron distribution of gallium and oxygen atoms in the vicinity of the Fermi level. Remarkably, β-Ga2O3 exhibits superior ultraviolet light absorption performance, and the incorporation of transition metals such as Cu, Ag, and Au facilitates the expansion of the absorption region from the ultraviolet to the visible light range. This transformation not only enhances the material's light-harvesting capability but also improves the electron transition capability of the intrinsic β-Ga2O3, providing a crucial theoretical foundation for the development of novel β-Ga2O3-based optoelectronic devices.

Pressure-regulated bandgap narrowing and photoelectric activity enhancement in layered halide compound GeI2

Layered semiconductors offer distinct advantages for optoelectronically responsive heterojunction devices due to their strong light–matter interactions and weak interlayer van der Waals interactions, which enable exfoliation into adjustable thicknesses. However, their practical utility is often restricted by excessively wide bandgaps, which limit spectral response within the visible light range and reduce light absorption efficiency, thereby constraining broadband detection capabilities. In this study, pressure was employed as a tuning parameter to modulate the bandgap and optimize the photoelectric performance of the layered semiconductor GeI2. Structural stability under moderate compression (5 GPa) was confirmed through in situ Raman spectra and x-ray diffraction, with no evidence of phase transition. At 5 GPa, a remarkable five-order-of-magnitude enhancement in photoelectric activity was observed. In situ UV-visible absorption spectroscopy, supported by theoretical calculations, revealed that this enhancement is primarily driven by pressure-induced narrowing of the bandgap. These findings offer critical insights for designing two-dimensional broadband photodetectors with tailored bandgap properties and enhanced photoelectric response, contributing to advancing next-generation flexible optoelectronic devices.

Synthesis, characterization, and photocatalytic activity of a carboxymethyl cellulose sodium-based hybrid material for efficient degradation of hexavalent chromium.

Synthesis, characterization, and photocatalytic activity of a carboxymethyl cellulose sodium-based hybrid material for efficient degradation of hexavalent chromium.

Improving the bandwidth of microstructured multimode W-type POFs in the visible light range

The bandwidth of multimode W-type microstructured plastic optical fibers (mPOFs) is analyzed using the time-dependent power flow equation (TD PFE). The results demonstrate that increasing the wavelength enhances the bandwidth in W-type mPOFs, depending on the inner cladding width and the launch beam distribution width. We observed that bandwidth improves with thinner and shallower inner cladding, as well as a narrower centrally launched beam. This characterization aligns with the fibers’ effectiveness in increasing bandwidth, allowing for the customization of various W-type optical fibers for specific applications at different wavelengths.

Modification of Cs2AgBiCl6 Double-Perovskite Photocatalytic Activity by Br Doping.

Developing highly efficient photocatalysts is crucial for photocatalysis technology. Many reports have demonstrated that element doping was an effective strategy for developing highly efficient photocatalysts by broadening the visible light absorption range and suppressing the recombination of photogenerated carriers. Herein, we doped the Br element into Cs2AgBiCl6 perovskite to widen the visible light absorption and enhance the charge transfer ability and then developed a highly efficient visible-light photocatalyst based on Cs2AgBiCl6. The results showed that Br doping could not only broaden the visible light absorption range of samples but also modulate the charge transfer ability of samples significantly. Among all the as-prepared samples, Cs2AgBiCl4Br2 has the highest photocatalytic activity due to the best charge transfer ability, long lifetime of carriers, and broadened visible light absorption range, which can degrade 99.9% of methyl red in 28 min. Moreover, the cyclic experiments demonstrate that Cs2AgBiCl4Br2 has good cycle stability. This study could provide a promising strategy for designing and developing new, highly efficient halide perovskite photocatalysts.

Plasma-Assisted Synthesis of N-Doped ZnO for Photocatalytic H2O2 Production

Nonthermal plasma is a convenient, efficient and environmentally friendly technology for the synthesis and modification of materials. In this study, microwave plasma, a type of nonthermal plasma, was utilized to facilitate the rapid synthesis of hierarchical porous ZnO materials with N2 as feeding gas. It was observed that ZnO precursor could be transformed into hexagonal ZnO crystals after a short duration of plasma treatment while successfully incorporating N atoms into its lattice structure. The plasma-treated samples exhibit an increased number of smaller mesopores without compromising the hierarchical structure of the ZnO precursor. Furthermore, due to their enlarged specific surface area and extended visible light response range, the N-doped ZnO samples demonstrate excellent performance in photocatalytic H2O2 production performance. This work provides novel insight on exploring a new highly effective and efficient tools for material synthesis.

First-principles analysis on the electronic structure, magnetic and optical properties of Fe-incorporated boron nitride zigzag nanotubes

The influence of incorporating iron on the electronic structure, magnetic and optical properties of zigzag (10,0) boron nitride nanotubes (BNNTs) was investigated using first-principles calculations. The structures were incorporated with Fe according to B1[Formula: see text]Fe xN at various (x) contents (0.10, 0.20 and 0.30). Our calculations exhibited that adding additional Fe atoms reduced the energy gap of the structure. Incorporating more iron atoms creates additional sharp peaks within Fermi levels that come from the contribution of Fe-3d states. Doping with (Fe) also introduced magnetic moments in the BNNT structure. The optical parameters of the Fe-incorporated boron nitride nanotube are calculated. The real part of the dielectric function of pristine BNNT started to increase up to the middle of the UV region and then rapidly decreased between the wavelength range of 310–390 nm. Also, the pure boron nitride nanotube has no absorption in the visible light range and only detects UV radiation. The optical calculations showed that incorporating Fe shifted the absorption peaks of BNNTs into risky UV radiations, which helps researchers develop a vision for controlling and developing advanced materials for various electronic applications.

Investigation of the behaviour of tunable chalcogenide-Bismuth based perovskite BiTl (SxSe1-x)3(X = 0, 0.33, 0.67, 1): first principles calculations

Density functional theory (DFT) driven by the quantum ESPRESSO code was used in this study to investigate the structural, opto-electronic, and thermoelectric properties of ternary perovskite chalcogenide compound. This is to examine their possible use in optoelectronics and reducing the dependency on silicon and fossil fuel. The Perovskite compounds crystalize in the cubic phase with a space group Pm-3m. The volume versus energy is fitted by the Birch-Murnaghan equation of state which yielded the equilibrium lattice constant of 8.353, 8.488, 8.629 and 8.806, bulk modulus of 255.8, 242.7, 233.5 and 222.4, for BiTlS3 , BiTlS2 Se1 , BiTlS1 Se2 and BiTlSe3 . Indirect band gaps of 2.6 eV, 2.7 eV, 2.9 eV, and 3.2 eV were obtained for BiTlS3 , BiTlS2 Se1 , BiTlS1 Se2 and BiTlSe3 compounds, respectively. Also, increment in the energy from 0 eV to 10 eV resulted in optical properties fluctuation within 0 cm-1 to 1.5 × 109 cm-1 for absorption coefficient in the compounds. However, a variation from 10 eV to 20 eV moved the absorption coefficient to 4.2 × 109 cm-1 for all the compounds from visible to the UV range. Furthermore, the observed properties show that the value of figure of merit obtained is 0.125 for BiTlS3 , 0.100 for BiTlS2 Se1 , 0.068 for BiTlS1 Se2 and 0.055 for BiTlSe3 at 300 K. By adjusting the chalcogen ratio, BiTlX3 (X = S, Se) possess the tunable band gap in the whole visible light range, which is of great significance for the development of new-type, high-efficient semiconductor material and optoelectronic devices, while the low thermoelectric values predict the compounds use as sensors. The proposed results may pave the way for further investigations into the use of the perovskite compounds for optoelectronic devices.