Wavelength UV Light Research Articles

Oxazine as an efficient precursor for the development of photochromic spiropyrans

Spiropyran derivatives were synthesized through an alternate synthetic route that passed through a photochromic [1,3]-oxazine. The structures of the new spiropyran derivatives were established with the assistance of spectroscopic methods and single-crystal X-ray crystallography. The photochemistry of the spiropyran derivatives was investigated using a suitable wavelength of UV and visible light. Density functional theory (DFT) was exploited as a predictive tool to understand the unique organic transformation, which supported the conversion of photochromic oxazine into the spiropyran through consideration of the stability of the intermediates, transition state, and H-bonds. A comparison of solvation energies calculated for different isomers suggested greater solvation of colored isomers of oxazine structure as compared to the colored isomers of spiropyran form.

Bio-based light-healing isocyanate-free polyurethanes derived from carbonated soybean oil and coumarin

ABSTRACT In response to environmental concerns and restrictions on isocyanate-based materials, researchers and the coatings industry are focused on developing eco-friendly isocyanate-free polyurethanes. This article introduces a novel class of environmentally-friendly, initiator/catalyst-free, UV-curable, self-healing non-isocyanate polyurethanes (NIPUs) synthesized from bio-based carbonated soybean oil (CSO) and non-toxic coumarin. The synthesis of these polymers is based on using a photo-reactive coumarin that undergoes a reversible [2 + 2] cycloaddition upon exposure to the wavelength of UV light. UV-curable three coumarin-terminated isocyanate-free polyurethane prepolymers were synthesized using CSO and three different amines and epoxy coumarin. Subsequently, a set of cross-linked NIPU polymers were obtained with exposure of 365 nm UV irradiation. The photo-reversible nature of these polymers was investigated in response to various wavelengths of UV radiation. Additionally, their self-healing ability and the thermal and mechanical properties of NIPU coatings were studied using optical microscopy, thermogravimetric analysis, differential scanning calorimetry, and a universal testing machine. The outcomes demonstrate that this polyurethane has the potential to provide a sustainable alternative to isocyanate-based materials. Two examples of stimulated healing are given, that of healing a scratch and the other being the healing of a sample that has been mechanically stressed to failure in a tensile mode.

The effect of process parameters on mechanical characteristics of specimens obtained via DLP additive manufacturing technology

Digital Light Process (DLP) is one of the Additive Manufacturing (AM) methods to produce three-dimensional (3D) polymeric components with high dimensional stability. The technique is based on light-induced polymerization, consisting in spreading the light of a suitable wavelength in a spatially controlled area according to the component’s digital model. Starting from a liquid monomer solution, a 3D solid polymeric object is created. The mechanical and fracture properties of such components are highly influenced by the process parameters which must be carefully considered when load bearing parts have to be produced by AM. This paper investigates the effect of the DLP process parameters on tensile properties using dog bone specimens and fracture toughness determined by using Single Edge Notch Specimens loaded in three-point bending. Five different process parameters were considered by testing six specimens; for each of them, the influence of the printing orientation on the fracture toughness of UV-sensitive resin “translucent green” (curing UV light wavelength 405 nm) is considered. Among the various parameters, the study considers also the post-processing effects on the fracture toughness.

Treatment of pharmaceutical wastewater using photocatalytic reactor and hybrid system integrated with biofilm based process: Mechanistic insights and degradation pathways

Diclofenac and tetracycline, the pharmaceutically active compounds, are ubiquitously found in water bodies. The inability of conventional processes has mandated the use of advanced treatment techniques. This study has demonstrated the use of sulfur-doped g-C3N4/ZnO (SCZ) catalyst for removing diclofenac and tetracycline and achieved ∼94 % and ∼97 % degradation efficiencies, respectively, in 240 min using UV light (wavelength: 320–400 nm). The SCZ catalyst exhibited enhanced mineralization efficiency (∼95 %) in 600 min and reusability (11 cycles) for targeted contaminants. The physicochemical characterization of the used catalyst depicted the presence of crystalline structures, defects, and roughness, similar to that of the pristine catalyst. The degradation pathways of diclofenac and tetracycline delineated the possible reaction mechanisms for the transformed product formations. The SCZ catalyst was used in the continuous photocatalytic reactor to treat synthetic and real wastewater spiked with pharmaceuticals. Additionally, moving and stationary bed bioreactor-sedimentation tank was coupled with the continuous photocatalytic reactor removing suspended and biodegradable impurities, which enhanced the organic removal efficiency from ∼70–94 %. The SCZ catalyst showed ∼85 % degradation efficiency for the targeted pharmaceutical compounds from the solution mixture. The results of this study suggest that SCZ catalyst and the hybrid photocatalytic system can be a promising solution for the treatment of pharmaceuticals from real wastewater.

Synthesis and characterization of photo-responsive azobenzene side-chain liquid crystalline polystyrenes with a mesogenic phase of wide temperature range

Polystyrenes (PSs) that provide photochemical stability are commonly used as the chromophore macromolecular carriers. Herein, PS-based alternating copolymers, i.e., alt-P(D-SiH/Ip), alt-P(D-2SiH/Ip) and alt-P(D-SiH/St), are synthesized through anionically copolymerized Si–H functionalized 1,1-diphenylethylene (DPE-SiH/2SiH) with isoprene (Ip)/styrene (St). Anionically polymerized (4-vinylphenyl)-dimethyl-silane is used as the uniform hydrosilylated PS, i.e., Uni.-P(St-SiH). A series of photo-responsive azobenzene side-chain liquid crystalline PSs combine the above PS-based main chains and the mesogenic moiety composed of azobenzene (Azo) and cholesterol (Chol) groups, i.e., Azo-Chol (M), via the hydrosilylation. The polarized optical microscopic (POM) morphologies and thermal properties of Azo-Chol (M) and Azo-Chol-PSs are studied. As desired, they produce the cholesteric phase of wide temperature range due to the PSs and Chol-groups. Moreover, the photo-responsive behavior irradiated under UV-light of different wavelengths are quantitatively evaluated by time-dependent UV–Vis spectroscopy. Azo-Chol-PSs undergo rapid and reversible trans-cis isomerization under the alternating irradiation of UV and visible light. The trans-to-cis isomerization efficiency under 365 nm UV-light is over that under 290–320 nm UV-light, while over 80% of cis-to-trans efficiency can be realized under 400–500 nm Vis-light irradiation This work would provide guidelines for the effective design of photo-responsive anisotropic materials.

Antifungal features and properties of Pickering emulsion coating from alginate/lemongrass oil/cellulose nanofibers

SummaryThis study investigated the antifungal features of sodium alginate (Alg) 1% combined with lemongrass essential oil (LGO) 0.25%, 0.5% and 0.75% as a Pickering emulsion coating to control Penicillium digitatum and P. italicum, identified as citrus fruit pathogens. Cellulose nanofibers 0.24%, 42.55 ± 9.34 nm, were selected as a stabiliser. Confocal laser scanning microscopy and Fourier‐transform infrared spectroscopy were used to analyse the droplet size and morphology and chemical interaction of emulsified coating, respectively. The effective dosage of lemongrass oil (0.75%) may enhance the antifungal action confirmed with a series of in vitro tests on spore germination by 88.28% (P. digitatum) and 91.94% (P. italicum), germ tube elongation by 89.28% (P. digitatum) and 90.13% (P. italicum) and membrane integrity by 41.67% (P. digitatum) and 63% (P. italicum). Additionally, the incorporation of LGO Pickering emulsion improved the beneficial properties of Alg‐based coating film, including light transmission at UV and visible light wavelengths and hydrophobicity. Scanning electron microscopy was performed to evaluate the interior microstructure of the coating film. Pickering emulsion‐based coatings described in this study may have potential applications for active packaging, particularly for citrus fruit commodities.

Novel green emitting Tb3+ doped KCaF3 phosphor for WLEDs and TLD applications

Multifunctional green emitting (Potassium Calcium Fluoride: x Trivalent Terbium) KCaF3: xTb3+ (x = 0.01, 0.03, 0.05, 0.07, 0.09, and 0.11 mol%) phosphor was synthesized by solid state reaction method. Crystal structure, morphology, photoluminescence and thermoluminescence properties were investigated in detail. Photoluminescence emission spectrum showed the characteristic maximum intensity peak at 543 nm corresponding to Tb3+ emission band when excited using an UV light of wavelength 374 nm. The concentration quenching effect of Tb3+ in KCaF3 phosphor was caused by dipole – quadrupole interaction between Tb3+ ions. CIE coordinates of KCaF3: xTb3+ (x = 0.05 mol%) was found to be x = 0.2959 and y = 0.6592 positioning at green region. Beta irradiated thermoluminescence glow curve was recorded on KCaF3: xTb3+ (x = 0.05 mol%) phosphor. Low temperature signals in TL glow curve were removed using bleaching or preheating technique. The optimization of preheat temperature was performed using different temperature and found 125 °C (peak 1) and 210 °C (peak 2) as an optimized temperature. Temperature of maximum TL intensity (Tm) of peak 1 and peak 2 was found to be 181 °C and 292 °C, respectively. The activation energy (Ea) and frequency factor (s) of peak 1 and peak 2 were calculated using peak shape method and variable heating rate method (VHR). Characteristic studies for dosimetry application such as dose response and reusability of KCaF3: xTb3+ (x = 0.05 mol%) were investigated in detail.

Self-powered silicon carbide ultraviolet photodetector via gold nanoparticle plasmons for sustainable optoelectronic applications

In recent years, it is becoming inevitable to design/construct eco-friendly sustainable electronic and photonic devices to minimize the footprints of these as part of the fight against global problems like resource depletion and pollution. To this end, scientists have been researching to produce sustainable, self-powered electronic and photonic devices capable of meeting the standards of consumers along with minimal adverse effects on the environment. In this study, we fabricated and analyzed a high-performance self-powered silicon carbide ultraviolet photodetector (SiC-UVPD) through functionalizing with gold nanoparticles (Au NPs). The effect of Au NPs on the improvement of the photodetector was systematically investigated. The self-powered SiC-UVPD exhibited a very good responsitivity of 0.30 A W−1 and a detectivity of 7.0 × 1011 cm.Hz1/2.W−1 under 254 nm wavelength UV light irradiation without any external power. The photodetector also provided quick responses to incident UV light with 28 ms rise time and 88 ms fall time. To sum up, the performance of the fabricated self-powered SiC-UVPD shows that SiC-UVPDs can offer new solutions for high performance emerging sustainable energy and eco-friendly optoelectronic devices.

Coal-based carbon quantum dots-sensitized TiO2 NRs/PTTh heterostructure for self-powered UV detection

In recent years, TiO2-based UV photodetectors (UVPDs) have gained widespread attention owing to their abundant raw materials and low synthesis cost. However, the low responsivity, slow response speed and high-power consumption limit the application of these UVPDs. In this study, p-n heterojunction self-powered UVPDs consisting of n-type coal-based carbon quantum dot-sensitized TiO2 nanorod arrays (TiO2 NRs:C-CQDs) and p-type poly(2, 2′:5′, 2′'-trithiophene) (PTTh) are reported. The structure, morphology and photoresponse properties of the TiO2 NRs:C-CQDs/PTTh heterojunctions are methodically investigated. These results indicate that the sensitization of C-CQDs has a significant impact on the electrical and optical properties of p-n heterojunction UVPDs. The performance study results of UVPDs at different optical power densities show that the device is able to accurately detect UV light of specific wavelengths, and the device achieved a maximum responsivity (R) (1.45 mA/cm2) and a high detectivity (D*) (4.94 × 1010 Jones) when the light intensity is 0.35 mW/cm2, while the rise and fall times shortened to 91.2 ms and 3.19 ms, respectively.These indicate that TiO2 NRs:C-CQDs/PTTh achieves the high performance self-powered UV light detection. This work offers theoretical support and technical route for TiO2 based self-powered UVPDs.

Enhanced photocatalytic activity of reduced graphene oxide-TiO2 nanocomposite for picric acid degradation

The rGO-TiO2 nanocomposite was synthesised via a hydrothermal method. Numerous analytical and spectroscopic techniques have been used to characterise rGO-TiO2. The findings indicate that TiO2 has a tetragonal rutile phase and that TiO2 nanoparticles were densely packed on the GO sheet. In this study, the photocatalytic degradation of organic pollutant (picric acid) with rGO-TiO2 nanocatalyst linked with Fenton reagent [Fe 2+/H2O2] at various pH levels (3, 7 and 10) was investigated using UV light (wavelengths 254,265 and 395 nm), visible light, and sunlight. Among the various light irradiation conditions, visible light and sun light demonstrated the highest degradation efficiency due to the presence of rGO-incorporated TiO2 catalyst (rGO-TiO2 nanocompsite). Photolysis of picric acid of 200 mg/L was completed in 15 min and 18 min at the optimal pH of 3 and FeSO4·7H2O concentration of 1 mM, as well as the catalyst dosage of 50 mg/L under visible light and sun light. The rGO-TiO2 nanocomposite catalyst's superior adsorption and degradation properties make it an ideal solar-driven catalyst for organic pollutant degradation.

Gatifloxacin photocatalytic degradation in different water matrices: Antimicrobial activity and acute toxicity reduction

The main goal of this study is to evaluate the feasibility of using heterogeneous photocatalysis to degrade the organic contaminant gatifloxacin (GAT) and reduce the antimicrobial activity and acute toxicity from different water matrices. Assays were performed using four water matrices (ultrapure water - UW, mineral water - MW, potable water - PW, and simulated surface water - SW) fortified with gatifloxacin (500 µg L−1) as a model antibiotic contaminant and its quantification was followed using online SPE-UHPLC-MS/MS. Initially, the photocatalytic process efficiency towards GAT removal as a function of UV light wavelength (UVA and UVC), catalyst type (TiO2-P25 or TiO2-PC500), photocatalyst loading (from 1 to 200 mg TiO2 L−1), solution pH (from 4 to 9), GAT initial concentration (from 50 μg GAT L−1 to 5000 μg GAT L−1) and water matrix (UW, MW, SW or PW) was assessed. In this context, the TiO2-PC500 system using UVA showed the best removal performance of GAT. With TiO2-PC500 loadings higher than 10 mg L−1, > 90% of GAT degradation was achieved after only 40 min of reaction. Finally, the system efficiency was evaluated according to its ability to reduce the antimicrobial activity of the solutions against Gram-negative and Gram-positive bacteria as well as their acute toxicity to A. fischeri bacterium. The antimicrobial activity in the solutions dropped along the reaction time, but no toxicity variation was observed.

Spectral dependence of UV light penetration into powder TiO2 anatase

The penetration depth of UV monochromatic light into deposited TiO2 anatase powder was investigated. The light penetration depth was considered in units of numbers of surface hole, Ns, and electron, NO2, centers activated during irradiation. The numbers of hole centers Ns were obtained from photostimulated oxygen isotope exchange reaction registered by means of mass spectrometry. The numbers of electron centers NO2 were obtained from subsequent thermo-programmed desorption spectroscopy of photoadsorbed oxygen O2-. It was shown that the depth D of UV light penetration into UV absorbing TiO2 powder coat depends on the wavelength and intensity I0 of incident UV light and obeys to the equation DI0=1kefflg(I0/Im) obtained from the Beer–Lambert–Bouguer law with effective extinction coefficient keff and minimal value of light intensity Im, below which the photoactivation is considered negligible. Commonly, the value Im has an order of a few microwatts/cm2 for activation of electron and hole type centers except for a case of 334 nm falling into the band of the first direct band-to-band transition of anatase, where relatively high threshold value Im=0.063 mW/cm2 for photoactivation of hole centers was revealed. Effective extinction coefficient keff may be considered proportional to the absorption coefficient of TiO2 in the region of fundamental absorption, whereas, in the non-fundamental absorption region, keff exceeds significantly that of TiO2 due to, probably, dominating scattering processes. At small intensities of the incident light, there is a strong sensitivity of the penetration depth (and activated surface) to the intensity.

Rare-earth-doped electrospun scheelite CaWO4 nanofibers with excitation-dependent photoluminescence and high-linearity cathodoluminescence for ratiometric UV wavelength and radiation sensors

Scheelite structured AWO4 compounds (A = Ba, Ca, Pb and Sr) are efficient hosts for rare-earth dopants. In this work, high-aspect-ratio AWO4 (A = Ba, Ca, Pb and Sr) nanofibers, doped with 5 mol.% Tb and 5 mol.% Eu on A site, were synthesized using a sol-gel electrospinning technique, and their performances as a ratiometric sensor for the detection of UV light wavelength were comparatively studied. High-resolution electron microscopy reveals the presence of nanosized grains composing the nanofibers. The AWO4:5Tb-5Eu nanofibers exhibit strong characteristic photoluminescence (PL) and cathodoluminescence (CL) emission from both Tb3+ and Eu3+ ions. In the case of CaWO4 lattice, the emission intensity ratio of Tb3+/Eu3+ is found to show a linear relationship with the excitation wavelength in the tested range of 240–330 nm, with efficient energy transfer from host lattice to rare-earth ions. However, a similar result is not observed in other scheelite structured BaWO4, PbWO4, and SrWO4 nanofibers. The unique PL emission characteristics of CaWO4:5Tb-5Eu under different UV excitation wavelengths are due to its unique excitation band. This study reveals a potential new application of CaWO4:5Tb-5Eu as a fluorescent probe for UV wavelength detection. Additionally, the CL intensities from CaWO4:5Tb-5Eu nanofibers exhibit highly linear dependences on the applied voltage and current without saturation, which can be utilized for radiation detection.

Photo-bleaching of firefly luciferin with UV irradiation

We quantitatively investigated the photo-bleaching of d-luciferin in aqueous solutions by UV-light irradiation at 325-, 365-, and 405-nm wavelengths. As a function of UV-light irradiation duration, we measured the numbers of undamaged d-luciferin molecules by quantitative bioluminescence experiments. Single-exponential fitting was performed to obtain the photo-bleaching rate per irradiation time, from which we extracted the photo-bleaching cross-sections σB defined as product ϕ×σA of the photo-absorption cross-section σA and photo-bleaching quantum yield ϕ of photo-excited d-luciferin. σB was about 0.8–4.5 × 10−20 cm2, while σA was about 1.3–6.3 × 10−17 cm2. Our findings showed that ϕ is 7 × 10−4 independently of UV-light wavelength.

A green approach for synthesis of highly fluorescent carbon dots from waste engine oil: A strategy for waste to value added products

In this present work, waste engine oil was explored as a precursor for the synthesis of carbon dots (CDs) by hydrothermal route for the first time. The obtained CDs showed excellent water solubility, photostability, bright blue emission under UV light (wavelength 365 nm), pH stability, high quantum yield, and greater biocompatibility. It was thoroughly studied by vital characterization techniques such as HR-TEM, UV–Visible spectroscopy, FTIR, SEM, PSA, Fluorescence spectroscopy with lifetime analysis. The fluorescence of synthesized CDs was quenched by the addition of Fe3+ as it showed excellent selectivity and sensitivity towards Fe3+. The sensing probe showed a good linear response (R2 = 0.9986) with a limit of detection 0.055 μM in the linear range of 0.6–3.3 μM. Due to excellent fluorescence properties of CDs, it have been applied as fluorescent ink for information storage. In addition, CDs coated polymer matrix was made and used for bead-based detection of Fe3+. Finally, the presented system could be considered as an efficient probe for Fe3+ detection and paved a way for efficient utilization of waste into value-added products.

Synthesis, photophysical properties and catalytic activity of Ƙ3-SCS pincer palladium (II) complex of N,N'-di-tert-butylbenzene-1,3-dicarbothioamide supported by DFT analysis

The title complex [PdCl(L)] (1), is obtained from the reaction of SCS pincer ligand HL (where, HL = N,N'-di-tert-butylbenzene-1,3-dicarbothioamide) with lithium tetrachloropalladate (II) in methanol. The compound 1 is characterized by elemental analysis, FTIR, 1H, and 13C NMR spectroscopy, UV–Vis spectroscopy, and X-ray crystallographic techniques. At room temperature, 1 emits luminescence light of wavelength 460 nm in the solid state upon excitation by UV light of wavelength 280 nm. The average emission lifetime indicates that, both the ligand and complex emission is fluorescence in nature and involves mainly ligand centers π-π* deexcitation. It also shows good catalytic activity towards Mizoroki-Heck and Suzuki-Miyaura cross-coupling reactions of aryl bromides with tert-butyl acrylate and p-tolylboronic acid respectively. For both type of reactions, >99% conversion of the substrates is found to occur for electronically activated p-nitro bromobenzene using 1 mol % of 1. Further, modern DFT calculations are performed to decipher the mechanistic insight on the preferable pathways of the Mizoroki-Heck cross-coupling reaction. Stepwise free energy of reactions for various probable reaction pathways suggest that the catalytic route has profound preference for Pd(0)-Pd(II) over Pd(II)-Pd(IV) pathway.

In vivo study of light-driven naproxen release from gated mesoporous silica drug delivery system

A drug delivery system based on mesoporous particles MCM-41 was post-synthetically modified by photo-sensitive ligand, methyl-(2E)-3-(4-(triethoxysilyl)-propoxyphenyl)-2-propenoate (CA) and the pores of MCM-41 particles were loaded with Naproxen sodium salt (NAP). The CA was used as a photoactive molecule that can undergo a reversible photo-dimerization by [2π + 2π] cycloaddition when irradiated with UV light of specific wavelengths. Thus, it has a function of gate-keeper that is responsible for opening/closing the pores and minimizing premature release of NAP. The physicochemical properties of the prepared system were studied by infrared spectroscopy (IR), nitrogen adsorption measurements, thermogravimetric analysis (TGA), scanning transmission electron microscopy (STEM) and energy dispersive X-ray spectroscopy (EDX). The mechanism of the opening/closing pores was confirmed by UV measurements. In vitro and in vivo drug release experiments and the concentration of released NAP was determined by UV spectroscopy and high-performance liquid chromatography (HPLC). In vivo drug release in the blood circulatory system of rats has demonstrated the effective photo-cleavage reaction of CA molecules after UV-light stimulation. The localization and morphological changes of the particles were studied in the blood and liver of rats at different time intervals. The particles in the blood have been shown to retain their original rod-like shape, and the particles in the liver have been hydrolysed, which has resulted in spherical shape with a reduced size.

N-ZnO/p-CuZnS heterostructure deposited by spray pyrolysis for photosensor application in the UV region

In this work, n-ZnO/p-CuZnS heterojunction-based UV photodetector is fabricated using the spray pyrolysis technique. The current-voltage (I-V) characterization under dark condition demonstrated good rectifying behavior. For the fixed bias voltage, upon illumination with UV light (wavelength, λ = 385 nm), the current has increased. At 1 V bias, a responsivity of 0.255 A/W was recorded. Using the thermionic emission (TE) and Chueng models, the carrier transport properties of the photodetector were explained. Upon illumination, barrier height decreased from 0.89 to 0.79. Low-temperature Raman analysis was carried out to investigate the temperature-dependent strain between the layers. Photoluminescence study employed for defect analysis showed suppressed emissions indicating better absorption

Antifungal features and properties of chitosan/sandalwood oil Pickering emulsion coating stabilized by appropriate cellulose nanofiber dosage for fresh fruit application

A novel composite edible coating film was developed from 0.8% chitosan (CS) and 0.5% sandalwood oil (SEO). Cellulose nanofibers (CNFs) were used as a stabilizer agent of oil-in-water Pickering emulsion. We found four typical groups of CNF level-dependent emulsion stabilization, including (1) unstable emulsion in the absence of CNFs; (2) unstable emulsion (0.006–0.21% CNFs); (3) stable emulsion (0.24–0.31% CNFs); and (4) regular emulsion with the addition of surfactant. Confocal laser scanning microscopy was performed to reveal the characteristics of droplet diameter and morphology. Antifungal tests against Botrytis cinerea and Penicillium digitatum, between emulsion coating stabilized with CNFs (CS-SEOpick) and CS or CS-SEO was tested. The effective concentration of CNFs (0.24%) may improve the performance of CS coating and maintain CS-SEO antifungal activity synergistically confirmed with a series of assays (in vitro, in vivo, and membrane integrity changes). The incorporation of CNFs contributed to improve the functional properties of CS and SEO-loaded CS including light transmission at UV and visible light wavelengths and tensile strength. Atomic force microscopy and scanning electron microscopy were employed to characterize the biocompatibility of each coating film formulation. Emulsion-CNF stabilized coating may have potential applications for active coating for fresh fruit commodities.

Impacts of Mixing Mode on Photocatalytic Reduction of Hexavalent Chromium over Titanium Dioxide Nanomaterial under Various Environmental Conditions

This study explores the effects of initial Cr(VI) concentration, wavelength, hole-scavenger (absence and presence of salicylic acid), and oxygen conditions (aeration by air, nitrogen gas, and mechanical stir only) on photocatalytic reduction of hexavalent chromium over titanium dioxide photocatalyst and the chromic species distribution after photocatalysis. The experimental results show the existence of strong interactions between these factors. The factor of hole-scavenger was more important than the UV light wavelength condition for a reduction of 3 mg Cr(VI) L−1, whereas both factors became important when Cr(VI) concentration increased to 20 mgL−1. The higher the UV wavelength was, the less the amount of chromium retained on the TiO2 surface. The influence of oxygen-containing conditions in the solution on the reduction of 3 mgL−1 Cr(VI) was unobvious, whereas its influence became remarkable for the reduction of 20 mgL−1 Cr(VI) in the presence of SA. The interaction between oxygen-containing factor and other environmental factors, such as Cr(VI) concentration and scavenger presence (SA in this study), is a key factor about the degree of oxygen effect on Cr(VI) photo-reduction and the chromic species distribution. Simple stirring obtained better photocatalytic efficiency than aeration by air or nitrogen gas.