Visible LED Light Research Articles

Chitosan adorned with ZIF-67 on ZIF-8 biocomposite: A potential LED visible light-assisted photocatalyst for wastewater decontamination

The current investigation has utilized a simple and constructive stratified method to synthesize a binary (Cs/Z-8: chitosan (Cs) and zeolitic imidazolate framework-8 (Z-8)) and ternary Cs/Z-8/Z-67 (Z-67: ZIF-67) biocomposites at room temperature. A certain amount of Cs/Z-8 (0.05, 0.1, and 0.2 g) was used to prepare ternary biocomposites (denoted as Cs/Z-8/Z-67-0.05, Cs/Z-8/Z-67-0.1, and Cs/Z-8/Z-67-0.2, respectively). The synthesized materials were characterized. Through the adornment Cs, a non-toxic biopolymer, with Z-8 and Z-67, the desired efficacy in removing pollutants (TCN: Tetracycline, AB92: Acid Blue 92, and MB: Methylene Blue) was achieved under LED visible light. TCN removal in the presence of visible light by Cs, Z-8, Cs/Z-8, Cs/Z-8/Z-67-0.05, Cs/Z-8/Z-67-0.1, and Cs/Z-8/Z-67-0.2 was 22.6 %, 47.3 %, 69.0 %, 77.0 %, 95.5 %, and 65.0 %, respectively. The trapping test showed that TCN degradation by adding ascorbic acid, methanol, and IPA was 44.8 %, 66.9 %, and 78.5 %, respectively. It could be concluded that the O2– play the decisive role for the destruction of TCN. The reusability of Cs/Z-8/Z-67-0.1 as a photocatalyst indicated that it had the capability to preserve its stability and performance for three successive cycles of use (95.5 %, 89.0 %, and 84.0 %). Also, Cs/Z-8/Z-67 had dye degradation ability (39.0 % for Methylene Blue and 81.0 % for Acid Blue 92).

Visible LED-light driven photocatalytic activity by a novel magnetically separable CoFe2O4/Mn3O4 nanocomposite

A novel magnetic separable CoFe2O4/Mn3O4 semiconductor catalyst was synthesized by sol-gel-cum-hydrothermal method, successfully. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman, and Fourier transformed infra-red spectrometers were used to characterize the prepared samples. Mn3O4 and CoFe2O4 exhibit in tetragonal and cubic phases, respectively. The obtained direct optical band gap of the samples belongs to the visible region. These catalysts were employed in photo-degradation of methylene blue (MB) dye under an LED visible light. Coupling of CoFe2O4 with Mn3O4, which formed type-II heterojunction, enhances the photocatalytic efficiency, provides magnetic separable features, and prevents the charge carriers’ recombination. Synthesized CoFe2O4/Mn3O4 nanocomposites show excellent photocatalytic activity with a high value of rate constant ∼ 0.03889 minute−1. The scavenging test reveals that the holes and superoxide radicals were dominant reactive species in the degradation of dye. Magnetic separable feature of nanocomposite helps to recover the catalysts from degraded MB dye solution for the next photo-degradation cycles.

ZnO-modified glass capillaries as a portable photocatalytic reactor for real-time measurements

Abstract Here, we have developed a photocatalytic reactor using glass capillaries which acts both as a flow cell and a thin film-supported photocatalyst due to the Zinc Oxide (ZnO) nanostructures grown on the inner surface of the glass capillaries. The structural, morphological, elemental, and optical characteristics of the ZnO nanostructures were investigated through characterization methods such as x-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Energy-Dispersive x-ray spectroscopy (EDAX), UV–Visible spectroscopy, and Raman spectroscopy. Further, dye-sensitized ZnO nanostructures were used for photocatalytic application under visible light irradiation. A custom-made setup is developed using ZnO-modified glass capillaries for simultaneous decay and measurement of the dye degradation process under visible LED light. This developed model could have future technological applications in designing portable photocatalytic reactors that can accurately monitor the dye degradation process using real-time measurements.

Fe(III)-incorporated UiO-66(Zr)–NH2 frameworks: Microwave-assisted scalable production and their enhanced photo-Fenton degradation catalytic activities

In this work, the photocatalytic feasibility of UiO-66(Zr)–NH2 was tuned by combining a scalable producing approach and incorporating Fe3+. Different contents of Fe3+ were effectively incorporated into the UiO-66(Zr)–NH2 frameworks utilizing a microwave-assisted continuous flow tubular reactor within 10 min. It was observed that with increasing the Fe3+ content from 0.5 to 1.0, 2.0 and 3.0 M %, the production rate diminished from ∼ 1.72 to 1.65, 1.55, and 1.46 g/h, respectively. The hybrid Fe@UiO-66-NH2 (Fe@UON) showed enhanced light absorption and charge carrier separation efficiency owing to the newly formed heterostructures, Zr-O-Fe linkages, and –H2N:→ Fe3+ chelating. The optimal Fe@UON catalyst achieved the highest photo-Fenton degradation efficiency of ∼ 96 % towards tetracycline (TC) under energy-saving visible LED light (VLEL) conditions. The photodegradation was predominantly governed by the photo-induced species of ·O2–, h+, and •OH and facilitated by the Fe3+/Fe2+ cycles. At the same time, LC/MS analyses detailedly revealed the reaction pathways for the degradation. After several consecutive tests, the constructed hybrid Fe@UiO-66-NH2 catalysts maintained good catalytic durability, and there was an insignificant Fe leak to the environment. The findings showed that hybrid Fe3+@UiO-66(Zr)–NH2 derived from energy-effective, environmental and scalable methods could be a good material for treating antibiotic-polluted effluents.

Photocatalytic Polyaromatic hydrocarbons (PAH) utilizing magnetic CrFe2O4 nanoparticle: Green synthesis, characterization, ab initio studies, electronic, magnetic features and water treatment application

Polyaromatic hydrocarbons (PAHs) are priority pollutants due to their mutagenicity, persistence, and proven carcinogenicity. Consequently, we investigated the photooxidative degradation of prototypical toxic PAHs, namely anthracene (ANTH) and phenanthrene (PHEN), and naphthalene (NAPH) utilizing magnetic CrFe2O4 nanoparticles under visible light LED irradiation. The prepared nanoparticles, characterized by P-XRD, IR, and SEM, reveal a cubic (FCC) structure and an average particle size of 25.6 nm. On Ab initio study we employed spin polarized first-principle calculations using the Full-Potential Linearized Augmented Plane-Wave (FLAPW) method with GGA-mBJ potentials implemented in the Wien2k package to investigate the properties of CrFe2O4 spinel compound; the calculations reveal that CrFe2O4 adopts a cubic crystal structure with space group 227 (Fd-3 m), and exhibits semiconductor characteristics in both spin channels, featuring indirect band gaps of 1.12 eV (spin-up) and 0.43 eV (spin-down) at the Γ-L and K-Γ points, respectively. Furthermore, the material demonstrates ferromagnetic behavior, with a spin magnetic moment of 20 µB per unit cell. Optical spectra analysis concurs with band structure calculations, suggesting the suitability of this material for photovoltaic applications. The CrFe2O4 magnetic nanoparticles were synthesized through an eco-friendly approach using Boswellia carteri resin as a natural surfactant in an aqueous medium. Our synthesized materials exhibited excellent photocatalytic performance, leading to a rapid exponential decay of ANTH and PHEN over 3 h under visible LED light. The effect of different radical scavengers revealed the role of the percentage of active species OH, h+, and ˙O2− in the oxidation of selected PAHs. At neutral pH, the photo-degradation of PAHs (200 g L−1) by CrFe2O4 (10 mg) followed first-order kinetics and the Langmuir model (R2: 0.99). Exceptional degradation efficiencies were achieved, with ANTH exhibiting a removal efficiency of 99 %, PHEN of 90 %, and NAPH of 86 %. These results show the effectiveness of the synthesized materials as benign and environmentally friendly magnetic nanoparticles for removing carcinogenic PAHs, offering a sustainable, green, and reusable (n = 7) catalytic system to address this environmental challenge.

In Situ Synthesis of Cu2O Nanoparticles Using Eucalyptus globulus Extract to Remove a Dye via Advanced Oxidation.

Water pollution, particularly from organic contaminants like dyes, is a pressing issue, prompting exploration into advanced oxidation processes (AOPs) as potential solutions. This study focuses on synthesizing Cu2O on cellulose-based fabric using Eucalyptus globulus leaf extracts. The resulting catalysts effectively degraded methylene blue through photocatalysis under LED visible light and heterogeneous Fenton-like reactions with H2O2, demonstrating reusability. Mechanistic insights were gained through analyses of the extracts before and after Cu2O synthesis, revealing the role of phenolic compounds and reducing sugars in nanoparticle formation. Cu2O nanoparticles on cellulose-based fabric were characterized in terms of their morphology, structure, and bandgap via SEM-EDS, XRD, Raman, FTIR, UV-Vis DRS, and TGA. The degradation of methylene blue was pH-dependent; photocatalysis was more efficient at neutral pH due to hydroxyl and superoxide radical production, while Fenton-like reactions showed greater efficiency at acidic pH, primarily generating hydroxyl radicals. Cu2O used in Fenton-like reactions exhibited lower reusability compared to photocatalysis, suggesting deterioration. This research not only advances understanding of catalytic processes but also holds promise for sustainable water treatment solutions, contributing to environmental protection and resource conservation.

Green and environmentally friendly architecture of starch-based ternary magnetic biocomposite (Starch/MIL100/CoFe2O4): Synthesis and photocatalytic degradation of tetracycline and dye

The presence of tetracycline and dye as organic contaminants has led to the poisoning of wastewater. The aim of this study is to synthesize a novel biocomposite material by decorating natural starch polymer granules with metal-organic framework (MIL100) and cobalt ferrite magnetic (CoFe2O4) nanoparticles. The synthesized ternary magnetic biocomposite (Starch/MIL100/CoFe2O4) was used for the photocatalytic degradation of methylene blue (MB) and tetracycline (TCN) using LED visible light. The synthesis of the biocomposite was confirmed through comprehensive analyses (XRD, SEM, FTIR, BET, EDX, MAP, DRS, pHzpc, TGA, and Raman). The evaluation examined the influence of initial pollutant concentration, catalyst dosage, pH, and the impact of anions on pollutant removal. The results show that the pollutant degradation ability of biocomposite has been significantly improved, so that the base biopolymer, starch, achieved 18% tetracycline degradation, but when decorated with MIL100 and cobalt ferrite, it increased to 91.2%. It was observed that the degradation for methylene blue improved from 12% for starch to 96.6% for the magnetic biocomposite. The tetracycline degradation decreased by more than 20% in the presence of NaCl, NaNO3, and Na2SO4. The finding shows that the biocomposite adheres to first-order kinetics for both pollutants. The scavengers test identified hydroxyl radicals as the most effective active species in the degradation process. High stability, even after passing 5 cycles of recycling was observed for the biocomposite. The results indicated that the facile and green synthesized Starch/MIL100/CoFe2O4 magnetic biocomposite could be used as an effective photocatalyst for the degradation of Tetracycline and dye at room temperature.

The highly efficient photodegradation of 4-bromophenol by TiO2/g-C3N4 nano photocatalyst with LED visible light

Since traditional photocatalysts have suffered from higher charge carrier recombination and moderate photocatalytic efficiency, developing photocatalysts is crucial for water treatment objectives. Hence, the various ratios of TiO2 on g-C3N4 (CN) to form nano photocatalysts were synthesized by the solvothermal method. The 30%TiO2/CN showed the best performance to degradation and debromination of 4-bromophenol (4-BP) solution completely (kobs = 6.6 × 10−2 min−1) under visible light emitted by LED (420 nm) in 30 min. Remarkably, the photocatalyst showed superior stability and reusability, maintaining its efficiency after four cycles of 4-BP degradation. The dominant ROS participating in 4-BP degradation were ●O−2 and photogenerated holes (h+), as investigated by free radical scavenging tests. The optical properties analysis revealed that the introduction of TiO2 to the bulk CN decreases electron-hole recombination and improve photocatalytic performance by facilitating electrons transfer through the TiO2 nanoparticles in a chain. The findings of this study showed that the TiO2/CN photocatalyst is a promising catalyst for the degradation of 4-BP. It exhibits a higher rate constant and photocatalytic efficiency compared with previous studies conducted under visible light irradiation.

In situ-growth of Fe2S3 ultrathin layer on CdS nanorod through cation-exchange for efficient photocatalytic degradation of organic pollutants under visible light coupled oxidant activation

A new core-shell structure CdS@Fe2S3 material was synthesized by in situ cation exchange method to enhance the degradation of organic pollutants in water under visible light. It is proved that Fe2S3 nanolayer is successfully loaded on CdS nanorods by TEM and UV-Vis spectra and other means. The representative Rhodamine B was selected as the target pollutant and the results of degradation experiment showed that after 60 min of exposure to LED visible light with a low energy (25 W), the removal efficiency for this dye could reach 98 % in the presence of peroxymonosulfate (PMS) forming free radicals, which displayed a observed kinetic rate constant exceeding 0.62 min−1 that is approximately 5 times higher than the system without PMS addition and 10 times than the system with original CdS as catalyst. The result of inhibition experiments shows that sulfate radical (SO4·-) and singlet oxygen (1O2) play as important roles during the photocatalytic process. In addition, this core-shell material can be recycled at least four times. Generally, this study can make full use of visible light which can be easily obtained and effectually resolve the organic pollution problems.

Enhancing performance of SnS2 based self-powered photodetector and photocatalyst by Na incorporation

Sn and S are environmentally friendly elements that are abundant in nature. The SnS2 compound formed with these elements has intrinsic n-type electrical conductivity and a direct forbidden band gap of ∼2.2 eV. Therefore, it is a very promising compound for visible light optoelectronic applications. In this study, SnS2thin films were coated on p-Si substrates and pn heterojunction structures were obtained. By adding certain amounts of Na element to SnS2, the photosensitivity of the heterojunction devices increased tremendously and reached a high value of 3.2 × 104 under zero bias condition. It was observed that the prepared devices had excellent speeds and stability with rise and decay times of as low as 28 m s and 23 m s. Moreover, the devices were found to be sensitive to visible light even at ultra-low light intensity of ∼0.3 μW/cm2. Furthermore, the responsivity and specific detectivity values of the prepared photodetectors reach very high values of 11 A/W and 8.4 × 1013 Jones at this low light intensity. The NEP value drops to a low level of 2.7 × 10−15 WHz −1/2. In addition, the photocatalytic properties of Na-doped and undoped SnS2 compound were also examined under visible LED light. Compared to undoped samples, photocatalytic efficiency increased by ∼42 % in Na-doped SnS2 thin films. The findings clearly reveal that Na improves both photodetector device performance and the photocatalytic effect of the SnS2 semiconductor.

Nitrogen-Rich Triazine-Based Covalent Organic Frameworks as Efficient Visible Light Photocatalysts for Hydrogen Peroxide Production.

Covalent organic frameworks (COFs) have been widely used in photocatalytic hydrogen peroxide (H2O2) production due to their favorable band structure and excellent light absorption. Due to the rapid recombination rate of charge carriers, however, their applications are mainly restricted. This study presents the design and development of two highly conjugated triazine-based COFs (TBP-COF and TTP-COF) and evaluates their photocatalytic H2O2 production performance. The nitrogen-rich structures and high degrees of conjugation of TBP-COF and TTP-COF facilitate improved light absorption, promote O2 adsorption, enhance their redox power, and enable the efficient separation and transfer of photogenerated charge carriers. There is thus an increase in the photocatalytic activity for the production of H2O2. When exposed to 10 W LED visible light irradiation at a wavelength of 420 nm, the pyridine-based TTP-COF produced 4244 μmol h-1 g-1 of H2O2 from pure water in the absence of a sacrificial agent. Compared to TBP-COF (1882 μmol h-1 g-1), which has a similar structure but lacks pyridine sites, TTP-COF demonstrated nearly 2.5 times greater efficiency. Furthermore, it exhibited superior performance compared to most previously published nonmetal COF-based photocatalysts.

Influence of visible light LEDs modulation techniques on photocatalytic degradation of ceftriaxone in a flat plate reactor

In this paper, the effect of light modulation on photocatalytic ceftriaxone (CEF) degradation in aqueous solution was investigated. The experimental set-up consisted of a fixed bed photocatalytic reactor with a flat plate geometry and visible LEDs for irradiation. Fe-N-codoped TiO2 photocatalyst was immobilized on a polystyrene plate (PS) by solvent casting method to achieve a structured photocatalyst (Fe-N-TiO2/PS), which was loaded in the photoreactor. Raman and UV–Vis diffuse reflectance spectroscopy confirmed the presence of Fe-N-TiO2 on the PS surface and its uniform distribution on the polymer support. Various LEDs dimming techniques were tested with fixed and variable duty-cycle values. In particular, the following modulations were used: fixed duty-cycle (FD), sinusoidal variable duty-cycle (S-VD), triangular variable duty-cycle (T-VD), square wave variable duty-cycle (SW-VD), saw-tooth variable duty-cycle (ST-VD), pulse variable duty-cycle (P-VD), and pseudo-sinusoidal variable duty-cycle (PS-VD). The optimal light modulation was the S-VD, with an average fed current between 25 and 75 mA and a period of 30 s. Indeed, by using S-VD modulation, the highest value of the apparent CEF degradation kinetic constant (resulting 0.0082 min−1) and the highest total organic carbon (TOC) removal (70 %) were achieved. By comparing the electric energy consumption (EE/O) with S-VD modulation used in this work with those found in other literature studies dealing with the photocatalytic ceftriaxone degradation, a significant decrease of EE/O was evidenced. Moreover, toxicity test showed that the photocatalytic treatment allowed to significantly reduce the toxicity of CEF solution when compared to untreated effluent.

Urea-driven g-C3N4 nanostructures for highly efficient photoreduction of Cr(vi) under visible LED light: effects of calcination temperature.

Graphitic carbon nitride (g-C3N4) nanostructures were synthesized via the calcination of urea at various temperatures ranging between 400 and 600 °C and were utilized for photoreduction of Cr(vi) in aqueous medium. Due to the low adsorption of Cr(vi) on the g-C3N4 surface, a more accurate assessment of the photocatalytic performance of the samples was carried out. Although the characterization showed that the specific surface of samples increased as the calcination temperature increased, the most efficient product in terms of the photoreduction duration of Cr(vi) was produced through the calcination process carried out at 450 °C, which reduced the concentration by more than 99% in 40 minutes. These results demonstrate that the structural and surface properties of g-C3N4 are critical factors that impact the photocatalytic performance. Alongside the calcination temperatures, the concentration of citric acid as a hole scavenger, the source of illumination, pH levels, and the recycling ability of the produced specimen at 450 °C were also investigated. Conspicuously, the photocatalyst works better when more citric acid is present and the pH level decreases. Out of all the cases studied regarding the light source, the 400 nm LED light source was found to be the most efficient. Additionally, even after going through the photoreduction process four times, the photocatalyst still remained highly efficient.

The impressive photocatalytic performance of TiO2/CeCoO3/PMO-IL nanohybrid toward the selective generation of aldehydes under a visible-LED light source

The construction of perovskite-based wide bandgap semiconductors with uniform dispersion is one of the main strategies to improve the catalytic activity of semiconductor materials. Here, a heterojunction catalyst was obtained by nucleating TiO2 on CeCoO3 nanopowders and producing TiO2/CeCoO3 hetero nanostructures at 450 °C. Then by putting them on the PMO-IL as a porous substrate, TiO2/CeCoO3/PMO-IL nanohybrid was prepared. The properties of nanohybrid were characterized by FE-SEM, EDS, XRD, BET, XPS, HRTEM, SAED, FT-IR, DRS, and PL spectroscopy. The photocatalytic efficiency of TiO2/CeCoO3 and TiO2/CeCoO3/PMO-IL toward the selective fabrication of aldehydes was studied under the irradiation of visible light. The synthesized nanohybrid demonstrated excellent catalytic activity compared to TiO2/CeCoO3 and PMO-IL alone. Therefore, this nanohybrid could be used as a capable heterogeneous photocatalyst due to its high activity, selectivity, and recyclability.

Visible-light photocatalytic degradation of two textile dyes by recyclable ZnO-Perlite: kinetic models and cost analysis

ABSTRACT Zinc oxide (ZnO), as an n-type semiconductor photocatalyst, is often selected due to its excellent photocatalytic performance and is supported on commercial expanded perlite (EP) to enhance interfacial charge separation efficiency under visible LED light. The structure and photocatalytic properties of the synthesised photocatalyst via the co-precipitation route were studied through XRD, FT-IR, SEM, EDX and pHpzc analyses. The photocatalytic response was evaluated by studying the degradation of two toxic and refractory azo dyes, reactive black 5 (RB5) and acid red 14 (AR14). Azo dyes (20 mg L−1) were completely degraded in the studied system, which occurred at pH 7 and 3, with catalyst amounts of 2 and 1 g L−1, and in the presence of H2O2 at 2 and 10 mM under LED light (15 W) within 2 h for RB5 and AR14, respectively. The degradation of RB5 and AR14 followed first-order kinetics with Kobs values of 0.0218 and 0.0169 min−1 and R2 values of 0.9271 and 0.8325, respectively. The assessment of energy consumption (EEO) and total operation cost (OC) confirmed that the supported ZnO offered the lowest power and cost requirements to transform selected pollutants into the acquired effluent, with values of 20.65 and 25.13 kWh m−3 and 3.11 and 3.205 USD kg−1 for RB5 and AR14, respectively, compared to using only VIS/ZnO, VIS/EP and VIS. Furthermore, the catalyst exhibited stability without the need for any additional chemicals for up to 10 h (5 reuse cycles). Additionally, the presence of major anions (sulphate, chloride and alkalinity) reduced the degradation efficiency in a real water matrix (1.74 and 1.47 times for RB5 and AR14, respectively) compared to that in distilled water.

Highly efficient Bi2O2CO3 coupled with interlayer expanded MoS2 photocatalyst with oxygen vacancy mediated direct Z-scheme charge transfer for photocatalytic degradation of organic pollutant

The development of photocatalysts to degrade organic pollutants from wastewater under visible light has attracted a lot of interest. Herein, a series of Bi2O2CO3 (BOC) coupled with interlayer expanded MoS2 (IEM) photocatalysts were synthesized via a facile two-pot hydrothermal technique. Among all the samples, 5 % of BOC with IEM (5 % BOC-IEM) nanocomposite exhibited the highest photodegradation with 94 % (4.97 × 10−2 min−1) for Methylene Blue (MB) dye removal under 1 W LED visible light. The performance by 5 % BOC-IEM is 1.5 times and 13.4 times higher than the parent IEM and BOC, respectively. Increased photocurrent density, lowest PL intensity, and smallest EIS arc further evidenced the lowered charge carrier’s recombination rate in the optimized 5 % BOC-IEM heterostructure. Moreover, the outstanding photocatalytic performance of 5% BOC-IEM was due to the presence of oxygen vacancies, enhanced light absorption, and improved migration and separation of charge carriers. An Ohmic contact formed on the interfaces of BOC and IEM boosts the Z-scheme charge transfer mechanism, which greatly improves the photocatalytic activity of 5% BOC-IEM.

Oxygen defects coupled with LSPR effect for enhancing photocatalytic hydrogen evolution of Z-scheme 1D@2D/2D WO2.72/ZnIn2S4 composites

Reasonable construction of multifunction Z-type heterojunction is the key to improve the ability of photocatalytic hydrogen evolution. Herein, we designed the Z-scheme heterojunctions coupled with efficient defect introduction and local surface plasmon resonance (LSPR) effect from ultrathin ZnIn2S4 nanosheets (2D) grown on the surface of ball-flower like WO2.72 (WO) using an easy oil bath method. The ball-flower like WO material was composed of nanoneedles (1D) and nanosheets (2D), which was beneficial for growing ZnIn2S4 nanosheets to form 1D@2D/2D WOZIS-x photocatalysts. The photocatalytic H2-production performances of WOZIS-x with various mass ratios were explored under visible LED light. Through adjusting the mass of WO, the WOZIS-3 composite showed much higher hydrogen evolution performance than pure ZIS up to the rate of 8.12 mmol·g−1·h−1 and good hydrogen evolution ability under pure water. The multipurpose Z-scheme heterojunction can obtain hot electrons and localized electric field (LEF) from LSPR effect caused by oxygen vacancies, which could accelerate the spatial segregation of carries and improve the light absorption range and intensity. The development of multipurpose Z-type WOZIS heterojunction provide an interesting thought to take full advantage of WO with oxygen vacancy and LSPR characteristic and improve the hydrogen evolution ability of ZIS.

Wireless Networks using Visible Light Communication: A Review

Provisioning of quality of service (QoS) is a critical issue in visible light communication (VLC) systems and other wireless communication systems. LED lights are becoming widely used for homes and offices for their luminous efficacy improvement. VLC is a new way of wireless communication. Typical transmitters used for visible-light communication are visible-light LEDs, and receivers are photodiodes and image sensors. We present new applications that will be made possible by visible light communication technology. Especially location-based services are considered suitable for visible light communication applications.

Diurnal-independent, visible-light-storing of Ag2O@SrAl2O4:Eu2+,Dy3+ for the round-the-clock decomposition of ciprofloxacin

A round-the-clock photocatalyst that can efficiently separate charge carriers will break through the practical application of photocatalytic-based advanced oxidation processes (PC-AOPs) in wastewater treatment. In this work, an energy-storable p-n heterojunction Ag2O@SrAl2O4:Eu2+,Dy3+ (Ag2O@SAED) was successfully prepared to achieve round-the-clock photocatalytic degradation of ciprofloxacin (CIP). Ag2O@SAED can efficiently degrade ∼ 80 % of CIP (with ∼ 56 % mineralization) under low power consumption of 12 W LED visible light source radiation for 2 h. In addition, surprisingly, Ag2O@SAED also shows certain energy storage properties, so that it can effectively reduce the energy consumption of the treatment process compared with conventional photocatalytic processes. Non-radical singlet oxygen (1O2) is the main reactive species, which is produced mainly from intermediate superoxide radicals (·O2−). Moreover, the site of CIP attacked by 1O2 was tentatively confirmed by Fukui index based on density functional theory (DFT) calculations. The activities of round-the-clock degradation of CIP in different water matrices were examined. The degradation efficiency in tap water, Yangtze River and wastewater plant effluent were 61.88 %, 57.61 % and 55.87 %, respectively. The synergistic effect of p-n heterojunctions is effective in degrading CIP during daytime, and the light released from SAED activates the activity of Ag2O to degrade CIP at night. This study contributes to further understanding the principles and mechanisms of round-the-clock photocatalysts for degradation of organic pollutants and provides directions for the practical application of photocatalytic technology.

Enhanced photocatalytic degradation of amoxicillin using a spinning disc photocatalytic reactor (SDPR) with a novel Fe3O4@void@CuO/ZnO yolk-shell thin film nanostructure

Antibiotics are resistant compounds with low biological degradation that generally cannot be removed by conventional wastewater treatment processes. The use of yolk-shell nanostructures in spinning disc photocatalytic reactor (SDPR) enhances the removal efficiency due to their high surface-to-volume ratio and increased interaction between catalyst particles and reactants. The purpose of this study is to investigate the SDPR equipped to Fe3O4@void@CuO/ZnO yolk-shell thin film nanostructure (FCZ YS) in the presence of visible light illumination in the photocatalytic degradation of amoxicillin (AMX) from aqueous solutions. Stober, co-precipitation, and self-transformation methods were used for the synthesis of FCZ YS thin film nanostructure and the physical and chemical characteristics of the catalyst were analyzed by XRD, VSM,, EDX, FESEM, TEM, AFM, BET, contact angle (CA), and DRS. Then, the effect of different parameters including pH (3–11), initial concentration of AMX (10–50 mg/L), flow rate (10–25 mL/s) and rotational speed (100–400 rpm) at different times in the photocatalytic degradation of AMX were studied. The obtained results indicated that the highest degradation efficiency of 97.6% and constant reaction rate of AMX were obtained under LED visible light illumination and optimal conditions of pH = 5, initial AMX concentration of 30 mg/L, solution flow rate of 15 mL/s, rotational speed of 300 rpm and illumination time of 80 min. The durability and reusability of the nanostructure were tested, that after 5 runs had a suitable degradation rate. Considering the appropriate efficiency of amoxicillin degradation by FCZ YS nanostructure, the use of Fe3O4@void@CuO/ZnO thin film in SDPR is suggested in water and wastewater treatment processes.