Visible LED Light Research Articles

Effective Photocatalytic Activity of Sulfate-Modified BiVO4 for the Decomposition of Methylene Blue Under LED Visible Light.

In this study, we investigated sulfate-modified BiVO4 with the high photocatalytic activity synthesized by a sol-gel method in the presence of thiourea, followed by the annealing process at different temperatures. Its structure was characterized by thermal gravimetric analysis (TGA), powder X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS), X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS). The BiVO4 synthesized in the presence of thiourea and calcined at 600 °C (T-BVO-600) exhibited the highest photocatalytic degradation efficiency of methylene blue (MB) in water; 98.53% MB removal was achieved within 240 min. The reaction mechanisms that affect MB photocatalytic degradation on the T-BVO-600 were investigated via an indirect chemical probe method, using chemical agents to capture the active species produced during the early stages of photocatalysis, including 1,4-benzoquinone (scavenger for O2−), ethylenediaminetetraacetic acid disodium salt (scavenger for h+), and tert-butanol (scavenger for HO•). The results show that holes (h+) and hydroxyl radicals (HO•) are the dominant species of MB decomposition. Photoluminescence (PL) measurement results of terephthalic acid solutions in the presence of BiVO4 samples and BiVO4 powders confirm the involvement of hydroxyl radicals and the separation efficiency of electron-hole pairs in MB photocatalytic degradation. Besides, the T-BVO-600 exhibits good recyclability for MB removal, achieving a removal rate of above 83% after five cycles. The T-BVO-600 has the features of high efficiency and good recyclability for MB photocatalytic degradation. These results provide new insight into the purpose of improving the photocatalytic activity of BiVO4 catalyst.

Photocatalytic Synthesis of p‐Anisaldehyde in a Mini Slurry‐Bubble Reactor under Solar Light Irradiation

Dense photocatalyst slurry was employed for the synthesis of p‐anisaldehyde under solar light irradiation. An Fe‐modified rutile TiO 2 (Fe‐TiO 2, 34.5 m 2/g) photocatalyst was used as a visible‐light‐responsive photocatalyst. A conventional TiO 2 (P25, 35 m 2/g) photocatalyst was also examined as a reference catalyst. XRD patterns and diffuse reflectance spectra showed that Fe‐TiO 2 consists of 100 % rutile phase and absorbs more visible light compared to P25, respectively. The catalyst powder was suspended in an ethyl acetate solution of p‐methoxytoluene in the mini‐reactor, with oxygen bubbling, under a solar simulator, visible light, and UV LEDs. p‐anisaldehyde, as a reaction product, was analyzed by sampling using gas‐chromatograph. Regardless of the light source, Fe‐TiO 2 always outperformed P25 in terms of both generation rates (GR) of p‐anisaldehyde and energy requirements (ER). It was demonstrated that the highly dense Fe‐TiO 2 slurry was efficient for the synthesis under solar light owing to the small size of the reactor. The small amount of Pt and ZrO 2 cocatalysts significantly enhanced the GR under solar light. By adopting a visible light responsive Fe‐TiO 2 photocatalyst, the mini slurry‐bubble reactor under solar light achieved a high GR per catalyst mass (CM), which is one to two orders higher than that reported by most previous studies with high‐power lamps.

Visible-Light Plasmonic Enhancement of Catalytic Activity of Anisotropic Silver Nanoparticles.

Synthesis of silver nanoparticles (AgNPs) in presence of copper salt (as the etchant) led to the formation of nanoparticle samples with different fractions of anisotropic particles. The proportion of anisotropic nanoparticles decreased with increase in ratio of precursor Cu salt in the preparation protocol. These AgNPs samples were found to catalyse p-nitrophenol reduction by glycerol and Fenton oxidation of methyl orange. The catalytic activity of these AgNPs samples for these reactions increased with the fraction of anisotropic nanoparticles in the catalyst samples. On conducting these reactions under cool white LED visible light, the catalytic activity of AgNPs catalyst samples increased by 2 to 3 times compared to that observed in dark. The photo-Fenton MO degradation catalytic activity obtained is among the best reported in literature. However, the order of the reaction did not change whether the reaction was conducted under visible light or in dark. Direct plasmonic catalytic mechanisms are proposed to explain the enhancement in reactivity under visible light.

Multi-layered porous hierarchical TiO2/g-C3N4 hybrid coating for enhanced visible light photocatalysis

Traditional photocatalysts are difficile to conform the provision of visible light catalysis, conducive recycling and eminent efficiency, which limits their practical applications for decomposing organic pollutants in wastewater. Herein, a multi-layered porous hierarchical titanium dioxide/graphitic carbon nitride (TiO2/g-C3N4) hybrid coating is in-situ generated on titanium (Ti) substrate by sequentially employing plasma electrolytic oxidation (PEO), alkali immersing and hydrothermal reaction. The as-prepared coating exhibits surpassing photocatalytic performance to decay Rhodamine B (RhB) than g-C3N4 and TiO2 photocatalysts under 5 W LED visible light with 240 h cyclic stability. Moreover, the electrons transport and Z-scheme mechanism for TiO2/g-C3N4 hetero-junction is pursued to account for the ultralow recombination of photo-induced electron-hole and the enhanced catalytic properties. Not only that, it inhibits the secondary pollution which has further intensified its significance for degradation of organic pollution in sewage treatment systems.

Synthesis of N-doped TiO2 Nanoparticle by Solvothermal Method for Dye Treatment

Nitrogen-doped titanium dioxide (NT) was synthesized by solvothermal method. Titanium (IV) butoxide (TBOT) was used as a titanium source and diethyleneamine (DEA) was used as a nitrogen source. The DEA concentration was fixed at 5% mol. The effect of the synthesized temperatures was studied (150 °C to 200 °C). The characterization results showed that the XRD patterns of NT synthesized by solvothermal method exhibited only anatase structure of TiO2 at 25.56° (101), 37.76° (004), 48.04° (200), 48.18° (105), 54.06° (211), 55.24° (204), 62.76° (116), 69.04° (220), 70.32° (215) and 75.30° (303). The crystallite sizes of NT (13-14 nm) were smaller than that of TiO2 (22.39 nm) while the surface area of NT (31-47 m2g−1) was larger than that of TiO2 (6.42 m2g−1). This indicated that doping N on TiO2 had a significant effect on crystallite size and surface area of TiO2. The photocatalytic activities of NT were evaluated by decolorization of 10−5 M methylene blue (MB) under LED visible light irradiation. The result showed that the photocatalytic performance of TiO2 was significantly improved by N dopant with the efficiency of 90%. However, the synthesized temperatures had no significant effect on the physical properties and the photocatalytic reactivity of NT.

CO2 adsorption and its visible-light-driven reduction using CuO synthesized by an eco-friendly sonochemical method

One alternative to mitigate the high CO2 concentration in the atmosphere is its conversion into value added-products or solar fuels by heterogeneous photocatalysis. However, in these reactions, the CO2 fixation remains a challenge due to the inert nature of greenhouse gas. Thus, it is necessary to propose materials that presented good performances in both processes: CO2 adsorption and its photocatalytic conversion to solar fuels. Copper oxide is a potential material that could exhibit high efficiencies for both processes if it is prepared by adequate synthesis methods. In this work, CuO was obtained by a sonochemical method using an eco-friendly surfactant (Na3C6H5O7), low sonochemical time (15 min) and low temperatures (80 °C). The materials were evaluated in a combined process that involves CO2 adsorption and its photocatalytic conversion to liquid fuels (CH3OH) under LED visible-light at 25 °C. CuO particles were characterized by X-ray powder diffraction, Scanning Electronic Microscopy, N2 physisorption, FTIR spectroscopy, Diffuse Reflectance Spectroscopy, and X-ray photoelectron spectroscopy. CuO pure showed the best efficiencies for CO2 adsorption: 318 mgCO₂ g−1 and CH3OH production: 3.7 μmol g-1 h-1, which was associated with it’s the high number of active sites. Bohem titrations were used to calculate the active: acid/basic sites in the samples, which results demonstrated a higher contribution of basic sites (2.4 mmol). These active sites favored the formation of monodentate bonds between CO2 and CuO, which promoted its photoconversion to solar fuels such as CH3OH. Additionally, CuO/Cu(OH)2 mixtures with the high surface area were identified at higher concentrations of Na3C6H5O7. However, these mixtures did not show high efficiencies for both processes. A mechanism of combined CO2 adsorption and its photocatalytic conversion to methanol under visible light was proposed. The stability and recyclability of CuO as CO2 adsorbent and as a photocatalyst was demonstrated after three consecutive cycles without compromise its efficiency in the combined process.

In situ deposition of Ag/AgCl on the surface of magnetic metal-organic framework nanocomposite and its application for the visible-light photocatalytic degradation of Rhodamine dye.

Herein, NH2-MIL-125(Ti) (NMT) as one of the known stable metal-organic frameworks (MOFs) in aqueous solution was successfully magnetized with CoFe2O4 nanoparticles through the hydrothermal method. The Ag/AgCl as a plasmonic photocatalyst was assembled on the CoFe2O4/NMT (CFNMT) at room temperature by in situ deposition, and photo-reduction methods to improve the photocatalytic activity of CFNMT under LED visible light. The prepared materials were fully characterized by SEM/EDX, TEM, FTIR, XRD, UV-DRS, and VSM analysis. Rhodamin B (RhB) was selected as the pollutant model. The results showed that the Ag/AgCl@CFNMT had super-fast degradation ability of RhB molecule due to the synergetic effect between Ag/AgCl and CFNMT in comparison with NMT and CFNMT. The introduced Ag/AgCl on the surface of CFNMT increased absorption of photons in the visible region and enhanced the transfer and separation of the produced charge on the contact area between Ag/AgCl and CFNMT. Also, after seven times recycling, besides the simple magnetic separation of Ag/AgCl@CFNMT from liquid media, the composite still showed high photodegradation ability (89%).

Energy-efficient carbon-doped titanium dioxide nanoparticles: synthesis, characterization, and catalytic properties under visible LED irradiation for degradation of gemifloxacin

Synthesis and characterization of energy-efficient visible-light-responsive carbon-doped titanium dioxide nanoparticles (C-TiO2NP) is reported. The characterization results of C-TiO2NP using BET, TEM, DLS, and XRD indicate the following: (1) the C-TiO2NP have high surface area (77.02 m2/g), (2) size range of 5.00–10.00 nm and (3) zeta potential of 19 (pH 4.0), 4 (pH 7.0) and −21 (pH 10.0) while (4) the XRD results shows a peak pattern indicating that C-TiO2NP is mostly in the anatase phase. The photocatalytic properties of C-TiO2NP is investigated in this study using gemifloxacin antibiotic under LED in the visible region (λmax ~ 450 nm). Results shows that C-TiO2NP have significant catalytic properties under LED visible light (up to ~ 74% within 60 min). On the other hand, no degradation is observed for control TiO2NP using LED visible light under equivalent experimental conditions. Using control TiO2NP with H2O2 under LED visible light results in a percentage degradation of ~ 33.0%. Upon using C-TiO2NP with H2O2, the %degradation increases from ~ 33.0 to 64.0%. Although H2O2 generally enhances the activity of bare TiO2NP under UV irradiation, the %degradation under LED in the presence of C-TiO2NP and H2O2 (~ 64%) is smaller than that in the presence of C-TiO2NP only (~ 74%). Results demonstrates the applicability of C-TiO2NP as an energy-efficient and cost-effective photocatalyst under LED visible light for pharmaceutical wastewater treatment.

An efficient and stable narrow bandgap carbon dot-brookite composite over other CD-TiO2 polymorphs in rhodamine B degradation under LED light

Carbon dot (CD) obtained from pine bark was loaded on three TiO2 polymorphs (anatase, rutile, and brookite abbreviated in this study as Ana, Rut, and Brk respectively) to evaluate their photocatalytic performance in rhodamine B (RhB) degradation under visible-LED light. The materials were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), x-ray powder diffraction (XRD), N2 sorption isotherm, and Fourier transform infrared (FT-IR), UV-diffused reflectance spectroscopy (UV-DRS), and x-ray photoelectron spectroscopy (XPS). The x-ray result shows that the different pure pristine polymorphs and their composites were successfully prepared with Rut and CD-Rut composite having the highest crystallite size of 23.06 and 21.64 nm respectively. The N2 sorption isotherm of the materials shows Ana, Brk and their composite exhibited type IV isotherm with H series hysteresis loop, which implies that they are mesoporous materials. The isotherm exhibited by Rut and CD-Rut suggests that they are non-porous. However, their pore size distribution (PSD) shows that the materials possess mesopores that may have resulted from interparticle voids due to particle aggregation. Results from the photocatalytic degradation experiments showed that the materials performed in the following order CD-Brk>Brk>CD-Ana>CD-Rut>Rut>Ana with a corresponding percentage RhB removal of 99.91, 76.78, 36.28, 27.50, 22.65, and 12% respectively. The excellent performance of CD-Brk and Brk over the others is attributed to their narrow bandgap energy of 2.00 eV making them more active under the visible-LED light. CD-Brk performed better than Brk because it possesses more surface-active sites resulting from its relatively higher surface area. In terms of degradation mechanism, CD-Brk which was stable after 4 cycles of degradation, showed that superoxide anion radical (O2•−) played major role in the degradation process.

Synthesis of porous TiO2/ZrO2 photocatalyst derived from zirconium metal organic framework for degradation of organic pollutants under visible light irradiation

Zirconium based metal-organic frameworks (Zr-MOFs) are promising candidates for photocatalytic wastewater treatment due to their excellent properties such as high chemical and thermal stability and high photodegradation ability. Herein, we report a novel porous TiO2/ZrO2 photocatalyst derived from UiO-66 and Titania hybrids. UiO-66 nanoparticles was synthesized through solvothermal method and utilized as catalyst support to grow TiO2 particles on its surface. The prepared Titania/MOF nanocomposite was calcined to obtain porous TiO2/ZrO2 photocatalyst for degradation of organic pollutants from colored wastewater under LED visible light. The prepared materials were fully characterized with FTIR, XRD, SEM/EDS, TEM, BET, UV-DRS and ICP analysis. The results showed that the developed TiO2/ZrO2 enhanced photodegradation ability of Rhodamin B (RhB) in comparison with the mixture of prior UiO-66 and TiO2 and was found to affect the photocatalytic activity by increasing the adsorption of photons in visible region and enhanced the transfer and separation of produced charge. The decolorization kinetics followed first-order kinetic model. In addition, after four times recycling, the regenerated nanocomposite still showed high stability and photodegradation ability (90%).

The design of analog signal communication system based on visible light

With the rapid development of science and technology, communication mode has made a great leap forward, and visible optical communication has also been developed around the word. This paper mainly studies the audio signal transmission of LED visible light indoor communication. The system uses audio chip to generate audio signal. We have not only established a channel model, but also received optical signal through BH1750FVI module. In addition, we adopt the direct pulse counting frequency discrimination method for modulation and demodulation, and finally recover the original signal, achieving the purpose of voice signal transmission.

Construction of g-C3N4/PDI@MOF heterojunctions for the highly efficient visible light-driven degradation of pharmaceutical and phenolic micropollutants

A novel g-C3N4/PDI@MOF heterojunction was synthesized by the in situ growth of NH2-MIL-53(Fe) onto the g-C3N4/PDI layer. The heterojunction was applied as a photocatalyst for the removal of pharmaceutical and phenolic micropollutants in the present of H2O2 and visible LED light (420 < λ < 800 nm). The synergistic heterojunction displays excellent photocatalytic performance for the removal of several water-soluble and toxic organic pollutants (50 ppm) under visible light irradiation, with a maximum efficiency of up to 90% (1 h) for tetracycline (TC), 78% (2.5 h) for carbamazepine (CBZ), 100% (10 min) for bisphenol A (BPA) and 100% (30 min) for p-nitrophenol (PNP). Furthermore, the low concentration of phenolic organic pollutants (2 ppm) can also be rapidly degraded into small molecules (analyzed by HPLC) within 10 min. This performance is superior to some previously reported visible-light photocatalysts. The improved photocatalytic activity is attributed to the efficient formation of heterojunctions derived from the interface contact and electronic band structure matching between g-C3N4/PDI and NH2-MIL-53(Fe), which is beneficial to charge separation and facilitates the photodegradation process. Repeated experimental studies and structural analysis of photocatalyst before and after degradation (XRD and FT-IR) demonstrated that the photocatalyst exhibits good stability and reusability. This work provides a new insight into the construction of heterojunction photocatalysts based on Fe-MOF for the heterogeneous photodegradation of organic contaminants with H2O2 under visible light.

Improved Reactor Productivity for the Safe Photo‐Oxidation of Citronellol Under Visible Light LED Irradiation

AbstractThe front cover artwork is provided by Jaqueline Leib, the Laboratoire de Génie des Procédés Catalytiques (UMR CNRS 5285, Université de Lyon/CPE Lyon) and the Conservatoire National des Arts et Métiers. The image shows the transformation of citronellol (main constituent of the essential oil from geranium, Pelargonium graveolens) by photo‐oxygenation to give rose oxide, a floral green note, with a strong, diffusive rose scent. The productivity as well as the safety of the process was improved using a photo‐microreactor. Read the full text of the Communication at 10.1002/cptc.201800201.

Graphene oxide/titania photocatalytic ozonation of primidone in a visible LED photoreactor.

A graphene oxide-titania (GO/TiO2) composite was synthesized via sol-gel method, and studied in aqueous Primidone mineralization with ozone and LED visible light. The photocatalyst was characterized by different techniques (XRD, TEM, SBET, TGA, UV-vis diffuse reflectance spectroscopy). The band gap value decrease from 3.14 eV for bare TiO2 samples to 2.5 eV in GO/TiO2 composites clearly shows the interaction of GO with TiO2 structure. Approximately 20 mg L-1 of Primidone was removed in less than 20 min if ozone was applied, regardless of the presence or absence of light and catalyst. However, reactivity tests show a synergism effect between photocatalysis and ozonation for mineralization purposes. The combination of ozone and GO improved the activation of TiO2 under visible light. Process optimization led us to select a catalyst dosage of 0.25 g L-1, a light radiance of 359 W m-2 and a GO loading in the catalyst around 0.75%. At these conditions, with photocatalytic ozonation, the presence of GO in the catalyst improved mineralization up to 82% in 2 h compared to 70% reached with bare TiO2. Catalyst reusability shows no decrease of photocatalytic activity. Scavenger tests point to hydroxyl radicals as the main species responsible for Primidone removal.

Synthesis of the BIVO4 nanoparticle as an efficient photocatalyst to activate hydrogen peroxide for the degradation of methylene blue under visible light irradiation

In this study, we investigated the synthesis of BiVO4 nanoparticles via the hydrothermal method and their photocatalytic activity for the degradation of methylene blue (MB) under LED visible light mediated by H2O2. The obtained BiVO4 catalyst was characterized by XRD, Raman, SEM, and UV-vis DRS. The effect of H2O2 concentrate, pH, and MB initial concentration on the removal rate of MB was carefully studied. The results showed that MB was decolorized entirely after 30 min in the BiVO4/H2O2/Vis process whereas the decomposition rate of BiVO4 with the absence of H2O2 is 78% after 60 min. The accelerated degradation of MB by in the BiVO4/H2O2/Vis process is due to H2O2 acts as the external electron acceptor, which could promote the separation of photo-induced electrons and holes.

Improved Reactor Productivity for the Safe Photo‐Oxidation of Citronellol Under Visible Light LED Irradiation

AbstractA simple continuous flow photochemical reactor was optimized for the safe photo‐oxidation of citronellol into precursors of rose oxide, a flagrance of commercial value. The reactor productivity was increased by a factor of 4 compared to the current literature for a conversion above 99 % and in safe conditions (up to 0.72 mM min−1 mLreactor−1). The reactor was based on a classical design described by Booker‐Milburn et al., i. e. multiple loops of perfluoroalkoxy (PFA) tubing wrapped tightly around a visible LED lamp under slug flow conditions. The influence of the type of visible white LED light (6500 K vs. 3000 K), of photosensitizers (tetraphenylporphyrin vs. methylene blue), of solvent (CH2Cl2 vs. MeOH), concentration of citronellol (0.1 M vs. 2 M) and of mass efficiency of the reactors (PFA tubing of 0.75 mm to 0.25 mm) was paramount to increase the productivity of the reactor.

A magnetic ZnFe2O4/ZnO/perlite nanocomposite for photocatalytic degradation of organic pollutants under LED visible light irradiation

New magnetically ZnFe2O4/ZnO/perlite nanocomposites with different molar ratios were successfully synthesized. The as-prepared samples were characterized physically and chemically using Fourier-transform infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), scanning electron microscopy imaging (SEM), energy-dispersive X-ray spectroscopy (EDX), vibrating sample magnetometer (VSM) and diffuse reflectance spectroscopy (DRS). ZnFe2O4/ZnO/perlite nanocomposites were explored for their photocatalytic performance by the decomposition of methylene blue (MB) and 4-nitrophenol (4-NP) under visible LED light radiation. This experiment indicated that nanocomposite with a molar ratio of 2:1 ZnFe2O4:ZnO on perlite showed the highest photocatalytic activity and degraded 97 and 67% of MB (20 mgL−1) and 4-NP (10 mgL−1) aqueous solutions within 150 min, respectively. The enhanced photocatalytic activity of this composite ascribed to the efficient separation of photoinduced electrons and holes. In addition, it can be separated easily by an external magnet and reused twice more.

Investigation of Characteristics of Human’s Warm Sensation Heated by Visible Light LEDs

Investigation of Characteristics of Human’s Warm Sensation Heated by Visible Light LEDs

One-step green conversion of benzyl bromide to aldehydes on NaOH-modified g-C3N4 with dioxygen under LED visible light

NaOH-modified g-C3N4 facilitates a green and sustainable route for the oxidation of benzyl bromide to benzaldehyde with 99% conversion.

Smart Farming using IoT, a solution for optimally monitoring farming conditions

Internet of Things (IoT) is present and future of every field impacting everyone’s life by making everything intelligent. It is a network of different devices which make a self-configuring network. The new developments of Smart Farming with use of IoT, by day turning the face of conventional agriculture methods by not only making it optimal but also making it cost efficient for farmers and reducing crop wastage. The aim is to propose a technology which can generate messages on different platforms to notify farmers. The product will assist farmers by getting live data (Temperature, humidity, soil moisture, UV index, IR) from the farmland to take necessary steps to enable them to do smart farming by also increasing their crop yields and saving resources (water, fertilizers). The product proposed in this paper uses ESP32s Node MCU, breadboard, DHT11 Temperature and Humidity Sensor, Soil Moisture Sensor, SI1145 Digital UV Index / IR / Visible Light Sensor, Jumper wires, LEDs and live data feed can be monitored on serial monitor and Blynk mobile. This will allow farmer to manage their crop with new age in farming.