Visible light photocatalytic reduction of 4-Nitrophenol using CdS in the presence of Na2SO3

B and N Codoped Cellulose-Supported Ag-/Bi-Doped Mo(S,O)3 Trimetallic Sulfo-Oxide Catalyst for Photocatalytic H2 Evolution Reaction and 4-Nitrophenol Reduction

Cellulose plays a significant role in designing efficient and stable cellulose-based metallic catalysts, owing to its surface functionalities. Its hydroxyl groups are used as anchor sites for the nucleation and growth of metallic nanoparticles and, as a result, improve the stability and catalytic activity. Meanwhile, cellulose is also amenable to surface modifications to be more suitable for incorporating and stabilizing metallic nanoparticles. Herein, the Ag-/Bi-doped Mo(S,O)3 trimetallic sulfo-oxide anchored on B and N codoped cellulose (B-N-C) synthesized by a facile approach showed excellent stability and catalytic activity for PHER at 573.28 μmol/h H2 with 25 mg of catalyst under visible light, and 92.3% of the 4-nitrophenol (4-NP) reduction was achieved within 135 min by in situ-generated protons. In addition to B and N codoping, our use of the calcination method for B-N-C preparation further increases the structural disorders and defects, which act as anchoring sites for Ag-/Bi-doped Mo(S,O)3 nanoparticles. The Ag-/Bi-doped Mo(S,O)3@B-N-C surface active site also stimulates H2O molecule adsorption and activation kinetics and reduces the photogenerated charge carrier's recombination rate. The Mo4+ → Mo6+ electron hopping transport and the O 2p and Bi 6s orbital overlap facilitate the fast electron transfer by enhancing the electron's lifetime and photoinduced charge carrier mobility, respectively. In addition to acting as a support, B-N-C provides a highly conductive network that enhances charge transport, and the relocated electron in B-N-C activates the H2O molecule, which enables Ag-/Bi-doped Mo(S,O)3@B-N-C to have appreciable PHER performance.

Green synthesis of ZnO nanoparticles and comparison of 2,4-dinitrophenol removal efficiency using photocatalytic, sonocatalytic, and adsorption processes

In the present work, the extract of a paper-flower species called Bougainvillea spectabilis was used to green synthesis of ZnO nanoparticles (NPs). The synthesized ZnO NPs was confirmed by XRD, SEM, TEM, EDS, and FTIR techniques. Then, the ability of ZnO NPs to remove 2,4-dinitrophenol from aqueous solutions was investigated using photocatalytic and sonocatalytic processes. All experiments were carried out in a batch system and the effects of pH, NPs dosage, concentration, and contact time were evaluated. The findings of this study showed that the pseudo-second-order kinetic model could well describe the removal of 2,4-dinitrophenol by ZnO NPs. Langmuir, Freundlich, Temkin, and BE-T isotherm models were also assessed in a dark condition. The Freundlich isotherm model was able to provide the best fit with the experimental data. Examination of the results showed that the degradation of 2,4-dinitrophenol at the presence of ultraviolet (UV) and ultrasonic (US) waves was able to increase the removal efficiency to about twice as much as removal by adsorption alone. Also, The obtained results showed that the maximum removal of 2,4-dinitrophenol under photocatalytic and sonocatalytic conditions occurred at the presence of 25 mg of NPs, solution pH of 4, and 2,4-dinitrophenol concentration of 20 ppm. The best rates of photocatalytic and sonocatalytic degradation under the optimal conditions were 84.42% and 77.13% during 60 min, respectively. Thermodynamic studies indicated that the degradation of 2,4-dinitrophenol by ZnO NPs is a spontaneous and endothermic process in the direction of increasing entropy. The zinc oxide NPs have better performance in the removal of 2,4-dinitrophenol at the presence of UV and US waves.

Highly Efficient Simulated Solar Light-Driven Photocatalytic Degradation of 4-Nitrophenol over CdS/Carbon/MoSx Hybrids

Among the various organic pollutants and industrial chemicals, 4-nitrophenol has been one of the most monitored substances in aqueous environments, due to its enhanced solubility in such systems. This research reports for the first time the microwave-assisted synthesis of CdS/carbon/MoS_x hybrids and the subsequent utilization of such systems as photocatalysts for 4-nitrophenol degradation. The hybrids demonstrated a variable photocatalytic activity, by using a variety of organic substances as precursors for the solvothermal carbonization step. By using ascorbic acid as precursor, the corresponding ternary composite exhibited excellent photocatalytic activity, with the 4-nitrophenol concentration been almost quantitatively decayed within 45 min of irradiation. This could be ascribed due to the generation of a high population of heterojunctions as well as the chemical speciation of Mo-based nanostructures. Such ternary hybrids may be utilized as potential photocatalytic systems in processes, where removal of toxic water-soluble substances is the key issue.

New insights into the role of sulfite in BiOX photocatalytic pollutants elimination: In-operando generation of plasmonic Bi metal and oxygen vacancies

Photocatalysis has been regarded as a sustainable strategy for wastewaters remediation, and sulfite addition could significantly accelerate the photocatalytic performances. However, the related mechanisms are still not well understood. Here, we for the first time found that plasmonic Bi and oxygen vacancies were in-operando generated on BiOX (X = Cl, Br, I) in the presence of sulfite under light irradiation. The oxidative degradation rate constants of 4-nitrophenol, bisphenol A, and phenol were improved by about 11.5, 4.7, and 12.2 times on BiOBr and 9.1, 1.6, and 3.1 times on BiOCl with addition of 5 mM sulfite, while the photocatalytic reduction rate of 4-nitrophenol to 4-aminophenol was promoted by approximate 31.7 times on BiOI. The results indicated that sulfite could improve the photooxidation ability of BiOBr and BiOCl and the photoreduction performance of BiOI, resulted from the improved light absorption and separation of photogenerated charge carriers. This work can provide exploratory platforms for understanding and maximizing the sulfite-assisted BiOX photocatalysis.

CdS quantum dots-decorated InOOH: Facile synthesis and excellent photocatalytic activity under visible light

For the first time, CdS quantum dots (QDs)-decorated InOOH (CdS-In for short) was synthesized by a facile photodeposition method. The experiment results showed that CdS-In samples exhibited excellent activity and stability towards photocatalytic reduction of nitro aromatics. The conversion ratio of 4-nitroaniline (4-NA) over CdS-In sample that was prepared with photodeposition time of 120 min (CdS-In-120) reached up to 99.4% under visible light irradiation for 40 min, which was even higher than that achieved over commercial CdS (86.2%). Besides the significant enhancement of visible light absorption, quantum sized CdS were decorated evenly on the surface of InOOH, which was very beneficial for the high activity. Furthermore, the heterogeneous junction formed at the interface of CdS QDs and InOOH can significantly increase the separation efficiency of photogenerated charge carriers. Active species control experiment and electron spin resonance (ESR) technique have proved that photogenerated electrons are the main active species towards photocatalytic reduction of nitro aromatics. It is anticipated that our study would offer meaningful insights for exploring novel InOOH-based visible light photocatalysts towards efficient reduction of nitro aromatics.

Single source precursor synthesized CuS nanoparticles for NIR phototherapy of cancer and photodegradation of organic carcinogen

Herein, we report cost effective and body compatible CuS nanoparticles (NPs) derived from a single source precursor as photothermal agent for healing deep cancer and photocatalytic remediation of organic carcinogens. These NPs efficiently kill MCF7 cells (both in vivo and in vitro) under NIR irradiation by raising the temperature of tumor cells. Such materials can be used for the treatment of deep cancer as they can produce a heating effect using high wavelength and deeply penetrating NIR radiation. Furthermore, CuS NPs under solar light irradiation efficiently convert p-nitrophenol (PNP), an environmental carcinogen, to p-aminophenol (PAP) of pharmaceutical implication. In a nutshell, CuS can be used for the treatment of deep cancer and for the remediation of carcinogenic pollutants. There seems an intrinsic connection between the two functions of CuS NPs that need to be explored in length.

Boosting photocatalytic chlorophenols remediation with addition of sulfite and mechanism investigation by in-situ DRIFTs

Sulfite is recently found to be promising in enhancing photocatalytic pollutants degradation, which is a byproduct from flue gas desulfuration process. Herein, 4-chlorophenol (4-CP) photodegradation was systematically investigated in a sulfite mediated system with g-C₃N₄ as photocatalyst. The degradation efficacy was improved by about 3 times with addition of 25 mM Na₂SO₃. The dominant responsible reactive oxygen species for chlorophenols remediation in the presence of sulfite included O₂^·-, SO₃^·-, and SO₄^·- as confirmed by radical quenching experiments and electron spin resonances technology. In-situ DRIFTs results indicated the improved cleavage of CCl and CH bonds with the simultaneous formation of CO and CC bonds when bisulfite was added. Degradation intermediates such as 4-chlorocatechol, hydroquinone, and muconic acid were detected by HPLC-MS. Furthermore, the photodegradation mechanisms of 4-CP were tentatively discussed . Other chlorophenols (phenol, 2-CP, 2,4-DCP, and their mixture) were also efficiently removed in the system, suggesting that sulfite could be universally applied in photocatalytic wastewater purification.

Ultrasound-accelerated synthesis of uniform DyVO4 nanoparticles as high activity visible-light-driven photocatalyst

In order to obtain a highly efficient photocatalyst for water treatment, the sonochemical procedure applied to fabrication of excellent DyVO₄ nanoparticles. A comparative study between two different synthesis routes (precipitation and sonochemical) was investigated in this work. Also, the influence of anionic, cationic and nonionic surfactant was studied on the formation of uniform particles. Further, the photocatalytic performance over the DyVO₄ nanoparticles was studied under visible light by modifying the operational variables. Investigation of the photocatalytic mechanism process was conducted using hole scavengers for capturing reactive species. It was found that the DyVO₄ nanoparticles sonochemically (a ultrasound probe with power of 60 W (18 KHz)) synthesized in presence of CTAB as an optimum condition, are uniform with average size of ~24 nm. The results showed that DyVO₄ could remove near 88% of erythrosine, under the optimum condition of 0.05 g catalyst dosage and at initial pH 4. The DyVO₄ maintained relatively high stability and reusability removal for erythrosine after five repeated cycles. The results could provide effective functional materials for elimination of chemical contaminants from wastewater through the photocatalytic process.

Enhanced photocatalysis and biomolecular sensing with field-activated nanotube-nanoparticle templates

The development of new catalysts for oxidation reactions is of central importance for many industrial processes. Plasmonic catalysis involves photoexcitation of templates/chips to drive and enhance oxidation of target molecules. Raman-based sensing of target molecules can also be enhanced by these templates. This provides motivation for the rational design, characterization, and experimental demonstration of effective template nanostructures. In this paper, we report on a template comprising silver nanoparticles on aligned peptide nanotubes, contacted with a microfabricated chip in a dry environment. Efficient plasmonic catalysis for oxidation of molecules such as p-aminothiophenol results from facile trans-template charge transfer, activated and controlled by application of an electric field. Raman detection of biomolecules such as glucose and nucleobases are also dramatically enhanced by the template. A reduced quantum mechanical model is formulated, comprising a minimum description of key components. Calculated nanotube-metal-molecule charge transfer is used to understand the catalytic mechanism and shows this system is well-optimized.

Plasmonic nanomaterials offer new frontiers as photocatalysis and sensor materials, yet elucidating factors controlling each is a challenge. Here, authors examine the role of electric fields in photocatalysis and biomolecule sensing abilities of peptide-nanotubesupported silver nanoparticles.

R. S, Nair BN, Karunakaran V, Mohamed AP, Warrier KGK, Hareesh US. A facile one pot synthetic approach for C3N4–ZnS composite interfaces as heterojunctions for sunlight-induced multifunctional photocatalytic applications

Herein, we report a facile one pot synthetic protocol for the creation of C₃N₄–ZnS composite interfaces by the co-pyrolysis of a precursor mix containing zinc nitrate, melamine, and thiourea at 550 °C in air.

Near-Infrared- and Visible-Light-Enhanced Metal-Free Catalytic Degradation of Organic Pollutants over Carbon-Dot-Based Carbocatalysts Synthesized from Biomass

Cost-efficient nanoparticle carbocatalysts composed of fluorescent carbon dots (CDs) embedded in carbon matrix were synthesized via one-step acid-assisted hydrothermal treatment (200 °C) of glucose. These as-synthesized CD-based carbocatalysts have excellent photoluminescence (PL) properties over a broad range of wavelengths and the external visible or NIR irradiation on the carbocatalysts could produce electrons to form electron-hole (e(-)-h(+)) pairs on the surface of carbocatalysts. These restant electron-hole pairs will react with the adsorbed oxidants/reducers on the surface of the CD-based carbocatalysts to produce active radicals for reduction of 4-nitrophenol and degradation of dye molecules. Moreover, the local temperature increase over CD-based carbocatalyst under NIR irradiation can enhance the electron transfer rate between the organic molecules and CD-based carbocatalysts, thus obviously increase the catalytic activity of the CD-based carbocatalyst for the reduction of 4-nitrophenol and the degradation of dye molecules. Such a type of CD-based carbocatalysts with excellent properties and highly efficient metal-free photocatalytic activities is an ideal candidate as photocatalysts for the reduction of organic pollutants under visible light and NIR radiation.

Synthesis of new ZnS–Bipy based hybrid organic–inorganic materials for photocatalytic reduction of 4-nitrophenol

4,4-Bipyridine ligand was attainted to react with ZnS surface forming ZnS–Bipy materials that are efficient catalysts for photoreduction of 4-nitrophenol.

Applications of a new type of poly(methyl methacrylate)/TiO2 nanocomposite as an antibacterial agent and a reducing photocatalyst

A new poly(methyl methacrylate)/TiO₂ nanocomposite film sensitized by an ionic liquid with a very low concentration of TiO₂ nanoparticles was fabricated and applied in the photoreduction of 4-nitrophenol and destruction of some bacteria.

Photo-synergistic promoted in situ generation of Bi0–BiSbO4 nanostructures as an efficient catalyst for nitrobenzene reduction

This work reports on the construction of Bi⁰–BiSbO₄ nanostructures to show photo-synergistic and efficient catalytic activity toward nitrobenzenes reduction.