Search

Synthetic dyes are widely used in various industries, which inevitably leads to increased water pollution. One of the recognized and waste-free techniques for water treatment is photocatalytic purification using semiconductor nanoparticles. However, the debate on how photocatalytic properties can be tuned through structural and morphological parameters using nanoparticle synthesis procedures remains open. In the present work, an approach to regulate UV-light-driven photocatalytic activity of spherical SnO2 nanoparticles using different structural parameters is demonstrated for the first time. Complex characterization of nanoparticles was provided using physicochemical methods with the help of computational methods. Special attention was paid to the development of a protocol of oxygen vacancy accounting within computer calculations for more realistic modeling of the interaction energy between nanoparticle surfaces and organic dye molecules of different natures. The photocatalysis mechanism was investigated according to the developed protocol, including the study of dye mixture kinetic degradation, dye-photocatalyst complex formation, and the ratio of oxygen vacancies and defects. It was shown that 93% of single dye decomposed in 7 min, and degradation of the dye mixture in a real water sample from Neva River achieved 60% after 40 min. It was possible to establish that this proof-of-concept study based on the combination of experimental and computational approaches can help develop the strategy of the rational design of photocatalysts promising for purification of real water samples. [ABSTRACT FROM AUTHOR]

The design of efficient photocatalysts for dye degradation is a challenging task for the scientific community. Semiconductor-based photocatalysts such as g-C3N4 and oxides, utilizing solar energy, have been proven to be effective and promising approaches to resolve this issue to some extent. Constructing Z-scheme heterostructures by coupling g-C3N4 with suitable oxide semiconductors has shown substantial enhancement of the photocatalytic performance. In this article, perovskite-type CeMnO3 (5, 15, 25%) nanoparticle-decorated g-C3N4 nanosheets are fabricated as heterostructures, using a hydrothermal synthesis process, for efficient photocatalysis of organic dyes. The formations of heterostructures are confirmed through structural, microstructural, and elemental state analysis. Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) characterization techniques exhibited enhanced surface area and pore sizes, respectively. Ultraviolet–visible (UV–vis) diffuse reflectance spectroscopy (DRS), Mott–Schottky, and linear sweep voltammetry (LSV) analyses along with density functional theory (DFT) calculations predicted a p–n junction heterostructure. Electron paramagnetic resonance (EPR) studies revealed a broad spectrum with sextet hyperfine lines corresponding to Mn4+ and Mn2+ ions and enhanced intensity as compared to the parent ones, signifying the creation of oxygen vacancies in the heterostructure. The CeMnO3 (25 wt %)/g-C3N4 heterostructure showed highly efficient photocatalytic degradation of methylene blue under direct sunlight irradiation, with up to 99% degradation achieved in 120 min and excellent recyclability. The robustness of this photocatalyst was tested by adopting a similar process for methylene orange dye degradation, exhibiting 94% yield in 120 min. A tentative degradation mechanism is proposed based on the enhanced photodegradation efficiency and results obtained from electrochemical impedance (EIS), photoluminescence (PL), LSV, and first principal studies, which provides more insights into the photogenerated charge separation, enhanced photocurrent, and interfacial transfer efficiency through the Z-scheme charge transfer process. This study offers opportunities for designing high-performance Z-scheme hybrid photocatalysts for environmental remediation. [ABSTRACT FROM AUTHOR]

Organic dyes in wastewater jeopardize aquatic ecosystems and biodiversity, besides having several concerns of health hazards. Nanostructured materials of controlled textural features with active surface functionalities are gaining immense interest as effective adsorbents for wastewater treatment. The present work addresses a facile approach to synthesize fibrous aerogel-templated nanostructured boron carbon oxynitride (BCNO). The surface functionalities, structural heterogeneity, crystalline phases, and morphological features of BCNO are probed by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Raman, X-ray diffraction, and high-resolution transmission electron microscopy analyses. The nanostructured BCNO showed preferential and remarkably high adsorption of cationic dyes with a removal capacity of 1258 mg g–1 for malachite green (MG) dye. The adsorption of MG dye by nanostructured BCNO is carried out at different pH, ionic strength, and temperature to emphasize the influence of environmental factors. The spectroscopic analyses suggested multiple adsorption pathways, viz. electrostatic, π–π, hydrogen, and Lewis acid–base interactions for unprecedentedly higher adsorption of cationic dyes by BCNO. Batch-mode findings promise the potential of nanostructured BCNO for wastewater treatment applications. [ABSTRACT FROM AUTHOR]

Single dyes typically exhibit limited light absorption in dye-sensitized solar cells (DSSCs). Thus, cosensitization using two or more dyes to enhance light-harvesting efficiency has been explored; however, the aggregation of dyes can adversely affect electron injection capabilities. This study focused on the design and synthesis of three dyes with a common carbazole donor for DSSCs: DZ102 , TZ101 , and JM102 . JM102 broadens the absorption spectrum by replacing the benzoic acid electron acceptor of TZ101 with acetylenic benzoic acid. A cosensitized DSSC device based on CO-1 [ DZ102 : TZ101 = 1:1 (50 μM:50 μM)] achieved a short-circuit current density of 19.4 mA/cm 2 and a power conversion efficiency of 10.9%. For the first time, the molecular interactions between the dyes in the photoanode were demonstrated using cyclic voltammetry, which revealed the presence of intermolecular forces. Adsorption kinetics further indicated that these forces promoted the self-assembly of dyes during adsorption, which resulted in a cosensitization adsorption amount greater than the sum of the individual dye adsorptions. This study provides novel insights into the selection of cosensitizing dyes for DSSCs.

The same carbon-based nanomaterials have shown their potential photocatalytic applications toward environmental and energy-related problems based on their excellent light absorption abilities. Herein, we summarized the findings associated with visible light and sunlight-induced photocatalysis, specifically using carbon dots (CD), doped-CD, and their nanocomposite as an advanced photocatalytic material. Doped-CD and CD-based composite have improved light absorption abilities compared to bare CD, which is the essential parameter for photocatalysis applications. Various parameters, such as fabrication methodologies, efficiency, and stability, have also been discussed. The possible mechanistic insights involving the photocatalysis method applied in multiple chemical reactions have been discussed in detail, including degradation of organic dye, reduction of higher toxic oxidation states of metal ions, CO2 conversion, water splitting, organic transformation reaction, and NOx removal, etc. [ABSTRACT FROM AUTHOR]

Adsorption is a promising technique for the effective removal of dyes from dyeing wastewater resulting from the paper, textile, and leather industries. Herein, we report a facile strategy for preparing adsorption membrane-based aminated ultrathin polyacrylonitrile (UPAN-N) nanofibers to effectively remove the synthetic dyes from wastewater. The UPAN-N nanofibers were synthesized using a mixed solution electrospinning procedure, followed by triethylenetetramine modification. After the amino modification, the surface of the obtained UPAN-N nanofiber membrane is rich in amino groups, which endows the resulting membrane with an ultrahigh adsorption capacity of more than 1800 mg/g for the organic dye DR23 and a rapid adsorption rate for DR23 solutions with the concentrations ranging from 20 to 100 mg/L. This work not only provides a feasible method for the preparation of high-capacity adsorbents but also offers the possibility of preparing nanofibers by a mixed solution electrospinning procedure. [ABSTRACT FROM AUTHOR]

Iron single-atom catalysts (Fe SACs) hold great promise for peroxymonosulfate (PMS) activation and degradation of organic pollutants in wastewater. However, insights into crucial catalytic sites and activation mechanisms of biochar-based Fe SACs for PMS remain a challenge. Herein, cotton stalk-derived biochar-based Fe SACs (Fe SACs-BC) with an asymmetric Fe-N/O-C configuration were prepared, and their PMS activation and acid orange 7 (AO7) degradation mechanisms were investigated. The results showed that the removal efficiency of the Fe SACs-BC catalyst with Fe-N 3 O-C configuration for AO7 and other five investigated organic dyes reached 95-99% within 15 min. The EPR spectrums, quenching experiments, electrochemical analysis, masking experiments, XPS, and theoretical calculations indicated that degradations of organic dyes were dominated by singlet oxygen, which was generated by direct PMS conversion at the electron-deficient carbon and iron sites in the Fe-N 3 O-C configuration. The Fe SACs-BC/PMS exhibited high removal efficiency and strong tolerance in different water matrices with a wide pH range, various coexisting anions and interfering substances, showing great potential and applicability for efficient treatment of actual textile wastewaters.

Historically, two-photon absorption (2PA) cross sections reported in the literature have been derived from solution-phase measurements. However, such techniques fail to grasp the implications of how these cross sections can be impacted by varying degrees of aggregation or in the condensed phase as bulk solids or thin films. For a precise determination of how aggregation impacts 2PA at a molecular level, computational methods present themselves as ideal. Herein, a series of quadrupolar π-conjugated dyes were simulated by molecular dynamics (MD) in the gas phase and condensed phase. In the condensed phase, their intermolecular interactions and electronic coupling behavior were fully characterized, both quantitatively and qualitatively. Using quadratic-response time-dependent density functional theory, 2PA cross sections of structures derived from MD trajectories were calculated. Comparisons are made between gas-phase and condensed-phase results, and enhancement factors are defined to show how certain dyes may experience changes in their respective 2PA cross sections as a function of aggregation. It was found that these cross sections depend heavily on conformational locking in the condensed phase and relative stacking arrangements. J-aggregates were associated with enhanced 2PA and H-aggregates with quenched 2PA activity. However, in a highly disordered aggregate, the effects of these stacking arrangements are averaged out of the bulk result, and the effects of conformational locking dominate.