Novel 0D/1D ZnBi2O4/ZnO S-scheme photocatalyst for hydrogen production and BPA removal

Developing interfacial connections is one of the breakthrough strategies to improve the photocatalytic activity. Herein, ZnBi₂O₄ nanoparticles-ZnO nanorods heterojunction was successfully synthesized and used, as a dual-function photocatalyst, for photocatalytic degradation of Bisphenol A and hydrogen production with improved photocatalytic activity under simulated sunlight irradiation. The highest H₂ production (3.44 mmol g^?1 h^?1) was obtained for ZnO-20 wt% ZnBi₂O₄ sample, which is around 12.7 times higher than pure ZnO. According to the HRTEM result, the intimate interfacial connections are formed between ZnO and ZnBi₂O₄ which could act as trapping centers for charge carriers and results in the boosted photocatalytic activity. Further, a high aspect ratio of 1D ZnO nanorods and small size of 0D ZnBi₂O₄ nanoparticles (~10 nm) increases the number of interfacial contacts and thus the charge carriers’ recombination was suppressed more efficiently. Based on the trapping experiments, ESR and Mott-Schottky analysis, ZnBi₂O₄–ZnO hybrid photocatalyst followed the S-scheme charge transfer mechanism.     

Visualization of Heat Transport during Natural Convection Within Porous Triangular Cavities via Heatline Approach

In this article, natural convection in a porous triangular cavity has been analyzed. Bejan's heatlines concept has been used for visualization of heat transfer. Penalty finite-element method with biquadratic elements is used to solve the nondimensional governing equations for the triangular cavity involving hot inclined walls and cold top wall. The numerical solutions are studied in terms of isotherms, streamlines, heatlines, and local and average Nusselt numbers for a wide range of parameters Da (10^?5–10^?3), Pr (0.015–1000), and Ra (Ra = 10³–5 × 10⁵). For low Darcy number (Da = 10^?5), the heat transfer occurs due to conduction as the heatlines are smooth and orthogonal to the isotherms. As the Rayleigh number increases, conduction dominant mode changes into convection dominant mode for Da = 10^?3, and the critical Rayleigh number corresponding to the on-set of convection is obtained. Distribution of heatlines illustrate that most of the heat transport for a low Darcy number (Da = 10^?5) occurs from the top region of hot inclined walls to the cold top wall, whereas heat transfer is more from the bottom region of hot inclined walls to the cold top wall for a high Darcy number (Da = 10^?3). Interesting features of streamlines and heatlines are discussed for lower and higher Prandtl numbers. Heat transfer analysis is obtained in terms of local and average Nusselt numbers (Nu _l , Nu _t ) and the local and average Nusselt numbers are found to be correlated with heatline patterns within the cavity.     

Experimental Investigations of Pool Boiling Heat Transfer Characteristics on a Vertical Surface Using CuO Nanoparticles in Distilled Water

Experiments were conducted on pool boiling heat transfer using dilute dispersions of CuO nanoparticles in distilled water at and above atmospheric pressure. Pool boiling characteristics of CuO nanofluid were studied at different pressures and concentrations. Characterization of the heating surface was done both qualitatively and quantitatively by taking the scanning electron microscopy (SEM) images and by subsequent measurement of surface roughness of the heater. SEM images of the heater surface showed nanoparticle deposition on the heater surface, suggesting surface modification. Thorough visualization showed microcavities on the heater surface, which provide an excellent location for nucleation sites enhancing heat transfer. However, these microcavities, once filled up with the suspended nanoparticles, reduced active nucleation sites, deteriorating the boiling heat transfer coefficient. Based on the experimental investigations it was concluded that there is an optimum thickness of nanoparticles coating at which heat flux is maximum and beyond this coating boiling heat transfer coefficient decreases. At higher pressures, boiling heat transfer coefficient and specific excess temperature remained nearly the same. This showed that pressure has negligible or no role to play in boiling heat transfer using nanofluids.     

Investigations on the parameters limiting the performance of CdS/SnS solar cell

Debutant analysis of the parameters impeding the efficiency of the CdS/SnS‐based photovoltaic device is the chief novelty of the present report. We have developed thin‐film heterojunction solar cells with the stacking sequence: glass/Al‐doped ZnO/CdS/SnS/In. The two crucial issues, band offsets and cell studies, are discussed in detail. The band offsets at the CdS/SnS interface have been systematically evaluated by semidirect X‐ray photoelectron spectroscopy. The calculated valance band offset (ΔE_v) and conduction band offsets (ΔE_c) are found to be 1.46 and ?0.36 eV, respectively. The negative value of conduction band offset indicates that the junction formed is of type‐II (staggered‐type heterojunction). Electrical studies revealed power conversion efficiency of 0.32% with V_OC, J_SC, and fill factor as 170.61 mV, 7.26 mA/cm², and 0.26, respectively. The impact of the offset values on the cell studies is clearly elucidated. The reasons for the low efficiency are spotlighted. Collectively, this article gives the overview of the systematic approach undertaken to get obvious picture about the barriers that limit the conversion efficiency of the CdS/SnS‐based solar cell and the measurements required for enhancing the efficiency of the SnS‐based solar device.     

Sensitivity of Listeria monocytogenes Scott A to Nisin and Diacetyl after Starvation in Sodium Phosphate Buffered Saline

ABSTRACT:  This study determined the effectiveness of nisin and diacetyl to inhibit the growth of  Listeria monocytogenes  (Lm) under normal cell cultivation and starvation conditions in sodium phosphate buffered saline (SPBS). Inhibitory effects of nisin at 320 or 1000 AU/mL or diacetyl at 0.25%, 0.50%, or 1.0% and combinations on Lm in brain heart infusion (BHI), SPBS, and potassium phosphate buffered saline (KPBS) were determined on BHIA (nonselective medium) and PALCAM (selective medium) agar at 0 and 2 h posttreatment after 0, 7, 14, and 21 d of starvation. Two-hour exposure to 1000 AU/mL nisin and 1% diacetyl gave 8 to 9 log CFU/mL reductions of nonstarved control cells regardless of plating medium after suspension in BHI, SPBS, or KPBS with inhibitors, but with 7 d starved cells a 2-h exposure reduced Lm levels to less than the detection limit (20 CFU/mL). Cells starved in SPBS for 14 or 21 d then suspended in BHI plus inhibitors were reduced 5 to 6 log CFU/mL. SPBS suspensions on days 14 and 21 were reduced 4 log CFU/mL and 2 to 3 log CFU/mL, respectively, on BHI media and 5 to 6 log CFU/mL and 2 to 3 log CFU/mL on PALCAM. Recovery was the same regardless of plating medium, indicating treated cells were killed and not merely injured by the nisin and diacetyl treatments. This study showed that nisin and diacetyl combinations were more effective on Lm than when either chemical was used separately in BHI, SPBS, or KPBS. Lm cells starved for 14 or more days were much more resistant to the nisin and diacetyl combinations than were nonstarved control cells.     

Reduction of Listeria monocytogenes in Raw Catfish Fillets by Essential Oils and Phenolic Constituent Carvacrol

The antimicrobial activity of various essential oils and carvacrol was determined on fresh raw catfish fillets against a 4-strain Listeria monocytogenes mixture representing serotypes 1/2b, 3b, 4b, and 4c that were predominantly isolated from catfish processing environments. Thyme oil, oregano oil and carvacrol exhibited concentration and time dependent responses in broth against L. monocytogenes; for example 0.5% concentrations resulted in 4 log CFU/mL reduction within 30 min whereas 0.1% concentrations required more than 24 h for the same level of reduction. Lemon, orange, and tangerine oils, at 0.5% showed listeriostatic effect in which 4 log CFU/mL of the initial L. monocytogenes load was unchanged at 4 °C in 10 d whereas 1% concentrations were listericidal in a time dependent manner. Apart from carvacrol, efficacy of tested essential oils in reducing L. monocytogenes and total microbial load from catfish fillet was very limited. Dipping treatment of catfish fillets in 2% carvacrol solution for 30 min at 4 °C reduced L. monocytogenes to an undetectable level from their initial load of 5 log CFU/g and reduced total microbial load from catfish fillets by approximately 5 log CFU/g. In sensory analysis trained panelist preferred control samples over 2% carvacrol treated samples implying potential limitation in applicability of carvacrol for fillet treatments.     

Rheological behavior of syrups containing sugar substitutes

The rheological properties of syrups prepared using bulk sweeteners such as sorbitol and bulking agents like maltodextrin and polydextrose along with aspartame were studied. The apparent viscosity, consistency index, yield stress, and flow behavior index were determined from the shear stress versus shear rate data. The Herschel–Bulkley model was found to adequately describe the flow behavior of the syrups. The activation energy for all the syrups at different concentrations was determined from the Arrhenius equation. The yield stress, flow behavior index, and consistency index were dependent on the temperature and concentration of the syrups. The apparent viscosity increased from 8.8 to 129 mPa·s for sugar and sorbitol syrups, respectively, over the concentration range from 35 to 65%. In general, the rheological characteristic of sorbitol syrup was similar to that of sugar syrup, while syrups made with polydextrose and its mixture with maltodextrin were significantly different from those of sugar syrup.     

Continuous Synthesis of Glucoamylase by Immobilized Fungal Mycelium of Aspergillus niger

The extracellular glucoamylase enzyme (EC 3.2.1.3) was synthesized continuously by the immobilized mycelial fragments of A. niger. Of the several polymeric matrices attempted for immobilization k-carrageenan and alginate were found to be the most effective. However, the enzyme activity exhibited by the immobilized mycelia (I.M.) was 15-20% lower than that of free cells under batch conditions. The immobilized cells have retained nearly the same enzymatic activity (120IU/g of I.M.) for 6 repeated batches and thereafter decline in activity was noticed. An aerated packed bed reactor with I.M. was operated continuously for 360 h. The volumetric productivity of the reactor was 1600IU/L/h for 192 h and reduced to 25% in 360 h.     

Development of an Alternate Route for the Hydrolysis of Cassava Flour

Moldy wheat bran as such is used as a source of amyloglucosidase enzyme (EC 3.2.1.3) in the hydrolysis of cassava flour. 92–94% of glucose was obtained in the hydrolysate after 16 h of hydrolysis. The process was found to be economical compared to the hydrolysis using commercially available liquid enzymes.