A facile two-step method was developed to prepare core/shell ZnO/rGO particles from ZIF-8/rGO composites. ZIF-8 particles were first grown at the surface of rGO sheets. Next, ZIF-8 particles were transformed into ZnO particles by thermal decomposition under air at 500 °C. All materials were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectroscopy, thermogravimetric analysis, and Brunauer–Emmett–Teller analyses. Results obtained show that ZIF-8 particles strongly associate with rGO sheets and that the calcination of this material produces porous core/shell ZnO/rGO particles with an average diameter of ca. 40 nm. The wt % of rGO associated with ZIF-8 particles was varied from 5 to 20%. The ZnO/rGO (10%) particles exhibit the highest photocatalytic activity for the degradation of the Orange II dye under simulated solar light irradiation of weak intensity (5 mW/cm 2 ). This high photocatalytic activity was demonstrated to originate from superoxide O 2 •– radicals due to the efficient trapping of photogenerated electrons in ZnO by rGO.

Alloyed CuInZnxS2+ x (ZCIS) quantum dots (QDs) were successfully associated to ZnO nanoparticles by a thermal treatment at 400 °C for 15 min. The ZnO/ZCIS composite was characterized by TEM, SEM, XRD, XPS and UV–vis absorption spectroscopy. ZCIS QDs, with an average diameter of ≈4.5 nm, were found to be homogeneously distributed at the surface of ZnO nanoparticles. ZCIS-sensitized ZnO nanoparticles exhibit a high photocatalytic activity under simulated solar light irradiation for the degradation of Orange II dye (>95% degradation after 180 min of irradiation at an intensity of 5 mW/cm2). The heterojunction built between the ZnO nanoparticle and ZCIS QDs not only extends the light adsorption range by the photocatalyst but also acts to decrease electron/hole recombination. Interestingly, the ZnO/ZCIS composite was found to produce increased amounts of H2O2 and singlet oxygen 1O2 compared to ZnO, suggesting that these reactive oxygen species play a key role in the photodegradation mechanism. The activity of the ZnO/ZCIS composite is retained at over 90% of its original value after ten successive photocatalytic runs, indicating its high stability and its potential for practical photocatalytic applications.

Luminescent materials become one of interesting issues for white LED-based lighting devices (WLEDs) due to their high performances for converting the monochromatic light from UV/blue LED chips into white light. Nevertheless, the availability of rare earth materials, the low color rendering index (CRI) and too-cold color temperature of the white LEDs remain some drawbacks to penetrate into the general LED lighting markets. Herein, we report the development of rare-earth-free luminescent nanocomposites combined with a UV/blue LED chip in order to provide white light. Gradient alloyed cadmium selenide/zinc sulfide (CdSe) x (ZnS)1–x and copper indium sulfide/zinc sulfide (CuInS2) x (ZnS)1–x quantum dots have been used to achieve the luminescent nanocomposite films in silicone as polymer matrix. The optical performances were investigated upon LED excitation. The photometric parameters of systems consisting of luminescent nanocomposites and LEDs including color rendering index (CRI), correlated color temperature (CCT), Commission Internationale de l’Eclairage (CIE) chromaticity coordinates, and luminous efficacy can be tuned by controlling the compositions and thickness of nanocomposite films. Furthermore, the thermal stability and the reliability of these luminescent nanocomposite films were investigated.

Among the possible solutions for the intensification of photocatalytic reactions, the use of microreactors is emerging. Such an approach was applied to the photodegradation of Ifosfamide in a flow microreactor with an immobilized catalyst composed of ZnO sensitized with CuInZnxS2+x quantum dots. The conversion yield at a low flow rate was investigated. A computational flow simulation allows to determine an apparent constant rate and the diffusion coefficient towards the photocatalyst surface. Photocatalytic degradation of Ifosfamide can be fitted by the Langmuir-Hinshelwood model. The Sherwood number and the average value of Damköhler show that the photocatalytic reaction under our experimental conditions is limited by the mass transfer.

This paper aims to evaluate the kinetics of hydroxylation for two distinct magnesias from Brazilian mineral sources regarding their purity: A -92.44wt% and B -98.20wt% of MgO. The magnesias were characterized and hydroxylated in a CSTR (1,0L) under: 80°C, stirring rate of 950rpm and 30%w/w of solids, in triplicate. The results showed that the presence of natural impurities in caustic magnesia (Fe, Mn, Al, Ca) hindered the advance of the reaction, but not at the beginning, when the hydroxylation was similar for both samples, what is associated with the similar values of their surface area. The reaction stabilization was observed after two hours for both samples: Sample A -35.15%; Sample B -46.43%. The natural impurities of caustic magnesia influenced the development of hydroxylation after 30 minutes, causing a retardant effect probably due to their behavior as a physical-chemical barrier, hindering the ions diffusion though the solid matrix.