Tuning the photocatalytic properties of sol–gel-derived single, coupled, and alloyed ZnO–TiO2 nanoparticles

International audienc

The zeta potential of laolin suspensions measured by electrophoresis and electroacoustics

Zeta potenciál zředěných a koncentrovaných kaolinových disperzí byl pozorován metodou elektroforézy a elektroakusticky. Vliv přídavku soli (KCl), a polymerního materiálu (Triton X-100) a anionického tenzidu (Sodium dodecylsulfátu, SDS) na vlastnosti suspenze byl studován elektroforetickými metodami. Elektroakustické metody byly použity pro měření zeta potenciálu pro nejvyšší možné koncentrace kaolinu v suspenzi a byl pozorován také vliv zřeďování. Vliv stárnutí čerstvě připravených vzorků a izoelektrický bod kaolinu byly také studovány. Použitím obou technik bylo zjištěno, že pro tento typ disperzí nebyl detegován izoelektrický bod, jenom maximum v hodnotě zeta potenciálu pro suspenzi kaolinu. Tato maxima byla pozorována také po přídavku Triton X-100 a SDS. Se zvyšující se koncentrací KCl a SDS ve vodní suspenzi se tato maxima posouvají více do kyselé oblasti, přičemž v přítomnosti Triton X-100 se poloha maxima zeta potenciálu nemění a zůstává konstantní. Elektroakustickými technikami bylo zjištěno, že čerstvě připravené koncentrované suspenze vyžadují kolem 6 hodin pro ustálení hodnoty zeta potenciálu. Zřeďování koncentrovaných suspenzí vedlo ke snížení zeta potenciálu tím, že ionty se vážou na desorbovaný povrch, čímž stlačují povrchový náboj. Maxima zeta potenciálu zůstala nezměněna také po zahřátí prášku v žíhací peci při teplotě 200°C (pro odstranění organických zbytků), což naznačuje nejmožnější vysvětlení vzniklých maxim jako důsledek izomorfní substituce.The zeta potentials of kaolin dilute and concentrated suspensions were monitored using the techniques of electrophoresis and electroacoustics, respectively. The effect of addition of salt (KCl), a polymer material (Triton X-100), and an anionic surfactant (sodium dodecyl sulphate, SDS) on the suspension properties was investigated by electrophoresis. Electroacoustics was employed for the measurement of zeta potentials for the highest possible kaolin content in suspension and the effect of dilution. The effect of aging of a freshly prepared sample and kaolin isoelectric point was also studied. Using both techniques it was noted that there was no isoelectric point, just a maximum value in the magnitude of the kaolin suspension zeta potential. These maxima were observed also in the presence of Triton X-100 and SDS. An increase of the concentration of KCl and SDS in suspension shifted the maxima towards more acidic values, while in the presence of Triton X-100 the position of the zeta potential maxima remained constant. Electroacoustic techniques revealed that a freshly prepared concentrated suspension requires about six hours to equilibrate to achieve a steady zeta potential. Diluting the concentrated suspensions led to decrease of the zeta potential as ions bound to the surface desorbed and screened the surface charge. The zeta potential maxima remained unchanged even after heating the powder in an oven at 200 degrees C (to remove any organic material) thereby suggesting that the most likely explanation for the maxima is isomorphic substitution

Chemical bath deposition of cerium doped BiVO4

The preparation of Ce doped BiVO4 coatings on glass, by the thermal treatment of aqueous solutions containing a bismuth (III) ethylenediaminetetra-acetate chelate, vanadium (V) and cerium (III) species, is described here. The influence of cerium content on the colour properties of the coating was investigated. The coatings consist on morphological well-defined particles forming dense monolayers

Cytotoxic constituents of Pachyrhizus tuberosus from Peruvian Amazon

Investigations into the chemical constituents of the seeds of the neglected tuber crop Pachyrhizus tuberosus (Leguminosae) resulted in the isolation of seven components: five rotenoids [12a-hydroxyerosone (1), 12a-hydroxydolineone (2), erosone (3), 12a-hydroxyrotenone (4) and rotenone (6)], a phenylfuranocoumarin [pachyrrhizine (5)] and an isoflavanone [neotenone (7)]. The compounds were isolated using several chromatography techniques and characterized and verified by NMR and HPLC/MS. The MTT assay was used to examine the selective cytotoxic effects of the methanolic P. tuberosus extract and isolated compounds in two human cancer cell lines [breast (MCF-7) and colorectal (HCT-116)] and in non-transformed human fibroblasts (MRC-5); IC50 values were calculated. The methanolic P. tuberosus extract displayed respectable cytotoxic effects against HCT-116 and MCF-7 cells with IC50 values of 7.3 and 6.3 mu g/mL, respectively. Of the compounds, 6 exacted greatest cytotoxicity and selectivity towards the cancer cell lines tested, yielding IC50 values of 0.3 mu g/mL against both MCF-7 and HCT-116 cells, and a 6-fold reduced activity against MRC-5 fibroblasts. Compound 4 also demonstrated cytotoxicity against MCF-7 and HCT-116 (1.1 and 1.8 mu g/mL, respectively), and reduced cytotoxicity towards MRC-5 cells (7.5 mu g/mL). The results revealed from the in vitro cytotoxic MTT assay are worthy of further antitumor investigation

Cytotoxic constituents of Pachyrhizus tuberosus from Peruvian Amazon

Investigations into the chemical constituents of the seeds of the neglected tuber crop Pachyrhizus tuberosus (Leguminosae) resulted in the isolation of seven components: five rotenoids [12a-hydroxyerosone (1), 12a-hydroxydolineone (2), erosone (3), 12a-hydroxyrotenone (4) and rotenone (6)], a phenylfuranocoumarin [pachyrrhizine (5)] and an isoflavanone [neotenone (7)]. The compounds were isolated using several chromatography techniques and characterized and verified by NMR and HPLC/MS. The MTT assay was used to examine the selective cytotoxic effects of the methanolic P. tuberosus extract and isolated compounds in two human cancer cell lines [breast (MCF-7) and colorectal (HCT-116)] and in non-transformed human fibroblasts (MRC-5); IC50 values were calculated. The methanolic P. tuberosus extract displayed respectable cytotoxic effects against HCT-116 and MCF-7 cells with IC50 values of 7.3 and 6.3 mu g/mL, respectively. Of the compounds, 6 exacted greatest cytotoxicity and selectivity towards the cancer cell lines tested, yielding IC50 values of 0.3 mu g/mL against both MCF-7 and HCT-116 cells, and a 6-fold reduced activity against MRC-5 fibroblasts. Compound 4 also demonstrated cytotoxicity against MCF-7 and HCT-116 (1.1 and 1.8 mu g/mL, respectively), and reduced cytotoxicity towards MRC-5 cells (7.5 mu g/mL). The results revealed from the in vitro cytotoxic MTT assay are worthy of further antitumor investigation