Highly efficient NIR to NIR upconversion of ZnMoO4:Tm3+,Yb3+ phosphors and their application in biological imaging of deep tumors.

ZnMoO4:Tm3+,Yb3+,K+ nano-phosphors with intense NIR to NIR (excitation by 980 nm, emission at ∼800 nm) upconversion were synthesized by a facile hydrothermal method. The nanoparticles were of the order of 200-400 nm. The XRD patterns confirmed a single phase triclinic structure despite doping small amounts of RE3+ and alkali ions. The optimum concentration of Tm3+, Yb3+ and alkali ions were determined to be 0.1 mol%, 10 mol% and 10 mol%, respectively. Besides charge neutrality, the doped K+ ions affected the crystal field symmetry around the Tm3+ ions which increased the f-f transition probabilities of the RE3+ ions, and hence increased the UC intensities. Compared with ZnMoO4:Tm3+,Yb3+, the NIR to NIR upconversion emission intensity of 10 mol% K+ substituted ZnMoO4:Tm3+,Yb3+ nanocrystals increased by 21-fold and can be pumped by less than 1 mW laser power. The brightest ZnMoO4:Tm3+,Yb3+,K+ nano-phosphor was applied for non-invasively visualizing the tumors in nude mice and successfully detected deep tumors in the thigh muscles. So far, this is the first report of oxide based UCNPs used for in vivo NIR-to-NIR biological imaging and opens the door to the possibility of achieving improved features using non-fluoride based UCNPs.

Effect of transition metal doping under reducing calcination atmosphere on photocatalytic property of TiO2 immobilized on SiO2 beads.

TiO2 immobilized on SiO2 (TiO2/SiO2) have been prepared by sol-gel method and various ions of transition metals (Cr3+, Co2+ Ni2+, CU2+, and Zn2+) were doped on the photocatalyst using wet impregnation method under reducing calcination atmosphere. The photocatalytic activity of metal doped TiO2/SiO2 towards phenol degradation under black light irradiation were investigated and compared with undoped TiO2/SiO2. The results showed that the photoresponse of Cu2+ and Zn2+ doped TiO2/SiO2 were larger than undoped TiO2/SiO2, indicating that the photogenerated carriers were separated more efficiently in Cu2+ and Zn2+ doped TiO2/SiO2. The reactivity was in the order of Cu2+ > Zn2+ > Ni2+ > Cr3+ > Co2+. The different photoreactivity was ascribed to combine effect of the different ionic radii and photocorrison tendency of the dopants. The sample was also characterized by surface analytical methods such as X-ray diffraction, scanning electron micrograph/electron dispersive X-ray analyzer and UV-Vis absorption spectrum.

Chemical modification of carbonized wheat and barley straw using HNO3 and the adsorption of Cr(III).

The effects of oxidation using HNO(3) on the properties of the carbonized wheat and barley straw were investigated by measuring different properties such as specific surface area, PZC, total surface acidic groups as well as FTIR and TG-DTA. A small decrease in the specific surface area due to pore blockage was observed after oxidation. After oxidation, the acidity was increased considerably and the point of zero charge shifted from approximately pH 9 to pH 2 in both types of carbon. By the oxidation of the carbon with nitric acid, carboxylic groups were produced as shown by absorption peaks at 1750 cm(-1) in the FTIR spectra. Boehm titration results showed that the number of carboxyl groups increased by approximately 11-fold after oxidation. The oxidized carbon samples were compared with the unoxidized original carbon samples for Cr(III) adsorption. It was observed that the oxidized carbons exhibit high adsorption efficiencies for Cr(III) ions compared to the original carbonized straws and this can be correlated to the decrease in PZC which is mainly due to the increase in carboxylic functional groups in the oxidized carbonized straws and these are responsible for their cation ion exchange phenomenon.

Grape waste as a biosorbent for removing Cr(VI) from aqueous solution.

Grape waste generated in wine production is a cellulosic material rich in polyphenolic compounds which exhibits a high affinity for heavy metal ions. An adsorption gel was prepared from grape waste by cross-linking with concentrated sulfuric acid. It was characterized and utilized for the removal of Cr(VI) from synthetic aqueous solution. Adsorption tests were conducted in batch mode to study the effects of pH, contact time and adsorption isotherm of Cr(VI), which followed the Langmuir type adsorption and exhibited a maximum loading capacity of 1.91 mol/kg at pH 4. The adsorption of different metal ions like Cr(VI), Cr(III), Fe(III), Zn(II), Cd(II) and Pb(II) from aqueous solution at different pH values 1-5 has also been investigated. The cross-linked grape waste gel was found to selectively adsorb Cr(VI) over other metal ions tested. The results suggest that cross-linked grape waste gel has high possibility to be used as effective adsorbent for Cr(VI) removal.