Robust Protection of III-V Nanowires in Water Splitting by a Thin Compact TiO2 Layer.

Narrow-band-gap III-V semiconductor nanowires (NWs) with a suitable band structure and strong light-trapping ability are ideal for high-efficiency low-cost solar water-splitting systems. However, due to their nanoscale dimension, they suffer more severe corrosion by the electrolyte solution than the thin-film counterparts. Thus, short-term durability is the major obstacle for using these NWs for practical water-splitting applications. Here, we demonstrated for the first time that a thin layer (∼7 nm thick) of compact TiO2 deposited by atomic layer deposition can provide robust protection to III-V NWs. The protected GaAs NWs maintain 91.4% of its photoluminescence intensity after 14 months of storage in ambient atmosphere, which suggests the TiO2 layer is pinhole-free. Working as a photocathode for water splitting, they exhibited a 45% larger photocurrent density compared with unprotected counterparts and a high Faraday efficiency of 91% and can also maintain a record-long highly stable performance among narrow-band-gap III-V NW photoelectrodes; after 67 h photoelectrochemical stability test reaction in a strong acid electrolyte solution (pH = 1), they show no apparent indication of corrosion, which is in stark contrast to the unprotected NWs that fully failed after 35 h. These findings provide an effective way to enhance both stability and performance of III-V NW-based photoelectrodes, which are highly important for practical applications in solar-energy-based water-splitting systems.

Zn and N Codoped TiO2 Thin Films: Photocatalytic and Bactericidal Activity.

We explore a series of Zn and N codoped TiO2 thin films grown using chemical vapor deposition. Films were prepared with various concentrations of Zn (0.4-2.9 at. % Zn vs Ti), and their impact on superoxide formation, photocatalytic activity, and bactericidal properties were determined. Superoxide (O2•-) formation was assessed using a 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazolium sodium salt (XTT) as an indicator, photocatalytic activity was determined from the degradation of stearic acid under UVA light, and bactericidal activity was assessed using a Gram-negative bacterium E. coli under both UVA and fluorescent light (similar to what is found in a clinical environment). The 0.4% Zn,N:TiO2 thin film demonstrated the highest formal quantum efficiency in degrading stearic acid (3.3 × 10-5 molecules·photon-1), while the 1.0% Zn,N:TiO2 film showed the highest bactericidal activity under both UVA and fluorescent light conditions (>3 log kill). The enhanced efficiency of the films was correlated with increased charge carrier lifetime, supported by transient absorption spectroscopy (TAS) measurements.

Multimodal Prussian blue analogs as contrast agents for X-ray computed tomography.

Prussian blue analogs (PBAs) are versatile materials with a wide range of applications. Due to their tunability, intrinsic biocompatibility, as well as low toxicity, these nanoscale coordination polymers have been successfully studied as multimodal contrast agents for multiple imaging techniques. Herein, we report the expanded biomedical application of PBAs to X-ray computed tomography (CT). In our systematic study of the series A{MnII[FeIII(CN)6]} (A = K+, Rb+, Cs+), we showed that derivatives incorporating Rb+ and Cs+ ions in the tetrahedral sites of the parent face-centered cubic cyano-bridged networks exhibited substantially increased X-ray attenuation coefficients, thus yielding significant contrast compared to the clinically approved X-ray contrast agent iohexol at the same concentrations. Additionally, our µ-CT studies revealed that these PBAs could be useful as dual-energy CT contrast agents for different biological specimens by using the lower varying scanning X-ray tube voltages. Finally, in vitro studies using U87-Luc cells treated with PBAs, including cellular CT imaging and bioluminescence cell viability assays, revealed that PBAs were taken up by the glioblastoma cells, with moderate biocompatibility at concentrations below the mM range.

(E)-4-Meth-oxy-N'-(3,4,5-trimeth-oxy-benzyl-idene)benzohydrazide.

In the asymmetric unit of the title compound, C(18)H(20)N(2)O(5), there are two crystallographic independent mol-ecules. Both mol-ecules are twisted; the dihedral angle between the two benzene rings is 7.2 (5)° in one mol-ecule, whereas it is 85.9 (4)° in the other. Of the three meth-oxy groups in the 3,4,5-trimeth-oxy-phenyl unit, two meth-oxy groups at meta positions are approximately coplanar with the benzene plane [C-O-C-C torsion angles of -2.3 (13)-4.8 (11)°], but the other meth-oxy, at the para position, is out of the plane [C-O-C-C of 72.8 (9)° in one mol-ecule and -77.5 (9)° in the other]. In the crystal, mol-ecules are linked by N-H⋯O hydrogen bonds and weak C-H⋯O inter-actions into tapes along the b axis. C-H⋯π inter-actions are also present.

(E)-N'-(3-Eth-oxy-4-hy-droxy-benzyl-idene)-4-meth-oxy-benzohydrazide.

In the mol-ecule of the title benzohydrazide derivative, C(17)H(18)N(2)O(4), the dihedral angle between the benzene rings is 6.86 (11)°. The meth-oxy group of the 4-meth-oxy-phenyl fragment deviates slightly [C(methyl)-O-C-C = 10.0 (4)°] with respect to the benzene ring, whereas the eth-oxy group of the 3-eth-oxy-4-hy-droxy-phenyl fragment is is almost coplanar [C-O-C-C(methyl) = 178.5 (2)°]. In the crystal, mol-ecules are linked by N-H⋯O, O-H⋯O and C-H⋯O hydrogen bonds into a two-dimensional network parallel to the ab plane. C-H⋯π inter-actions and C⋯O [2.980 (3) Å] short contacts are also observed.

(E)-N'-(2,3-Dihy-droxy-benzyl-idene)-4-meth-oxy-benzohydrazide.

The mol-ecule of the title benzohydrazide derivative, C(15)H(14)N(2)O(4), is twisted and exists in a trans conformation with respect to the C=N double bond. The dihedral angle between the benzene rings is 56.86 (9)° and the C atom of the meth-oxy group deviates slightly [C-O-C-C = -10.4 (3)°] from its attached benzene ring. An intra-molecular O-H⋯N hydrogen bond generates an S(6) ring. In the crystal, mol-ecules are linked by N-H⋯O and bifurcated N-H⋯(O,O) hydrogen bonds, as well as weak C-H⋯O inter-actions, into two-dimensional networks lying parallel to the bc plane. A weak C-H⋯π inter-action also occurs.

(E)-N'-(3-Hy-droxy-4-meth-oxy-benzyl-idene)-4-meth-oxy-benzohydrazide.

The title mol-ecule, a benzohydrazide derivative, C(16)H(16)N(2)O(4), is twisted with a dihedral angle of 69.97 (5)° between the two benzene rings. An intra-molecular O-H⋯O hydrogen bond generates an S(5) ring motif. In the crystal, mol-ecules are linked by N-H⋯O and weak C-H⋯O hydrogen bonds into a chain along the c axis. C-H⋯π inter-actions are also present.