A colloidal heterostructured quantum dot sensitized carbon nanotube-TiO 2 hybrid photoanode for high efficiency hydrogen generation

Solar-driven photoelectrochemical (PEC) hydrogen (H 2 ) generation is a promising approach to harvest solar energy for the production of a clean chemical fuel. However, the low photon-to-fuel conversion efficiency and long-term stability of PEC devices are major challenges to be addressed to enable large-scale commercialization. Here we report a simple, fast and cost-effective approach to fabricate high efficiency and stable PEC devices for H 2 generation, by fabricating a hybrid photoanode obtained by incorporating small amounts of multiwall carbon nanotubes (MWCNTs) into a TiO 2 mesoporous film and sensitizing with colloidal heterostructured CdSe/(CdSe x S 1-x ) 5 /(CdS) 2 quantum dots (QDs). The latter were specially designed to accelerate the exciton separation through a band engineering approach. The PEC devices based on the TiO 2 /QD-MWCNT (T/Q-M) hybrid photoanode with an optimized amount of MWCNTs (0.015 wt%) yield a saturated photocurrent density of 15.90 mA cm -2 (at 1.0 V RHE ) under one sun illumination (AM 1.5G, 100 mW cm -2 ), which is 40% higher than that of the reference device based on TiO 2 /QD (T/Q) photoanodes. This is attributed to a synergistic effect of the promising optoelectronic properties of the colloidal heterostructured QDs and improved electron transport (reduced charge transfer resistance) within the TiO 2 -MWCNT hybrid anodes enabled by the directional path of MWCNTs for the photo-injected electrons towards FTO. Furthermore, the PEC device based on the T/Q-M hybrid photoanode is more stable (∼19% loss of its initial photocurrent density) when compared with the T/Q photoanode (∼35% loss) after two hours of continuous one sun illumination. Our results provide fundamental insights and a different approach to improve the efficiency and long-term stability of PEC devices and represent an essential step towards the commercialization of this emerging solar-to-fuel conversion technology

Hepatitis B virus infection on Kwajalein Atoll, Marshall Islands: a seroprevalence, knowledge and attitudes study

YesObjective: A study was conducted to determine the seroprevalence of chronic hepatitis B virus (HBV) infection among children and their mothers on Kwajalein Atoll in the Marshall Islands two decades after routine vaccination was introduced in the 1990s. Mothers’ knowledge and attitudes towards HBV disease and vaccination were also assessed. Methods: Results of a national seroprevalence survey conducted in 2016–2017 and antenatal records were used to determine the prevalence of HBV seropositivity in children aged 6–8 years and their biological mothers. The associations between demographic, social and vaccination-related factors and seropositivity were explored using Fisher’s exact tests. Results: HBV seroprevalence was 0.3% in children and 6.8% in their mothers (during pregnancy). Coverage of timely HBV vaccination was 90.3% for the birth dose and was significantly associated with factors related to place of residence (P < 0.001), place of birth (P < 0.001) and number of antenatal visits (P < 0.001). Maternal attitudes towards infant vaccination and antenatal screening were largely positive (95.8% and 96.7%, respectively) despite low vaccination rates (20.9%) among mothers. Knowledge levels were low for disease complications, treatment and transmission. Discussion: Prevalence of HBV in children and mothers residing on Kwajalein Atoll in 2016–2017 was lower than the national average for the Marshall Islands. Timely birth dose administration appears to have been effective in preventing mother-to-child transmission of HBV in this setting and should be promoted in remote settings where antiviral therapy is not available. Provision of out-of-cold-chain HBV vaccines should be considered to improve access in remote settings

Highly efficient and stable spray assisted nanostructured Cu2S/Carbon paper counter electrode for quantum dots sensitized solar cells

The counter electrode (CE) plays a significant role in determining the overall performance and long-term stability of quantum dots (QDs) sensitized solar cells (QDSCs) by collecting the electrons from the external circuit and catalyzing the regeneration of the oxidized electrolyte. In this work, we report a simple, low cost and large area scalable spray deposition approach to fabricate nanostructured Cu2S CE on a carbon fiber paper (CP). The QDSCs were assembled with optimized spray assisted nanostructured Cu2S/CP CEs, and yield a photoconversion efficiency (PCE) of 5.06%, which is 28% higher than QDSCs based on Cu2S/Brass CEs. The PCE can be further boosted to 5.89% upon optimization of the photoanode structure. In addition, QDSCs with Cu2S/CP CEs exhibit better long-term stability than QDSCs with Cu2S/Brass CE. This excellent performance and satisfactory long-term stability of QDSCs with Cu2S/CP CEs is mainly attributed to the synergistic effect of excellent conductivity of CP and high and stable catalytic activity of nanostructured Cu2S, which is confirmed by cyclic voltammetry and electrochemical impedance spectroscopy. Thus, our results define a cost-effective and large area scalable approach to fabricate highly efficient and stable CEs, which is an important step toward the fabrication of solar driven optoelectronic devices

Graphene nanoribbon-TiO2-quantum dots hybrid photoanode to boost the performance of photoelectrochemical for hydrogen generation

We report the effect of incorporation of graphene nanoribbons (GNR) into a TiO2 mesoporous film sensitized with colloidal CdSe/CdS core/shell quantum dots (QDs) on the efficiency and long-term stability of a photoelectrochemical (PEC) cell for hydrogen (H2) generation. The GNR-TiO2 hybrid photoanodes were prepared by using simple, low-cost and large-area scalable doctor-blade method. The presence of GNR in the hybrid photoanode was confirmed by ultraviolet-visible absorption measurements, scanning electron microscopy and Raman spectroscopy. Our results demonstrate that an optimum loading of 0.02 wt% GNR increases the photocurrent density (at 0.8 V vs RHE) of the PEC device up to 5.51 mA/cm2, which is 30% higher than that of the control device. This improvement in photocurrent density can be attributed to enhanced electron transport (reduced charge transport resistance) in GNR-TiO2 hybrid anodes as confirmed by electrochemical impedance spectroscopy. In addition, PEC cells based on GNRs-TiO2/QDs hybrid photoanode maintain ∼65% of the initial photocurrent density after 7200 s of continuous one sun illumination, which is 15% higher than PEC cell based on a standard TiO2/QDs photoanode. Our findings offer a simple, large area scalable and low-cost approach to fabricate photoanode for high-performance optoelectronic devices, such as improving the performance of PEC cells for hydrogen generation

CuS/graphene nanocomposite as a transparent conducting oxide and pt-free counter electrode for dye-sensitized solar cells

We report a simple, low temperature and solution-processable approach to prepare a composite film of copper sulfide/graphene (CuS-G) as a transparent conducting oxide (TCO) and platinum (Pt)-free CE for Dye-Sensitized Solar Cells (DSSCs). We find that CuS with 3.3 vol% of graphene (CuS-3G) yields the highest power conversion efficiency (PCE) of 4.83%, which is about 12% higher than DSSCs based on CEs made of pristine CuS. After optimizing the graphene concentration, the PCE of the DSSC assembled with the optimized CuS-3G is comparable to that based on Pt CE. The similar performance of the CuS-3G CE compared with Pt CE is mainly attributed to the small series resistance and high electrocatalytic activity of the CuS-3G CE; this is confirmed by cyclic voltammetry and electrochemical impedance spectroscopy. These results indicate a straightforward methodology for the low cost and easy synthesis of an alternative CE in DSSCs

A Novel Synthesis Route of Mesoporous γ-Alumina from Polyoxohydroxide Aluminum

Mesoporous gamma-aluminas (gamma-Al2O3) were synthesized starting from an unusual precursor of polyoxohydroxide aluminum (POHA). This precursor was obtained from aluminum oxidation in alkaline water-ethanol solvent in the presence of d-glucose that induces the formation of a gel, which leads to the POAH powder after ethanolic treatment Precipitated POHAs were calcined at different temperatures (300, 400, 700 and 900 degrees C) resultmg m the metastable gamma-Al(2)0(3) phase. Whereas at 300 degrees C no gamma-Al(2)0(3) phase was formed, unexpectedly, mesoporous gamma-Al(2)0(3) was obtained at 400 degrees C having a high specific surface area (282 m(2)/g) and a narrow pore size distribution At higher temperatures, the aluminas had the expected decrease in surface area 166 m(2)/g (700 degrees C) and 129 m(2)/g (900 degrees C), respectively The structural change from POHA to alumina calcined at 400 degrees C occurs directly without the need to isolate the hydroxide or oxyhydroxide aluminum precursors Both POHA and transition aluminas were characterized by Fourier Transform Infrared spectroscopy (FTIR), X-ray diffraction (XRD), N-2 sorption and Scanning Electron Microscopy (SEM) These findings show an alternative route to produce high standard aluminas.Fundacao de Apoio a Pesquisa do Estado de Sao Paulo - FAPESPCAPESCNPqUniv Sao Paulo, Dept Engn Quim DEQ, Escola Engn Lorena, Estr Municipal Campinho S-N, BR-12602810 Lorena, SP, BrazilUniv Fed Sao Paulo UNIFESP, Dept Ciencias Exatas & Terra, Rua Sao Nicolau 210, BR-09913030 Diadema, SP, BrazilUniv Fed ABC, Ctr Engn Modelagem & Ciencias Sociais Aplicadas, Santo Andre, SP, BrazilUniv Sao Paulo, Inst Quim, Ave Prof Lineu Prestes 748, BR-05508900 Sao Paulo, SP, BrazilUniv Sao Paulo, Escola Engn Lorena, Polo Ind, Dept Engn Mat DEMAR, Gleba Al-6 S-N, BR-12602810 Lorena, SP, BrazilUniv Fed Sao Paulo UNIFESP, Dept Ciencias Exatas & Terra, Rua Sao Nicolau 210, BR-09913030 Diadema, SP, BrazilFAPESP: 2015/06064-6, 2013/08166-5, 2016/05496-2Web of Scienc

8-Hydroxy-2-methylquinolinium tetrachlorido(quinolin-8-olato-kappa N-2,O) stannate(IV) acetonitrile monosolvate

In the title solvated salt, (C10H10NO)[SnCl4(C9H6NO)]center dot-CH3CN, the Sn-IV atom is chelated by the N,O-bidentate 8-hydroxyquinolinate ligand and four chloride ions, generating a distorted SnONCl4 octahedral coordination geometry for the metal. In the crystal, the cations are linked to the anions and the solvent molecules by O-H center dot center dot center dot O and N-H center dot center dot center dot N hydrogen bonds, respectively

Formation of R-4(4) (8) ring in chloride salts of 8-hydroxyquinolinium derivatives: synthesis, structural, and theoretical studies

The molecular structures of chloride salts of 2and 5- substituted derivatives of 8- hydroxyquinoline, MeH 2 Q+ u Cl- ([ C 10 H 10 NO] Cl) and Cl- H 2 Q+ u Cl- ([ C 9 H 7 ClNO]+ u Cl-), were determined by single crystal X- ray diffraction methods; the latter is a new polymorph. In the crystal structures of these salts, several intra- and inter- molecular interactions result in a step- shaped centrosymmetric 4 4 R ( 8) ring. Unlike most quinolinium salts, there was no solvent present in these structures. Protonation of the quinoline N atom had an effect on the N uuu O bite distances and C- N- C angle and greater conjugation of the benzene ring with a hydroxyl group was also observed. p- p Interactions between each pair of quinolinium rings were observed in Me- H 2 Q+ u Clbut not in Cl- H 2 Q+ u Cl-. In addition, the quantum chemical calculations were performed on the new structures as well as similar compounds for comparison. The optimized structures were compared with the experimental observations for the effect of protonation and of hydrogen bonding interactions

Formation of R-4(4) (8) ring in chloride salts of 8-hydroxyquinolinium derivatives: synthesis, structural, and theoretical studies

The molecular structures of chloride salts of 2and 5- substituted derivatives of 8- hydroxyquinoline, MeH 2 Q+ u Cl- ([ C 10 H 10 NO] Cl) and Cl- H 2 Q+ u Cl- ([ C 9 H 7 ClNO]+ u Cl-), were determined by single crystal X- ray diffraction methods; the latter is a new polymorph. In the crystal structures of these salts, several intra- and inter- molecular interactions result in a step- shaped centrosymmetric 4 4 R ( 8) ring. Unlike most quinolinium salts, there was no solvent present in these structures. Protonation of the quinoline N atom had an effect on the N uuu O bite distances and C- N- C angle and greater conjugation of the benzene ring with a hydroxyl group was also observed. p- p Interactions between each pair of quinolinium rings were observed in Me- H 2 Q+ u Clbut not in Cl- H 2 Q+ u Cl-. In addition, the quantum chemical calculations were performed on the new structures as well as similar compounds for comparison. The optimized structures were compared with the experimental observations for the effect of protonation and of hydrogen bonding interactions