Titanium Dioxide Nanomaterials: Synthesis, Properties, Modifications, and Applications

Excitonic solar cells1—including organic, hybrid organic–inorganic and dye-sensitized cells (DSCs)—are promising devices for inexpensive, large-scale solar energy conversion. The DSC is currently the most efficient2 and stable3 excitonic photocell. Central to this device is a thick nanoparticle film that provides a large surface area for the adsorption of light-harvesting molecules. However, nanoparticle DSCs rely on trap-limited diffusion for electron transport, a slow mechanism that can limit device efficiency, especially at longer wavelengths. Here we introduce a version of the dye-sensitized cell in which the traditional nanoparticle film is replaced by a dense array of oriented, crystalline ZnO nanowires. The nanowire anode is synthesized by mild aqueous chemistry and features a surface area up to one-fifth as large as a nanoparticle cell. The direct electrical pathways provided by the nanowires ensure the rapid collection of carriers generated throughout the device, and a full Sun efficiency of 1.5% is demonstrated, limited primarily by the surface area of the nanowire array.

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Nanowire dye-sensitized solar cells

A surface science perspective on TiO2 photocatalysis

This Review focuses on recent developments in the use of ZnO nanostructures for dye-sensitized solar cell (DSC) applications. It is shown that carefully designed and fabricated nanostructured ZnO films are advantageous for use as a DSC photoelectrode as they offer larger surface areas than bulk film material, direct electron pathways, or effective light-scattering centers, and, when combined with TiO2, produce a core–shell structure that reduces the combination rate. The limitations of ZnO-based DSCs are also discussed and several possible methods are proposed so as to expand the knowledge of ZnO to TiO2, motivating further improvement in the power-conversion efficiency of DSCs.

https://depts.washington.edu/solgel/documents/pub_docs/journal_docs/2009/advanced_material2009.pdf

ZnO Nanostructures for Dye-Sensitized Solar Cells

Novel unsymmetrical organic sensitizers comprising donor, electron-conducting, and anchoring groups were engineered at a molecular level and synthesized for sensitization of mesoscopic titanium dioxide injection solar cells. The unsymmetrical organic sensitizers 3-(5-(4-(diphenylamino)styryl)thiophen-2-yl)-2-cyanoacrylic acid (D5), 3-(5-bis(4-(diphenylamino)styryl)thiophen-2-yl)-2-cyanoacrylic acid (D7), 5-(4-(bis(4-methoxyphenylamino)styryl)thiophen-2-yl)-2-cyanoacrylic acid (D9), and 3-(5-bis(4,4'-dimethoxydiphenylamino)styryl)thiophen-2-yl)-2-cyanoacrylic acid (D11) anchored onto TiO2 and were tested in dye-sensitized solar cell with a volatile electrolyte. The monochromatic incident photon-to-current conversion efficiency of these sensitizers is above 80%, and D11-sensitized solar cells yield a short-circuit photocurrent density of 13.90 +/- 0.2 mA/cm(2), an open-circuit voltage of 740 +/- 10 mV, and a fill factor of 0.70 +/- 0.02, corresponding to an overall conversion efficiency of 7.20% under standard AM 1.5 sun light. Detailed investigations of these sensitizers reveal that the long electron lifetime is responsible for differences in observed open-circuit potential of the cell. As an alternative to liquid electrolyte cells, a solid-state organic hole transporter is used in combination with the D9 sensitizer, which exhibited an efficiency of 3.25%. Density functional theory/time-dependent density functional theory calculations have been employed to gain insight into the electronic structure and excited states of the investigated species.

Molecular Engineering of Organic Sensitizers for Dye-Sensitized Solar Cell Applications

Core−shell type nanoparticles with SnO2 and TiO2 cores and zinc oxide shells were prepared and characterized by surface sensitive techniques. The influence of the structure of the ZnO shell and the morphology of nanoparticle films on the performance was evaluated. X-ray absorption near-edge structure and extended X-ray absorption fine structure studies show the presence of thin ZnO-like shells around the nanoparticles at low Zn levels. In the case of SnO2 cores, ZnO nanocrystals are formed at high Zn/Sn ratios (ca. 0.5). Scanning electron microscopy studies show that Zn modification of SnO2 nanoparticles changes the film morphology from a compact mesoporous structure to a less dense macroporous structure. In contrast, Zn modification of TiO2 nanoparticles has no apparent influence on film morphology. For SnO2 cores, adding ZnO improves the solar cell efficiency by increasing light scattering and dye uptake and decreasing recombination. In contrast, adding a ZnO shell to the TiO2 core decreases the cell ef...

Morphological and photoelectrochemical characterization of core-shell nanoparticle films for dye-sensitized solar cells: Zn-O type shell on SnO2 and TiO2 cores.


 
 
 p.Arg4810Lys variant of the ring finger protein 213 (RNF213) vasculopathy is a nonsyndromatic vasculopathy involving multisystemic organs including pulmonary arteries. Peripheral pulmonary arterial stenosis (PPAS) with diffuse stenosis and beaded appearance is a unique feature of this disease and no treatment option has been tried before.
 
 
 
 We performed BPA for PPAS in RNF213 patients (n=7). Severity of pulmonary hypertension was assessed by echocardiography and right heart catheterization at the baseline. Several clinical and hemodynamic parameters were followed up after each BPA sessions.
 
 
 
 All of the patients had dyspnea on exertion. Right ventricular dysfunction was observed in six patients and NT-proBNP was elevated (949.2±1148.1 pg/mL). Baseline echocardiography showed severe pulmonary hypertension (70.1±19.2 mmHg). Pulmonary arterial ballooning was performed to all patients, but stenting (n=6) and cutting balloon (n=1) was necessary due to elastic recoil. Improvement of clinical and hemodynamic parameters was achieved in six patients after 5.3 sessions of BPA in average. Reperfusion edema was seen in four patients, eventually leading to death in one patient.
 
 
 
 Pulmonary arterial angioplasty, when coupled with stenting, is an effective treatment for PPAS with RNF213 vasculopathy. Although reperfusion injury was common and fatal in a few cases, it is the only modality to improve the patient's symptom and hemodynamics till now. Careful selection of the target population should be preceded to perform the intervention.
 
 
 
 Type of funding sources: None.


/pdf/pulmonary-arterial-angioplasty-in-peripheral-pulmonary-212gf2cs.pdf

Pulmonary arterial angioplasty in peripheral pulmonary arterial stenosis in RNF213 vasculopathy: effective but high-risk treatment with reperfusion injury

D.-K. Kim

Papers

Morphological and photoelectrochemical characterization of core-shell nanoparticle films for dye-sensitized solar cells: Zn-O type shell on SnO2 and TiO2 cores.

Pulmonary arterial angioplasty in peripheral pulmonary arterial stenosis in RNF213 vasculopathy: effective but high-risk treatment with reperfusion injury