Wafer-Level Manufacturing of MEMS H2 Sensing Chips Based on Pd Nanoparticles Modified SnO2 Film Patterns.

In this manuscript, a simple method combining atomic layer deposition and magnetron sputtering is developed to fabricate high-performance Pd/SnO2 film patterns applied for micro-electro-mechanical systems (MEMS) H2 sensing chips. SnO2 film is first accurately deposited in the central areas of MEMS micro hotplate arrays by a mask-assistant method, leading the patterns with wafer-level high consistency in thickness. The grain size and density of Pd nanoparticles modified on the surface of the SnO2 film are further regulated to obtain an optimized sensing performance. The resulting MEMS H2 sensing chips show a wide detection range from 0.5 to 500 ppm, high resolution, and good repeatability. Based on the experiments and density functional theory calculations, a sensing enhancement mechanism is also proposed: a certain amount of Pd nanoparticles modified on the SnO2 surface could bring stronger H2 adsorption followed by dissociation, diffusion, and reaction with surface adsorbed oxygen species. Obviously, the method provided here is quite simple and effective for the manufacturing of MEMS H2 sensing chips with high consistency and optimized performance, which may also find broad applications in other MEMS chip technologies.

(La0.65Sr0.3)0.95FeO3-δ perovskite with high oxygen vacancy as efficient bifunctional electrocatalysts for Zn-air batteries.

Developing low-cost, highly efficient electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is desirable for rechargeable metal-air batteries. Herein, a series of perovskite structured (La0.65Sr0.3)0.95FeO3-δ catalysts with A-site deficiency were synthesized through a scalable solid state synthesis method at different calcination temperatures. The electrocatalytic activities of these catalysts were investigated by thin-film RDE technique. The catalyst calcined at 1000 °C exhibits an outstanding bi-functional activity towards the ORR and OER in alkaline electrolyte, and it also exhibits an outstanding performance in primary and rechargeable Zn-air batteries, which is comparable with the commercial noble metals Pt/C and RuO2.

Design and Fabrication of a Novel Dual-Frequency Confocal Ultrasound Transducer for Microvessels Super-Harmonic Imaging.

Recently, super-harmonic ultrasound imaging technology has caused much attention due to its capability of distinguishing microvessels from the tissues surrounding them. However, the fabrication of a dual-frequency confocal transducer is still a challenge. In this work, 270- [Formula: see text] PMN-PT single crystal 1-3 composite and 28- [Formula: see text] PVDF thick film, acting as transmission layer and receiving layer, respectively, are integrated in a novel co-focusing structure. To realize delicate wave propagation control, microwave transmission line theory is introduced to design such structure. Two acoustic filter layers, 13- [Formula: see text] copper layer and 39- [Formula: see text] Epoxy 301 layer, are indispensable and should be added between two piezoelectric layers. Therefore, an acoustic issue can be overcome via an electrical method and the successful achievement of a dual-frequency (5 MHz/30 MHz) ultrasound transducer with a confocal distance of 8 mm can be realized. The super-harmonic ultrasound imaging experiment is conducted using this kind of device. The 3-D image of 110- [Formula: see text]-diameter phantom tube injected with microbubbles can be obtained. These promising results demonstrate that this novel dual-frequency (5 MHz/30 MHz) confocal ultrasound transducer is potentially usable for microvascular medical imaging application in the future.

A new coumarin compound DCH combats methicillin-resistant Staphylococcus aureus biofilm by targeting arginine repressor.

Staphylococcus aureus infection is difficult to eradicate because of biofilm formation and antibiotic resistance. The increasing prevalence of methicillin-resistant Staphylococcus aureus (MRSA) infection necessitates the development of a new agent against bacterial biofilms. We report a new coumarin compound, termed DCH, that effectively combats MRSA in vitro and in vivo and exhibits potent antibiofilm activity without detectable resistance. Cellular proteome analysis suggests that the molecular mechanism of action of DCH involves the arginine catabolic pathway. Using molecular docking and binding affinity assays of DCH, and comparison of the properties of wild-type and ArgR-deficient MRSA strains, we demonstrate that the arginine repressor ArgR, an essential regulator of the arginine catabolic pathway, is the target of DCH. These findings indicate that DCH is a promising lead compound and validate bacterial ArgR as a potential target in the development of new drugs against MRSA biofilms.

LncRNA-LALR1 upregulates small nucleolar RNA SNORD72 to promote growth and invasion of hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is one of the most prevalent cancers and currently the second leading cause of cancer-related mortality worldwide. One recent study reported that lncRNA-LALR1 promotes liver regeneration, the role and underlying mechanisms of lncRNA-LALR1 in HCC remain largely unknown. In this study, we demonstrated that lncRNA-LALR1 was significantly upregulated in HCC tissues compared with adjacent tissues and high expression of lncRNA-LALR1 was associated with advanced TNM stage, poor differentiation, and distant metastasis. RNA Fluorescence in situ hybridization analysis showed lncRNA-LALR1 was expressed not only in cytoplasm but also in nucleolus. Knockdown of lncRNA-LALR1 obviously inhibited HCC cells growth and invasion in vivo and in vitro. Besides, transcriptomic analysis and subsequent confirmation revealed that lncRNA-LALR1 upregulated small nucleolar RNA SNORD72 via binding with SNORD72 and stabilized ID2 mRNA. SNORD72 was overexpressed in HCC tissues and enhanced HCC cells proliferation, colony formation and invasion. Overexpression of SNORD72 could also stabilize ID2 mRNA and rescue the inhibitory effect of silencing lncRNA-LALR1. In conclusion, lncRNA-LALR1 is highly expressed in HCC and promotes tumor growth and invasion by upregulating SNORD72 to stabilize ID2 mRNA, implying that lncRNA-LALR1 might be a novel target for intervention of HCC.

Excessive Cu2+ deteriorates arsenite-induced apoptosis in chicken brain and resulting in immunosuppression, not in homeostasis.

Trace elements such as copper (Cu) and arsenic (As) are two of the major contaminants and well-known inducers of cognitive deficits and neurobehavioral changes. This study evaluated the immunotoxicity of their individual or combined exposure on different brain regions in chickens. Consequently, nuclear damage and organelle lesions, especially mitochondria were observed under Cu or/and As stress, in which positive regulation of key proteins, dynamin-related protein 1 (Drp1), Cytochrome C (Cyt c), BCL2-associated X (Bax), Caspases 3 and P53 was detected by qRCR and Western blot analyses, indicating disturbed mitochondrial dynamic equilibrium and apoptosis execution. In addition, qRCR analysis confirmed the involvement of cytokines secreted by different populations of helper T cells, indicative of cellular immunity. Gene expression studies showed marked up regulation of Th1/Th17 cytokines along with heat shock protein (HSP) 70, a synergism was noted in co-administration group. Interesting, lower apoptosis index was noted in brainstem compared to cerebrum and cerebellum. An intense immunosuppression and heat shock response against Cu or/and As was also seen in cerebrum and cerebellum but not in brainstem. In conclusion, our study suggests a synergistic neurotoxicity in chickens under Cu and As exposure. These findings provide a basic understanding of mitochondrial abnormality-initiated neuropathology in response to environmental pollutant mixtures, suggesting an adaptive response to the frangibility of the central nerve system.

Copper or/and arsenic induces autophagy by oxidative stress-related PI3K/AKT/mTOR pathways and cascaded mitochondrial fission in chicken skeletal muscle.

Autophagy is an ubiquitin proteasome system for degradation of intracellular damaged proteins and organelles. Both as environmental pollutants, flourishing data show arsenic (As) and copper (Cu) as robust oxidative stress inducers. Whether this kind of damage correlates with autophagy through the phosphoinositide-3-kinase/protein kinase b/mammalian target of rapamycin (PI3K/AKT/mTOR) pathway still remains elusive. A 12-week exposures of Cu or/and As to chicken time-dependently displayed significant element residue in the pectoralis. Aligning with previous results, a strong pro-oxidant nature of Cu and As was clearly indicated by enzyme/nonenzyme antioxidants. Fragmented mitochondria induced by oxidative damage were accompanied by overexpressed dynamin related protein-1 and decreased mitochondrial fusion-related genes. Upon comparative analysis, time-dependent conversion of light chain 3 (LC3)-I to LC3-II, increases in autophagy-related genes such as Bcl-2-interacting protein (Beclin-1) and inhibited PI3K/AKT/mTOR pathway firmly supported the fact that Cu or/and As induces autophagy. These results further coincided with ultrastructure showing clusters of vesicles and autophagosome in the skeletal muscle. Interestingly, the time-dependently elevated heat shock proteins observed in Cu or/and As treated chicken suggest the continuous adaptation and physiological acclimation of organisms to this stress responses. Interestingly, the combination of copper and arsenic elicited more serious oxidative damage and its-cascaded injuries than their individuals. Together, our results showed that after Cu or/and As insult and accumulation, inhibited PI3K/AKT/mTOR pathway activated autophagy and disturbed mitochondrial dynamic, forming a positive feedback with redox disorder.

Copper (II) and/or arsenite-induced oxidative stress cascades apoptosis and autophagy in the skeletal muscles of chicken.

Arsenic (As) is a ubiquitous environmental toxin and robust inducer of oxidative stress (OxS). Copper (Cu) is an essential microelement, which participates in OxS as a cofactor for certain enzymes, with narrow optimal range between essential and toxic concentrations. However, their effects are rarely studied in chicken skeletal muscles, which have soaring per capita consumption andare susceptible to oxidative damage. In the present study, we demonstrated that the administration of copper sulfate (300 mg kg-1) or arsenite (30 mg kg-1) individually or their co-administration leads to varying degrees of OxS in the skeletal muscles of chickens. Corresponding to the protein expression pattern, the mRNA levels of caspase, B-cell lymphoma-2 (Bcl-2) families, and autophagy-related genes were also compromised in the experimental groups, indicating the involvement of both apoptotic and autophagic cell death. Additionally, rampant mitochondrial fission caused the vicious cycle between imbalanced mitochondrial dynamics and OxS, thus tethering intracellular homeostasis. The abovementioned muscle damage and index anomalies were time dependent, and more deteriorated effects were observed in Cu2+ and arsenite co-administered groups than those in groups administered Cu2+ and arsenite alone. Intriguingly, in the studied skeletal muscles, namely wing biceps brachii and leg gastrocnemius, there were conspicuous differences in oxidative toxicity susceptibility, which needs further study. The present study showed that Cu and/or As induce oxidative damage in chicken skeletal muscles and discussed its mechanism in terms of apoptosis, autophagy, and mitochondrial dynamics, thus voicing concerns about poultry breeding areas cross-contaminated with Cu2+ and arsenite.

Copper and arsenic-induced oxidative stress and immune imbalance are associated with activation of heat shock proteins in chicken intestines.

Arsenic and copper, two ubiquitous pollutants, can be oxidative stress inducers when organisms are heavy or chronically exposed, causing adverse effects on digestion and absorption function, resulting in potential losses to poultry husbandry. The present study examined the effects of arsenic trioxide (30 mg/kg)- and copper sulfate (300 mg/kg)-mixed foods, administered alone or in combination for 12 weeks, on various biochemical indices of oxidative stress and immunity in the small intestines of Hy-line chickens. The results showed that for the first four weeks of exposure, both the redox and immune systems were unaffected. Subsequently, exposure to arsenic or copper significantly increased the level of lipid peroxidation (malondialdehyde and ability of anti-hydroxy radical) concomitant with a collapse of the antioxidant system (catalase and glutathione peroxidase), in a time-dependent manner. An increase in the mRNA and protein levels of pro-inflammatory indicators (nuclear factor kappa B, cyclooxygenases-2, tumor necrosis factor-α and prostaglandin E2 synthases) with a definite tendency toward Th1 (Th, helper T cell) cytokines was observed in both arsenic and copper treated chickens. Histologically, the destruction of the biofilm structure and inflammatory infiltrates was observed. Thus, in the intestine, heat shock proteins play protective roles against tissue damage. In some cases, we observed that the tissues of the small intestine were more sensitive to arsenic than to copper. Moreover, co-exposure induced more serious intestinal toxicity than single treatment group, and this mechanism needs further exploration.

Mitogen-Activated Protein Kinase and Intracellular Polyamine Signaling Is Involved in TRPV1 Activation-Induced Cardiac Hypertrophy.

BACKGROUND: The transient receptor potential vanilloid type 1 (TRPV1) is expressed in the cardiovascular system, and increased TRPV1 expression has been associated with cardiac hypertrophy. Nevertheless, the role of TRPV1 in the pathogenesis of cardiac hypertrophy and the underlying molecular mechanisms remain unclear. METHODS AND RESULTS: In cultured cardiomyocytes, activation of TRPV1 increased cell size and elevated expression of atrial natriuretic peptide mRNA and intracellular calcium level, which was reversed by TRPV1 antagonist capsazepine. Increased expression of phosphorylated calmodulin-dependent protein kinase IIδ and mitogen-activated protein kinases were found in TRPV1 agonist capsaicin-treated cardiomyocytes. Selective inhibitor of calmodulin-dependent protein kinase IIδ decreased phosphorylation of extracellular signal-regulated kinases and p38. Capsaicin induced an increase in expression of ornithine decarboxylase protein, which is the key enzyme in polyamine biosynthesis in cardiomyocytes. Nevertheless, there was no obvious change of ornithine decarboxylase expression in TRPV1 knockdown cells after capsaicin treatment, and specific inhibitors of calmodulin-dependent protein kinase IIδ or p38 downregulated the capsaicin-induced expression of ornithine decarboxylase. Capsazepine alleviated the increase in cross-sectional area of cardiomyocytes and the ratio of heart weight to body weight and improved cardiac function, including left ventricular internal end-diastolic and -systolic dimensions and ejection fraction and fractional shortening percentages, in mice treated with transverse aorta constriction. Capsazepine also reduced expression of ornithine decarboxylase and cardiac polyamine levels. Transverse aorta constriction induced increases in phosphorylated calmodulin-dependent protein kinase IIδ and extracellular signal-regulated kinases, and p38 and Serca2a were attenuated by capsazepine treatment. CONCLUSIONS: This study revealed that the mitogen-activated protein kinase signaling pathway and intracellular polyamines are essential for TRPV1 activation-induced cardiac hypertrophy.

Roemerine Improves the Survival Rate of Septicemic BALB/c Mice by Increasing the Cell Membrane Permeability of Staphylococcus aureus.

Staphylococcus aureus is one of the most frequently occurring hospital- and community-associated pathogenic bacteria featuring high morbidity and mortality. The occurrence of methicillin-resistant S. aureus (MRSA) has increased persistently over the years. Therefore, developing novel anti-MRSA drugs to circumvent drug resistance of S. aureus is highly important. Roemerine, an aporphine alkaloid, has previously been reported to exhibit antibacterial activity. The present study aimed to investigate whether roemerine can maintain these activities against S.aureus in vivo and further explore the underlying mechanism. We found that roemerine is effective in vitro against four S. aureus strains as well as in vivo against MRSA insepticemic BALB/c mice. Furthermore, roemerine was found to increase cell membrane permeability in a concentration-dependent manner. These findings suggest that roemerine may be developed as a promising compound for treating S. aureus, especially methicillin-resistant strains of these bacteria.

The cis-isomer performs better than the trans-isomer in porphyrin-sensitized solar cells: interfacial electron transport and charge recombination investigations.

We report characterizations and device performance for dye-sensitized solar cells using cis- and trans-isomers of 2D-π-2A zinc porphyrins with carboxyphenyl and thienyl groups in their meso-positions. Under identical experimental conditions with similar dye loadings, we observed overall power conversion efficiencies of 2.44% and 0.88% for devices made of cis-2S2A and trans-2S2A, respectively. This uneven performance among cis and trans isomers under the same experimental conditions can be rationalized with detailed investigations via spectroscopic, quantum chemical, and femtosecond fluorescence up-conversion investigations. Density functional theory (DFT) calculations show that a small amount of electron density is localized over carboxyphenyl groups in the LUMO of cis-2S2A, but there is no electron density populated on the carboxyphenyl groups in the LUMO of trans-2S2A. The femtosecond fluorescence decay measurements revealed that the excited-state lifetime of trans-2S2A on Al2O3 is half of that of cis-2S2A on Al2O3. Moreover, the dye-to-TiO2 electron injection time of trans-2S2A is 2.54 ps, which is shorter than that of cis-2S2A/TiO2 (2.95 ps). Electrochemical impedance spectra measured under one sun illumination also revealed that the charge recombination time of cis-2S2A is longer than that of trans-2S2A. This thorough understanding of isomeric effects on the performance of porphyrins will serve as a guideline for the design of future sensitizing dyes for solar cells.

Different sensing modes of fluoride and acetate based on a calix[4]arene with 25,27-bistriazolylmethylpyrenylacetamides.

25,27-Bis{1'-N-(1-pyrenyl)-aminocarbonylmethyl-1H-[1',2',3']tri-azolyl-4'-methoxy}-26,28-dihydroxycalix[4]arene, 4, is synthesized as a fluorescent chemosensor for the selective detection of both anions and ion pairs in MeCN. Sensor 4 uses bis-triazoles as ligands to bind a metal ion, bis-amides and bis-triazoles as the sites to recognize anions, and pyrenes as fluorophores. Among eight anions screened, chemosensor 4 showed a marked fluorescence change toward F(-), H2PO4(-) and AcO(-), but 4 responded to each anion in a distinct way. In the presence of F(-) at low concentrations, the dynamic excimer emission of compound 4 at λ(max) 482 nm was quenched, but an emission at λ(max) 472 nm appeared at large doses of F(-). A control compound 6 showed very similar red shifts in the UV-vis and excitation spectra as 4 did, and its 472 nm emission band grew as the fluoride doses increased. Thus, the growth of the 472 nm emission of 4 and 6 in the presence of excess F(-) may be because strong H-bonding interactions of amido protons with F(-) favoured the formation of pyrene dimers in the ground state with charge transfer characteristics. The addition of H2PO4(-), unlike F(-), to a solution of 4 showed an enhanced monomer emission but a decreased excimer emission (λ(max) 482 nm). Adding AcO(-) to 4 produced a systematic change from a dynamic excimer (λ(max) 482 nm) to λ(max) 472 nm but with very little change in the UV-vis spectrum. Time-resolved fluorescence measurements on compound 6 with F(-) and AcO(-) confirmed that the 472 nm emission band mainly came from static excimers for the former, but was partly from a dynamic excimer for the latter because it contained a growth component in the fluorescence decay traces. Without pre-treatment with an anion, chemosensor 4 showed recognition of only metal ions Cu(2+), Hg(2+) and Cr(3+), but it became sensitive to Ag(+) when it was pretreated with fluoride.

Novel expanded porphyrin sensitized solar cells using boryl oxasmaragdyrin as the sensitizer.

Oxasmaragdyrin boron complexes were prepared and applied in DSSCs. The HOMO-LUMO energy gap analyses and theoretical calculations revealed that these expanded porphyrins are ideal sensitizers for DSSCs. A device containing oxasmaragdyrin-BF2 as the sensitizer achieves an energy conversion efficiency of 5.7%.

Using gold nanoclusters as selective luminescent probes for phosphate-containing metabolites.

Glutathione-bound gold nanoclusters (AuNCs@GSH) can emit reddish photoluminescence under illumination of ultraviolet light. The luminescence of the AuNCs@GSH is quenched when chelating with iron ions (AuNCs@GSH-Fe(3+)), presumably resulting from the effective electron transfer between the nanoclusters and iron ions. Nevertheless, we found that the luminescence of the gold nanoclusters can be restored in the presence of phosphate-containing molecules, which suggested the possibility of using AuNCs@GSH-Fe(3+) complexes as the selective luminescent switches for phosphate-containing metabolites. Phosphate-containing metabolites such as adenosine-5'-triphosphate (ATP) and pyrophosphate play an important role in biological systems. In this study, we demonstrated that the luminescence of the AuNCs@GSH-Fe(3+) is switched-on when mixing with ATP and pyrophosphate, which can readily be observed by the naked eye. It results from the high formation constants between phosphates and iron ions. When employing fluorescence spectroscopy as the detection tool, quantitative analysis for phosphate-containing metabolites such as ATP and pyrophosphate can be conducted. The linear range for ATP and pyrophosphate is 50 µM to sub-millimolar, while the limit of detection for ATP and pyrophosphate are ∼43 and ∼28 µM, respectively. Additionally, we demonstrated that the luminescence of the AuNCs@GSH-Fe(3+) can also be turned on in the presence of phosphate-containing metabolites from cell lysates and blood plasma.

Photoactivation studies of zinc porphyrin-myoglobin system and its application for light-chemical energy conversion.

An artificial zinc porphyrin-myoglobin-based photo-chemical energy conversion system, consisting of ZnPP-Mb or ZnPE(1)-Mb as a photosensitizer, NADP(+) as an electron acceptor, and triethanolamine as an electron donor, has been constructed to mimic photosystem I. The photoirradiated product is able to reduce a single-electron acceptor protein cytochrome c, but cannot catalyze the two-electron reduction of acetaldehyde by alcohol dehydrogenase, thus demonstrating a single electron transfer mechanism. Furthermore, the artificial system can bifunctionally promote oxidoredox reactions, depending on the presence or absence of a sacrificial electron donor, thus suggesting its potential application in electrochemical regeneration steps involved in chemical transformation and/or energy conversion.

Effects of potential shift and efficiency of charge collection on nanotube-based porphyrin-sensitized solar cells with conjugated links of varied length.

For dye-sensitized solar-cell devices fabricated from porphyrin sensitizers with links of varied length (PE1-PE4) adsorbed on anodic titanium-oxide nanotube arrays, we measured induced photocurrent and photovoltage decays under constant bias illumination; the evaluated efficiencies of charge collection of the devices show a systematic trend PE4 > PE3 > PE2 > PE1 at a large short-circuit current, implying that a long link would improve the charge separation if the electrons were effectively injected into the semiconductor.

Functional gold nanoclusters as antimicrobial agents for antibiotic-resistant bacteria.

AIMS: Our aim was to demonstrate that lysozyme-directed generation of gold nanoclusters (Au NCs) are potential antimicrobial agents for antibiotic-resistant bacteria and broad labeling agents for pathogenic bacteria. MATERIALS & METHODS: Lysozyme is an enzyme that is capable of hydrolyzing the cell walls of bacteria. In this study, we demonstrated the generation of functional Au NCs by using lysozyme as the sequester and the reducing agent for Au precursors at 40 degrees C. In addition, to shorten the reaction time, the reaction was conducted under microwave irradiation within a short period of time for the first time. RESULTS: The bioactivity of the lysozyme on the Au NCs was retained. Therefore, the as-prepared lysozyme-Au NCs with desirable fluorescence feature were successfully employed to be broad-band labeling agents for pathogenic bacteria. Furthermore, we also demonstrated that the lysozyme-Au NCs can be used to effectively inhibit the cell growth of notorious antibiotic-resistant bacteria, including pan-drug-resistant Acinetobacter baumannii and vancomycin-resistant Enterococcus faecalis. CONCLUSION: The potential of employing the lysozyme-Au NCs for bacterial labeling and as antimicrobial agents is expected.

Novel steroid-sensing model and characterization of protein interactions based on fluorescence anisotropy decay.

Intramolecular binding of a ligand with an alkyl link, (-CH(2))(3), covalently bound to a residue near the active site of the protein forms a novel steroid-sensing model. A genetically engineered big up tri, open(5)-3-ketosteroid isomerase (KSI) was designed to conjugate uniquely with this ligand at its Cys-86 through the formation of a disulfide bond. The steady-state protein-ligand binding, mediated by hydrophobic interactions, was confirmed with fluorescence spectra, and the fluorophore-labeled peptide sequence was identified with tandem mass spectra. A comparison of steady-state fluorescence spectra of various fluorophore-labeled KSI mutants reveals that the emission characteristics vary with environmental factors. An evaluation of the decay of the fluorescence anisotropy of the fluorophore indicates the existence of an intramolecular protein-ligand binding interaction. The measurement of time-resolved fluorescence anisotropy of various protein-ligand complexes yielded values of anisotropy decay representing the degrees of freedom of the fluorophore related to its location, inside or outside the steroid-binding domain. When 19-norandrostenedione (19-NA) was added to this protein-ligand system, competitive binding between the ligand and the steroid was observed; this finding confirms the feasibility of the design of steroid detection with engineered KSI. On integration of this protein-ligand system with a silicon-based nanodevice (a p-type field-effect transistor with an ultrathin body), a noncharged steroid, 19-NA, became detectable at a micromolar level ( Biosens. Bioelectron. 2008 , 23 , 1883 ).

Effects of aggregation and electron injection on photovoltaic performance of porphyrin-based solar cells with oligo(phenylethynyl) links inside TiO(2) and Al(2)O(3) nanotube arrays.

Porphyrins with phenylethynyl links of varied length (PE1-PE4) were sensitized on vertically oriented, anodic titanium-oxide (ATO) nanotube arrays for application as dye-sensitized solar cells (DSSC). The efficiency of power conversion decreased systematically from the dye with a short link to the dye with a long link. We measured the efficiency of conversion of incident photons to current (IPCE), the photocurrent decay of the devices, and steady-state and time-resolved fluorescence spectra of the thin-film samples to understand how the cell performance depends on the length of the link. Measurements of femtosecond fluorescence confirmed that the efficiency of electron injection depended on length because of dye aggregation that significantly increased the rate of aggregate-induced energy transfer for porphyrins with a long link. The rate of electron injection depended on the length of the link with an attenuation factor beta approximately 0.1 A(-1). Resonant energy transfer (RET) kinetics of porphyrins sensitized on anodic aluminium-oxide (AAO) nanotube arrays were performed with picosecond time-correlated single-photon counting and four molecular densities for each porphyrin. The kinetic data of PE1 and PE2 are described satisfactorily according to a Förster model, whereas those of PE3 and PE4 conform to a Dexter formula. A formation of clusters is proposed to rationalize the observed density-dependent kinetics for the RET of porphyrins on semiconductor films.