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1.
Dermatol Surg ; 44(12): 1547-1554, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30379685

RESUMO

BACKGROUND: Understanding interrelationships among aging facial features is important in facial aesthetics as a global treatment approach becomes standard. OBJECTIVE: Examine empirical relationships between midface volume deficit and severity of tear troughs (TTs) and nasolabial folds (NLFs) in women and men of different racial/ethnic groups. METHODS: A web-based study was administered to health panel members (aged 18-75 years). Participants compared their midface volume, TTs, and NLFs against photonumeric scales depicting degrees of severity. Linear regressions were conducted to assess the relationship of midface volume on severity of TTs and NLFs, controlling for demographic factors. RESULTS: Of 4,086 participants (80.0% female), 3,553 had complete data. Increasing severity of midface volume deficit was associated with increasing severity of TTs and NLFs in both sexes (all p < .001). Race/ethnicity was associated with differences in severity in all 3 facial areas, although specific differences between races/ethnicities varied for women and men. Progression rates of severity differed between racial/ethnic groups. Correlations between midface volume deficit, TTs, and NLFs were positive and significant (all p < .001). CONCLUSION: Midface volume deficit was associated with severity of TT deformity and NLFs after controlling for age and other demographic variables.


Assuntos
Sulco Nasogeniano/patologia , Envelhecimento da Pele/etnologia , Envelhecimento da Pele/patologia , Adolescente , Adulto , Idoso , Povo Asiático , População Negra , Estudos Transversais , Feminino , Humanos , Internet , Masculino , Pessoa de Meia-Idade , Fatores Sexuais , Escala Visual Analógica , População Branca , Adulto Jovem
2.
Nanoscale ; 10(8): 4028-4035, 2018 Feb 22.
Artigo em Inglês | MEDLINE | ID: mdl-29431820

RESUMO

Single crystal, nanoscale diamond membranes are highly sought after for a variety of applications including nanophotonics, nanoelectronics and quantum information science. However, so far, the availability of conductive diamond membranes has remained an unreachable goal. In this work we present a complete nanofabrication methodology for engineering high aspect ratio, electrically active single crystal diamond membranes. The membranes have large lateral directions, exceeding ∼500 × 500 µm2 and are only several hundreds of nanometers thick. We further realize vertical single crystal p-n junctions made from the diamond membranes that exhibit onset voltages of ∼10 V and a current of several mA. Moreover, we deterministically introduce optically active color centers into the membranes, and demonstrate for the first time a single crystal nanoscale diamond LED. The robust and scalable approach to engineer the electrically active single crystal diamond membranes offers new pathways for advanced nanophotonic, nanoelectronic and optomechanical devices employing diamond.

3.
Front Neurosci ; 11: 659, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-29230164

RESUMO

Wireless neural stimulators are being developed to address problems associated with traditional lead-based implants. However, designing wireless stimulators on the sub-millimeter scale (<1 mm3) is challenging. As device size shrinks, it becomes difficult to deliver sufficient wireless power to operate the device. Here, we present a sub-millimeter, inductively powered neural stimulator consisting only of a coil to receive power, a capacitor to tune the resonant frequency of the receiver, and a diode to rectify the radio-frequency signal to produce neural excitation. By replacing any complex receiver circuitry with a simple rectifier, we have reduced the required voltage levels that are needed to operate the device from 0.5 to 1 V (e.g., for CMOS) to ~0.25-0.5 V. This reduced voltage allows the use of smaller receive antennas for power, resulting in a device volume of 0.3-0.5 mm3. The device was encapsulated in epoxy, and successfully passed accelerated lifetime tests in 80°C saline for 2 weeks. We demonstrate a basic proof-of-concept using stimulation with tens of microamps of current delivered to the sciatic nerve in rat to produce a motor response.

4.
J Urol ; 198(4): 897-904, 2017 10.
Artigo em Inglês | MEDLINE | ID: mdl-28536084

RESUMO

PURPOSE: We present the long-term effects of repeat onabotulinumtoxinA 100 U treatment on health related quality of life in patients with overactive bladder and urinary incontinence who had an inadequate response to and/or were intolerant of an anticholinergic. MATERIALS AND METHODS: Patients who completed either of 2, 24-week phase III trials could enter a 3-year extension study and request multiple onabotulinumtoxinA 100 U treatments as needed. Results of the I-QOL (Incontinence-Quality of Life) and KHQ (King's Health Questionnaire) are reported for up to 6 treatments. Consistency of the response to repeat onabotulinumtoxinA treatments was evaluated by classifying patients by the I-QOL response to the first treatment and analyzing responses to treatments 2 to 6. RESULTS: After onabotulinumtoxinA treatments 1 to 6, improvements in I-QOL scores were consistently 2 to 3 times the minimally important difference, and improvements in KHQ role limitations and social limitations domain scores were 5 to 6 and 3 to 4 times the minimally important difference, respectively. Most patients achieved or exceeded the minimally important difference for I-QOL and KHQ domain scores. Furthermore, 72.9% of patients who achieved or exceeded the minimally important difference for I-QOL after treatment 1 did so for all subsequent treatments. Of patients with a poor response after treatment 1, 38.3% achieved improvements greater than the minimally important difference for all subsequent treatments. CONCLUSIONS: In patients with overactive bladder and incontinence consistent and clinically meaningful improvements in health related quality of life were observed with repeat onabotulinumtoxinA 100 U treatments. A positive response after treatment 1 tended to predict similar responses to subsequent treatments, whereas a lack of response to treatment 1 did not preclude positive response(s) to later treatments.


Assuntos
Inibidores da Liberação da Acetilcolina/uso terapêutico , Toxinas Botulínicas Tipo A/uso terapêutico , Qualidade de Vida , Bexiga Urinária Hiperativa/tratamento farmacológico , Incontinência Urinária/tratamento farmacológico , Inibidores da Liberação da Acetilcolina/farmacologia , Idoso , Toxinas Botulínicas Tipo A/farmacologia , Feminino , Seguimentos , Humanos , Assistência de Longa Duração/métodos , Masculino , Pessoa de Meia-Idade , Retratamento/métodos , Resultado do Tratamento , Urodinâmica/efeitos dos fármacos
5.
BJU Int ; 119(6): 926-932, 2017 06.
Artigo em Inglês | MEDLINE | ID: mdl-28139068

RESUMO

OBJECTIVE: To examine whether response to first treatment with onabotulinumtoxinA is predictive of long-term treatment outcome in patients with neurogenic detrusor overactivity (NDO). PATIENTS AND METHODS: Patients with NDO who were enrolled in a 3-year extension study (after a 52-week phase III study) received onabotulinumtoxinA 'as needed', based on fulfilment of prespecified retreatment criteria. This post hoc analysis included patients who received only the 200-U dose during the phase III and extension studies. Data on mean percent reduction from baseline in urinary incontinence (UI) episodes at week 6 after the first treatment were analysed, and the patients were stratified into three response groups: <50% (group 1; n = 33), 50-74% (group 2; n = 23), and 75-100% (group 3; n = 139). The following were assessed: change from baseline in mean percent UI reduction; proportions of patients who achieved ≥50% and 100% UI reduction after each subsequent treatment, and patients who achieved ≥50% UI reduction after all subsequent treatments; change from baseline in Incontinence Quality of Life (I-QOL) total summary score; and the proportion of patients who achieved or exceeded the minimally important difference (MID; +11 points) in I-QOL score. Adverse events (AEs) were also assessed. RESULTS: The majority of the patients (83.1%; 162/195) experienced a ≥50% UI reduction after onabotulinumtoxinA treatment 1. Baseline characteristics were largely similar across the groups. After treatment 1, the mean percent reduction in UI remained consistent in subsequent treatments 2-6 for patients in response group 2 (range: 64.5-83.5%) and group 3 (range: 79.4-88.0%), but increased for those in the low response group (range: 36.3-60.3%). After treatment 1, the proportion of patients who achieved ≥50% reduction in UI episodes was consistent with subsequent treatments 2-6 in group 2 (range: 75.0-100%) and group 3 (range: 87.3-97.1%), but increased in the low response group (range: 48.3-72.7%). Even among those who achieved a low response after treatment 1, 37.9% of patients achieved ≥50% UI reduction in all subsequent treatments. Improvements in I-QOL scores in groups 2 and 3 were consistently 2-3 times the MID. In the low response group, at least 50% of the patients achieved or exceeded the MID with treatments 2-6. AEs were similar across all response groups and consistent across repeated treatments. CONCLUSION: Patients with NDO with a ≥50% UI reduction after their first onabotulinumtoxinA treatment continued to experience consistent improvements in UI and quality of life with subsequent treatments over the duration of 4 years. A <50% UI reduction after first treatment did not necessarily predict low response with subsequent treatments. Thus, these results underscore the importance of attempting at least a second treatment with onabotulinumtoxinA before deeming patients unsuitable for onabotulinumtoxinA therapy.


Assuntos
Toxinas Botulínicas Tipo A/administração & dosagem , Bexiga Urinária Hiperativa/tratamento farmacológico , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Qualidade de Vida , Fatores de Tempo , Resultado do Tratamento
6.
J Urol ; 196(3): 801-8, 2016 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-27091236

RESUMO

PURPOSE: We assessed the year-to-year consistency of outcomes in patients with urinary incontinence due to neurogenic detrusor overactivity who completed 4 years of onabotulinumtoxinA treatment. MATERIALS AND METHODS: Eligible patients who completed a 52-week phase 3 trial of onabotulinumtoxinA for urinary incontinence could enter a 3-year open label extension study of onabotulinumtoxinA 200 or 300 U administered as needed for symptom control. This analysis focused on 227 patients who completed the 4-year study. Outcomes assessed by year of treatment included mean treatments per year, mean change from baseline at week 6 in urinary incontinence episodes per day and the I-QOL (Incontinence Quality of Life) total summary score, the proportion of patients with 50% or greater and 100% reductions in urinary incontinence episodes per day, duration of effect and adverse events. RESULTS: Patients reported 4.3 urinary incontinence episodes per day at baseline and received 1.4 to 1.5 onabotulinumtoxinA treatments per year. The decrease in urinary incontinence following onabotulinumtoxinA consistently ranged from -3.4 to -3.9 episodes per day across 4 years. A high proportion of patients achieved 50% or greater and 100% urinary incontinence reductions in each year (range 86.6% to 94.1% and 43.6% to 57.4%, respectively). Consistent and clinically relevant improvements in I-QOL scores were observed in each treatment year. The overall median duration of effect of onabotulinumtoxinA was 9.0 months or greater (range 3.0 to 49.2) and 26.0% or more of patients experienced a duration of effect of 12 months or greater. The most common adverse event was urinary tract infection with no increased incidence with time. CONCLUSIONS: Patients with neurogenic detrusor overactivity who completed 4 years of onabotulinumtoxinA treatment experienced a consistent duration of treatment effect and year-to-year improvements in urinary incontinence and quality of life with no new safety signals.


Assuntos
Toxinas Botulínicas Tipo A/administração & dosagem , Qualidade de Vida , Bexiga Urinaria Neurogênica/tratamento farmacológico , Urodinâmica/efeitos dos fármacos , Inibidores da Liberação da Acetilcolina/administração & dosagem , Adulto , Idoso , Cistoscopia , Relação Dose-Resposta a Droga , Feminino , Humanos , Injeções Intramusculares/métodos , Masculino , Pessoa de Meia-Idade , Resultado do Tratamento , Bexiga Urinaria Neurogênica/fisiopatologia , Bexiga Urinaria Neurogênica/psicologia
7.
J Urol ; 196(3): 791-800, 2016 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-27038769

RESUMO

PURPOSE: These are the final results of the prospective, multicenter, long-term (3.5-year) study of the efficacy/safety of onabotulinumtoxinA for overactive bladder syndrome. MATERIALS AND METHODS: Patients who completed either of 2, 24-week phase 3 trials could enter a 3-year extension and continue treatment with onabotulinumtoxinA 100 U as needed to control overactive bladder symptoms. Data were analyzed by the treatment(s) received (up to 6) and in discrete subgroups that received 1, 2, 3, 4, 5 or 6 treatments (to evaluate the consistency of the response after repeat treatments in the same patient groups). Assessments included the change from baseline in the number of urinary incontinence episodes per day and the proportion of patients who reported improvement/great improvement in urinary symptoms on the TBS (Treatment Benefit Scale) at week 12 as co-primary end points. Other end points were the change from baseline in I-QOL (Incontinence Quality of Life), the number of urgency and micturition episodes per day; duration of effect; the number of adverse events; and the initiation of intermittent catheterization. RESULTS: Consistent mean reductions in urinary incontinence were observed following continued onabotulinumtoxinA treatment, ranging from -3.1 to -3.8 in the overall population and -2.9 to -4.5 in the discrete subgroups. Durable improvements were seen in overactive bladder symptoms and quality of life. A high proportion of patients rated their condition as improved/greatly improved. The median duration of effect was 7.6 months. The most common adverse event was urinary tract infection. The rate of de novo catheterization after the first treatment was 4.0% and it ranged from 0.6% to 1.7% after subsequent treatments. CONCLUSIONS: Long-term onabotulinumtoxinA treatment consistently decreased overactive bladder symptoms and improved quality of life with no new safety signals.


Assuntos
Toxinas Botulínicas Tipo A/administração & dosagem , Qualidade de Vida , Bexiga Urinária Hiperativa/tratamento farmacológico , Urodinâmica/fisiologia , Inibidores da Liberação da Acetilcolina/administração & dosagem , Feminino , Seguimentos , Humanos , Injeções Intramusculares , Masculino , Pessoa de Meia-Idade , Inquéritos e Questionários , Fatores de Tempo , Resultado do Tratamento , Bexiga Urinária Hiperativa/fisiopatologia , Bexiga Urinária Hiperativa/psicologia
8.
J Microbiol Immunol Infect ; 49(1): 46-51, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-26454421

RESUMO

BACKGROUND/PURPOSE: Methicillin-resistant Staphylococcus aureus (MRSA) nosocomial pneumonia (NP) is associated with higher resource utilization, increased hospital stays, and mortality. We present a health economics model to understand the impact of using linezolid as the first-line treatment of MRSA NP in Taiwan. METHODS: We developed a cost-effectiveness model to estimate the costs and clinical outcomes of using linezolid 600 mg b.i.d. versus vancomycin 15 mg/kg b.i.d. as the first-line treatment of MRSA NP in Taiwan. The model is a decision-analytic analysis in which a MRSA-confirmed patient is simulated to utilize one of the treatments, using data from a clinical trial. Within each treatment arm, the patient can or cannot achieve clinical cure. Regardless of whether the clinical cure was achieved or not, the patient may or may not have experienced an adverse event. The per-protocol results for clinical cure were 57.6% and 46.6% for linezolid and vancomycin, respectively. RESULTS: The total cost of linezolid was $376 more per patient than that of vancomycin. Drug costs were higher for linezolid than for vancomycin ($1108 vs. $233), and hospitalization costs were lower ($4998 vs. $5496). With higher cost and higher cure rates for linezolid, the incremental cost per cure was $3421. CONCLUSION: This study projects linezolid to have higher drug costs, lower hospital costs, and higher overall costs compared with vancomycin. This is balanced against the higher clinical cure rate for linezolid. Depending on the willingness to pay for clinical cure, linezolid could be cost effective as the first-line treatment of NP in Taiwan.


Assuntos
Antibacterianos/economia , Antibacterianos/uso terapêutico , Infecção Hospitalar/tratamento farmacológico , Linezolida/uso terapêutico , Staphylococcus aureus Resistente à Meticilina/isolamento & purificação , Pneumonia Estafilocócica/tratamento farmacológico , Análise Custo-Benefício , Infecção Hospitalar/microbiologia , Feminino , Humanos , Linezolida/economia , Masculino , Pneumonia Estafilocócica/microbiologia , Taiwan , Resultado do Tratamento
9.
Artigo em Inglês | MEDLINE | ID: mdl-26274208

RESUMO

Recordings in the human medial temporal lobe have found many neurons that respond to pictures (and related stimuli) of just one particular person of those presented. It has been proposed that these are concept cells, responding to just a single concept. However, a direct experimental test of the concept cell idea appears impossible, because it would need the measurement of the response of each cell to enormous numbers of other stimuli. Here we propose a new statistical method for analysis of the data that gives a more powerful way to analyze how close data are to the concept-cell idea. Central to the model is the neuronal sparsity, defined as the total fraction of stimuli that elicit an above-threshold response in the neuron. The model exploits the large number of sampled neurons to give sensitivity to situations where the average response sparsity is much less than one response for the number of presented stimuli. We show that a conventional model where a single sparsity is postulated for all neurons gives an extremely poor fit to the data. In contrast, a model with two dramatically different populations gives an excellent fit to data from the hippocampus and entorhinal cortex. In the hippocampus, one population has 7% of the cells with a 2.6% sparsity. But a much larger fraction (93%) respond to only 0.1% of the stimuli. This can result in an extreme bias in the responsiveness of reported neurons compared with a typical neuron. Finally, we show how to allow for the fact that some identified units correspond to multiple neurons and find that our conclusions at the neural level are quantitatively changed but strengthened, with an even stronger difference between the two populations.


Assuntos
Modelos Neurológicos , Neurônios/fisiologia , Lobo Temporal/fisiologia , Potenciais de Ação/fisiologia , Humanos , Funções Verossimilhança , Modelos Estatísticos
10.
Nanoscale ; 6(17): 10027-32, 2014 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-25031102

RESUMO

Controlled engineering of isolated solid state quantum systems is one of the most prominent goals in modern nanotechnology. In this letter we demonstrate a previously unknown quantum system namely silicon carbide tetrapods. The tetrapods have a cubic polytype core (3C) and hexagonal polytype legs (4H)--a geometry that creates spontaneous polarization within a single tetrapod. Modeling of the tetrapod structures predicts that a bound exciton should exist at the 3C-4H interface. The simulations are confirmed by the observation of fully polarized and narrowband single photon emission from the tetrapods at room temperature. The single photon emission provides important insights into understanding the quantum confinement effects in non-spherical nanostructures. Our results pave the way to a new class of crystal phase nanomaterials that exhibit single photon emission at room temperature and therefore are suitable for sensing, quantum information and nanophotonics.

11.
Nat Commun ; 5: 3523, 2014 Mar 24.
Artigo em Inglês | MEDLINE | ID: mdl-24662922

RESUMO

Lanthanides are vital components in lighting, imaging technologies and future quantum memory applications owing to their narrow optical transitions and long spin coherence times. Recently, diamond has become a pre-eminent platform for the realisation of many experiments in quantum information science. Here we demonstrate a promising approach to incorporate Eu ions into diamond, providing a means to harness the exceptional characteristics of both lanthanides and diamond in a single material. Polyelectrolytes are used to electrostatically assemble Eu(III) chelate molecules on diamond and subsequently chemical vapour deposition is employed for the diamond growth. Fluorescence measurements show that the Eu atoms retain the characteristic optical signature of Eu(III) upon incorporation into the diamond lattice. Computational modelling supports the experimental findings, corroborating that Eu(III) in diamond is a stable configuration. The formed defects demonstrate the outstanding chemical control over the incorporation of impurities into diamond enabled by the electrostatic assembly together with chemical vapour deposition growth.

13.
J R Soc Interface ; 11(93): 20130942, 2014 Apr 06.
Artigo em Inglês | MEDLINE | ID: mdl-24478280

RESUMO

Cuttlefish, Sepia officinalis, possess neurally controlled, pigmented chromatophore organs that allow rapid changes in skin patterning and coloration in response to visual cues. This process of adaptive coloration is enabled by the 500% change in chromatophore surface area during actuation. We report two adaptations that help to explain how colour intensity is maintained in a fully expanded chromatophore when the pigment granules are distributed maximally: (i) pigment layers as thin as three granules that maintain optical effectiveness and (ii) the presence of high-refractive-index proteins-reflectin and crystallin-in granules. The latter discovery, combined with our finding that isolated chromatophore pigment granules fluoresce between 650 and 720 nm, refutes the prevailing hypothesis that cephalopod chromatophores are exclusively pigmentary organs composed solely of ommochromes. Perturbations to granular architecture alter optical properties, illustrating a role for nanostructure in the agile, optical responses of chromatophores. Our results suggest that cephalopod chromatophore pigment granules are more complex than homogeneous clusters of chromogenic pigments. They are luminescent protein nanostructures that facilitate the rapid and sophisticated changes exhibited in dermal pigmentation.


Assuntos
Cromatóforos , Decapodiformes , Pigmentos Biológicos/metabolismo , Pigmentação da Pele/fisiologia , Animais , Cromatóforos/citologia , Cromatóforos/metabolismo , Decapodiformes/anatomia & histologia , Decapodiformes/fisiologia
14.
Nano Lett ; 13(3): 1210-5, 2013 Mar 13.
Artigo em Inglês | MEDLINE | ID: mdl-23432630

RESUMO

Recently, significant research efforts have been made to develop complex nanostructures to provide more sophisticated control over the optical and electronic properties of nanomaterials. However, there are only a handful of semiconductors that allow control over their geometry via simple chemical processes. Herein, we present a molecularly seeded synthesis of a complex nanostructure, SiC tetrapods, and report on their structural and optical properties. The SiC tetrapods exhibit narrow line width photoluminescence at wavelengths spanning the visible to near-infrared spectral range. Synthesized from low-toxicity, earth abundant elements, these tetrapods are a compelling replacement for technologically important quantum optical materials that frequently require toxic metals such as Cd and Se. This previously unknown geometry of SiC nanostructures is a compelling platform for biolabeling, sensing, spintronics, and optoelectronics.

15.
Nanoscale ; 4(11): 3405-9, 2012 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-22572920

RESUMO

A highly porous electrode comprised of biologically templated iridium oxide-gold (IrO(2)-Au) hybrid nanowires is introduced for electrochromic applications. A filamentous M13 virus is genetically engineered to display IrO(2)-binding peptides on the viral surface and used as a template for the self-assembly of IrO(2) nanoclusters into a nanowire. The open porous morphology of the prepared nanowire film facilitates ion transport. Subsequently, the redox kinetics of the IrO(2) nanowires seems to be limited by the electric resistance of the nanowire film. To increase the electron mobility in the nanowires, gold nanoparticles are chemically linked to the virus prior to the IrO(2) mineralization, forming a gold nanostring structure along the long axis of the virus. The resulting IrO(2)-Au hybrid nanowires exhibit a switching time of 35 ms for coloration and 25 ms for bleaching with a transmission change of about 30.5% at 425 nm. These values represent almost an order of magnitude faster switching responses than those of an IrO(2) nanowire film having the similar optical contrast. This work shows that genetically engineered viruses can serve as versatile templates to co-assemble multiple functional molecules, enabling control of the electrochemical properties of nanomaterials.


Assuntos
Ouro/química , Irídio/química , Nanofios/química , Bacteriófago M13/química , Dimetilpolisiloxanos/química , Técnicas Eletroquímicas , Nanopartículas/química , Oxirredução , Peptídeos/química
16.
Opt Express ; 20(8): 8891-7, 2012 Apr 09.
Artigo em Inglês | MEDLINE | ID: mdl-22513599

RESUMO

Optical coupling of an ensemble of silicon-vacancy (SiV) centers to single-crystal diamond microdisk cavities is demonstrated. The cavities are fabricated from a single-crystal diamond membrane generated by ion implantation and electrochemical liftoff followed by homo-epitaxial overgrowth. Whispering gallery modes spectrally overlap with the zero-phonon line (ZPL) of the SiV centers and exhibit quality factors ∼ 2200. Lifetime reduction from 1.8 ns to 1.48 ns is observed from SiV centers in the cavity compared to those in the membrane outside the cavity. These results are pivotal in developing diamond integrated photonics networks.

17.
Adv Mater ; 24(10): OP54-9, 2012 Mar 08.
Artigo em Inglês | MEDLINE | ID: mdl-22290655

RESUMO

Homoepitaxial growth of single crystal diamond membranes is demonstrated employing a microwave plasma chemical vapor deposition technique. The membranes possess excellent structural, optical, and spin properties, which make them suitable for fabrication of optical microcavities for applications in quantum information processing, photonics, spintronics, and sensing.


Assuntos
Diamante/química , Equipamentos e Provisões Elétricas , Membranas Artificiais , Teoria Quântica , Gases em Plasma/química , Volatilização
18.
Nat Nanotechnol ; 5(5): 340-4, 2010 May.
Artigo em Inglês | MEDLINE | ID: mdl-20383127

RESUMO

Over several billion years, cyanobacteria and plants have evolved highly organized photosynthetic systems to shuttle both electronic and chemical species for the efficient oxidation of water. In a similar manner to reaction centres in natural photosystems, molecular and metal oxide catalysts have been used to photochemically oxidize water. However, the various approaches involving the molecular design of ligands, surface modification and immobilization still have limitations in terms of catalytic efficiency and sustainability. Here, we demonstrate a biologically templated nanostructure for visible light-driven water oxidation that uses a genetically engineered M13 virus scaffold to mediate the co-assembly of zinc porphyrins (photosensitizer) and iridium oxide hydrosol clusters (catalyst). Porous polymer microgels are used as an immobilization matrix to improve the structural durability of the assembled nanostructures and to allow the materials to be recycled. Our results suggest that the biotemplated nanoscale assembly of functional components is a promising route to significantly improved photocatalytic water-splitting systems.


Assuntos
Bacteriófago M13/metabolismo , Luz , Nanofios/química , Porfirinas/metabolismo , Água/química , Bacteriófago M13/ultraestrutura , Catálise/efeitos da radiação , Irídio/metabolismo , Nanofios/ultraestrutura , Oxirredução/efeitos da radiação , Oxigênio/análise
19.
J Am Chem Soc ; 132(5): 1462-3, 2010 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-20078048

RESUMO

Biological molecules can be used as versatile templates for assembling nanoscale materials because of their unique structures and chemical diversities. Supramolecular organization of molecular pigments, as is found in the natural light-harvesting antenna, has drawn attention for its potential applications to sensors, photocatalytic systems, and photonic devices. Here we show the arrangement of molecular pigments into a one-dimensional light-harvesting antenna using M13 viruses as scaffolds. Chemical grafting of zinc porphyrins to M13 viruses induces distinctive spectroscopic changes, including fluorescence quenching, the extensive band broadening and small red shift of their absorption spectrum, and the shortened lifetime of the excited states. Based on these optical signatures we suggest a hypothetical model to explain the energy transfer occurring in the supramolecular porphyrin structures templated with the virus. We expect that further genetic engineering of M13 viruses can allow us to coassemble other functional materials (e.g., catalysts and electron transfer mediators) with pigments, implying potential applications to photochemical devices.


Assuntos
Bacteriófago M13/química , Metaloporfirinas/análise , Transferência de Energia , Metaloporfirinas/química , Modelos Moleculares , Fotoquímica , Espectrometria de Fluorescência
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