Photodetection with Active Optical Antennas Knight, Mark W.; Sobhani, Heidar; Nordlander, Peter ...
Science (American Association for the Advancement of Science),
05/2011, Letnik:
332, Številka:
6030
Journal Article
Recenzirano
Nanoantennas are key optical components for light harvesting; photodiodes convert light into a current of electrons for photodetection. We show that these two distinct, independent functions can be ...combined into the same structure. Photons coupled into a metallic nanoantenna excite resonant plasmons, which decay into energetic, "hot" electrons injected over a potential barrier at the nanoantenna-semiconductor interface, resulting in a photocurrent. This dual-function structure is a highly compact, wavelength-resonant, and polarization-specific light detector, with a spectral response extending to energies well below the semiconductor band edge.
Plasmon-resonant nanoparticle complexes show highly promising potential for light-triggered, remote-controlled delivery of oligonucleotides on demand, for research and therapeutic purposes. Here we ...investigate the light-triggered release of DNA from two types of nanoparticle substrates: Au nanoshells and Au nanorods. Both light-triggered and thermally induced release are distinctly observable from nanoshell-based complexes, with light-triggered release occurring at an ambient solution temperature well below the DNA melting temperature. Surprisingly, no analogous measurable release was observable from nanorod-based complexes below the DNA melting temperature. These results suggest that a nonthermal mechanism may play a role in plasmon resonant, light-triggered DNA release.
Abstract
Van der Waals materials and heterostructures that manifest strongly bound exciton states at room temperature also exhibit emergent physical phenomena and are of great promise for ...optoelectronic applications. Here, we demonstrate that nanostructured, multilayer transition metal dichalcogenides (TMDCs) by themselves provide an ideal platform for excitation and control of excitonic modes, paving the way to exciton-photonics. Hence, we show that by patterning the TMDCs into nanoresonators, strong dispersion and avoided crossing of exciton, cavity photons and plasmon polaritons with effective separation energy exceeding 410 meV can be controlled with great precision. We further observe that inherently strong TMDC exciton absorption resonances may be completely suppressed due to excitation of hybrid light-matter states and their interference. Our work paves the way to the next generation of integrated exciton optoelectronic nano-devices and applications in light generation, computing, and sensing.
Aluminum for Plasmonics Knight, Mark W; King, Nicholas S; Liu, Lifei ...
ACS nano,
01/2014, Letnik:
8, Številka:
1
Journal Article
Recenzirano
Unlike silver and gold, aluminum has material properties that enable strong plasmon resonances spanning much of the visible region of the spectrum and into the ultraviolet. This extended response, ...combined with its natural abundance, low cost, and amenability to manufacturing processes, makes aluminum a highly promising material for commercial applications. Fabricating Al-based nanostructures whose optical properties correspond with theoretical predictions, however, can be a challenge. In this work, the Al plasmon resonance is observed to be remarkably sensitive to the presence of oxide within the metal. For Al nanodisks, we observe that the energy of the plasmon resonance is determined by, and serves as an optical reporter of, the percentage of oxide present within the Al. This understanding paves the way toward the use of aluminum as a low-cost plasmonic material with properties and potential applications similar to those of the coinage metals.
Plasmonic absorption of light can lead to significant local heating in metallic nanostructures, an effect that defines the subfield of thermoplasmonics and has been leveraged in diverse applications ...from biomedical technology to optoelectronics. Quantitatively characterizing the resulting local temperature increase can be very challenging in isolated nanostructures. By measuring the optically induced change in resistance of metal nanowires with a transverse plasmon mode, we quantitatively determine the temperature increase in single nanostructures with the dependence on incident polarization clearly revealing the plasmonic heating mechanism. Computational modeling explains the resonant and nonresonant contributions to the optical heating and the dominant pathways for thermal transport. These results, obtained by combining electronic and optical measurements, place a bound on the role of optical heating in prior experiments and suggest design guidelines for engineered structures meant to leverage such effects.
Vivid, full-color aluminum plasmonic pixels Olson, Jana; Manjavacas, Alejandro; Liu, Lifei ...
Proceedings of the National Academy of Sciences - PNAS,
10/2014, Letnik:
111, Številka:
40
Journal Article
Recenzirano
Odprti dostop
Aluminum is abundant, low in cost, compatible with complementary metal-oxide semiconductor manufacturing methods, and capable of supporting tunable plasmon resonance structures that span the entire ...visible spectrum. However, the use of Al for color displays has been limited by its intrinsically broad spectral features. Here we show that vivid, highly polarized, and broadly tunable color pixels can be produced from periodic patterns of oriented Al nanorods. Whereas the nanorod longitudinal plasmon resonance is largely responsible for pixel color, far-field diffractive coupling is used to narrow the plasmon linewidth, enabling monochromatic coloration and significantly enhancing the far-field scattering intensity of the individual nanorod elements. The bright coloration can be observed with p-polarized white light excitation, consistent with the use of this approach in display devices. The resulting color pixels are constructed with a simple design, are compatible with scalable fabrication methods, and provide contrast ratios exceeding 100:1.
Significance Full-color displays are typically fabricated using a combination of chromatic materials of various types, introduced into an addressable pixel-based electronic device. Here we show that brightly colored, highly vivid pixels, directly suitable for RGB displays, can be fabricated using periodic areas of Al nanorods in each pixel. Both nanorod length and spacing are critically important in achieving strong and spectrally distinct scattering signatures across the visible spectrum. This use of a low-cost, abundant metal for achieving full-spectrum coloration is compatible with complementary metal-oxide semiconductor manufacturing methods and directly applicable to current liquid crystal display technology.
Au nanoparticles with plasmon resonances in the near-infrared (NIR) region of the spectrum efficiently convert light into heat, a property useful for the photothermal ablation of cancerous tumors ...subsequent to nanoparticle uptake at the tumor site. A critical aspect of this process is nanoparticle size, which influences both tumor uptake and photothermal efficiency. Here, we report a direct comparative study of ∼90 nm diameter Au nanomatryoshkas (Au/SiO2/Au) and ∼150 nm diameter Au nanoshells for photothermal therapeutic efficacy in highly aggressive triple negative breast cancer (TNBC) tumors in mice. Au nanomatryoshkas are strong light absorbers with 77% absorption efficiency, while the nanoshells are weaker absorbers with only 15% absorption efficiency. After an intravenous injection of Au nanomatryoshkas followed by a single NIR laser dose of 2 W/cm2 for 5 min, 83% of the TNBC tumor-bearing mice appeared healthy and tumor free >60 days later, while only 33% of mice treated with nanoshells survived the same period. The smaller size and larger absorption cross section of Au nanomatryoshkas combine to make this nanoparticle more effective than Au nanoshells for photothermal cancer therapy.
The translation of genome sequencing into routine health care has been slow, partly because of concerns about affordability. The aspirational cost of sequencing a genome is $1000, but there is little ...evidence to support this estimate. We estimate the cost of using genome sequencing in routine clinical care in patients with cancer or rare diseases.
We performed a microcosting study of Illumina-based genome sequencing in a UK National Health Service laboratory processing 399 samples/year. Cost data were collected for all steps in the sequencing pathway, including bioinformatics analysis and reporting of results. Sensitivity analysis identified key cost drivers.
Genome sequencing costs £6841 per cancer case (comprising matched tumor and germline samples) and £7050 per rare disease case (three samples). The consumables used during sequencing are the most expensive component of testing (68-72% of the total cost). Equipment costs are higher for rare disease cases, whereas consumable and staff costs are slightly higher for cancer cases.
The cost of genome sequencing is underestimated if only sequencing costs are considered, and likely surpasses $1000/genome in a single laboratory. This aspirational sequencing cost will likely only be achieved if consumable costs are considerably reduced and sequencing is performed at scale.
When plasmonic nanostructures serve as the metallic counterpart of a metal–semiconductor Schottky interface, hot electrons due to plasmon decay are emitted across the Schottky barrier, generating ...measurable photocurrents in the semiconductor. When the plasmonic nanostructure is atop the semiconductor, only a small percentage of hot electrons are excited with a wavevector permitting transport across the Schottky barrier. Here we show that embedding plasmonic structures into the semiconductor substantially increases hot electron emission. Responsivities increase by 25× over planar diodes for embedding depths as small as 5 nm. The vertical Schottky barriers created by this geometry make the plasmon-induced hot electron process the dominant contributor to photocurrent in plasmonic nanostructure-diode-based devices.
Interventions based on behavioral science might reduce inappropriate antibiotic prescribing.
To assess effects of behavioral interventions and rates of inappropriate (not guideline-concordant) ...antibiotic prescribing during ambulatory visits for acute respiratory tract infections.
Cluster randomized clinical trial conducted among 47 primary care practices in Boston and Los Angeles. Participants were 248 enrolled clinicians randomized to receive 0, 1, 2, or 3 interventions for 18 months. All clinicians received education on antibiotic prescribing guidelines on enrollment. Interventions began between November 1, 2011, and October 1, 2012. Follow-up for the latest-starting sites ended on April 1, 2014. Adult patients with comorbidities and concomitant infections were excluded.
Three behavioral interventions, implemented alone or in combination: suggested alternatives presented electronic order sets suggesting nonantibiotic treatments; accountable justification prompted clinicians to enter free-text justifications for prescribing antibiotics into patients' electronic health records; peer comparison sent emails to clinicians that compared their antibiotic prescribing rates with those of "top performers" (those with the lowest inappropriate prescribing rates).
Antibiotic prescribing rates for visits with antibiotic-inappropriate diagnoses (nonspecific upper respiratory tract infections, acute bronchitis, and influenza) from 18 months preintervention to 18 months afterward, adjusting each intervention's effects for co-occurring interventions and preintervention trends, with random effects for practices and clinicians.
There were 14,753 visits (mean patient age, 47 years; 69% women) for antibiotic-inappropriate acute respiratory tract infections during the baseline period and 16,959 visits (mean patient age, 48 years; 67% women) during the intervention period. Mean antibiotic prescribing rates decreased from 24.1% at intervention start to 13.1% at intervention month 18 (absolute difference, -11.0%) for control practices; from 22.1% to 6.1% (absolute difference, -16.0%) for suggested alternatives (difference in differences, -5.0% 95% CI, -7.8% to 0.1%; P = .66 for differences in trajectories); from 23.2% to 5.2% (absolute difference, -18.1%) for accountable justification (difference in differences, -7.0% 95% CI, -9.1% to -2.9%; P < .001); and from 19.9% to 3.7% (absolute difference, -16.3%) for peer comparison (difference in differences, -5.2% 95% CI, -6.9% to -1.6%; P < .001). There were no statistically significant interactions (neither synergy nor interference) between interventions.
Among primary care practices, the use of accountable justification and peer comparison as behavioral interventions resulted in lower rates of inappropriate antibiotic prescribing for acute respiratory tract infections.
clinicaltrials.gov Identifier: NCT01454947.
PDF
