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Interferometric scattering microscopy is increasingly employed in biomedical research owing to its extraordinary capability of detecting nano-objects individually through their intrinsic elastic scattering. To significantly improve the signal-to-noise ratio without increasing illumination intensity, we developed photonic resonator interferometric scattering microscopy (PRISM) in which a dielectric photonic crystal (PC) resonator is utilized as the sample substrate. The scattered light is amplified by the PC through resonant near-field enhancement, which then interferes with the, Here, the authors present photonic resonator interferometric scattering microscopy, which utilises a dielectric photonic crystal as the sample substrate. The resonant near-field enhancement leads to improved signal to noise ratio without increasing illumination intensity.

Plasmonic nanoparticles (NPs) hold tremendous promise for catalyzing light-driven chemical reactions. The conventionally assumed detrimental absorption loss from plasmon damping can now be harveste...

We report 3,000-fold signal enhancement with blinking suppression capability and single QD sensitivity using low-NA lens. Applied toward miRNA detection assays, we achieve single-base mutation selectivity, and 10-attomolar detection limit.

Newly demonstrated advanced biosensor imaging technologies utilize the unique electromagnetic capabilities of photonic metamaterials to enhance the interaction between light and biological matter. The resulting capabilities address gaps in existing technologies for biomolecular analysis that rely upon enzymatic and chemical amplification, costly instrumentation, and complex assay protocols. Through amplification of the excitation/extraction efficiency of light emitting tags, absorption efficiency of nanoparticle tags, and scattering efficiency of biological analytes, technology platforms have been demonstrated that are capable of ultrasensitive, digital-resolution, room temperature, isothermal, rapid, and highly quantitative biomolecular analysis.

We developed photonic resonator interferometric scattering microscopy for the label-free detection of nano-objects at low illumination density using a non-immersion objective. Photonic crystals are utilized as the imaging substrates to enhance the intrinsic scattering signal.

We introduce a freeform metamaterial with a subwavelength-scale distribution of grayscale dielectric constants as a new class of electromagnetic material that exploits all possible material degrees of freedom and achieves supreme optical performances.

One of the frontiers in the field of biosensors is the ability to quantify specific target molecules with enough precision to count individual units in a test sample, and to observe the characteristics of individual biomolecular interactions. Technologies that enable observation of molecules with "digital precision" have applications for in vitro diagnostics with ultra-sensitive limits of detection, characterization of biomolecular binding kinetics with a greater degree of precision, and gaining deeper insights into biological processes through quantification of molecules in complex specimens that would otherwise be unobservable. In this review, we seek to capture the current state-of-the-art in the field of digital resolution biosensing. We describe the capabilities of commercially available technology platforms, as well as capabilities that have been described in published literature. We highlight approaches that utilize enzymatic amplification, nanoparticle tags, chemical tags, as well as label-free biosensing methods.

Activate capture and digital counting (AC + DC) is a rapid, 2-step, and ultrasensitive assay for protein quantification from a single droplet through the nanoparticle-photonic crystal coupling embedded in a self-powered microfluidic cartridge.

Nanoantennas offer the ultimate spatial control over light by concentrating optical energy well below the diffraction limit, whereas their quality factor (Q) is constrained by large radiative and dissipative losses. Dielectric microcavities, on the other hand, are capable of generating a high Q-factor through an extended photon storage time but have a diffraction-limited optical mode volume. Here we bridge the two worlds, by studying an exemplary hybrid system integrating plasmonic gold nanorods acting as nanoantennas with an on-resonance dielectric photonic crystal (PC) slab acting as a low-loss microcavity and, more importantly, by synergistically combining their advantages to produce a much stronger local field enhancement than that of the separate entities. To achieve this synergy between the two polar opposite types of nanophotonic resonant elements, we show that it is crucial to coordinate both the dissipative loss of the nanoantenna and the Q-factor of the low-loss cavity. In comparison to the antenna-cavity coupling approach using a Fabry-Perot resonator, which has proved successful for resonant amplification of the antenna's local field intensity, we theoretically and experimentally show that coupling to a modest-Q PC guided resonance can produce a greater amplification by at least an order of magnitude. The synergistic nanoantenna-microcavity hybrid strategy opens new opportunities for further enhancing nanoscale light-matter interactions to benefit numerous areas such as nonlinear optics, nanolasers, plasmonic hot carrier technology, and surface-enhanced Raman and infrared absorption spectroscopies., Revised version after acceptance

Nanoantenna-microcavity hybrid systems offer unique platforms for the study and manipulation of light at the nanoscale, since their constituents have either low mode volume or long photon storage time. A nearby dielectric optical cavity can modify the photonic environment surrounding a plasmonic nanoantenna, presenting opportunities to sculpt its spectral response. However, matching the polar opposites for enhanced light-matter interactions remains challenging, as the antenna can be rendered transparent by the cavity through destructive Fano interferences. In this work, we tackle this issue by offering a new plasmonic-photonic interaction framework. By coupling to a photonic crystal guided resonance, a gold nanostar delivers 1 order of magnitude amplified absorption, and the ultrasharp Lorentzian-line-shaped hybrid resonance is continuously tunable over a broad spectral range by scanning of the incidence angle. Our intuitive coupled mode model reveals that a distinct optical pathway highlighting the cavity-mediated activation of nanoantennas is key for absorption enhancement. Moreover, we show that the line width of the enhancement can be widely tunable, and that the maximum power transferred to the antennas is attained under critical coupling. The cooperative hybrid system opens up new opportunities to boost a wealth of applications including ultrasensitive molecular spectroscopy, plasmonic hot carrier chemistry, thermoplasmonic, spontaneous emission enhancement, nanolasers, and many more.

We demonstrate a rapid, 2-step, and ultrasensitive assay approach for quantification of target protein molecules from a single droplet test sample. The assay is comprised of antibody-conjugated gold nanoparticles (AuNPs) that are “activated” when they are mixed with the test sample and bind their targets. The resulting liquid is passed through a microfluidic channel with a photonic crystal (PC) biosensor that is functionalized with secondary antibodies to the target biomarker, so that only activated AuNPs are captured. Utilizing recently demonstrated hybrid optical coupling between the plasmon resonance of the AuNP and the resonance of the PC, each captured AuNP efficiently quenches the resonant reflection of the PC, thus enabling the captured AuNPs to be digitally counted with high signal-to-noise. To achieve a 2-step assay process that is performed on a single droplet test sample without washing steps or active pump elements, controlled single-pass flow rate is obtained with an absorbing paper pad waste reservoir embedded in a microfluidic cartridge. We use the activate capture and digital counting (AC + DC) approach to demonstrate HIV-1 capsid antigen p24 detection from a 40 μL spiked-in human serum sample at a one thousand-fold dynamic range (1–103 pg mL−1) with only a 35-minute process that is compatible with point-of-care (POC) analysis. The AC + DC approach allows for ultrasensitive and ultrafast biomolecule detection, with potential applications in infectious disease diagnostics and early stage disease monitoring. This work is supported by the National Institutes of Health (NIH) R01 AI20683, F30AI122925, and the Carl Woese Institute for Genomic Biology postdoctoral fellowship.

We report on the implementation of an automated platform for detecting the presence of an antibody biomarker for human papillomavirus-associated oropharyngeal cancer from a single droplet of serum, in which a nanostructured photonic crystal surface is used to amplify the output of a fluorescence-linked immunosorbent assay. The platform is comprised of a microfluidic cartridge with integrated photonic crystal chips that interfaces with an assay instrument that automates the introduction of reagents, wash steps, and surface drying. Upon assay completion, the cartridge interfaces with a custom laser-scanning instrument that couples light into the photonic crystal at the optimal resonance condition for fluorescence enhancement. The instrument is used to measure the fluorescence intensity values of microarray spots corresponding to the biomarkers of interest, in addition to several experimental controls that verify correct functioning of the assay protocol. In this work, we report both dose-response characterization of the system using anti-E7 antibody introduced at known concentrations into serum and characterization of a set of clinical samples from which results were compared with a conventional enzyme-linked immunosorbent assay (ELISA) performed in microplate format. The demonstrated capability represents a simple, rapid, automated, and high-sensitivity method for multiplexed detection of protein biomarkers from a low-volume test sample.

Coupling of electromagnetic energy from macroscale external light sources to nanometer-scale volumes associated with plasmonic and dielectric nanoantennas is utilized for excitation of Raman scattering on nanoparticles, excitation of semiconductor quantum dots, and resonant optical absorption. These phenomena are used in the context of detection of biomolecules for applications that include disease diagnostics from single-droplet test samples derived from bodily fluids.

Using nanoparticles as nanoantennas that are engineered to efficiently couple with the resonant modes of a photonic crystal surface, amplification of surface enhanced Raman spectroscopy and resonant enhanced absorption provides high signal-to-noise mechanisms for sensing biomolecular interactions with single-event resolution. This talk will summarize the underlying theory, sensor/instrument design, and applications in sensing viral pathogens, miRNA biomarkers for cancer, and proteins.

We theoretically and experimentally study integration of the dielectric photonic crystal slab (as a photonic microcavity) and gold nanorod (as a plasmonic nanoantenna) as an exemplary photonic-plasmonic hybrid system for highly cooperative near-field enhancement.

4-Aryl-NH-1,2,3-triazoles are valuable compounds in organic chemistry and pharmaceutical chemistry. In this paper, we describe a novel multicomponent reaction of aldehydes, nitroalkanes, and sodium azide for the synthesis of 4-aryl-NH-1,2,3-triazoles. In this transformation, it was found that both the slow addition of nitroalkane and the presence of NaHSO3/Na2SO3 are advantageous to promote the reaction results. Additionally, a series of aldehydes and nitro compounds were investigated.

We study a nanoantenna-microcavity hybrid approach for synergistic hotspot enhancement. We demonstrate that coupling to the photonic crystal guided resonance boosts the hotspot intensity of the gold nanorod (AuNR) by at least 1 order of magnitude in comparison to the Fabry-Perot cavity enhanced (~5x) AuNR.

The design of an all-dielectric nanoantenna based on nonradiating "anapole" modes is studied for biosensing applications in an aqueous environment, using FDTD electromagnetic simulation. The strictly confined electromagnetic field within a circular or rectangular opening at the center of a cylindrical silicon disk produces a single point electromagnetic hotspot with up to 6.5x enhancement of |E|, for the 630-650 nm wavelength range, and we can increase the value up to 25x by coupling additional electromagnetic energy from an underlying PEC-backed substrate. We characterize the effects of the substrate design and slot dimensions on the field enhancement magnitude, for devices operating in a water medium.

We report a photonic crystal (PC) biosensor that incorporates a porous TiO 2 film to boost sensitivity by enlarged surface area and enhanced interaction with the resonant electromagnetic fields. In the context of sensing small molecule interactions with proteins, the porous PC achieves 3.7x larger resonant wavelength shifts than an equivalent nonporous structure. Utilizing the porous PC as the wavelength selective element in an external cavity laser, the system provides narrow resonant linewidth via stimulated emission, and therefore establishes sub-picometer accuracy, representing a record high figure of merit for label free optical biosensors.

We present an approach to enhance particle nanoplasmonics by using coupling to the high-Q dielectric photonic crystal (PC) resonance. The PC-coupled gold nanorods (AuNRs) exhibit strong amplification (>9x) of the SERS signal compared to the PC-uncoupled AuNRs.

4-Aryl-NH-1,2,3-triazoles are valuable compounds in organic chemistry and pharmaceutical chemistry. In this paper, we describe a novel multicomponent reaction of aldehydes, nitroalkanes, and sodium azide for the synthesis of 4-aryl-NH-1,2,3-triazoles. In this transformation, it was found that both the slow addition of nitroalkane and the presence of NaHSO3/Na2SO3 are advantageous to promote the reaction results. Additionally, a series of aldehydes and nitro compounds were investigated.

We report the design, fabrication, and testing of a photonic crystal (PC) biosensor structure that incorporates a porous high refractive index TiO2 dielectric film that enables immobilization of capture proteins within an enhanced surface-area volume that spatially overlaps with the regions of resonant electromagnetic fields where biomolecular binding can produce the greatest shifts in photonic crystal resonant wavelength. Despite the nanoscale porosity of the sensor structure, the PC slab exhibits narrowband and high efficiency resonant reflection, enabling the structure to serve as a wavelength-tunable element of an external cavity laser. In the context of sensing small molecule interactions with much larger immobilized proteins, we demonstrate that the porous structure provides 3.7× larger biosensor signals than an equivalent nonporous structure, while the external cavity laser (ECL) detection method provides capability for sensing picometer-scale shifts in the PC resonant wavelength caused by small molecule binding. The porous ECL achieves a record high figure of merit for label-free optical biosensors.

Using station rainfall data and NCEP/NCAR reanalysis from 1978-2007, we charac- terize the spatial variations of the heavy rainfall (Meiyu) during June-July over the Jiang-Huai basin (JHB, ~28°-34° N and 110°-122° E) in East China and their associated atmospheric circula- tions. An empirical orthogonal function (EOF) analysis of the Meiyu rainfall revealed 2 other sig- nificant modes besides the dominant basin-wide in-phase mode. They include a north-south dipole (out-of-phase) pattern (EOF 2) and a roughly east-west dipole pattern (EOF 3). During the 'south flood and north drought' (SF/ND) phase of EOF 2, the western Pacific subtropical high (WPSH) is displaced southward, which prevents the East Asian summer monsoon from reaching as far north as in normal years. A cyclonic anomaly circulation at 850 hPa occurs over Southeast China and an ascending (descending) anomaly motion south (north) of ~30° N is seen over the JHB, which contributes to the excess (lack) of Meiyu rainfall south (north) of ~30° N over the JHB during the SF/ND years. During the opposite phase of this mode, these anomaly circulation pat- terns are roughly reversed. During the 'east wet and west dry' phase of EOF 3, the WPSH is dis- placed eastward, and a cyclonic anomaly circulation centered south of Japan brings more mois- ture from the Yellow and East China Seas into the eastern part of the JHB; while southwesterly vapor fluxes past over the western part of the JHB and converges over North China, leaving the western part of the JHB relatively dry. During the opposite phase, the WPSH is shifted northwest- ward, and the anomaly moisture transports are reversed over the JHB.

A series of compounds was rationally designed as inhibitors of dimer formation of the inducible isoform of nitric oxide synthase, and subsequent nitric oxide production. The conformation of two fragments obtained from a crystal structure was utilized to design a tether connecting those same two fragments. The resulting compounds were potent dimerization inhibitors that bound to the enzyme in a similar conformation as the fragments.

We demonstrate the first external cavity lasers with an emission wavelength that is tuned by selective adsorption of biological analytes on the surface of an optically resonant surface in a liquid environment.

Molecule-scale structure effects at indium tin oxide (ITO) anode−hole transport layer (HTL) interfaces in organic light-emitting diode (OLED) heterostructures are systematically probed via a self-assembly approach. A series of ITO anode-linked silyltriarylamine precursors differing in aryl group and linker density are synthesized for this purpose and used to probe the relationship between nanoscale interfacial chemical structure and charge-injection/electroluminescence properties. These precursors form conformal and largely pinhole-free self-assembled monolayers (SAMs) on the ITO anode surface with angstrom-level thickness control. Deposition of a HTL on top of the SAMs places the probe molecules precisely at the anode−HTL interface. OLEDs containing ITO/SAM/HTL configurations have dramatically varied hole-injection magnitudes and OLED responses. These can be correlated with the probe molecular structures and electrochemically derived heterogeneous electron-transfer rates for such triarylamine fragments. ...

Hole transporting materials are widely used in multilayer organic and polymer light-emitting diodes (OLEDs, PLEDs, respectively) and are indispensable if device electroluminescent response and durability are to be truly optimized. This contribution analyzes the relative effects of tin-doped indium oxide (ITO) anode-hole transporting layer (HTL) contact versus the intrinsic HTL materials properties on OLED performance. Two siloxane-based HTL materials, N,N'-bis(p-trichlorosilylpropyl)-naphthalen-1-yl)-N,N'-diphenyl-biphenyl-4,4'-diamine (NPB-Si(2)) and 4,4'-bis[(p-trichlorosilylpropylphenyl)phenylamino]biphenyl (TPD-Si(2)), are designed and synthesized. They have the same hole transporting triarylamine cores as conventional HTL materials such as 1,4-bis(1-naphthylphenylamino)biphenyl (NPB) and N,N-diphenyl-N,N-bis(3-methylphenyl)-1,1-biphenyl)-4,4-diamine (TPD), respectively. However, they covalently bind to the ITO anode, forming anode-HTL contacts that are intrinsically different from those of the anode to TPD and NPB. Applied to archetypical tris(8-hydroxyquinolato)aluminum(III) (Alq)-based OLEDs as (1) the sole HTLs or (2) anode-NPB HTL interlayers, NPB-Si(2) and TPD-Si(2) enhance device electroluminescent response significantly versus comparable devices based on NPB alone. In the first case, OLEDs with 36 000 cd/m(2) luminance, 1.6% forward external quantum efficiency (eta(ext)), and 5 V turn-on voltages are achieved, affording a 250% increase in luminance and approximately 50% reduction in turn-on voltage, as compared to NPB-based devices. In the second case, even more dramatic enhancement is observed (64 000 cd/m(2) luminance; 2.3% eta(ext); turn-on voltages as low as 3.5 V). The importance of the anode-HTL material contact is further explored by replacing NPB with saturated hydrocarbon siloxane monolayers that covalently bind to the anode, without sacrificing device performance (30 000 cd/m(2) luminance; 2.0% eta(ext); 4.0 V turn-on voltage). These results suggest new strategies for developing OLED hole transporting structures.

The integrity of anode/organic interfacial contact is shown to be crucial to the performance and stability of archetypical small molecule organic light-emitting diodes (OLEDs). In this contribution, vapor-deposited lipophilic, hole-transporting 1,4-bis(phenyl-m-tolylamino)biphenyl (TPD) and 1,4-bis(1-naphthylphenylamino)biphenyl (NPB) thin films are shown to undergo decohesion on ITO anode surfaces under mild heating. An effective approach to ameliorate such interfacial decohesion is introduction, via self-assembly or spin-coating, of covalently bound N(p-C6H4CH2CH2CH2SiCl3)3 (TAA)- and 4,4‘-bis[(p-trichlorosilylpropylphenyl)phenylamino]biphenyl (TPD-Si2)-derived adhesion/injection layers at the anode/hole transport layer interface. The resulting angstrom-scale hole transport layers prevent decohesion of vapor-deposited hole transport layers and significantly enhance OLED hole injection fluence. OLEDs fabricated with these modified interfaces exhibit appreciably reduced turn-on voltages, considerably high...