Nanoantenna-Microcavity Hybrids with Highly Cooperative Plasmonic-Photonic Coupling

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.Comment: Revised version after acceptanc

Cytotoxicity Effects of Amoora rohituka and chittagonga on Breast and Pancreatic Cancer Cells

Chemotherapeutic agents for cancer are highly toxic to healthy tissues and hence alternative medicine avenues are widely researched. Majority of the recent studies on alternative medicine suggested that Amoora rohituka possesses considerable antitumor and antibacterial properties. In this work, rohituka and chittagonga, fractionated with petroleum ether, dichloromethane, and ethanol, were explored for their anticancer potential against two breast cancer (MCF-7 and HTB-126) and three pancreatic cancer (Panc-1, Mia-Paca2, and Capan1). The human foreskin fibroblast, Hs68, was also included. Cytotoxicity of each extract was analyzed using the MTT assay and label-free photonic crystal biosensor assay. A concentration series of each extract was performed on the six cell lines. For MCF-7 cancer cells, the chittagonga (Pet-Ether and CH2Cl2) and rohituka (Pet-Ether) extracts induced cytotoxicity; the chittagonga (EtoAC) and rohituka (MeOH) extracts did not induce cytotoxicity. For HTB126, Panc-1, Mia-Paca2, and Capan-1 cancer cells, only the chittagonga CH2Cl2 extract showed a significant cytotoxic effect. The extracts were not cytotoxic to normal fibroblast Hs68 cells, which may be correlated to the specificity of Amoora extracts in targeting cancerous cells. Based on these results, further examination of the potential anticancer properties Amoora species and the identification of the active ingredients of these extracts is warranted

Nanostructured Optical Photonic Crystal Biosensor for HIV Viral Load Measurement

Detecting and quantifying biomarkers and viruses in biological samples have broad applications in early disease diagnosis and treatment monitoring. We have demonstrated a label-free optical sensing mechanism using nanostructured photonic crystals (PC) to capture and quantify intact viruses (HIV-1) from biologically relevant samples. The nanostructured surface of the PC biosensor resonantly reflects a narrow wavelength band during illumination with a broadband light source. Surface-adsorbed biotarget induces a shift in the resonant Peak Wavelength Value (PWV) that is detectable with <10 pm wavelength resolution, enabling detection of both biomolecular layers and small number of viruses that sparsely populate the transducer surface. We have successfully captured and detected HIV-1 in serum and phosphate buffered saline (PBS) samples with viral loads ranging from 104 to 108 copies/mL. The surface density of immobilized biomolecular layers used in the sensor functionalization process, including 3-mercaptopropyltrimethoxysilane (3-MPS), N-gamma-Maleimidobutyryl-oxysuccinimide ester (GMBS), NeutrAvidin, anti-gp120, and bovine serum albumin (BSA) were also quantified by the PC biosensor

Point-of-use detection of ascorbic acid using a spectrometric smartphone-based system

A rapid and portable analytical methodology has been developed for ascorbic acid (Vitamin C) quantification from aqueous samples using a spectrometric smartphone-based system for the first time. The method employs point-of-use approaches both for sample preparation and sample measurement, demonstrating the capability for mobile quality control of pharmaceutical and food products. Our approach utilizes an oxidation–reduction reaction between ascorbic acid and methylene blue, followed by a dispersive liquid–liquid microextraction (DLLME) to extract the aqueous-phase methylene blue into organic media. Then, a back-extraction procedure is employed to transfer the methylene blue to aqueous media, followed by analysis of the sample’s absorption spectrum using the spectrometric smartphone-based system. The DLLME and back-extraction procedures are optimized by use of a two-step multivariate optimization strategy. Finally, vitamin C supplements and orange juice are used as real-world samples to assess the applicability of the smartphone-based method, which is successfully compared with the standard laboratory-based approach.We would like to acknowledge the National Science Foundation for their support of this work via Grant no. CBET 12-64377. M.A.A. is grateful to Generalitat Valenciana (Spain) (APOSTD/2016/076) for his Post-Doctoral fellowship and the financial support from the European Social Fund (ESF). K.D.L. is supported by a Ruth L. Kirschstein Pre-Doctoral Fellowship (NIH F30AI122925)

Detection and Digital Resolution Counting of Nanoparticles with Optical Resonators and Applications in Biosensing

The interaction between nanoparticles and the electromagnetic fields associated with optical nanostructures enables sensing with single-nanoparticle limits of detection and digital resolution counting of captured nanoparticles through their intrinsic dielectric permittivity, absorption, and scattering. This paper will review the fundamental sensing methods, device structures, and detection instruments that have demonstrated the capability to observe the binding and interaction of nanoparticles at the single-unit level, where the nanoparticles are comprised of biomaterial (in the case of a virus or liposome), metal (plasmonic and magnetic nanomaterials), or inorganic dielectric material (such as TiO2 or SiN). We classify sensing approaches based upon their ability to observe single-nanoparticle attachment/detachment events that occur in a specific location, versus approaches that are capable of generating images of nanoparticle attachment on a nanostructured surface. We describe applications that include study of biomolecular interactions, viral load monitoring, and enzyme-free detection of biomolecules in a test sample in the context of in vitro diagnostics.M.Á.A. is grateful to Generalitat Valenciana (Spain) (APOSTD/2016/076) for his Postdoctoral fellowship and the financial support from the European Social Fund (ESF). K.D.L. is supported by a Ruth L. Kirschstein Pre-Doctoral Fellowship (NIH F30AI122925). S.L.M. thanks the Department of Science and Technology (DST) and the Council of Scientific and Industrial Research (CSIR) of South Africa. We are also grateful for financial support from the National Science Foundation (grant 1512043) and the National Institutes of Health (R01 AI120683)

Geochemical mapping of a blue carbon zone: investigation of the influence of riverine input on tidal affected zones in Bull Island

Bull Island (BI) is a coastal sand spit that formed as an unintended consequence of the construction of two walls, built over 200 years ago in Dublin Port, Ireland to alleviate silting of the shipping route. A large lagoon, on the land side of the island was separated in 1964 by the construction of a causeway to produce two separate lagoons that are now impacted by different water sources. Here we investigate the influence of riverine inputs on the two adjacent but unconnected tidal wetland lagoons. The South lagoon (SL) is supplied by tidal water passing through the eutrophic R. Liffey and R. Tolka estuary zones, while the North Lagoon (NL) is supplied by seawater and to a lesser degree, freshwater from the R. Liffey plume. Within each of these zones a clear ecotone exists between the mudflats (MF) and vegetated saltmarshes (SM). We determined the quantity and distributions of bulk geochemical characteristics across BI’s sediments, including total organic carbon (TOC), total nitrogen (TN), metals, and also, 16 individual polyromantic hydrocarbon’s (PAH’s) as an indication of anthropogenic input. Primary focus was placed on studying the blue carbon sediments of the lagoon zones. Significant differences in analytical results showed major influences exerted on sediment geochemistry within each lagoon. This study highlights the ability of a functioning coastal wetland to flourish and sequester elevated levels of carbon, metals and pollutants under the constraints of increasing anthropogenic impact. As the inadvertent result of geo-engineering, BI and its environs is a very important site to investigate the potential of artificially constructed wetlands to act as blue carbon reservoirs