This PDF file contains the front matter associated with SPIE Proceedings Volume 8234, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Silver nanoparticles embedded in glass are prepared by two different two-step ion exchange methods. In both of these methods, silver ions are introduced into glass in the first silver ion exchange step, but silver ions are reduced into metallic silver using two different second process steps: either post-annealing or subsequent potassium ion exchange. The formed particles are characterized by optical absorption measurements, scanning electron microscopy, transmission electron microscopy and atomic force microscopy. Their application in SERS is demonstrated, and the optimal surface features in terms of SERS enhancement are discussed. With post-annealing, high iron content in glass is needed to achieve high concentration of silver metal nanoclusters. Using double ion exchange, with the second step of potassium ion exchange, reduction of silver ions into metal nanoclusters occurs below aluminium mask. Using such mask, fabrication of silver nanoparticle patterns is also demonstrated.

We present results from the development of plasmonic chips for surface enhanced Raman spectroscopy (SERS). Our technological approach is based on the patterning of a resist film (PMMA) on a quartz substrate by electron beam lithography. The samples consist of periodic arrays of square shaped dots with lateral sizes around 300 nm, a period of 400 nm, and a height of 120 nm. This patterned surface is covered with a 10 nm Al₂O₃ film and a 40 nm Ag film. The electromagnetic field distribution as a function of the wavelength and incidence angle was simulated. The results show that field enhancements in the order of 10 can be achieved at 488 nm excitation wavelength. The SERS effect of the samples was investigated experimentally using crystal violet as a model analyte substance. The enhancement shows a good reproducibility and the values are consistent with the simulations.

Surface-enhanced Raman scattering (SERS) can be used to amplify Raman signals by several orders of magnitude, by utilizing Plasmon polariton (photonic and surface Plasmon mode) coupling to test molecules disposed on a textured metallo-dielectric surface. Previously the 'Klarite^TM' substrate consisting of an inverted array of square pyramidal nanostructures patterned onto a Silicon substrate has been demonstrated to afford highly reproducible SERS signals. In this paper, we investigate a new rectangular lattice arrangement and investigate the effect of aspect ratio on SERS enhancement factor. Nanostructured test substrates are coated with gold by thermal evaporation, followed by a monolayer of benzenethiol or benzyl mercaptan which provides a stable test molecule for signal enhancement comparison. SERS signals are analyzed with Renishaw (MS20) Invia Raman Spectrometer at a wavelength of 785nm. The resulting SERS enhancement shows an improvement in signal level of 786% (~ 8 times) compared to standard Klarite. In addition to high enhancement we are able to maintain less than 8.8% relative standard deviation for the peak signal.

Surface-enhanced Raman scattering (SERS) is a powerful technique to study the biological molecules and structures. SERS of proteins is always difficult due to their complex, flexible and diverse structures. This difficulty is one of the major obstacles hindering the applicability of SERS for the label-free detection and identification. In this study, we have employed several sample preparation approaches involving the packing AgNPs with protein molecules in a proper manner to allow the polarization of the electron system of proteins in coherence with the nanostructured noble metal system. The applicability of heat denaturation kinetics is perused for the detection and identification of proteins in model protein mixtures. Human serum albumin, transferrin, hemoglobin and the binary mixtures of these proteins are used as models. We have found that the SERS spectrum of each protein in the protein mixture is rather different at an increased temperature, which could be used to distinguish a protein in the protein mixture.

Nanocrescents have become an important surface enhanced Raman scattering (SERS) structure because unlike structures that rely on a few nanometer gap inter-particle plasmonic coupling to achieve high electrical field, nanocrescents are fabricated on hundreds of nanometer template sacrificial nanoparticles, where intra-particle plasmonic coupling between the cavity modes and the tip edges are utilized to achieve high electrical field. Unlike previous efforts, our fabrication approach creates three dimensional (3-D) up-right oriented nanocrescent structures with controllable cavity rim opening. Randomly-distributed silica nanoparticles are spun onto a substrate coated with a photoresist layer. Reactive ion etching is then used to etch into the photoresist to create small narrow pedestal with the nanoparticles serving as etching masks. The etching recipe and time will determine the diameter of the pedestal and ultimately, the cavity rim opening of the nanocrescents. We have fabricated and measured nanocrescent structures with as smaller as ~50 nm cavity rim opening. A maximum enhancement factor ~10⁷ has been achieved so far. Moreover, the repeatability of the enhancement factor (EF) from one nanocrescent to the next within the same substrate is better than 80%. We attributed the measurement consistency to the up-right orientation of the nanocrescent structures.

Metallic nanoparticle inks - colloidal suspensions of silver or gold nanoparticles in water or other organic solvents - can be sintered at relatively low temperatures (70 - 200°C). With appropriate thermal treatment the sintering can be controlled to fabricate nanoparticle substrates with a distribution of clusters sizes and interparticle distances. Such substrates exhibit relatively high (10⁸ - 10⁹) surface enhanced Raman scattering (SERS) amplification factors (AFs). The high AFs in such substrates arise from several mechanisms. The 'dimers' - two nanoparticles separated by a nanometersize gap - are known to produce amplification of the local electric field orders of magnitude larger than at the surface of an isolated single nanoparticle due to surface plasmon resonance. Furthermore, the lack of translational symmetry in the clusters leads to localizations of electromagnetic excitations to very small regions that can create SERS hot spots. Here we report that microwave absorption (~ 10 GHz) as a function of thermal annealing in dry-drop substrates can be used to monitor the sintering process in metallic nanoparticle inks. The predominant contribution to microwave absorption comes from electrically resistive weak links that are formed between nanoparticles as a result of the thermal treatment. Just before the creation of these weak links, such nanoparticle pairs are also the ones that make a major contribution to the SERS AFs. This leads to a correlation between the observed microwave absorption and the SERS signal intensities. We also present a simple model that describes the microwave absorption as a function of the isothermal annealing treatment.

Metal-enhanced fluorescence (MEF) is a newly emerging phenomenon in which the near-field interactions of fluorophores with the plasmons in metallic nanostructures can lead to substantial fluorescence enhancements. In the present study, we have investigated the use of silver-gold nanocomposite (Ag-Au-NC) structures, prepared by the galvanic replacement reaction of silver with gold, as plasmonic substrates for MEF. We have observed significant enhancement in the fluorescence intensities and decrease in the fluorescence lifetimes of two commonly used dyes, ATTO655 and Cy5, using the fabricated Ag-Au-NC substrates. Interestingly, the fluorescence enhancement depends on the amount of residual silver present in the substrates after the galvanic replacement reaction. Our results show that the galvanic replacement reaction is a very facile and powerful route to prepare Ag-Au-NC substrates that can be suitable for various MEF based applications.

Our aim is to create and validate a novel SERS-based nanoprobe for optical imaging of the epidermal growth factor receptor (EGFR). Gold and silver nanoparticles (Au/AgNPs) of various sizes were synthesized and coupled to epidermal growth factor (EGF) via a short ligand, α-lipoic acid (206 g/mol), which binds strongly to both Au and Ag nanoparticles via its disulfide end group. We used carbodiimide chemistry to couple EGF to α-lipoic acid. These nanoprobes were tested for binding affinity using Enzyme Linked ImmunoSorbent Assay (ELISA) and, in-vitro, using EGFRoverexpressing A431 cells. The nanoprobes show excellent EGFR-specific binding. Time of Flight Mass Spectrometry demonstrate the carbodiimide based linking of the carboxylic acid end-group of α-lipoic acid to one or more of the three (terminal, or 2 lysine) amine groups on EGF. ELISA confirms that the linked EGF is active by itself, and following conjugation with gold or silver nanoparticles. Compared with bare nanoparticles, UV-Vis spectroscopy of Ag-based nanoprobes exhibit significant plasmon red-shift, while there was no discernable shift for Au-based ones. Dark field microscopy shows abundant uptake by EGFR overexpressing A431 cells, and serves to further confirm the excellent binding affinity. Nanoprobe internalization and consequent aggregation is thought to be the basis of enhanced light scattering in the dark field images, supporting the notion that these nanoprobes should provide excellent SERS signals at all nanoprobe sizes. In summary, novel EGFR-specific nanoprobes have been synthesized and validated by standard assay and in cell culture for use as SERS optical imaging probes.

Intravital microscopy has been demonstrated to be a powerful technique for studying the delivery of contrast or therapeutic agents to tumours growing in a realistic 3D environment at high resolution. Surface enhanced Raman scattering (SERS)-active nanoparticle contrast agents provide the ability to improve in-vivo detection of tumour tissue through multiplex detection of their uniquely bright spectral lines. However, most work to date has been carried out in-vitro or in ex-vivo tissues. Here we present the results from confocal Raman microscopy in a dorsal skinfold window chamber in mice using SERS-active gold nanoparticle contrast agents directed towards an overexpressed tumour receptor tyrosine kinase.

Strongly localized electromagnetic fields in the vicinity of nanoparticles and nanogaps greatly enhance spectroscopic signals near them such as in surface-enhanced Raman spectroscopy (SERS). In this work we combine this plasmonic surface enhancement with coherent anti-Stokes Raman spectroscopy (CARS) on reproducible nanostructured surfaces. Surface-enhanced CARS (SECARS) gives rise to very strong enhancements and we find that an enhancement of ~10⁵ can be obtained over standard CARS. Using our nanostructured surfaces, we demonstrate strong correlation between plasmon resonances and surface-enhanced CARS intensities. Furthermore, fast imaging of molecular monolayers is performed. Our work paves the way for reliable single molecule Raman spectroscopy and fast molecular imaging on plasmonic surfaces.

SERS spectroscopy is currently gaining wider acceptance in biological research due to its ability to obtain signals from very low quantities of material, and to obtain information from within live cells. SERS spectroscopy yields very narrow bands (10-100 times narrower than typical fluorescence bands) and spectra suffer from minimal interference from aqueous media, making SERS spectroscopy ideal for multiplex detection of intracellular components. Typically for sensing, nanoparticles are labelled with suitable sensing molecules such as a dye or thiol. Nanoparticle labelling involves two different types of interaction between the label and the enhancing surface, chemisorption and physisorption. The former is considerably stronger and more stable than the latter and hence chemisorbed labels are more appropriate for intracellular nanosensor design. In this paper, we demonstrate the difference in stability of both types of Raman label inside live cells over periods of time. Chinese hamster ovary (CHO) cells were infused with a mixture of differently labelled stable nanosensors and were imaged using SERS microspectroscopy. We also demonstrate the applicability of SERS mapping for high-throughput multiplex detection using micropatterned cell arrays.

Early malaria diagnosis is important because malaria disease can develop into fatal illness within hours upon the appearance of the first symptom. The low concentration of the diagnosis biomarker, hemozoin, at the early stage of malaria disease makes early diagnosis difficult. In this paper, we present a magnetic field-enriched surface-enhanced resonance Raman spectroscopy (SERRS) strategy for the sensitive detection of β - hematin crystals, which is equivalent to hemozoin in the characteristics of Raman spectrum, by using magnetic nanoparticles. We observe several orders of magnitude enhancement in the SERRS signal of enriched β - hematin in comparison to the Raman signal of β - hematin in the cases of SERRS alone or magnetic enrichment alone, showing the great potential of this method towards early malaria diagnosis.

Raman spectroscopy and its various derivatives continue to offer the analyst fast, powerful, non-invasive and nondestructive means by which to identify multiple analytes simultaneously and in real time. By virtue of the huge enhancements possible in Raman scattering, generated by both surface enhancement and the resonance Raman effect, or when coupled with other techniques such as confocal microscopy, Raman spectroscopy is becoming more and more applicable to the types of assay being conducted in lab-on-a-chip applications, such as flow cytometry, cell patterning and trapping, and microarrays, all of which often involve the detection of extremely low quantities of analyte. Surface enhanced Raman scattering (SERS, or when coupled with the resonance Raman phenomenon, SERRS) spectroscopy has proven to be of particular use as a robust optical detection method in microfluidic environments. In this paper, we demonstrate the use of SERRS multiplex detection to quantitatively characterize individual microdroplets in a continuous stream whose contents are gradually varied using a bespoke pump control algorithm.

Surface Plasmons Resonance (SPR) architectures involving multi-wavelength interrogation is an attractive alternative for droplet biosensing. In this work, we address two detection formats experimentally investigated by our research group. The first one involves an angular scanning combining one near-IR and one visible light probes. It enables to increase the number of parameters for numerical fitting, which improves the precision of measurement. The second concept involves the SPR Coupler and Disperser sensor principle, where the spectrum analysis is performed on each detector pixel using the same diffraction grating that is employed for the optical coupling of the incident light with the surface plasmons.

We theoretically investigate the dependence of the different parameters of an optical biosensor for the detection of Hydrogen peroxide (H₂O₂) based on absorption enhancement of Cytochrome c molecules near gold nanoparticles. H₂O₂ is a major reactive oxygen species which is involved in signaling pathways and oxidative stress in cells. We use the Green's function approach as well as confirm the corresponding simulation results using the surface integral formulation. Further we show that this technique can be applied for detection of other small molecules, like oxygen and carbon monoxide.

The anti-cancer drug, methotrexate (MTX) as a strong inhibitor of human dihydrofolate reductase (hDHFR) has been studied in localized surface plasmon resonance (LSPR) and surface plasmon resonance (SPR) competitive binding assays with folic acid stabilized gold nanoparticles (FA AuNP). The latter with a diameter of 15 nm were prepared in a simple step with sequential characterization using UV-Vis, FTIR, and Raman. A LSPR competitive binding assay between different concentrations of MTX and FA AuNP for hDHFR in solution was designed to quantify MTX by using UV-Vis spectroscopy. Sensitivity of the assay was optimized with respect to both concentrations of the enzyme and FA. The detection and quantification of spiked MTX was demonstrated in phosphate buffer saline and in fetal bovine serum accompanied by solid-phase extraction treatment of the serum. In addition, this assay could also provide as a screening tool for potential inhibitors of hDHFR. In another perspective, MTX was measured in a competitive binding assay with FA AuNP for histidine-tagged hDHFR immobilized on a SPR sensitive surface. In this case, FA AuNP offer a secondary amplification of the analytical response which is indirectly proportional to the concentration of MTX. This alternative approach could contribute to the realization of direct detection of MTX in complex biological fluids. A comparison of characteristics and analytical parameters such as sensitivity, dynamic range and limit of detection between the LSPR and SPR sensing platforms will also be presented. Both assays offer potential in tackling real biological samples for the purpose of monitoring and validating anti-cancer drug levels in human serum during chemotherapy.

During the past several years we have studied the effects of metallic surfaces and nanostructures with fluorophores. We have demonstrated the metal-enhanced fluorescence (MEF) and the significant changes in the photophysical properties of fluorophores in the presence of metallic nanostructures and nanoparticles using ensemble spectroscopic studies. These studies have shown dramatic increases in brightness and photostability, especially for low quantum yield fluorophores. Much of this work was performed using visible or NIR fluorophores. In the present study, we have extended our studies to UV wavelengths and have shown that aluminum and platinum particles can enhance the emission of UV fluorophores including intrinsic protein fluorescence from 300 to 420 nm. We used the finite-difference timedomain (FDTD) method to calculate the effects of aluminum nanoparticles on nearby fluorophores that emit in the UV. And also we performed experiments to investigate the effect of metallic nanoparticles on fluorescence intensity of DNA bases and DNA G-quadruplex. We observed increase in fluorescence intensities of DNA bases varied range changing from 20 to 3-fold in steady-state fluorescence emission measurements. We obtained ~5-fold increase in fluorescence intensity of DNA G-quadruplex on both Al and Pt metallic substrates when compared with control quartz substrates.

With 3-D finite difference time domain (FDTD) method, we investigate the effect of the geometry parameters and near field distribution on sensitivity of the bowtie type nanoresonator biosensor in terms of refractive index. The calculation results show that the geometry parameters including gap (G), radius of curvature (R) and tip angle (A) have different effects on bulk sensitivity of bowtie metallic nanostructure. The sensitivity linear decreases as G increases while exponential decreases as R increases. Moreover, with A taking 15° to 135°, the sensitivity descends initially and then rises. As for the influence of near field on sensitivity, we can conclude that sensitivity is proportional to maximal local field and the scale factor of fitted curve for R is larger than the one for G.

Due to their extreme sensitivity to refractive index changes, surface plasmon resonance (SPR) sensors have long been established as extremely valuable tools for biosensing. In the past few years researchers have begun investigating various other metallic nanostructures as candidates for localized SPR (LSPR) sensing. Although LSPR is not nearly as sensitive to bulk refractive index changes as standard SPR, is has the advantage of being extremely sensitive to local refractive index changes, thereby providing detection on the level of a single molecule. In practice such sensitivity criterion is of paramount importance since the analyte layer under investigation is often only a few nanometers thick and deposited directly on the surface of the metal. Most desirable, however, is a sensor that retains the total integrated sensitivity of a traditional SPR sensor and at the same time localizes this sensitivity right at the sensor surface. For this reason, we have investigated a hybrid structure composed of a 2D Au nanoparticle array coupled to a Au film. We show that this structure, when excited in the Kretschmann configuration, retains to a surprising degree the total integrated sensitivity of an ideal SPR sensor and is able to concentrate that sensitivity within a few nanometers of the sensor surface, thereby yielding a hybrid sensor with the advantages of both LSPR and SPR sensing, i.e. both a high local sensitivity and a high figure of merit (FOM).

Surface Plasmon Resonance (SPR) based sensors enable the rapid, label-free and highly sensitive detection of a large range of biomolecules. We have previously shown that, using silver coated optical fibres with an high surface roughness, a re-scattering of the surface plasmons is possible, turning SPR into a radiative process. This approach overcomes limitations associated with current SPR technologies such as the tight tolerance on the metallic coating thickness, and results in a more compact, versatile, robust and cost-effective approach. However, the specific detection of small molecules is a challenge in SPR systems, regardless of the SPR architecture that is used. This new sensing platform, which has proved effective for the detection of large molecules such as viruses, is now demonstrated to be able to detect small proteins thanks to an improved surface functionalization procedure, a key point for reliable and robust immunosensors. Avidin, a tetrameric biotin-binding protein, was used to link biotinylated antibodies to the biotinylated surface, with a given orientation, to enable efficient sensing of the analyte. This approach may offer significant advantages compared to protein A surface functionalization strategies such as a limited cross reactivity with free IgG antibodies in clinical samples. We demonstrate that by bringing together this novel emission-based fibre SPR platform, with an improved surface functionalization process, is possible to rapidly and specifically detect human apolipoprotein E, a low molecular weight protein (~39kDa) known to be involved in cardiovascular diseases, in Alzheimer's disease and in gastric cancer. The results obtained clearly show that this new sensing platform has the potential to serve as a tool for point-of-decision medical diagnostics.

An alternative method to plasmon techniques for the enhancement, control and detection of fluorescence is proposed. The role of the metallic layer is played by a silicon-based one-dimensional photonic crystal that can sustain Bloch surface waves (BSWs), which can be regarded as the dielectric analogue of surface plasmon polaritons (SPPs) for metals. Throughout the paper we explore the route that leads to an enhanced, directionally-controlled and selfreferencing fluorescence-detection scheme. We first consider a 1DPC that is functionalized with a thin, flat and homogeneous polymeric layer decorated with a fluorescent dye. The enhancement of the BSW-coupled fluorescence emission is studied against a similar scheme that uses a common thin glass coveslip. An enhancement as large as 560 is found. We further investigate the BSW coupling of the illuminating laser light into 30-nm thin polymeric waveguides. Imaging the BSW-coupled emitted fluorescence through the leakage radiation microscopy is used for the purpose. The possibility of coupling BSWs into nanometric guiding ridges makes feasible the design of a spatially-resolved and multiplexing fluorescence-detection scheme, which can be most useful for self-referencing in the biosensing field. We conclude the paper by investigating the effects on the fluorescence emission of a multistack that consists of a dielectric multilayer and a thin metallic layer deposited on top. The implications of using a metallo-dielectric structure for the coupling of the emitted fluorescence with BSW and SPP modes is discussed.

An optical biosensor system using surface-plasmon field-enhanced fluorescence has been developed, which allows high sensitivity and fast measurement available. Intensity of fluorophores in SPFS is highly dependent upon the distance from metal surface. The resonant evanescent electric field excites fluorophores within the penetration area. On the other hand, fluorescence quenching in close proximity to a metal surface interfere with the excitation. We have developed a new technology for fluorescent nanoparticles that could receive the energy from metal surface effectively. This enables technology of detecting strong and stable SPFS signals, as well as homogeneous assay method that allows us to eliminate binding/free separation process for unreacted fluorescent particles. A rate assay method has also been employed, which resolves affect from diffusion-limited access, in order to realize a fast surface immunoreaction in a microchannel. Taking advantage of these two developments, as eliminating an enzyme response process such as CLEIA, our system reaches much faster reaction time of 2 minutes to detect thyroid stimulating hormone (TSH) of canine serum sample at 0.1ng/mL. We believe our system with these new technologies is a powerful tool for in-vitro diagnosis which meets various clinical requirements.

The effect of a population of fluorophores coupling to weakly bound surface plasmons in dielectric/metal/dielectric structures is investigated for the purpose of fluorescence enhancement near interfaces and live cell fluorescence surface imaging. We show theoretically and experimentally that for sufficient fluorophore concentrations near such SPP supporting structures significant enhancements in the radiative emission intensity can be observed, with a spectral modification that can be correlated to the average separation of the fluorophores from the substrate. We will discuss the theory behind the effect and some experimental results on imaging labeled proteins in the focal adhesion sites of cells.

Nanoparticles are viewed as a promising tool for numerous medical applications, for instance imaging and photothermal therapy (PTT) has been proposed using gold nanorods. We are developing multi-functional gold nanorods (m-GNRs) which have potential for image guided endoscopic surgery of tumour tissue with a modified laparoscope system. A new synthesis method potentially allows any useful acid functionalised molecules to be bonded at the surface. We have created fluorescent m-GNRs which can be used for therapy as they absorb light in the infrared, which may penetrate deep into the tissue and produce localised heating. We have performed a tissue based experiment to demonstrate the feasibility of fluorescence guided PTT using m- GNRs. Ex vivo tests were performed using sheep heart. This measurement, correlated with the fluorescence signal of the m-GNRs measured by the laparoscope allows the clear discrimination of the artery system containing m-GNRs. A laser diode was used to heat the m-GNRs and a thermal camera was able to record the heat distribution. These images were compared to the fluorescence images for validation.

We present a commercial platform for both label-free and labeled bioanalysis based on Localized Surface Plasmon Resonance. The platform relies on mass-produced nanostructured thin films with robust and reproducible plasmon resonances. The physical properties of these films (reproducibility, optical properties) as well as their stability, noise level, and intrinsic detection limits will be discussed. Also, we will illustrate the performance and strength of the platform in real-life assays. We will show how the sensitivity barrier can be lowered from the ng/mL range to the pg/mL range using the very same chip and different implementations. The examples will demonstrate how rich, fast, simple and reliable the platform is.

We have analyzed and compared the spectral differential phase sensing performance for conventional and long-range (LR) surface plasmon resonance (SPR) across a wide sample refractive index range (i.e. dynamic range) of 1.3330- 1.3505 using Fresnel's Equations and Transfer Matrix method. We demonstrate that wide-range detection limit as high as 7.9×10^-9 RIU (Refractive Index Unit) for conventional SPR can be achieved with a set of optimized sensing parameters and a phase measurement resolution of 2×10^-4 rad, whereas best detection limit for LRSPR is lower. We have also investigated for the effect of sensing parameters including angle of incidence, metal film material and thickness. LRSPR is found to be quite tolerant to the choice of material and thickness of metal film. This work presents a comprehensive comparison between conventional and LR SPR for spectral-phase configuration.

In the past several years we have demonstrated the metal-enhanced fluorescence (MEF) and the significant changes in the photophysical properties of fluorophores in the presence of metallic nanostructures and nanoparticles using ensemble spectroscopic studies. In the represented study, we explored the distance effect on intrinsic fluorescence of proteins adsorbed on our layer-by-layer assembled metallic nanostructures. The study is expected to provide more information on the importance of positioning the proteins at a particular distance for enhanced fluorescence from metallic structures. For the present study, we considered using easy and inexpensive LbL technique to provide welldefined distance from metallic surface. The explored proteins were adsorbed on different numbers of alternate layers of poly(styrene sulfonate) (PSS) and poly(allylamine hydrochloride) (PAH). SA and BSA were electrostatically attached to the positively charged PAH layer. We obtained a maximum of ~11-fold and 9-fold increase in fluorescence intensity from SA and BSA, respectively. And also we observed ~3-fold decrease in BSA lifetime on metallic nanostructures than those on bare control quartz slides. This study reveals the distance dependence of protein fluorescence.

The cell morphology is a valuable indicator of the physical condition and general status of the cell. Here we demonstrate a methodology for noninvasive biosensing of adherent living cells. Our method is based on infrared reflection spectroscopy of living cells cultured on thin Au film. To characterize cell morphology we utilized the unique properties of the infrared surface plasmon (λ=1-3 μm) and infrared guided wave that travel inside the cell monolayer. We demonstrate that our method enables monitoring of submicron variations in cell morphology in real-time and in a labelfree manner. In addition to morphological characterization, our method allows investigation of chemical composition and molecular structure of cells through infrared absorption spectroscopy analysis.

Recently there have been tremendous interests about the fabrication of the solid state nanopore due to the capability of the solid state nanopore as a single molecule sensor. The SiN nanopore and the SiO2 nanopore have been fabricated with high energy electron beam exposure such as transmission electron microscopy, field emission electron microscopy, and focused ion beam sculpting. However, the plasmonic Au nano-pore can be utilized as a nanobio optical sensor due to the 10⁶ fold increase of the Raman signal intensity. Hence, in this report, the fabrication of the plasmonic nanopore with less than ~ 10 nm on the apex of the micronsize pyramidal structure using various high energy electron beam exposure. Under the electron beam exposure of FESEM followed by EPMA, the widening and the shrinking of the Au nanopore were observed depending upon the EPMA probe current. The diameters of the Au nanopore was also reduced successively from ~ 5 nm down to zero using 200 keV TEM. From these experimental results, the dynamics of the nanopore formation are found to depend on the viscosity of the membrane, radiation damage, and evaporation of the materials under high vacuum condition. This fabricated plasmonic nano-pore device can be utilized as geneome sequencing device or a single-molecule sensor.

We study the reflection of a tightly focused Gaussian beam off a near symmetric resonant tunneling structure comprising two identical coupled waveguides. The coupled waveguides are loaded on each side by a spacer layer and a high index prism. Reflection of a Gaussian beam from such a resonant structure is associated with beam distortion and even beam splitting. We start with the distortion of the beam profile for a symmetric structure as a function of various parameters of the system. The broken spatial symmetry is introduced through the reference channel on one side and the sample channel on the other side as spacer layers. We monitor the dip in the beam profile when the two channels are filled with the sample and the reference liquid. We show that presence and absence of hemoglobin and its oxygenation states can be quantified by looking at the beam profile dip. Our results may find applications in high resolution sensing.

A novel transient nanoprobe was developed whose biomedical functions can be dynamically and selectively tuned inside living cells. This probe is not a nanoparticle, but a transient event, a vapor nanobubble generated with a laser pulse around gold (plasmonic) nanoparticles. This is a phenomenon that we recently discovered and named plasmonic nanobubbles (PNBs). PNBs represent an entirely new class of probes due to their dynamic tunability in situ, including single cells. We show that PNB provides highly sensitive diagnosis and immediate follow-up and guided treatment with true nanoscale precision at the level of single cells.

Raman spectroscopy is a useful technique in the identification and characterisation of compounds, but in terms of sensitivity its application is limited. With respect to this the discovery of the surface-enhanced Raman scattering (SERS) phenomenon has proved monumental, and much research has been carried out over the past 30 years developing the technique. Pterins are biological compounds that are found in nature in colour pigmentation and in mammalian metabolic pathways. Moreover, they have been identified in abnormal concentrations in cancer patients, suggesting potential applications in cancer diagnostics. SERS is an ideal technique to identify these compounds, and both nanoparticle suspensions and pulsed laser deposited nanoparticle substrates have been used to examine the spectra of xanthopterin, both in aqueous solution and in different pH environments.

We present a novel waveguide sensor platform, combining monolithically integrated sensor waveguides with thin-film organic photodiodes on a single substrate. Aiming at the parallel detection of multiple parameters in a single sensor chip different sensing principles can be applied on the same basic sensor platform. Utilizing absorbance as sensing principle is demonstrated by an integrated carbon dioxide sensor, fluorescence as sensing principle is demonstrated by an integrated oxygen sensor. The versatility of this integrated waveguide platform is further demonstrated by employing surface plasmon resonance as sensing principle, enabling real-time and label-free detection of a wide range of analytes.

We have developed an experimental system with the potential for the delivery and localized release of an encapsulated agent with high spatial and temporal resolution. We previously introduced liposome-supported plasmon resonant gold nanoshells; in this composite structure, the liposome allows for the encapsulation of substances, such as therapeutic agents, neurotransmitters, or growth factors, and the plasmon resonant structure facilitates the rapid release of encapsulated contents upon laser light illumination. More recently, we demonstrated that these gold-coated liposomes are capable of releasing their contents in a spectrally-controlled manner, where plasmon resonant nanoparticles only release content upon illumination with a wavelength of light matching their plasmon resonance band. We now show that this release mechanism can be used in a biological setting to deliver a peptide derivative of cholecystokinin to HEK293 cells overexpressing the CCK2 receptor. Using directed laser light, we may enable localized release from gold-coated liposomes to enable accurate perturbation of cellular functions in response to released compounds; this system may have possible applications in signaling pathways and drug discovery.

We present a novel three-dimensional nano-hole array structure in an optically thick gold film, which benefits from Surface Plasmon (SP) energy matching between the top and bottom of the gold film. We have experimentally evaluated both a conventional and an SP energy-matched nano-hole array structure for Surface Plasmon Resonance (SPR) sensing. Also, detection of various bulk refractive index liquids has been tested for both structures based on the transmission intensity differences in a narrow detection band. We observed a 2-fold higher sensitivity during SPR sensing with the new structure compared to a conventional nano-hole array.

A Kretschmann prism configuration uses a laser line generator, which includes a laser diode and a pair of cylindrical lenses having different optical powers in x and y directions. A metal layer is directly coated on one side of the prism. The line generator determines the length of the laser line and the divergent angle of the fan-shape light sheet. The length of the laser line on the metal layer is determined by the separation of the focus position of the laser light from the metal layer.

In this study, three-dimensional (3D) crosslinked bovine serum albumin (BSA) microstructures containing gold nanorods (AuNRs) at different absorption wavelengths were fabricated via multiphoton excited photochemistry using rose Bengal (RB) as the photoactivator. After the processing, a higher laser power, greater than the threshold of the AuNR photothermal damage at the matched wavelength for the longitudinal plasmon resonance of AuNR, is adopted to reshape the AuNRs into gold nanospheres at the designed positions of the 3D structure. As a result, 3D BSA microstructures containing different color AuNRs at the designed positions can be successfully fabricated. The AuNRs-doped BSA multicolor microstructures not only can be applied in biomedical scaffolds with plasmonic properties such as two-photon luminescence imaging and photothermal therapy but also can be a specific 3D biomaterial microdevice for plasmonic field.