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A handheld, spatially offset Raman spectroscopy (SORS) system was successfully used to obtain Surface-enhanced Raman Scattering (SERS) spectra of fentanyl under simulated field conditions. A series of aqueous fentanyl solutions were prepared with commercially available gold nanoparticle solution, at concentrations ranging from 0.003 to 1697 μM. These SERS spectra were then used to generate two concentration calibration models (via a plot of peak area (1026 cm-1 ) versus concentration, and quantitative spectral decomposition using partial least squares (PLS1)). For both models, the relationship followed Langmuir adsorption and became non-linear at concentrations above ~0.2 μM, with a limit of detection (LOD) of approximately 3 nM. The same technique was successfully used to measure fentanyl in the presence of two common "cutting agents," heroin and glucose, at 1% and 2% fentanyl proportions (w/w). Fentanyl detection was successfully achieved, but mixture interference from the cutting agents prevented a calibration model being generated. Four fentanyl analogues were also investigated-butyrylfentanyl, furanylfentanyl, acetylfentanyl, and ocfentanyl. A concentration calibration model for each species was successfully generated, but differentiation from fentanyl proved more challenging, although several potential diagnostic peaks were identified. These results identified a pathway forward in using handheld equipment for the reliable detection of ultra-low concentrations of fentanyl and fentanyl analogues via SERS, even when mixed with diluents. However, quantitative detection is negatively impacted in the presence of heroin and glucose. This also provides a starting point for a SERS-based spectral library of fentanyl analogues, in combination with a range of different diluents.

Our paper investigates aspects of initial contact between the Sobaipuri O’odham and Spanish missionaries at San Xavier del Bac in the late 1600s to early 1700s. Cultural contact and change are of e...

In the past decade, consumption of illegal and controlled street drugs has steadily increased. According to the latest World Drug Report, released by the United Nations Office on Drugs and Crime (UNODC)1, more people are using drugs, and there are more drugs, and more types of drugs, than ever. Around 269 million people used drugs worldwide in 2018, which is 30 per cent more than in 20091. The growth in global drug supply and demand poses challenges to law enforcement, compounds health risks and complicates efforts to prevent and treat drug use disorders. Due to COVID-19, traffickers may have to find new routes and methods and opioid shortages may result in people seeking out more readily available substances such as alcohol, benzodiazepines or mixing with synthetic drugs.1 Herein, we study the use of Raman SORS technology for rapid identification of narcotics in a range of concentrations – from pure form (as it is smuggled or transported) to street forms and products, often mixed with conventional cutting agents, with the potential to improve safety, efficiency and critical decision making in incident management, search operations, policing and ports and border operations.

Raman spectroscopy allows the acquisition of molecularly specific signatures of pure compounds and mixtures making it a popular method for material identification applications. In hazardous materials, security and counter terrorism applications, conventional handheld Raman systems are typically limited to operation by line-of-sight or through relatively transparent plastic bags / clear glass vials. If materials are concealed behind thicker, coloured or opaque barriers it can be necessary to open and take a sample. Spatially Offset Raman Spectroscopy (SORS)[1] is a novel variant of Raman spectroscopy whereby multiple measurements at differing positions are used to separate the spectrum arising from the sub layers of a sample from the spectrum at the surface. For the first time, a handheld system based on SORS has been developed and applied to hazardous materials identification. The system - "Resolve" - enables new capabilities in the rapid identification of materials concealed by a wide variety of non-metallic sealed containers such as; coloured and opaque plastics, paper, card, sacks, fabric and glass. The range of potential target materials includes toxic industrial chemicals, explosives, narcotics, chemical warfare agents and biological materials. Resolve has the potential to improve the safety, efficiency and critical decision making in incident management, search operations, policing and ports and border operations. The operator is able to obtain a positive identification of a potentially hazardous material without opening or disturbing the container - to gain access to take a sample - thus improving safety. The technique is fast and simple thus suit and breathing gear time is used more efficiently. SORS also allows Raman to be deployed at an earlier stage in an event before more intrusive techniques are used. Evidential information is preserved and the chain of custody protected. Examples of detection capability for a number of materials and barrier types are presented below.

Recently, ACS had the opportunity to conduct data recovery and archival research for the Hayden Flour Mill property redevelopment project in Tempe, Arizona, which produced significant results for understanding the use of the property and buildings over time and the mill’s influence on early Tempe. The results of this project not only illustrate an understudied aspect of the development of territorial Arizona (flour milling) but also demonstrate the often invaluable correlation between historic archaeology and archival documents. The latter aspect is becoming increasingly important as the number of historic properties is expected to soar in the next few decades as more and more sites enter the “historic” age as defined by the Secretary of Interior’s standards.

A novel wide-field approach for the real-time Surface Enhanced Raman Scattering (SERS) imaging of multiple silver nanoparticle clusters suspended in solution is described. This method enables direct correlation of the SERS activity of a single nanoparticle aggregate and its size through measurement of the cluster diffusion coefficient and can also be performed in a high-throughput basis. As a first demonstration, we investigate the salt-induced aggregation of silver nanoparticles in the presence of a reporter tag molecule, which has a high affinity for the nanoparticle surface. In addition to tracking individual particles, direct comparison of Rayleigh and SERS videos of the same colloid solution enabled measurement of the fraction of individual clusters that are SERS active and the dependence of this value on the relative concentration of the tag molecule. Furthermore, given the ability to also rapidly profile any nonuniformity in particle size distributions, we expect this approach will not only provide a new tool for the fundamental understanding of SERS but also significantly contribute to the development of an array of emerging nanoparticle-enhanced biomolecule and imaging detection platforms.

Reproducible control of stem cell populations, regardless of their original source, is required for the true potential of these cells to be realised as medical therapies, cell biology research tools and in vitro assays. To date there is a lack of consistency in successful output when these cells are used in clinical trials and even simple in vitro experiments, due to cell and material variability. The successful combination of single chemistries in nanoarray format to control stem cell, or any cellular behaviour has not been previously reported. Here we report how homogenously nanopatterned chemically modified surfaces can be used to initiate a directed cellular response, particularly mesenchymal stem cell (MSC) differentiation, in a highly reproducible manner without the need for exogenous biological factors and heavily supplemented cell media. Successful acquisition of these data should lead to the optimisation of cell selective properties of materials, further enhancing the role of nanopatterned substrates in cell biology and regenerative medicine. The successful design and comparison of homogenously molecularly nanopatterned surfaces and their direct effect on human MSC adhesion and differentiation are reported in this paper. Planar gold surfaces were patterned by dip pen nanolithography (DPN®) to produce arrays of nanodots with optimised fixed diameter of 70 nanometres separated by defined spacings, ranging from 140 to 1000 nm with terminal functionalities of simple chemistries including carboxyl, amino, methyl and hydroxyl. These nanopatterned surfaces exhibited unprecedented control of initial cell interactions and subsequent control of cell phenotype and offer significant potential for the future.

SERRS (surface-enhanced resonance Raman scattering) is a vibrational spectroscopy which allows extremely sensitive and selective detection of labelled DNA sequences with detection limits which rival, and in most cases surpass, that of fluorescence. SERRS relies on a visible chromophore adsorbing on to an enhancing surface. DNA itself is not SERRS-active, as it lacks a suitable visible chromophore and has poor adsorption properties on to the surfaces used for enhancement. The surface normally used for enhancement in these sorts of studies are metallic nanoparticles and, through modification of DNA probes by the addition of suitable SERRS labels, signals can be obtained that are highly sensitive and very selective. The aggregation state of the nanoparticles is critical to the sensitivity, and, in the present paper, we show how straightforward detection of labelled DNA probes can be achieved using SERRS in a quantitative manner and with a variety of different commercially available labels. In a second approach, we show how the properties of aggregation to turn on the SERRS effect can be exploited through DNA hybridization to give identification of a particular DNA sequence. This approach lends itself to closed-tube formats and is a promising way forward for molecular diagnostics using SERRS.

The detection of subclinical early inflammation in autoimmune diseases is an important but currently technically demanding approach to direct initial diagnosis and subsequent choice of therapy. Recent advances in imaging using NP provides the potential to detect cellular recruitment, vascular activation or leakage at a subclinically stage of disease and may provide predictive "biomarkers" of future pathogenesis. The NP used are either untargeted and taken up by phagocytic cells, or are linked to a ligand, targeting localisation to the site of inflammation. Techniques, varying from MRI and fluorescence to Raman spectroscopy are being employed. In this short review, we summarise many of the recent developments in the field of NP imaging related to inflammation.

The preparation and use of tri-functional linkers for surface complexation to both gold and silver nanoparticles is reported. These molecules confer excellent stability towards nanoparticles ensuring particle monodispersity in biological buffers, and also incorporate dyes to allow use of the functionalised nanoparticles as SERRS reporters. Biomolecule conjugation and quantitation has been illustrated using Alexafluor 680 labelled streptavidin. Variation of the chromophore has been introduced, which allows for exquisite control of the SERRS by manipulation of laser wavelength. This demonstrates the potential of SERRS functionalised nanoparticles for multiple, simultaneous monitoring of excitation events, an area of research where the capability of molecular fluorophores and quantum dots is limited.

A series of surface-enhanced resonance Raman scattering (SERRS) based probes for the detection of lipase activity are reported. A number of novel SERRS-active 8-hydroxylquinolinyl azo dyes have been prepared and via synthetic esterification or subsequent enzymatic hydrolysis at the 8-hydroxyl position the SERRS signal can be "switched" on or off. In the first instance, the technique has been demonstrated for the successful detection of lipase from Pseudomonas cepacia, and these new compounds offer a limit of detection of 0.2 ng mL-1 enzyme, up to a 100-fold lower limit than observed for benzotriazolyl dyes used in previous studies. The chemical synthesis is straightforward and allows for facile introduction of a wide range of different masking groups, using commonly known synthetic methodologies. The potential for multiplexing analysis of enzyme activity using this technology is presented within.

Surface-enhanced resonance Raman scattering (SERRS) from silver nanoparticles using 514.5-nm excitation has been shown to offer huge potential for applications in highly sensitive multiplexed DNA assays. If the technique is to be applied to real biological samples and integrated with other methods, then the use of gold nanoparticles and longer wavelengths of excitation are desirable. The data presented here demonstrate that dye-labeled oligonucleotide sequences can be directly detected by SERRS using gold nanoparticles in a quantitative manner for the first time. The performance of gold and silver nanoparticles as SERRS substrates was assessed using 514.5-, 632.8-, and 785-nm excitation and a range of 13 commercially available dye-labeled oligonucleotides. The quantitative response allowed the limit of detection to be determined for each case and demonstrates that the technique is highly effective, sensitive, and versatile. The possibility of excitation at multiple wavelengths further enhances the multiplexing potential of the technique. The importance of effectively combining the optical properties of the nanoparticle and the dye label is demonstrated. For example, at 632.8-nm excitation, the dye BODIPY TR-X and gold nanoparticles make a strong SERRS combination with very little background fluorescence. This study allows the choice of nanoparticle and dye label for particular experimental setups, and significantly expands the applicability of enhanced Raman scattering for use in many disciplines.

This paper discusses the results of analysis conducted on Mimbres ceramics from the Lake Roberts Vista site, LA 71877, Gila National Forest, New Mexico. Two related Mimbres pottery seriation techniques, one broad-scale and the other fine-scale, were used to date pithouse fill deposits in the absence of radiometric dates. The study found that the two seriation techniques were useful for placing fill deposits and pit structures into period and phase categories, and that the fine-scale seriation apparently delineated smaller units of time within these broader categories. The benefits and potential problems of such an approach to dating archaeological fill deposits are discussed. I suggest that the microseriation technique is useful because it provides a way to date pit structures when chronometric dates are not available and delineates possible clusters of contemporaneously occupied structures at pithouse villages.

Modified anilino squaraine dyes provide unique SERRS spectra that can be identified at low concentrations within any mixture of current reporters using longer, biologically compatible wavelengths of excitation.

Dysfunctional intracellular enzymatic activity is believed to be an underlying cause of a myriad of diseases. We present the first use of surface enhanced Raman scattering (SERS) as a detection technique capable of reporting intracellular activity of a specific enzyme. Careful choice of reagents allowed the preparation of high resolution cellular activity maps highlighting the specific conversion of the commonly used ELISA reagent 5-bromo-4-chloro-3-indolyl β-D-galactopyranoside (X-Gal), by wild type β-galactosidase enzymes. Further, through co-addition of X-Gal substrate and inhibitors we were able to demonstrate that intracellular substrate conversion occurred predominantly through an enzymatically specific pathway. The data presented therefore supports the application of SERS probes as sensitive, specific sensors of biochemical activity and demonstrates the use of SERS probes for the first time as beacons capable of high resolution subcellular localisation of native enzymes.

Advances in the application of Quantum Cascade Lasers (QCL) to trace gas detection will be presented. The solution is real time (~1 μsec per scan), is insensitive to turbulence and vibration, and performs multiple measurements in one sweep. The QCL provides a large dynamic range, which is a linear response from ppt to % level. The concentration can be derived with excellent immunity from cross interference. Point sensing sensors developed by Cascade for home made and commercial explosives operate by monitoring key constituents in real time and matching this to a spatial event (i.e. sniffer device placed close to an object or person walking through portal (overt or covert). Programmable signature detection capability allows for detection of multiple chemical compounds along the most likely array of explosive chemical formulation. The advantages of configuration as "point sensing" or "stand off" will be discussed. In addition to explosives this method is highly applicable to the detection of mobile drugs labs through volatile chemical release.

We demonstrate how molecular spectroscopy methods using NIR and MIR lasers can provide rapid detection and identification of many threat materials. It is increasingly recognised that one spectroscopic method will not be suited to every target in every scenario, both in terms of spectroscopic selectivity and the context e.g. vapour phase or within a sealed container. The orthogonal selection rules and capabilities of IR and Raman in combination allow the identification of a very broad range of targets, both in liquid and vapour phase. Therefore, we introduce the benefits of the combining infra-red absorbance based on Quantum Cascade lasers (QC-IR) and NIR Raman spectroscopy for nitrogenous and peroxide based materials. Rapid scan rates up to 10Hz for QC-IR and Raman and are demonstrated using current technology. However, understanding of the chemistry and spectroscopic signatures behind such materials is necessary for accurate fast fitting algorithms to benefit of the full advantage with advances in hardware. This is especially true as future users requirements move towards rapid multiplexed analysis and data fusion from a variety of sensors.

Following the development of point sensing improvised explosive device (IED) technology[1] Cascade Technologies have initial work in the development of equivalent stand-off capability. Stand-off detection of IEDs is a very important technical requirement that would enable the safe identification and quantification of hazardous materials prior to a terrorist attack. This could provide advanced warning of potential danger allowing evacuation and mitigation measures to be implemented. With support from the UK government, Cascade Technologies is currently investigating technology developments aimed at addressing the above stand-off IED detection capability gap. To demonstrate and validate the concept, a novel stand-off platform will target the detection and identification of common high vapor pressure IED precursor compounds, such as hydrogen peroxide (H2O2), emanating from a point source. By actively probing a scene with polarized light, the novel platform will offer both enhanced selectivity and sensitivity as compared to traditional hyperspectral sensors, etc. The presentation will highlight the concept of this novel detection technique as well as illustrating preliminary results.

Metallic nanoparticles can be used as basic materials for a wide variety of purposes including building blocks for nanoassemblies, substrates for enhanced spectroscopies such as fluorescence and Raman and as labels for biomolecules. In the present paper, we report how silver and gold nanoparticles can be functionalized with specific biomolecular probes to interact in a specific manner with a target molecule to provide a change in the properties of the nanoparticles which can be measured to indicate the molecular recognition event. Examples of this approach include DNA hybridization to switch on SERRS (surface-enhanced resonance Raman scattering) when a specific target sequence is present, the use of nanoparticles for in vivo SERRS imaging and the use of nanoparticles functionalized with antibodies to provide a new type of immunoassay. These examples indicate how nanoparticles can be used to provide highly sensitive and informative data from a variety of biological systems when used in combination with SERRS.

The development of homogenously nano-patterned chemically modified surfaces that can be used to initiate a cellular response, particularly stem cell differentiation, in a highly controlled manner without the need for exogenous biological factors has never been reported, due to that fact that precisely defined and reproducible systems have not been available that can be used to study cell/material interactions and unlock the potential of a material driven cell response. Until now material driven stem cell (furthermore any cell) responses have been variable due to the limitations in definition and reproducibility of the underlying substrate and the lack of true homogeneity of modifications that can dictate a cellular response at a sub-micron level that can effectively control initial cell interactions of all cells that contact the surface. Here we report the successful design and use of homogenously molecularly nanopatterned surfaces to control initial stem cell adhesion and hence function. The highly specified nano-patterned arrays were compared directly to silane modified bulk coated substrates that have previously been proven to initiate mesenchymal stem cell (MSC) differentiation in a heterogenous manner, the aim of this study was to prove the efficiency of these previously observed cell responses could be enhanced by the incorporation of nano-patterns. Nano-patterned surfaces were prepared by Dip Pen Nanolithography® (DPN®) to produce arrays of 70 nm sized dots separated by defined spacings of 140, 280 and 1000 nm with terminal functionalities of carboxyl, amino, methyl and hydroxyl and used to control cell growth. These nanopatterned surfaces exhibited unprecedented control of initial cell interactions and will change the capabilities for stem cell definition in vitro and then cell based medical therapies. In addition to highlighting the ability of the materials to control stem cell functionality on an unprecedented scale this research also introduces the successful scale-up of DPN® and the novel chemistries and systems to facilitate the production of homogeneously patterned substrates (5 mm2) that are applicable for use in in vitro cell conditions over prolonged periods for complete control of material driven cell responses.

There is a need for fast, reliable and sensitive biosensor arrays. We have used nanostructured plasmonic gold surfaces for the detection of biological species by surface enhanced resonance Raman scattering (SERRS). Careful, directed placement by Dip-Pen Nanolithography (DPN) of the biological species or capture chemistry, within the array facilitates efficient read out via fast Raman line mapping. In addition, we can apply parallel deposition methods to enhance the throughput of these combined techniques. SERRS is an extremely sensitive spectroscopic technique that offers several advantages over conventional fluorescence detection. For example, the high sensitivity of the method allows detection of DNA capture from single plasmonic array "pixels" ~1 μm 2 in area. Additionally, the information rich nature of the SERRS spectrum allows multiple levels of detection to be embedded into each pixel, further increasing the information depth of the array. By moving from micro- to nano-scale features, sensor chips can contain up to 105 times more information, dramatically increasing the capacity for disease screening.

Functionalised nanoparticles have been used in a number of studies including detection of DNA at ultra low concentrations, immuno-histochemistry and more recently as substrates for surface enhanced resonance Raman scattering (SERRS) based imaging approaches. The advantages of using metallic nanoparticles are that they are very bright in terms of their optical characteristics and also can be functionalised to provide a SERRS response and hence provide a unique Raman fingerprint. Here we present the functionalisation of gold and silver nanoparticles in such a way that the enhancement effect can be greatly increased through biological interaction and as such effectively turn on the SERRS effect. In an advancement of this nanoparticles have been used as imaging agents for single cells when functionalised with an appropriate antibody and can give information on the expression of specific receptors on cell surfaces as well as sub-cellular compartmentalisation information.

Bone marrow-derived immune cells (macrophages) treated with gold and silver nanoparticles before fixation and dye staining have been analysed by multiple wavelength line scanning surface enhanced resonance Raman scattering (SERRS) mapping. The method yields high selectivity and sensitivity within short analysis times, identifying nanoparticle aggregates in secondary lysosomes. Using routine cell stains, the output from fluorescence, Raman and SERRS is quantified at four wavelengths of excitation, demonstrating the potential at longer biologically compatible wavelengths of using nanoparticles with cell stains for superior cell mapping.

We demonstrate the powerful combination of dip-pen nanolithography (DPN) performed on non-flat plasmonic gold surfaces and subsequent detection by surface enhanced resonance Raman scattering (SERRS).

A low cost technique is reported for the rapid screening of containers for materials that potentially could be used for terrorist activities. For peroxide based samples it is demonstrated that full characterisation can be achieved in a continuous curve fitting monitoring mode acquiring up to 10 spectra per second. This clearly demonstrates the potential for a Raman based method to be incorporated into a check-point whilst retaining fast throughput. A number of precursor compounds to nerve agents and peroxide and nitrate based improvised explosive materials have been studied. The potential strengths and weaknesses of using Raman for multiple target identification are discussed with regard to the common vibrations associated with each group of agents. Within this context we also introduce the use of fast Raman line mapping into the trace analysis of multiple component targets. The method presented is suited to volatile or light sensitive samples (such as derived peroxides) and can be employed on a variety of surfaces. As speed and throughput are traded against spectral bandwidth categorising threat compounds into groups based on common functionalities allows the full potential for multiplexed targeting to be realised.

There is a growing need for fast reliable biosensor arrays for disease screening. We have used nanostructured plasmonic gold surfaces for the detection of biological species by surface enhanced resonance Raman scattering (SERRS). Careful, directed placement by Dip-pen Nanolithography (DPN) of the biological species or capture chemistry, within the array facilitates efficient read out via ultra fast Raman line mapping. Further, we can transition the serial placement of biological species / capture chemistry to a massively parallel deposition method, and this flexibility is key to enhancing the throughput of these combined techniques by many orders of magnitude. SERRS is an extremely sensitive spectroscopic technique that offers several advantages over conventional fluorescence detection. For example, the high sensitivity of the method allows detection of DNA capture from single plasmonic array "pixels" ~1 µm2 in area. Additionally, the information rich nature of the SERRS spectrum allows multiple levels of detection to be embedded into each pixel, further increasing the information depth of the array. By moving from micro- to nano-scale features, sensor chips can contain up to 105 times more information, dramatically increasing the capacity for disease screening.

Oligonucleotide-gold-nanoparticle (OGN) conjugates are now recognized as both powerful tools for ultrasensitive detection and building blocks for the controlled creation of nanostructures (see image). The first use of both OGN and oligonucleotide-silver nanoparticle (OSN) conjugates are used to create mixed-metal nanostructures with novel optical properties. (Abstract from: http://www3.interscience.wiley.com/journal/121357719/abstract)

A micro-bead sandwich assay for P38 mitogen-activated protein kinase using surface enhanced resonance Raman spectroscopy (SERRS) detection is reported. Monoclonal capture antibodies were immobilised on a solid phase of magnetic micro-beads with secondary detection using a rhodamine-labelled antibody. Quantitative SERRS detection of the secondary antibody was possible with a limit of detection of 9.5 x 10(-12) mol dm(-3). The sandwich assay was quantitative and sensitive to 6 ng ml(-1). The mechanism of the SERRS detection in the immunoassay was investigated. The addition of SERRS aggregating agents causes the dissociation of the immuno-complex from the magnetic beads. Scanning electron microscopy images indicate that the colloidal suspension rather than adsorbed silver nanoparticles on the beads provide the SERRS signals, that the aggregate size is partially controlled and that there is some inhomogeneity in the distribution of organic matter on the nanoscale.

Surface-enhanced Raman scattering (SERS) is shown to give linear and sensitive concentration-dependent detection of folic acid using silver nanoparticles created via ethylene-diaminetetraacetic acid (EDTA) reduction. Optical detection by SERS overcomes the primary limitation of photodissociation encountered during the application of other shorter wavelength ultraviolet (UV)/near-UV techniques such as fluorescence based microscopy. The SERS approach in water-based samples was demonstrated and optimized using several longer wavelengths of excitation (514.5, 632.8, and 785 nm). Excitation in the green (514.5 nm) was found to achieve the best balance between photodissociation and SERS efficiency. Linear concentration dependence was observed in the range of 0.018 to 1 μM. The importance of folic acid in a clinical setting and the potential applications of this technique in a biological environment are highlighted. We demonstrate the potential to transfer this technique to real biological samples by the detection of folic acid in human serum samples by SERS.

Raman spectroscopy provides a very effective method of identifying an illicit substance in situ without separation or contact other than with a laser beam. The equipment required is steadily improving and is now reliable and simple to operate. Costs are also coming down and hand held portable spectrometers are proving very effective. The main limitations on the use of the technique are that it is insensitive in terms of the number of incident photons converted into Raman scattered photons and fluorescence produced in the sample by the incident radiation interferes. Newer methods, still largely in the development phase, will increase the potential for selected applications. The use of picosecond pulsed lasers can discriminate between fluorescence and Raman scattering and this has been used in the laboratory to examine street samples of illicit drugs. Surface-enhanced Raman scattering, in which the analyte requires to be adsorbed onto a roughened metal surface, creates a sensitivity to compete with fluorescence and quenches fluorescence for molecules on a surface. This provides the ability to detect trace amounts of substances in some cases. The improving optics, detection capability and the reliability of the new methods indicate that the potential for the use of Raman spectroscopy for security purposes will increase with time.

Careful control of surface chemistry results in strong surface enhanced resonance Raman scattering from dye-labelled oligonucleotides assembled on nanostructured gold surfaces, releasing their potential as reliable enhancing surfaces.

Surface enhanced Raman scattering (SERS) has been used to detect specific pterin molecules at sub-nanomolar concentrations. SERS is fast becoming a widely used technique for the sensitive and specific detection of multiple analytes. The information-rich and concentration-dependent spectra obtained from SERS make the technique ideally placed for high speed, low cost analysis of almost any analyte. Further, to show the feasibility of SERS in the detection of biologically relevant targets, a synthetic pterin analogue of the naturally occurring pterin cofactor, tetrahydrobiopterin, has been detected at a series of concentrations and the method used for the successful detection of the synthetic pterin in mouse serum. In this analysis, spectroscopic collection was optimized for water-based pteridine derivatives using two visible wavelengths of excitation (514.5 and 632.8 nm) and differing mesoscopic metal nanoparticles allowing the limits of detection to be calculated.

A method that enables reproducible synthesis of low aspect ratio, monodispersed and stable silver nanoparticle suspensions, uniform in its optical response and tunable over a range of diameters has been developed. The uniformity of the nanoparticles has been accurately determined using electron and atomic force microscopies for diameters down to 50 nm. These particles are highly suited to applications in optical nanotechnology.

A new approach to the synthesis of polymer beads that give surface-enhanced resonance Raman scattering (SERRS) is reported. Controlling the aggregation of silver nanoparticles by silica seeding prior to encapsulation into a polymer is shown to yield a highly reproducible bead with a relative standard deviation (RSD) diameter down to 5%. The reliable and intense SERRS response is attributed to the combined resonance of the reporter dye (435 nm) and the nanoparticle cluster (440 nm). The presence of heavier clustered particles within the bead core means the activity can be further improved to around 93% by means of sedimentation purification. This is a significant step towards a reproducible and reliable reporter unit for the many varied potential biodiagnostic applications of SERRS.

A recent model for molecular rectification has focused upon asymmetric alkyl tunnelling barriers that link the electrodes to a conjugated unit but experimental data reported here are contradictory: self-assembled monolayers (SAMs) exhibit symmetrical current–voltage characteristics when squaraine chromophores are located at one electrode and isolated from the other by extended alkanethiolate tails.