SERS Sensing of Dopamine with Fe(III)-Sensitized Nanogaps in Recleanable AuNP Monolayer Films

Sensing of neurotransmitters (NTs) down to nm concentrations is demonstrated by utilizing self-assembled monolayers of plasmonic 60 nm Au nanoparticles in close-packed arrays immobilized onto glass substrates. Multiplicative surface-enhanced Raman spectroscopy enhancements are achieved by integrating Fe(III) sensitizers into the precisely-defined <1 nm nanogaps, to target dopamine (DA) sensing. The transparent glass substrates allow for efficient access from both sides of the monolayer aggregate films by fluid and light, allowing repeated sensing in different analytes. Repeated reusability after analyte sensing is shown through oxygen plasma cleaning protocols, which restore pristine conditions for the nanogaps. Examining binding competition in multiplexed sensing of two catecholamine NTs, DA and epinephrine, reveals their bidentate binding and their interactions. These systems are promising for widespread microfluidic integration enabling a wide range of continuous biofluid monitoring for applications in precision health

Diamond nano-pillar arrays for quantum microscopy of neuronal signals

Modern neuroscience is currently limited in its capacity to perform long term, wide-field measurements of neuron electromagnetics with nanoscale resolution. Quantum microscopy using the nitrogen vacancy centre (NV) can provide a potential solution to this problem with electric and magnetic field sensing at nano-scale resolution and good biocompatibility. However, the performance of existing NV sensing technology does not allow for studies of small mammalian neurons yet. In this paper, we propose a solution to this problem by engineering NV quantum sensors in diamond nanopillar arrays. The pillars improve light collection efficiency by guiding excitation/emission light, which improves sensitivity. More importantly, they also improve the size of the signal at the NV by removing screening charges as well as coordinating the neuron growth to the tips of the pillars where the NV is located. Here, we provide a growth study to demonstrate coordinated neuron growth as well as the first simulation of nano-scopic neuron electric and magnetic fields to assess the enhancement provided by the nanopillar geometry.Comment: 18 pages including supplementary and references, 12 figure

Plasmonic Biosensing via Surface-Enhanced Raman Spectroscopy

[Restricted]Gates Cambridge Scholarshi

Ellipsometric detection of ferritin adsorption on gold after UV irradiation

The regulation of iron in a living organism is extremely important as it can have lethal damage to the organism. Ferritin is an iron-storing protein that plays an essential role in the biochemical reactions and the iron transport of all living organisms. As such, the ferritin can play a key role in diagnosing neurodegenerative and cancer diseases by detecting low quantities of iron. The reason for the study is based on the increased number of skin diseases due to the influence of UV radiation. We study the adsorption properties of the protein Ferritin on a gold surface after UV irradiation using Variable Angle Spectroscopic Ellipsometry (VASE) in situ. Special equipment for irradiation of samples with UV (405 nm) was made. The results obtained show that with increasing irradiation time, the initial thickness of the ferritin proteins decreases, resulting either in an increase in molecular density when iron ions are released or in the deformation of the ferritin proteins. The data show that the methods are applicable for analysis and characterization of adsorption of biomolecules.The authors acknowledge the financial support of EC ERASMUS MUNDUS: NANOPHI project

Exotic silicon phases synthesized through ultrashort laser-induced microexplosion: Characterization with Raman microspectroscopy

Exotic metastable phases of silicon formed under high pressure are expected to have attractive semiconducting properties including narrow band gaps that open up novel technological applications. Confined microexplosions induced by powerful ultrashort laser pulses have been demonstrated as an advanced tool for the creation of new high-pressure phases that cannot be synthesized by other means. Tightly focused laser pulses are used to generate localized modifications inside the material structure, providing the possibility for precise controlled band-gap engineering. In this study, noninvasive Raman spectroscopy was used for analysis of laser-modified zones in silicon and to determine the metastable high-pressure phases contained. Low laser energies induced the formation of amorphous-only silicon, while higher energies led to crystalline silicon polymorphs within the modifications, albeit under considerable residual stress up to 4.5 GPa. The presence of the structurally similar r8-Si, bc8-Si, and bt8-Si phases is revealed, as well as other yet to be identified phases, and the stacking-related 9R Si polytype is evidenced, presumably stress-induced by the highly compressed laser-modified zone. The ab initio random structure searching approach is used to calculate the Raman signatures and to help identify different Si polymorphs. These findings by Raman spectroscopy from ultrashort laser-induced microexplosion sites may yield insights into the local structure and properties of new silicon metastable phases and the prospect of utilizing exotic phases for extending current applications.The authors acknowledge the support by the Australian Government through the Australian Research Council’s Discovery scheme, Project No. DP170100131

SERS sensing of dopamine with Fe(III)-sensitised nanogaps in recleanable AuNP monolayer films

Sensing of neurotransmitters down to nM concentrations is demonstrated by utilising self assembled monolayers of plasmonic 60 nm Au nanoparticles in close-packed arrays immobilised onto glass substrates. Multiplicative SERS enhancements are achieved by integrating Fe(III) sensitisersinto the precisely-defined <1 nm nanogaps, to target dopamine sensing. The transparent glass substrates allow for efficient access from both sides of the monolayer aggregate films by fluid and light, allowing repeated sensing in different analytes. Repeated reusability after analyte sensing is shown through oxygen plasma cleaning protocols which restore pristine conditions for the nanogaps. Examining binding competition in multiplexed sensing of two catecholamine neurotransmitters, dopamine and epinephrine, reveals their bidentate binding and their interactions. These systems are promising for widespread microfluidic integration enabling a wide range of continuous biofluid monitoring for applications in precision health

Research data supporting "Controlling atomic-scale restructuring and cleaning of gold nanogap multilayers for SERS sensing"

This dataset contains raw spectral data associated with the main figures in a publication detailing a new thin-film multi-layer gold nanoparticle aggregate ('MLagg') surface-enhanced Raman spectroscopy (SERS) substrate. SERS and dark-field (DF) scattering measurements were collected by mapping spectra across the substrate surface. The DF data is referenced to a white light scattering target and has been background subtracted to remove dark counts. The dataset characterises the MLagg substrate, demonstrates surface cleaning and functionalisation control methods, as well as the substrate's application for in-flow sensing of paracetamol and detection of vapours such as toluene.The authors acknowledge financial support from EPSRC Grants (EP/L027151/1, RANT EP/R020965/1, EP/P029426/1) and ERC PICOFORCE (883703). D.-B.G. and S.M.S-T. are supported by EPSRC Grant EP/L015889/1 for the EPSRC Centre for Doctoral Training in Sensor Technologies and Applications. S.M.S.-T. is part supported by the University of Cambridge Harding Distinguished Postgraduate Scholars Programme. M.N. is supported by a Gates Cambridge fellowship (OPP1144). B.dN acknowledges support from the Royal Society (URF\R1\211162). R.A. acknowledges support from the Rutherford Foundation of the Royal Society Te Apārangi of New Zealand, and the Winton Programme for the Physics of Sustainability and Trinity College, University of Cambridge. The authors acknowledge the use of the Cambridge XPS System, part of Sir Henry Royce Institute Cambridge Equipment, EPSRC grant EP/P024947/1

SERS Sensing of Dopamine with Fe(III)-Sensitized Nanogaps in Recleanable AuNP Monolayer Films.

Sensing of neurotransmitters (NTs) down to nm concentrations is demonstrated by utilizing self-assembled monolayers of plasmonic 60 nm Au nanoparticles in close-packed arrays immobilized onto glass substrates. Multiplicative surface-enhanced Raman spectroscopy enhancements are achieved by integrating Fe(III) sensitizers into the precisely-defined <1 nm nanogaps, to target dopamine (DA) sensing. The transparent glass substrates allow for efficient access from both sides of the monolayer aggregate films by fluid and light, allowing repeated sensing in different analytes. Repeated reusability after analyte sensing is shown through oxygen plasma cleaning protocols, which restore pristine conditions for the nanogaps. Examining binding competition in multiplexed sensing of two catecholamine NTs, DA and epinephrine, reveals their bidentate binding and their interactions. These systems are promising for widespread microfluidic integration enabling a wide range of continuous biofluid monitoring for applications in precision health

In situ electrochemical regeneration of nanogap hotspots for continuously reusable ultrathin SERS sensors

Abstract Surface-enhanced Raman spectroscopy (SERS) harnesses the confinement of light into metallic nanoscale hotspots to achieve highly sensitive label-free molecular detection that can be applied for a broad range of sensing applications. However, challenges related to irreversible analyte binding, substrate reproducibility, fouling, and degradation hinder its widespread adoption. Here we show how in-situ electrochemical regeneration can rapidly and precisely reform the nanogap hotspots to enable the continuous reuse of gold nanoparticle monolayers for SERS. Applying an oxidising potential of +1.5 V (vs Ag/AgCl) for 10 s strips a broad range of adsorbates from the nanogaps and forms a metastable oxide layer of few-monolayer thickness. Subsequent application of a reducing potential of −0.80 V for 5 s in the presence of a nanogap-stabilising molecular scaffold, cucurbit[5]uril, reproducibly regenerates the optimal plasmonic properties with SERS enhancement factors ≈106. The regeneration of the nanogap hotspots allows these SERS substrates to be reused over multiple cycles, demonstrating ≈5% relative standard deviation over at least 30 cycles of analyte detection and regeneration. Such continuous and reliable SERS-based flow analysis accesses diverse applications from environmental monitoring to medical diagnostics

In situ electrochemical regeneration of nanogap hotspots for continuously reusable ultrathin SERS sensors.

Surface-enhanced Raman spectroscopy (SERS) harnesses the confinement of light into metallic nanoscale hotspots to achieve highly sensitive label-free molecular detection that can be applied for a broad range of sensing applications. However, challenges related to irreversible analyte binding, substrate reproducibility, fouling, and degradation hinder its widespread adoption. Here we show how in-situ electrochemical regeneration can rapidly and precisely reform the nanogap hotspots to enable the continuous reuse of gold nanoparticle monolayers for SERS. Applying an oxidising potential of +1.5 V (vs Ag/AgCl) for 10 s strips a broad range of adsorbates from the nanogaps and forms a metastable oxide layer of few-monolayer thickness. Subsequent application of a reducing potential of -0.80 V for 5 s in the presence of a nanogap-stabilising molecular scaffold, cucurbit[5]uril, reproducibly regenerates the optimal plasmonic properties with SERS enhancement factors ≈106. The regeneration of the nanogap hotspots allows these SERS substrates to be reused over multiple cycles, demonstrating ≈5% relative standard deviation over at least 30 cycles of analyte detection and regeneration. Such continuous and reliable SERS-based flow analysis accesses diverse applications from environmental monitoring to medical diagnostics