Gold and silver nanoparticles have been electrodeposited onto fluorine-doped tin oxide by a two pulse method. The
statistical distribution of the size and interparticle spacing of nanoparticles can be controlled by altering the
overpotential and duration of the nucleation and growth pulses. Isolated gold and silver nanoparticle covered surfaces
prepared in this way display a localized surface plasmon absorption. Raman spectra for immobilized trans-1,2-bis(4-
pyridyl) ethylene have been recorded from isolated gold and silver nanoparticle surfaces with different mean particle
size, and at different excitation wavelengths. The optimal SERS conditions determined for isolated gold and for silver
nanoparticles produce enhancement factors of 5.6 x 102 and 4.0 x 103 , respectively. Reproducibility is typically 20-
30% RSD due to variations in the SERS active area exposed in different measurements and perhaps variations in the
enhancement factor at different sites on a single electrodeposited surface.
Noble metal nanoparticles arrays are well established substrates for surface enhanced Raman spectroscopy (SERS).
Their ability to enhance optical fields is based on the interaction of their surface valence electrons with incident
electromagnetic radiation. In the array configuration, noble metal nanoparticles have been used to produce SER spectral
enhancements of up to 108 orders of magnitude, making them useful for the trace analysis of physiologically relevant
analytes such as proteins and peptides. Electrostatic interactions between proteins and metal surfaces result in the
preferential adsorption of positively charged protein domains onto metal surfaces. This preferential interaction has the
effect of disrupting the native conformation of the protein fold, with a concomitant loss of protein function. A major
historic advantage of Raman microspectroscopy has been is its non-invasive nature; protein denaturation on the metal
surfaces required for SER spectroscopy renders it a much more invasive technique. Further, part of the analytical power
of Raman spectroscopy lies in its use as a secondary conformation probe. The protein structural loss which occurs on
the metal surface results in secondary conformation readings which are not true to the actual native state of the analyte.
This work presents a method for chemical fabrication of noble metal SERS arrays with surface immobilized layers
which can protect protein native conformation without excessively mitigating the electromagnetic enhancements of
spectra. Peptide analytes are used as model systems for proteins. Raman spectra of alpha lactalbumin on surfaces and
when immobilized on these novel arrays are compared. We discuss the ability of the surface layer to protect protein
structure whilst improving signal intensity.
Noble metal nanoparticles interact strongly with visible light due to resonant excitation of conduction electron oscillations, an interaction referred to as a local surface plasmon resonance (LSPR) interaction. This LSPR interaction results in an enhancement of the electromagnetic field surrounding the nanoparticle, with a concomitant enhancement of optical signals. Recent interest in SER spectroscopy (SERS) has been rekindled by the observation of single molecule SERS. Nanofabrication provides a method for producing metal substrates for SERS with well-defined size and shape characteristics. Gold nanopillar structures are fabricated for this work by electron beam lithography. Rabbit skeletal-myosin-II HMM and actin can be produced in gram quantities and provide the basis for a highly reproducible in-vitro motility assay system. Using this well established assay linked with SERS we can look at how the heads of myosin interact with filaments of actin to produce steps in greater detail. This technique will provide information of subtle mechanistic interactions between components of a molecular motor, with the future possibility of providing a model system for measuring the “proximity effect” in ligand binding (e.g. protein-protein and DNA-DNA interactions) and LSPR-analyte interactions.
This paper describes a novel method for the fabrication of nanodot arrays with 30nm period which will be used as a platform for the highly sensitive and specific Surface enhanced Raman spectroscopy (SERS) detection of the polymerase chain reaction (PCR). The usual detection methods for PCR involve time consuming methods of DNA labelling, using labels that are capable of altering original DNA properties. We present a detection method which has the advantages of being label free, requiring small analyte volumes and achieving high sensitivity due to SERS enhancement. The required reproducible SERS environment is achieved by the nanofabrication of gold pillars on glass with the use of an electron-beam writer.
As part of an ongoing larger study of the molecular and supramolecular foundations of bone tissue biomechanics, we report thermal perturbations to bone mineral and related model compounds. The response of bone tissue to external mechanical and thermal loading under a variety of conditions is used to elucidate the response to physiologically relevant loads. Here NMR spectroscopy is used in conjunction with Raman spectroscopy to elucidate the mineral structure of the bone and track changes in the lattice due to temperature variation. Changes in the bone lattice are studied by examining the Raman spectral band widths and positions of the phosphate and carbonate bands. Expansion of the lattice leads to increased band widths as local ion motion is facilitated. Larger effects are found in undeproteinated bone powder than in deproteinated bone mineral powder. 1H MAS NMR is used to track the water content of deproteinated bone as a function of temperature. The differing effects observed in undeproteinated bone powder and deproteinated bone mineral powder suggest that mineral crystallite expansion may involve mechanical constraint by the bone matrix. 13C MAS NMR spectroscopy revealed a loss of carbonate in deproteinated bone mineral when heated to 225 C. This is a significantly lower temperature than previously reported for removal of carbonate from synthetic apatite material. The properties of bone mineral influenced by even small perturbations such as temperature elevation or reduction depend on the presence of matrix. It is reasonable to assume that bone tissue response to other external loads, including compression or bending under normal physiological conditions also depend on the interaction of mineral and matrix.