Orientational Mapping Augmented Sub-Wavelength Hyper-Spectral Imaging of Silk

Ryu, Meguya; Balčytis, Armandas; Wang, Xuewen; Vongsvivut, Jitraporn; Hikima, Yuta; Li, Jingliang; Tobin, Mark J.; Juodkazis, Saulius; Morikawa, Junko

doi:10.1038/s41598-017-07502-3

Cited by 44 publications

(57 citation statements)

References 48 publications

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“…It is therefore possible to achieve an ATR focus spot size of around 2 μm and a mapping step size of 0.25 μm. [47][48][49] In this study, ATR-FTIR spectroscopy was applied to image the distribution of eccrine and sebaceous material in individual droplets within fingermark ridges. The minimum size of the infrared beam on the sample was 1.88 µm, and the images were collected with a 0.25 µm pixel size.…”

Section: Investigating the Distribution Of Eccrine And Sebaceous Matementioning

confidence: 99%

Revealing the spatial distribution of chemical species within latent fingermarks using vibrational spectroscopy

Dorakumbura

Boseley

Becker

et al. 2018

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Latent fingermarks are an important form of crime-scene trace evidence and their usefulness may be increased by a greater understanding of the effect of chemical distribution within fingermarks on the sensitivity and robustness of fingermark detection methods. Specifically, the relative abundance and micro-distribution of sebaceous (lipophilic) and eccrine (hydrophilic) material in fingermarks have long been debated in the field, yet direct visualisation of relative abundance and micro-distribution was rarely achieved. Such a visualisation is nonetheless essential to provide explanations for the variation in reproducibility or robustness of latent fingermark detection with existing methods, and to identify new strategies to increase detection capabilities. In this investigation, we have used SR-ATR-FTIR and confocal Raman microscopy to probe the spatial micro-distribution of the sebaceous and eccrine chemical components within latent fingermarks, deposited on non-porous surfaces. It was determined that fingermarks exhibit a complex spatial distribution, influenced by the ratio of lipophilic to aqueous components, and to a first approximation resemble a water-in-oil or oil-in-water emulsion. Detection of a substantial lipid component in "eccrine enriched fingermarks" (wherein hands are washed to remove lipids) is noteworthy, as it provides a potential explanation for several scenarios of unexpected fingermark detection using methods previously thought unsuitable for "eccrine deposits". Furthermore, the pronounced distribution of lipids observed in natural fingermark deposits was intriguing and agrees with recent discussion in this research field that natural fingermarks contain a much higher lipid content than previously thought.

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Section: Investigating the Distribution Of Eccrine And Sebaceous Matementioning

confidence: 99%

Revealing the spatial distribution of chemical species within latent fingermarks using vibrational spectroscopy

Dorakumbura

Boseley

Becker

et al. 2018

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“…The birefringence originates from alignment of molecular bonds or secondary ordering and can be detected at different spectral ranges [17]. Molecular alignment of the amide-II at 1512 cm −1 (C-N) and amide-I β-sheets at 1628 cm −1 (C=O) was measured form micron-thick longitudinal silk slices [11].…”

Section: Resultsmentioning

confidence: 99%

“…In-plane perpendicular orientation between C=O and C-N bonds was revealed [11] using a longitudinal slice of silk fiber, which facilitated fidelity of measurements due to uniformity of thickness [18].…”

Section: Resultsmentioning

confidence: 99%

“…Inset in reflectivity panel shows a molecular orientation of the amide-I,II bands in β-sheet crystalline regions for the longitudinal slice (adopted form ref. [11]). Note, chemical bonding in the β-sheets plane only is shown; the C=O bonds have a radial distribution along the fiber direction and their second order momentum distribution was determined in Supplement of ref.…”

Section: Resultsmentioning

confidence: 99%

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Near-Field IR Orientational Spectroscopy of Silk

Ryu¹,

Honda²,

Reich³

et al. 2019

Preprint

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Orientational dependence of the IR absorbing amide bands of silk is demonstrated from two orthogonal longitudinal and transverse microtome slices only $\sim 100$~nm thick. A scanning near-field optical microscopy (SNOM) which preferentially probes orientation perpendicular to the sample's surface was used. Spatial resolution of silk-epoxy boundary was defined with a $\sim 100$~nm resolution while the spectra were collected by a $\sim 10$~nm tip. Ratio of the absorbance of the amide-II C-N at 1512~cm$^{-1}$ and amide-I C=O $\beta$-sheets at 1628~cm$^{-1}$ showed sensitivity of SNOM to the molecular orientation. SNOM characterisation is complimentary to the far-field absorbance which is sensitive to the in-plane polarisation. Volumes with cross sections smaller than 100~nm can be characterised for molecular orientation. A method of absorbance measurements at four angles of slice cut orientation, which is equivalent to the four polarisation angles absorbance measurement is proposed.

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“…21 Optical elements for spin and orbital angular momentum control are expected to provide new insights into complex secondary structures of polymers including bio-polymers such as silk which have strong signatures at IR-THz spectral range. [22][23][24][25] …”

Section: Discussionmentioning

confidence: 99%

All-dielectric metasurface for wavefront control at terahertz frequencies

Dharmavarapu

Bhattacharya

et al. 2018

Nanophotonics Australasia 2017

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Recently, metasurfaces have gained popularity due to their ability to offer a spatially varying phase response, low intrinsic losses and high transmittance. Here, we demonstrate numerically and experimentally a silicon metasurface at THz frequencies that converts a Gaussian beam into a Vortex beam independent of the polarization of the incident beam. The metasurface consists of an array of sub-wavelength silicon cross resonators made of a high refractive index material on substrates such as sapphire and CaF 2 that are transparent at IR-THz spectral range. With these substrates, it is possible to create phase elements for a specific spectral range including at the molecular finger printing around 10 µm as well as at longer THz wavelengths where secondary molecular structures can be revealed. This device offers high transmittance and a phase coverage of 0 to 2π. The transmittance phase is tuned by varying the dimensions of the meta-atoms. To demonstrate wavefront engineering, we used a discretized spiraling phase profile to convert the incident Gaussian beam to vortex beam. To realize this, we divided the metasurface surface into eight angular sectors and chose eight different dimensions for the crosses providing successive phase shifts spaced by π/4 radians for each of these sectors. Photolithography and reactive ion etching (RIE) were used to fabricate these silicon crosses as the dimensions of these cylinders range up to few hundreds of micrometers. Large 1-cm-diameter optical elements were successfully fabricated and characterised by optical profilometry.

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Orientational Mapping Augmented Sub-Wavelength Hyper-Spectral Imaging of Silk

Cited by 44 publications

References 48 publications

Revealing the spatial distribution of chemical species within latent fingermarks using vibrational spectroscopy

Revealing the spatial distribution of chemical species within latent fingermarks using vibrational spectroscopy

Near-Field IR Orientational Spectroscopy of Silk

All-dielectric metasurface for wavefront control at terahertz frequencies

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