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1.
Towards chemical analysis of nanostructures in biofilms II: tip-enhanced Raman spectroscopy of alginates 总被引:1,自引:1,他引:0
Schmid T Messmer A Yeo BS Zhang W Zenobi R 《Analytical and bioanalytical chemistry》2008,391(5):1907-1916
This study examines the feasibility of using tip-enhanced Raman spectroscopy (TERS) for label-free chemical characterization
of nanostructures in biological systems. For this purpose, a well-defined model system consisting of calcium alginate fibers
is studied. In a companion paper, calcium alginate fibers and their network structures were shown to be a good model for the
extracellular polysaccharides of biofilms at the nanoscale. TERS analysis of biological macromolecules, such as alginates,
is complicated by heterogeneity in their sequence, molecular weight, and conformations, their small Raman cross-section, and
the large number of functional groups, which can chemically interact with the silver surface of the tip and cause significant
band shifts. Due to these effects, Raman frequencies in TERS spectra of biopolymers do not necessarily resemble band positions
in the normal Raman spectrum of the bulk material, as is the case for less complex samples (e.g., dye molecules) studied so
far. Additionally, analyte decomposition due to laser heating can have a significant influence, and carbon contamination signals
can sometimes even overwhelm the weak analyte signals. Based on the investigation of alginates, strategies for spectra correction,
choice of appropriate reference samples, and data interpretation are presented. With this approach, characteristic frequency
ranges and specific marker bands can be found for biological macromolecules that can be employed for their identification
in complex environments.
Figure TERS spectrum of a calcium alginate fiber bundle 相似文献
2.
Alvarado Tarun Norihiko Hayazawa Satoshi Kawata 《Analytical and bioanalytical chemistry》2009,394(7):1775-1785
Tip-enhanced Raman spectroscopy (TERS), which utilizes the strong localized optical field generated at the apex of a metallic
tip when illuminated, has been shown to successfully probe the vibrational spectrum of today’s and tomorrow’s state-of-the-art
silicon and next-generation semiconductor devices, such as quantum dots. Collecting and analyzing the vibrational spectrum
not only aids in material identification but also provides insight into strain distributions in semiconductors. Here, the
potential of TERS for nanoscale characterization of strain in silicon devices is reviewed. Emphasis will be placed on the
key challenges of obtaining spectroscopic images of strain in actual strained silicon devices.
Figure Figure Concept of Tip Enhanced Raman Spectroscopy (TERS), which utilizes the strong localized optical field generated at the
apex of a metallic tip when illuminated. TERS has been demonstrated to successfully probe the vibrational spectrum of today’s
and tomorrow’s state-of-the-art silicon and next generation semiconductor devices 相似文献
3.
The detection and identification of dilute bacterial samples by surface-enhanced Raman spectroscopy has been explored by mixing
aqueous suspensions of bacteria with a suspension of nanocolloidal silver particles. An estimate of the detection limit of
E. coli was obtained by varying the concentration of bacteria. By correcting the Raman spectra for the broad librational OH band
of water, reproducible spectra were obtained for E. coli concentrations as low as approximately 103 cfu/mL. To aid in the assignment of Raman bands, spectra for E. coli in D2O are also reported.
Figure Light scattering apparatus used to detect bacteria 相似文献
4.
Raman spectroscopy on transition metals 总被引:2,自引:0,他引:2
Surface-enhanced Raman spectroscopy (SERS) has developed into one of the most important tools in analytical and surface sciences
since its discovery in the mid-1970s. Recent work on the SERS of transition metals concluded that transition metals, other
than Cu, Ag, and Au, can also generate surface enhancement as high as 4 orders of magnitude. The present article gives an
overview of recent progresses in the field of Raman spectroscopy on transition metals, including experimental, theory, and
applications. Experimental considerations of how to optimize the experimental conditions and calculate the surface enhancement
factor are discussed first, followed by a very brief introduction of preparation of SERS-active transition metal substrates,
including massive transition metal surfaces, aluminum-supported transition metal electrodes, and pure transition metal nanoparticle
assembled electrodes. The advantages of using SERS in investigating surface bonding and reaction are illustrated for the adsorption
and reaction of benzene on Pt and Rh electrodes. The electromagnetic enhancement, mainly lightning-rod effect, plays an essential
role in the SERS of transition metals, and that the charge-transfer effect is also operative in some specific metal–molecule
systems. An outlook for the field of Raman spectroscopy of transition metals is given in the last section, including the preparation
of well-ordered or well-defined nanostructures, and core-shell nanoparticles for investigating species with extremely weak
SERS signals, as well as some new emerging techniques, including tip-enhanced Raman spectroscopy and an in situ measuring
technique.
Figure Electric-field enhancement of a SERS-active Rh surface decorated with small nanohemispheres 相似文献
5.
The objective of this research was to investigate nanoindentation-induced residual stresses in human enamel using Raman microspectroscopy
and establish if this approach can be used as a stress meter. Healthy human premolars and sintered hydroxyapatite samples
were embedded, cut, and the surfaces were polished finely with a 0.05 μm polishing paste before Berkovich and spherical indentations
were made with a force of 100 mN. Spectra were collected using a Renishaw Raman InVia reflex microscope equipped with an air-cooled
charge-coupled device (CCD) camera. Sample excitation was achieved using either an argon ion laser emitting at 514.5-nm or
a NIR diode laser emitting at 830-nm. The residual micro stresses within and surrounding the indentation impressions were
monitored by mapping the position of the ν1(PO4) band of (crystalline) hydroxyapatite. The Raman maps coincided well with the optical micrographs of the samples. Despite
the presence of a fluorescence background from the organic component of human enamel, spectra collected using 514.5-nm excitation
exhibited more significant shifts in the position of the ν1(PO4) band than spectra collected using 830-nm excitation. This implies that the former excitation may be a more appropriate excitation
for stress detection. It was concluded that Raman microspectroscopy provides a novel high-resolution and non-destructive method
for exploring the role of microstructure on the residual stress distribution within natural biocomposites.
Figure Stress maps of nanoindentation impressions on both human enamel and hydroxyapatite disk via Raman Microspectroscopy 相似文献
6.
Kaindl R Sartory B Neidhardt J Franz R Reiter A Polcik P Tessadri R Mitterer C 《Analytical and bioanalytical chemistry》2007,389(5):1569-1576
A new method for chemical analyses of nitride-based hard coatings is presented. Raman band shifts in the spectra of Al
x
Cr1−x
N coatings, deposited by physical vapour deposition from Al
x
Cr1−x
targets with x
T,Al = 0, 0.25, 0.50, 0.70 and 0.85, are calibrated using compositional data of the coatings derived by elastic recoil detection
analysis (ERDA) and electron probe micro-analysis (EPMA). Inserting the composition-dependent Raman shift of a combinatorial
acoustic-optic lattice mode into an empirically derived equation allows the determination of Al/Cr ratios of the coating with
an accuracy of about ±2%. Spot, line and area analyses of coated cemented carbide and cold work steel samples by using a computer-controlled,
motorized x,y-stage are demonstrated and the most important errors influencing precision and accuracy are discussed.
Figure Raman map of a coated cold-work steel sample 相似文献
7.
Xian-Biao Zhang Yu-Fan Zhang Hang Li Jie Cui Song Jiang Ben Yang Yang Zhang Yao Zhang Zhen-Chao Dong 《化学物理学报(中文版)》2022,35(5):713-719
The quality of the scanning tip is crucial for tip-enhanced Raman spectroscopy (TERS) experiments towards large signal enhancement and high spatial resolution. In this work, we report a controllable fabrication method to prepare TERS-active tips by modifying the tip apex at the atomic scale, and propose two important criteria to in-situ judge the tip's TERS activity for tip-enhanced Raman measurements. One criterion is based on the downshift of the first image potential state to monitor the coupling between the far-field incident laser and near-field plasmon; the other is based on the appearance of the low-wavenumber Raman peaks associated with an atomistic protrusion at the tip apex to judge the coupling efficiency of emissions from the near field to the far field. This work provides an effective method to quickly fabricate and judge TERS-active tips before real TERS experiments on target molecules and other materials, which is believed to be instrumental for the development of TERS and other tip-enhanced spectroscopic techniques. 相似文献
8.
The integration of a range of technologies including microfluidics, surface-enhanced Raman scattering and confocal microspectroscopy
has been successfully used to characterize in situ single living CHO (Chinese hamster ovary) cells with a high degree of spatial (in three dimensions) and temporal (1 s per spectrum) resolution. Following the introduction of a continuous flow of ionomycin, the real time spectral response
from the cell was monitored during the agonist-evoked Ca2+ flux process. The methodology described has the potential to be used for the study of the cellular dynamics of a range of
signalling processes.
Figure Spectral mapping of a single CHO cell 相似文献
9.
Ali EM Edwards HG Hargreaves MD Scowen IJ 《Analytical and bioanalytical chemistry》2008,390(4):1159-1166
This study describes the application of Raman spectroscopy to the detection of drugs of abuse and noncontrolled substances
used in the adulteration of drugs of abuse on human nail. Contamination of the nail may result from handling or abusing these
substances. Raman spectra of pure cocaine hydrochloride, a seized street sample of cocaine hydrochloride (77%), and paracetamol
could be acquired from drug crystals on the surface of the nail. An added difficulty in the analytical procedure is afforded
by the presence of a nail varnish coating the nail fragment. By using confocal Raman spectroscopy, spectra of the drugs under
nail varnish could be acquired. Spectra of the drugs could be readily obtained nondestructively within three minutes with
little or no sample preparation. Raman spectra could be acquired from drug particles with an average size of 5–20 μm. Acquisition
of Raman point maps of crystals from both pure and street samples of cocaine hydrochloride under nail varnish is also reported.
Figure Raman spectrum and point Raman map of cocaine HCI 相似文献
10.
The stonelike otoliths from the ears of fish consist of calcium carbonate crystallites embedded in an organic matrix framework.
The organic matrix has long been known to play a pivotal role in the biomineralization of otoliths, and different methods
have been used to conduct investigations on it. A new sensitive method for the in situ study of the regular variations in
the organic matrix composition of serial small yellow croaker otoliths by Raman microspectroscopy and mapping is described.
The major collagen bands were always observed around 1,272 cm-1 (amide III) and 1600–1690 cm-1 (amide I), and 1443 and 2800–3100 cm-1 (bending and stretching modes of CH groups, respectively). Aromatic amino acids, such as phenylalanine and tyrosine, were
identified at 1,003 cm-1 and at 830 and 853 cm-1. Tryptophan was assigned at 1,555 cm-1, and it was firstly found in otoliths. A regular calcification process in otoliths was observed in Raman spectral mapping
results. Corresponding changes were clearly seen in the concentrations of the organic matrix and aragonite (CaCO3) in otoliths.
相似文献
11.
De Gelder J Scheldeman P Leus K Heyndrickx M Vandenabeele P Moens L De Vos P 《Analytical and bioanalytical chemistry》2007,389(7-8):2143-2151
Endospores and endospore-forming bacteria were studied by Raman spectroscopy. Raman spectra were recorded from Bacillus licheniformis LMG 7634 at different steps during growth and spore formation, and from spore suspensions obtained from diverse Bacillus and Paenibacillus strains cultured in different conditions (growth media, temperature, peroxide treatment). Raman bands of calcium dipicolinate
and amino acids such as phenylalanine and tyrosine are more intense in the spectra of sporulating bacteria compared with those
of bacteria from earlier phases of growth. Raman spectroscopy can thus be used to detect sporulation of cells by a characteristic
band at 1,018 cm–1 from calcium dipicolinate. The increase in amino acids could possibly be explained by the formation of small acid-soluble
proteins that saturate the endospore DNA. Large variations in Raman spectra of endospore suspensions of different strains
or different culturing conditions were observed. Next to calcium dipicolinate, tyrosine and phenylalanine, band differences
at 527 and 638 cm–1 were observed in the spectra of some of the B. sporothermodurans spore suspensions. These bands were assigned to the incorporation of cysteine residues in spore coat proteins. In conclusion,
Raman spectroscopy is a fast technique to provide useful information about several spore components.
Figure A difference spectrum between Raman spectra of B. licheniformis LMG 7634 cultured for 6 days and 1 day, together with the
reference Raman spectrum of calcium dipicolinate 相似文献
12.
A. Hartschuh H. Qian C. Georgi M. Böhmler L. Novotny 《Analytical and bioanalytical chemistry》2009,394(7):1787-1795
We review recent experimental studies on single-walled carbon nanotubes on substrates using tip-enhanced near-field optical
microscopy (TENOM). High-resolution optical and topographic imaging with sub 15 nm spatial resolution is shown to provide
novel insights into the spectroscopic properties of these nanoscale materials. In the case of semiconducting nanotubes, the
simultaneous observation of Raman scattering and photoluminescence (PL) is possible, enabling a direct correlation between
vibrational and electronic properties on the nanoscale. So far, applications of TENOM have focused on the spectroscopy of
localized phonon modes, local band energy renormalizations induced by charge carrier doping, the environmental sensitivity
of nanotube PL, and inter-nanotube energy transfer. At the end of this review we discuss the remaining limitations and challenges
in this field.
Figure Tip-enhanced Raman scattering and photoluminescence spectroscopy with sub 15 nm spatial resolution provides novel insights
into the electronic and vibronic properties of single-walled carbon nanotubes. 相似文献
13.
Rudolf Tuckermann Ljiljana Puskar Mahta Zavabeti Ryo Sekine Don McNaughton 《Analytical and bioanalytical chemistry》2009,394(5):1433-1441
An experimental apparatus combining Raman spectroscopy with acoustic levitation, Raman acoustic levitation spectroscopy (RALS),
is investigated in the field of physical and chemical analytics. Whereas acoustic levitation enables the contactless handling
of microsized samples, Raman spectroscopy offers the advantage of a noninvasive method without complex sample preparation.
After carrying out some systematic tests to probe the sensitivity of the technique to drop size, shape, and position, RALS
has been successfully applied in monitoring sample dilution and preconcentration, evaporation, crystallization, an acid–base
reaction, and analytes in a surface-enhanced Raman spectroscopy colloidal suspension.
Figure We have systematically investigated the analytical potential of Raman spectroscopy of samples in acoustically levitated drops. 相似文献
14.
Sapei L Gierlinger N Hartmann J Nöske R Strauch P Paris O 《Analytical and bioanalytical chemistry》2007,389(4):1249-1257
Horsetail (Equisetum spp.) is known as one of the strongest accumulators of silicon among higher terrestrial plants. We use the combination of
position-resolved analytical techniques, namely microtomography, energy-dispersive X-Ray elemental mapping, Raman microscopy,
as well as small-angle and wide-angle scattering of X-rays, to study the type, distribution and nanostructure of silica in
the internodes of Equisetum hyemale. The predominant silicification pattern is a thin continuous layer on the entire outer epidermis with the highest density
in particular knob regions of the long epidermal cells. The knob tips contain up to 33 wt% silicon in the form of pure hydrated
amorphous silica, while the silica content is lower in the inner part of the knobs and on the continuous layer. In contrast
to the knob tips, the silica in these regions lacks silanol groups and is proposed to be in close association with polysaccharides.
No mentionable amount of crystalline silica is detected by wide-angle X-ray scattering. The small-angle X-ray scattering data
are consistent with the presence of colloidal, sheet-like silica agglomerates with a thickness of about 2 nm. From these results
we conclude that there are at least two distinct forms of silica in E. hyemale which may have different functions. The close association of silica with cell wall polymers suggests that they may act as
a polymeric template that controls the shape and size of the colloidal silica particles similar to many other biominerals
and mineralised tissues. We propose that owing to its specific distribution in E. hyemale, a protective role and possibly also an important biomechanical role are among the most likely functions of silica in these
plants.
Figure 3D rendering of X-ray microtomography data from a dry Equisetum hyemale stalk. The red colour indicates high X-ray absorption values due to local silica accumulations 相似文献
15.
Edwards HG Currie KJ Ali HR Jorge Villar SE David AR Denton J 《Analytical and bioanalytical chemistry》2007,388(3):683-689
The mummification ritual in ancient Egypt involved the evisceration of the corpse and its desiccation using natron, a naturally occurring evaporitic mineral deposit from the Wadi Natrun, Egypt. The deposit typically contains sodium carbonate, sodium bicarbonate and impurities
of chloride and sulfate as its major elemental components. It is believed that the function of the natron was to rapidly remove the water from the cadaver to prevent microbial attack associated with subsequent biological tissue
degradation and putrefaction. Several specimens of natron that were recently collected from the Wadi Natrun contained coloured zones interspersed with the mineral matrix that are
superficially reminiscent of extremophilic cyanobacterial colonisation found elsewhere in hot and cold deserts. Raman spectroscopy
of these specimens using visible and near-infrared laser excitation has revealed not only the mineral composition of the natron, but also evidence for the presence of cyanobacterial colonies in several coloured zones observed in the mineral matrix.
Key Raman biosignatures of carotenoids, scytonemin and chlorophyll have been identified.
Figure The mummification ritual in ancient Egypt involved the evisceration of the corpse and its desiccation using natron, a naturally occurring evaporitic mineral deposit from the Wadi Natrun, Egypt. The deposit typically contains sodium carbonate, sodium bicarbonate and impurities
of chloride and sulfate as its major elemental components. It is believed that the function of the natron was to rapidly remove the water from the cadaver to prevent microbial attack associated with subsequent biological tissue
degradation and putrefaction. Several specimens of natron that were recently collected from the Wadi Natrun contained coloured zones interspersed with the mineral matrix that are
superficially reminiscent of extremophilic cyanobacterial colonisation found elsewhere in hot and cold deserts. Raman spectroscopy
of these specimens using visible and near-infrared laser excitation has revealed not only the mineral composition of the natron, but also evidence for the presence of cyanobacterial colonies in several coloured zones observed in the mineral matrix.
Key Raman biosignatures of carotenoids, scytonemin and chlorophyll have been identified. 相似文献
16.
The paper reviews the state-of-art for micro optical fluidic systems (MOFS), or optofluidics, which employs optics and fluidics
in a microsystem environment to perform novel functionalities and in-depth analysis in the biophysical area. Various topics,
which include the introduction of MOFS in biomedical engineering, the implementation of near-field optics and also the applications
of MOFS to biophysical studies, are discussed. Different optical detection techniques, such as evanescent wave, surface plasmon
resonance, surface enhanced Raman scattering, resonators and transistors, have been studied extensively and integrated into
MOFS. In addition, MOFS also provides a platform for various studies of cell biophysics, such as cell mass determination and
cell Young’s modulus measurement.
Figure Cell encapsulation and trapping for refractive index measurement in MOFS 相似文献
17.
This paper reports on an integrated analytical approach for the noninvasive characterization of Chinese nephrite samples,
encompassing both geological reference specimens and museum objects. Natural variations induced by cationic substitutions,
as well as human-induced alterations such as heating, which both affect color, are the focus of this contribution. Totally
noninvasive methods of analysis were used, including X-ray fluorescence spectroscopy, Raman microspectroscopy, visible reflectance
spectroscopy and X-ray diffraction; moreover, the feasibility of using a portable Raman spectrometer for the in-field identification
of jades has been demonstrated. Fe/Fe+Mg (% p.f.u.) ratios of the jades have been calculated based on hydroxyl stretching
Raman bands, which will provide an important addition to similar data that are being collected at major museums in the Western
and Eastern hemispheres.
相似文献
18.
Finite element (FE) models were built to define the optimal experimental conditions for tip-enhanced Raman spectroscopy (TERS) of thin samples. TERS experimental conditions were mimicked by including in the FE models dielectric or metallic substrates with thin dielectric samples and by considering the wavelength dependence of the dielectric properties for the metallic materials. Electromagnetic coupling between the substrate/sample and the SPM tips led to dramatic changes of both the spatial distribution and magnitude of the scattered electric field which depended on the substrate dielectric permittivity and excitation wavelength. Raman scattering as high as 10(8) with a spatial resolution of approximately 8 nm was estimated for gold SPM tips and gold substrate when excitation is performed at 532 nm (near-resonance wavelength). For dielectric samples (approximately 4 nm thick), the enhancement of Raman scattering intensity is estimated at approximately 10(5); this does not depend significantly on the sample dielectric permittivity for dielectric samples. These results suggest that TERS experimental conditions should be estimated and optimized for every individual application considering the geometric factors and electric properties of the materials involved. Such optimizations could enlarge the range of applications for TERS to samples eliciting weaker intrinsic Raman scattering, such as biological samples. 相似文献
19.
Raman spectroscopy is a versatile technique that has frequently been applied for the investigation of art objects. By using
mobile Raman instrumentation it is possible to investigate the artworks without the need for sampling. This work evaluates
the use of a dedicated mobile spectrometer for the investigation of a range of museum objects in museums in Scotland, including
antique Egyptian sarcophagi, a panel painting, painted surfaces on paper and textile, and the painted lid and soundboard of
an early keyboard instrument. The investigations of these artefacts illustrate some analytical challenges that arise when
analysing museum objects, including fluorescing varnish layers, ambient sunlight, large dimensions of artefacts and the need
to handle fragile objects with care. Analysis of the musical instrument (the Mar virginals) was undertaken in the exhibition
gallery, while on display, which meant that interaction with the public and health and safety issues had to be taken into
account.
Experimental set-up for the non-destructive Raman spectroscopic investigation of a textile banner in the National Museums
of Scotland 相似文献
20.
Thanyada Sukmanee Dr. Kanet Wongravee Dr. Yasutaka Kitahama Prof. Dr. Sanong Ekgasit Dr. Tamitake Itoh Dr. Prompong Pienpinijtham Prof. Dr. Yukihiro Ozaki 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(34):14672-14677
Discrimination between enantiomers is achieved by tip-enhanced Raman scattering (TERS) using a silver tip that is chemically modified by an achiral para-mercaptopyridine (pMPY) probe molecule. Differences in the relative intensities of the pMPY spectra were monitored for three pairs of enantiomers containing hydroxy (−OH) and/or amino (−NH2) groups. The N: or N+−H functionality of the pMPY-modified tip participates in hydrogen-bond interactions with a particular molecular orientation of each chiral isomer. The asymmetric arrangement of silver atoms at the apex of the tip induces an asymmetric electric field, which causes the tip to become a chiral center. Differences in the charge-transfer (CT) states of the metal-achiral probe system in conjunction with the asymmetric electric field produce different enhancements in the Raman signals of the two enantiomers. The near-field effect of the asymmetric electric field, which depends on the number of analyte functional groups capable of hydrogen-bond formation, improves the degree of discrimination. 相似文献