Raman Spectroscopy

Lyon, L. Andrew; Keating, Christine D.; Fox, Audrey P.; Baker, Bonnie E.; He, Lin; Nicewarner, Sheila R.; Mulvaney, Shawn P.; Natan, Michael J.

doi:10.1021/a1980021p

Cited by 255 publications

(175 citation statements)

References 532 publications

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“…The Raman process generates photons at a frequency that is up-or down-shifted (anti-Stokes or Stokes) from the frequency of the incident photons by an amount equivalent to the frequency of an internal oscillation of the material system, such as vibration, rotation, stretching, or translation (39). Raman gain has found many applications in biology, material science, sensing, environmental monitoring, optical communication, laser science, and spectroscopy (41)(42)(43)(44)(45). However, in most of the materials, such as silica, silicon, and CaF 2 , Raman gain is very small (of the order of 10 −13 m/W), requiring high-intensity pump lasers to drive the system above its lasing threshold.…”

Section: Resultsmentioning

confidence: 99%

Highly sensitive detection of nanoparticles with a self-referenced and self-heterodyned whispering-gallery Raman microlaser

Özdemir

Zhu

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

211

126

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Optical whispering-gallery-mode resonators (WGMRs) have emerged as promising platforms for label-free detection of nano-objects. The ultimate sensitivity of WGMRs is determined by the strength of the light-matter interaction quantified by quality factor/mode volume, Q/V, and the resolution is determined by Q. To date, to improve sensitivity and precision of detection either WGMRs have been doped with rare-earth ions to compensate losses and increase Q or plasmonic resonances have been exploited for their superior field confinement and lower V. Here, we demonstrate, for the first time to our knowledge, enhanced detection of single-nanoparticleinduced mode splitting in a silica WGMR via Raman gain-assisted loss compensation and WGM Raman microlaser. In particular, the use of the Raman microlaser provides a dopant-free, self-referenced, and self-heterodyned scheme with a detection limit ultimately determined by the thermorefractive noise. Notably, we detected and counted individual nanoparticles with polarizabilities down to 3.82 × 10 −6 μm 3 by monitoring a heterodyne beatnote signal. This level of sensitivity is achieved without exploiting plasmonic effects, external references, or active stabilization and frequency locking. Single nanoparticles are detected one at a time; however, their characterization by size or polarizability requires ensemble measurements and statistical averaging. This dopant-free scheme retains the inherited biocompatibility of silica and could find widespread use for sensing in biological media. The Raman laser and operation band of the sensor can be tailored for the specific sensing environment and the properties of the targeted materials by changing the pump laser wavelength. This scheme also opens the possibility of using intrinsic Raman or parametric gain for loss compensation in other systems where dissipation hinders progress and limits applications.optical sensor | active microresonator | particle sensing T here is an increasing demand for new technologies to detect small molecules, nanoparticles, and airborne species (1-4). In the past decade we have witnessed a boost in the number of label-free detection techniques with varying levels of sensitivities. Techniques relying on electrical conductance (5), light scattering and interferometry (6-8), surface and localized plasmon resonance (9, 10), nanomechanical resonators (11,12), and optical resonances (13-17) have been demonstrated.Whispering-gallery-mode (WGM) microresonators with their high quality factor, Q, and small mode volume, V, are known to enhance light-matter interactions and have extraordinary sensitivities to changes and perturbations in their structure or proximity (18,19). They have been of great interest for sensing biomarkers, DNA, and medium-size proteins at low concentrations, as well as for detecting viruses and nanoparticles at single-particle resolution (19-31). A particle or molecule entering the mode volume of a resonator or binding onto its surface induces a net change in the polarizability of the resonator-...

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Section: Resultsmentioning

confidence: 99%

Highly sensitive detection of nanoparticles with a self-referenced and self-heterodyned whispering-gallery Raman microlaser

Özdemir

Zhu

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

211

126

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“…It was discovered by Raman and Krishnan (1928). Raman scattering theory is covered in detail in Nakamoto (1997), Lewis and Edwards (2001) and Ferraro et al (2003), and in reviews such as Lyon et al (1998).…”

Section: Laser Raman Spectroscopymentioning

confidence: 99%

Optical tools for ocean monitoring and research

et al. 2009

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Abstract. Requirements for understanding the relationships between ocean color and suspended and dissolved materials within the water column, and a rapidly emerging photonics and materials technology base for performing optical based analytical techniques have generated a diverse offering of commercial sensors and research prototypes that perform optical measurements in water. Through inversion, these tools are now being used to determine a diverse set of related biogeochemical and physical parameters. Techniques engaged include measurement of the solar radiance distribution, absorption, scattering, stimulated fluorescence, flow cytometry, and various spectroscopy methods. Selective membranes and other techniques for material isolation further enhance specificity, leading to sensors for measurement of dissolved oxygen, methane, carbon dioxide, common nutrients and a variety of other parameters. Scientists are using these measurements to infer information related to an increasing set of parameters and wide range of applications over relevant scales in space and time.

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“…The necessity for process analysis could change this situation. A overview of this method's potential can be taken from the literature [60,61].…”

Section: Process Analytical Techniques/process Analysismentioning

confidence: 99%

New Developments in Chemical Engineering for the Production of Drug Substances

Behr

Brehme

Ewers³

et al. 2004

Engineering in Life Sciences

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The pharmaceutical industry is moving towards a profitability gap between increasing costs and decreasing prices. Finally, management has understood that mergers and acquisitions, high throughput screening, and biotechnology alone will not save the companies' earnings. Therefore, classical approaches like the optimization of production technologies for drug substances, that might help to increase profitability, are receiving increasing attention. This paper shows how the combination of innovative components will guide the way to very efficient and cost-effective production. The first component is the design and manufacturing of production facilities. The second component is a process streamlining of the production process. The key technologies discussed here are process control and miniplant technology. For these technologies a brief outlook on future trends is given.

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Raman Spectroscopy

Cited by 255 publications

References 532 publications

Highly sensitive detection of nanoparticles with a self-referenced and self-heterodyned whispering-gallery Raman microlaser

Highly sensitive detection of nanoparticles with a self-referenced and self-heterodyned whispering-gallery Raman microlaser

Optical tools for ocean monitoring and research

New Developments in Chemical Engineering for the Production of Drug Substances

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