Whispering gallery modes and effect of coating on Raman spectra of single microspheres

Dantham, Venkata Ramanaiah; Bisht, Prem B.; Dobal, P. S.

doi:10.1002/jrs.2868

Cited by 13 publications

(3 citation statements)

References 24 publications

(52 reference statements)

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“…The presence of whispering gallery modes (WGMs) was observed in all Raman spectra for the trapped droplets, indicating sphere formation (Figure S3). 26 WGMs occur in the optical cavity formed by the spherical droplets, as described by the Mie scattering theory. 27 The resonance positions are dependent on the droplet size and refractive index.…”

Section: Resultsmentioning

confidence: 99%

Operando Studies of Aerosol-Assisted Sol–Gel Catalyst Synthesis via Combined Optical Trapping and Raman Spectroscopy

et al. 2021

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New insights have been gained into chemical transformations occurring in the initial stages of aerosol-assisted sol–gel (AASG) synthesis of catalysts. This has been achieved through the combined application of optical trapping and Raman spectroscopy. AASG is an emerging technology in catalyst manufacturing that presents numerous advantages over conventional approaches, including the ability to access unique catalyst morphologies. However, the processes occurring during synthesis are largely inferred from bulk-phase analyses due to challenges in conducting in situ or operando measurements on moving aerosols within a flow tube. Herein, these obstacles are overcome through Raman spectroscopic interrogation of a single aerosol droplet constrained within an optical trap, which acts as a direct analogue for a particle moving along a flow tube. These studies represent the first operando investigations of AASG synthesis. The synthesis of Ni/Al2O3 catalysts has been studied, with spectroscopic interrogation conducted on each component of the precursor synthesis solution, where possible, up to and including a mixture containing all components necessary for catalyst synthesis. Raman spectroscopy confirms the formation of stable self-assembled macrostructures within the aerosol and provides direct insights into the reaction mechanisms. Crucially, evidence was obtained allowing alternative reaction pathways to be postulated within the confined environment of an aerosol droplet in comparison to bulk-phase syntheses. In aerosols where nickel was not present, but contained all other components, isothermal room-temperature studies showed the formation of stable but unreactive droplets of ∼1 μm, which were proposed to contain micelle-type structures. Upon heating, initial gelation transformations were seen to be achieved at temperatures higher than ∼56 °C. Notably, little loss of spectral intensity corresponding to the C–H stretch (ethanol) was observed from the heated aerosol, implying that evaporation is not a prerequisite for the reaction. When nickel is present in the synthesis solution reactive transformations occur at room temperature, proposed to result in a continuous Al–O–Ni–NO3 structure; a more rapid transformation takes place at elevated temperatures. These results provide the first direct evidence of the processes occurring within aerosols during AASG and shed new light on the mechanistic understanding of this technology. This therefore facilitates the design of new synthetic approaches and hence the production of catalysts and other materials with enhanced properties.

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Section: Resultsmentioning

confidence: 99%

Operando Studies of Aerosol-Assisted Sol–Gel Catalyst Synthesis via Combined Optical Trapping and Raman Spectroscopy

et al. 2021

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“…Experimentally, due to PNJ effect, the Raman intensity for a silicon substrate observed with a ∼40 µm diameter silica microsphere (n 1 = 1.45) has been found to increase by an order of magnitude as compared to that without a microsphere. Varying values of enhancement factor have been observed with the size and the refractive index of the microcavity in literature [47,50].…”

Section: Pnj With Variation Of Refractive Index Contrast Of Microcavitymentioning

confidence: 99%

Numerical investigations on a photonic nanojet coupled plasmonic system for photonic applications

Agrawal

Dey

Bhattacharya

et al. 2022

J. Opt.

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Photonic nanojet (PNJ) from a microcavity is a narrow and intense beam of light used to enhance the emerging electric field. Metal nanoparticles (NPs), on the other hand, confine strong field in their vicinity due to the resonance of the free electrons with the incident field. A hybrid combination of a microcavity with NP can drastically enhance the output field. In this work, a systematic numerical study of the microcavity-NP system has been carried out to investigate the effect of the shape of the metal NPs on the output field strength. The single and their dimer NPs with different dimer nanogaps with PNJ producing microcavity have been investigated. Splitting of the broad dipole mode of the NP has also been observed. As an application of this study, the surface enhanced Raman spectroscopy (SERS) factor of the order of 107 has been estimated for nano-cube dimer NP-microcavity hybrid system.

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“…Dantham and co‐workers studied the Raman spectra and fluorescence of BaTiO 3 and silica microspheres of different sizes. The observed whispering gallery modes were assigned using theoretical simulations based on the Lorenz–Mie theory . Gebert et al .…”

Section: Solid‐state Studiesmentioning

confidence: 99%

Recent advances in linear and nonlinear Raman spectroscopy. Part VI

Nafie

2012

J Raman Spectroscopy

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The purpose of this review is to provide a concise overview of recent advances in the broadly defined field of Raman spectroscopy as reflected in part by the many articles published each year in Journal of Raman Spectroscopy as well as in trends across all related journals publishing in this research area. Context for this review is derived from statistical data on article counts obtained from Thomson Reuters ISI Web of Knowledge by year and by subfield of Raman spectroscopy. Additional information is gleaned from presentations featuring Raman spectroscopy presented at the XXIII International Conference on Raman Spectroscopy in Bangalore, India, in August 2012 and at Scientific Exchange 2012 sponsored by the Federation of Analytical Chemistry and Spectroscopy Societies in Kansas City, Missouri, USA, October 2012. Papers published in the Journal of Raman Spectroscopy in 2011 are highlighted in this review and reflect trends at the cutting edge of Raman spectroscopy, a field that is expanding rapidly as a sensitive photonic probe of matter at the molecular level with an ever widening sphere of novel applications. Copyright © 2012 John Wiley & Sons, Ltd.

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Whispering gallery modes and effect of coating on Raman spectra of single microspheres

Cited by 13 publications

References 24 publications

Operando Studies of Aerosol-Assisted Sol–Gel Catalyst Synthesis via Combined Optical Trapping and Raman Spectroscopy

Operando Studies of Aerosol-Assisted Sol–Gel Catalyst Synthesis via Combined Optical Trapping and Raman Spectroscopy

Numerical investigations on a photonic nanojet coupled plasmonic system for photonic applications

Recent advances in linear and nonlinear Raman spectroscopy. Part VI

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