Low‐Frequency Raman Scattering from Nanocrystals Caused by Coherent Excitation of Phonons

Wu, Xingxin; Xiong, Shi‐Jie; Sun, Litao; Jin, Shangtai; Chu, Paul K.

doi:10.1002/smll.200901579

Cited by 10 publications

(8 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Wu et al [41] observed a similar effect with respect to temperature for the Ge 0.54 Si 0.46 nanocrystals embedded in SiO 2 matrix and have explained it with the help of the collective modes produced by the interference of Raman scattering from the individual QDs. They also found that the intensity of the LFRS mode increased with increasing temperature and the FWHM was independent of the temperature, similar to our observations.…”

Section: Unlike 25 Nm Nps the Qds Exhibit A Completely Different Ramamentioning

confidence: 74%

Electrochemical supercapacitor performance of SnO2 quantum dots

Bonu

Gupta

Chandra

et al. 2016

Electrochimica Acta

107

View full text Add to dashboard Cite

Metal oxide nanostructures are widely used in energy applications like super capacitors and Liion battery. Smaller size nanocrystals show better stability, low ion diffusion time, higher-ion flux and low pulverization than bigger size nanocrystals during electrochemical operation.Studying the distinct properties of smaller size nanocrystals such as quantum dots (QDs) can improve the understanding on reasons behind the better performance and it will also help in using QDs or smaller size nanoparticles (NPs) more efficiently in different applications. Aqua stable pure SnO 2 QDs with compositional stability and high surface to volume ratio are studied as an electrochemical super capacitor material and compared with bigger size NPs of size 25 nm.Electron energy-loss spectroscopic study of the QDs revealed dominant role of surface over the bulk. Temperature dependent study of low frequency Raman mode and defect Raman mode of QDs indicated no apparent volume change in the SnO 2 QDs within the temperature range of 80-300 K. The specific capacitance of these high surface area and stable SnO 2 QDs has showed only 9% loss while increasing the scan rate from 20 mV/S to 500 mV/S. Capacitance loss for the QDs is less than 2% after 1000 cycles of charging discharging, whereas for the 25 nm SnO 2 NPs, the capacitance loss is 8% after 1000 cycles. Availability of excess open volume in QDs leading to no change in volume during the electro-chemical operation and good aqua stability is attributed to the better performance of QDs over bigger sized NPs.

show abstract

Section: Unlike 25 Nm Nps the Qds Exhibit A Completely Different Ramamentioning

confidence: 74%

Electrochemical supercapacitor performance of SnO2 quantum dots

Bonu

Gupta

Chandra

et al. 2016

Electrochimica Acta

107

View full text Add to dashboard Cite

show abstract

“…The Raman spectrum acquisition time was 2 min. The high resolution and rejection rate of this measurement system allowed observation of the vibration signals close to the Rayleigh line to less than 5 cm −1 [5,6]. The acquired spectra were the same as those taken under excitation by the 488 nm line and no similar LF signals were observed for the used glass substrate.…”

Section: Methodsmentioning

confidence: 99%

“…Low-frequency (LF) Raman scattering in inorganic nanocrystals (NCs) has been an attractive research subject for the past two decades because of fundamental issues related to the size, shape, surface/interface structure, and confined property of NCs [1][2][3][4][5][6]. However, for organic molecule crystals which consist of nanoscale molecular building blocks, the collective (acoustic phonon) vibrations of the molecular groups (building blocks) have been seldom studied due to the structural complexity.…”

Section: Introductionmentioning

confidence: 99%

Low-frequency Raman scattering of bioinspired self-assembled diphenylalanine nanotubes/microtubes

Wu¹,

Xiong²,

Wang³

et al. 2012

Opt. Express

View full text Add to dashboard Cite

Low-frequency Raman scattering from self-assembled bioinspired diphenylalanine (FF) nanotubes/microtubes (NTs/MTs) has been observed for the first time. Four double peaks are identified as the three-dimensional localized collective (acoustic phonon) vibrations of FF molecules in the subnanometer crystalline structure (biological building block) forming the FF NTs/MTs. The increased energy separations between two subpeaks caused by the loss of water in the nanochannel cores are due to the enhancement of vibrational couplings between the FF molecules as a result of the reduction of the influence from water on the coupling. The results provide experimental evidence of localized but still weakly coupled vibrations in organic crystalline nanostructures in the low-frequency region.

show abstract

“…Detailed analysis of the quantum confinement effect in Si NSs (prepared using LIE), as identified by size-dependent changes in properties, has already been presented somewhere else. 26 The quantum confinement effect alone can explain the observation of a low-frequency Raman spectrum, but the asymmetry as observed by many researchers 23,25,27 is not obvious and thus needs further investigation. In quantum materials, like Si NSs, the electronic energy levels become quantized, 28,29 and different inter-and intraband transitions are possible and can be observed using Raman spectroscopy.…”

mentioning

confidence: 97%

Fano Scattering: Manifestation of Acoustic Phonons at the Nanoscale

Yogi

Mishra

Saxena

et al. 2016

J. Phys. Chem. Lett.

View full text Add to dashboard Cite

Size-dependent asymmetric low-frequency Raman line shapes have been observed from silicon (Si) nanostructures (NSs) due to a quantum confinement effect. The acoustic phonons in Si NSs interact with an intraband quasi-continuum to give rise to Fano interaction in the low-frequency range. The experimental asymmetric Raman line shape has been explained by developing a theoretical model that incorporates the quantum-confined phonons interacting with an intraband quasi-continuum available in Si NSs as a result of discretization of energy levels with unequal separation. We discover that a phenomenon similar to Brillouin scattering is possible at the nanoscale in the low-frequency regime and thus may be called "Fano scattering" in general. A method has been proposed to extract information about nonradiative transitions from the Fano scattering data where these nonradiative transitions are involved as an intraband quasi-continuum in modulation with discrete acoustic phonons.

show abstract

Low‐Frequency Raman Scattering from Nanocrystals Caused by Coherent Excitation of Phonons

Cited by 10 publications

References 35 publications

Electrochemical supercapacitor performance of SnO2 quantum dots

Electrochemical supercapacitor performance of SnO2 quantum dots

Low-frequency Raman scattering of bioinspired self-assembled diphenylalanine nanotubes/microtubes

Fano Scattering: Manifestation of Acoustic Phonons at the Nanoscale

Contact Info

Product

Resources

About