Size-Dependent Raman Shifts for nanocrystals

The structures of boron clusters, such as flat clusters and fullerenes, resemble those of carbon. Various two‐dimensional (2D) borophenes have been proposed since the production of graphene. The recent successful fabrication of borophene sheets has prompted extensive researches, and some unique properties are revealed. In this review, the recent theoretical and experimental progress on the structure, growth, and electronic and thermal transport properties of borophene sheets is summarized. The history of prediction of boron sheet structures is introduced. Existing with a mixture of triangle lattice and hexagonal lattice, the structures of boron sheets have peculiar characteristics of polymorphism and show significant dependence on the substrate. Due to the unique structure and complex BB bonds, borophene sheets have many interesting electronic and thermal transport properties, such as strong nonlinear effect, strong thermal transport anisotropy, high thermal conductance in the ballistic transport and low thermal conductivity in the diffusive transport. The growth mechanism and synthesis of borophene sheets on different metal substrates are also presented. The successful prediction and synthesis will shed light on the exploration of new novel materials. Besides, the outstanding and peculiar properties of borophene make them tempting platform for exploring novel physical phenomena and extensive applications.

show abstract

Section: Growth Of Borophenementioning

confidence: 99%

2D Boron Sheets: Structure, Growth, and Electronic and Thermal Transport Properties

Gao

Cheng

et al. 2019

Adv Funct Materials

143

101

View full text Add to dashboard Cite

show abstract

“…The phonon confinement model has been proposed to explain Raman spectra in nanosized systems because the surface states must be considered . According to Gao et al, the underlying mechanism behind the size‐dependent Raman shifts is still quite controversial and an open problem. They proposed a theoretical method to explain the quantum confinement effects on the Raman spectra of semiconductor nanocrystals indicating that their shift is originated by two overlapping effects: the quantum effect shift and the surface effect shift.…”

Section: Introductionmentioning

confidence: 99%

Effect of the crystal size on the infrared and Raman spectra of bio hydroxyapatite of human, bovine, and porcine bones

Londoño‐Restrepo

Zubieta‐Otero

Jeronimo‐Cruz

et al. 2019

J Raman Spectroscopy

View full text Add to dashboard Cite

The optical properties of hydroxyapatites (HAps) and bio HAps have been studied using Raman and infrared (IR) spectroscopies to describe their crystalline quality. However, the size of the HAp crystals and their crystalline order effects have not been considered yet. This paper focuses on the study of the effect of the change in the crystallites size have on the width of the IR and Raman spectra for defatted and deproteinized bones as well as incinerated biogenic HAp obtained from bovine, porcine, and human bones. Bone samples were analyzed through Raman and IR spectroscopies, X‐ray diffraction (XRD), transmission electron microscopy (TEM), inductively coupled plasma (ICP), and scanning electron microscopy (SEM). The Raman and IR spectra for raw samples showed broad bands but, after calcination at 720 °C, became narrow and well defined. TEM images showed that all raw crystallites are ordered nanoplates contrary to the so far well‐established concept that biogenic HAps have low crystalline quality. XRD data confirmed that raw samples display broad peaks that correlated with the HRTEM images of ordered nanocrystals. This fact confirmed that the broad Raman and IR bands of raw clean bones come from nanocrystal plates. SEM analysis confirmed the increase in the crystal size after calcination from nanomicron to submicron dimensions due to a coalescence phenomenon. These results imply that the interpretation of Raman and IR spectra in the case of HAp nanoparticles has been erroneous. These results contribute to the design of biomaterials for tissue engineering based on biogenic HAp for bone regeneration.

show abstract

“…21 Recently, we proposed a new method from chemical bond point of view. According to theory, 13 the shift of Raman spectra in nanocrystals can be result from the quantum effect and the surface effect. The size-dependent Raman shift of nanocrystal is expressed as…”

Section: Methodsmentioning

confidence: 99%

“…15 In this work, zinc blende CdSe nanocrystals with diameters down to the exciton Bohr radius were prepared, and Raman spectra of CdSe nanocrystals were obtained. A new theoretical method for the quantum confinement effects on the Raman spectra developed recently 13 was employed to determine Raman spectra of CdSe nanocrystals. It is found that the shift of Raman spectra in cubic CdSe nanocrystals could be result from two overlapping effects: the quantum effect shift and the surface effect shift.…”

Section: Introductionmentioning

confidence: 99%

“…8,9 Studies on the vibrational properties of nanocrystals are focused on an understanding of the fundamental physical properties of strongly confined phonons. [10][11][12][13] The Raman spectra of bulk CdSe are dominated by the longest wavelength longitudinal optical (LO) phonons. In bulk CdSe, the LO phonon mode generally appears as a narrow feature at 212 cm À1 .…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Synthesis of cubic CdSe nanocrystals and their spectral properties

Gao

Yin

2017

Nanomaterials and Nanotechnology

Self Cite

View full text Add to dashboard Cite

The cadmium selenide nanocrystals are prepared by colloidal chemistry under mild conditions. X-ray diffraction and high-resolution transmission electron microscopy measurements indicate that as-prepared cadmium selenide nanocrystals are zinc blende cubic structure. We carry out an analysis of quantum size effect in the Raman spectra of cadmium selenide nanocrystals performed by utilizing the chemical bond theory of Raman peak shift developed recently. It is revealed that the shifts of Raman peaks in cadmium selenide nanocrystals result from the overlapping of the quantum effect shifts and surface effect shifts. The sizes of the as-prepared cadmium selenide nanocrystals obtained by employing the Raman peak shift theory are in good agreement with the nanocrystal sizes determined by highresolution transmission electron microscopy.

show abstract

Size-Dependent Raman Shifts for nanocrystals

Cited by 58 publications

References 26 publications

2D Boron Sheets: Structure, Growth, and Electronic and Thermal Transport Properties

2D Boron Sheets: Structure, Growth, and Electronic and Thermal Transport Properties

Effect of the crystal size on the infrared and Raman spectra of bio hydroxyapatite of human, bovine, and porcine bones

Synthesis of cubic CdSe nanocrystals and their spectral properties

Contact Info

Product

Resources

About