Limits...
Photocurrent generation in carbon nanotube/cubic-phase HfO 2 nanoparticle hybrid nanocomposites

View Article: PubMed Central - HTML - PubMed

ABSTRACT

A hybrid material consisting of nonfunctionalized multiwall carbon nanotubes (MWCNTs) and cubic-phase HfO2 nanoparticles (NPs) with an average diameter of 2.6 nm has been synthesized. Free standing HfO2 NPs present unusual optical properties and a strong photoluminescence emission in the visible region, originating from surface defects. Transmission electron microscopy studies show that these NPs decorate the MWCNTs on topological defect sites. The electronic structure of the C K-edge in the nanocomposites was probed by electron energy loss spectroscopy, highlighting the key role of the MWCNT growth defects in anchoring HfO2 NPs. A combined optical emission and absorption spectroscopy approach illustrated that, in contrast to HfO2 NPs, the metallic MWCNTs do not emit light but instead expose their discrete electronic structure in the absorption spectra. The hybrid material manifests characteristic absorption features with a gradual merger of the MWCNT π-plasmon resonance band with the intrinsic defect band and fundamental edge of HfO2. The photoluminescence of the nanocomposites indicates features attributed to combined effects of charge desaturation of HfO2 surface states and charge transfer to the MWCNTs with an overall reduction of radiative recombination. Finally, photocurrent generation under UV–vis illumination suggests that a HfO2 NP/MWCNT hybrid system can be used as a flexible nanodevice for light harvesting applications.

No MeSH data available.


(a) Absorption spectrum of MWCNTs decorated with cubic HfO2 nanoparticles obtained from the transmittance measurements of colloidal suspension in ethanol (blue curve) against that of free-standing HfO2 nanoparticles from the diffuse reflectance measurements (red curve). (b) Tauc plots of the corresponding dependencies, absorbance (α) and Kubelka–Munk function (KM F(R)), representing the case of direct optical transitions.
© Copyright Policy - Beilstein
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC4979767&req=5

Figure 2: (a) Absorption spectrum of MWCNTs decorated with cubic HfO2 nanoparticles obtained from the transmittance measurements of colloidal suspension in ethanol (blue curve) against that of free-standing HfO2 nanoparticles from the diffuse reflectance measurements (red curve). (b) Tauc plots of the corresponding dependencies, absorbance (α) and Kubelka–Munk function (KM F(R)), representing the case of direct optical transitions.

Mentions: The distinctive optical properties of CNTs derive from electronic transitions within the one-dimensional density of states (DOS), which is discontinuous in nature and exhibits sharp peaks called van Hove singularities (vHS) [38]. The energy separations between the vHS in the valence and conduction bands depend on the nanotube structure, thus optical absorption and emission spectroscopy allow identification of the CNT chirality and diameter as well as quality in terms of nontubular carbon content and structural defects. The characterization of multiwalled CNTs, however, is challenging because of the involvement of several shells with different structure and typically higher defect concentration compared to single-walled CNTs. The optical absorption properties of the hybrid MWCNT:HfO2 nanocomposites deduced from the room temperature transmittance measurements of a colloidal suspension in ethanol are summarized in Fig. 2.


Photocurrent generation in carbon nanotube/cubic-phase HfO 2 nanoparticle hybrid nanocomposites
(a) Absorption spectrum of MWCNTs decorated with cubic HfO2 nanoparticles obtained from the transmittance measurements of colloidal suspension in ethanol (blue curve) against that of free-standing HfO2 nanoparticles from the diffuse reflectance measurements (red curve). (b) Tauc plots of the corresponding dependencies, absorbance (α) and Kubelka–Munk function (KM F(R)), representing the case of direct optical transitions.
© Copyright Policy - Beilstein
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4979767&req=5

Figure 2: (a) Absorption spectrum of MWCNTs decorated with cubic HfO2 nanoparticles obtained from the transmittance measurements of colloidal suspension in ethanol (blue curve) against that of free-standing HfO2 nanoparticles from the diffuse reflectance measurements (red curve). (b) Tauc plots of the corresponding dependencies, absorbance (α) and Kubelka–Munk function (KM F(R)), representing the case of direct optical transitions.
Mentions: The distinctive optical properties of CNTs derive from electronic transitions within the one-dimensional density of states (DOS), which is discontinuous in nature and exhibits sharp peaks called van Hove singularities (vHS) [38]. The energy separations between the vHS in the valence and conduction bands depend on the nanotube structure, thus optical absorption and emission spectroscopy allow identification of the CNT chirality and diameter as well as quality in terms of nontubular carbon content and structural defects. The characterization of multiwalled CNTs, however, is challenging because of the involvement of several shells with different structure and typically higher defect concentration compared to single-walled CNTs. The optical absorption properties of the hybrid MWCNT:HfO2 nanocomposites deduced from the room temperature transmittance measurements of a colloidal suspension in ethanol are summarized in Fig. 2.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

A hybrid material consisting of nonfunctionalized multiwall carbon nanotubes (MWCNTs) and cubic-phase HfO2 nanoparticles (NPs) with an average diameter of 2.6 nm has been synthesized. Free standing HfO2 NPs present unusual optical properties and a strong photoluminescence emission in the visible region, originating from surface defects. Transmission electron microscopy studies show that these NPs decorate the MWCNTs on topological defect sites. The electronic structure of the C K-edge in the nanocomposites was probed by electron energy loss spectroscopy, highlighting the key role of the MWCNT growth defects in anchoring HfO2 NPs. A combined optical emission and absorption spectroscopy approach illustrated that, in contrast to HfO2 NPs, the metallic MWCNTs do not emit light but instead expose their discrete electronic structure in the absorption spectra. The hybrid material manifests characteristic absorption features with a gradual merger of the MWCNT π-plasmon resonance band with the intrinsic defect band and fundamental edge of HfO2. The photoluminescence of the nanocomposites indicates features attributed to combined effects of charge desaturation of HfO2 surface states and charge transfer to the MWCNTs with an overall reduction of radiative recombination. Finally, photocurrent generation under UV–vis illumination suggests that a HfO2 NP/MWCNT hybrid system can be used as a flexible nanodevice for light harvesting applications.

No MeSH data available.