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Hot plasmonic electrons for generation of enhanced photocurrent in gold-TiO2 nanocomposites.

Brennan LJ, Purcell-Milton F, Salmeron AS, Zhang H, Govorov AO, Fedorov AV, Gun'ko YK - Nanoscale Res Lett (2015)

Bottom Line: The composite film demonstrates a significant increase in the short circuit current (I sc) compared to unmodified TiO2 when excited at or close to the plasmon resonance of the gold nanoparticles.Photo-electrochemical investigations revealed that the increase in photocurrent is attributed to the generation and separation of plasmonically generated hot electrons at the gold/TiO2 interface and also the inter-band generation of holes in gold nanoparticles by photons with λ < 520 nm.Theoretical modelling outputs perfectly match our results obtained from photo-physical studies of the processes leading to enhanced photocurrent.

View Article: PubMed Central - PubMed

Affiliation: School of Chemistry and CRANN Institute, Trinity College Dublin, Dublin 2, Ireland.

ABSTRACT
In this manuscript, for the first time, we report a combination of electrophoretic and sintering approaches for introducing gold nanoparticles into nanoporous TiO2 films to generate 'hot' electrons resulting in a strong enhancement of photocurrent. The Au-TiO2 nanocomposite material was prepared by the electrophoretic deposition of gold nanoparticles into a porous nanoparticulate titanium dioxide film, creating a photoactive electrode. The composite film demonstrates a significant increase in the short circuit current (I sc) compared to unmodified TiO2 when excited at or close to the plasmon resonance of the gold nanoparticles. Then, we employed a thermal ripening process as a method of increasing the I sc of these electrodes and also as a method of tuning the plasmon peak position, with a high degree of selectivity. Photo-electrochemical investigations revealed that the increase in photocurrent is attributed to the generation and separation of plasmonically generated hot electrons at the gold/TiO2 interface and also the inter-band generation of holes in gold nanoparticles by photons with λ < 520 nm. Theoretical modelling outputs perfectly match our results obtained from photo-physical studies of the processes leading to enhanced photocurrent.

No MeSH data available.


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TEM image of gold nanoparticles and EDX line mapping. A TEM image of gold nanoparticles adhered to the surface of TiO2 after EPD. B EDX line mapping recorded for a- TiO2, b- gold, c- tin and d- silicon. C EDX spectra of a- Ti, b- gold, c- tin and d- silicon.
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Fig1: TEM image of gold nanoparticles and EDX line mapping. A TEM image of gold nanoparticles adhered to the surface of TiO2 after EPD. B EDX line mapping recorded for a- TiO2, b- gold, c- tin and d- silicon. C EDX spectra of a- Ti, b- gold, c- tin and d- silicon.

Mentions: In our work, the EPD was carried out by submerging a TiO2 electrode and a blank FTO electrode into a solution of gold nanoparticles. A DC voltage of 250 V was applied across the electrodes for 15 min. It was observed that gold nanoparticles were favourably deposited into the TiO2 film (see TEM in Figure 1) rather than on the surface of the FTO coating, which would agree with findings by Kamat et al. who have also observed this trend [49]. UV–vis spectra (Figure 2A and Additional file 1) of gold nanoparticles electrophoretically deposited into TiO2 films have shown increasing plasmonic intensity with the growing concentration of nanoparticles in the deposition solution. As expected, the deposition of gold nanoparticles resulted in a very large increase in the optical absorption of the TiO2 films when studied with UV–vis spectroscopy and visually (see Additional file 1). The presence of a large plasmon band was also observed in the UV–vis spectra, indicative of the presence of gold nanoparticles in the TiO2 films. The plasmon peak position of the gold nanoparticles embedded in TiO2 closely matched that of the plasmon position for the gold particles in the liquid phase, confirming that after the EPD, the particles are still in the nanoparticulate form and have not coalesced into a bulk gold film.Figure 1


Hot plasmonic electrons for generation of enhanced photocurrent in gold-TiO2 nanocomposites.

Brennan LJ, Purcell-Milton F, Salmeron AS, Zhang H, Govorov AO, Fedorov AV, Gun'ko YK - Nanoscale Res Lett (2015)

TEM image of gold nanoparticles and EDX line mapping. A TEM image of gold nanoparticles adhered to the surface of TiO2 after EPD. B EDX line mapping recorded for a- TiO2, b- gold, c- tin and d- silicon. C EDX spectra of a- Ti, b- gold, c- tin and d- silicon.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4385105&req=5

Fig1: TEM image of gold nanoparticles and EDX line mapping. A TEM image of gold nanoparticles adhered to the surface of TiO2 after EPD. B EDX line mapping recorded for a- TiO2, b- gold, c- tin and d- silicon. C EDX spectra of a- Ti, b- gold, c- tin and d- silicon.
Mentions: In our work, the EPD was carried out by submerging a TiO2 electrode and a blank FTO electrode into a solution of gold nanoparticles. A DC voltage of 250 V was applied across the electrodes for 15 min. It was observed that gold nanoparticles were favourably deposited into the TiO2 film (see TEM in Figure 1) rather than on the surface of the FTO coating, which would agree with findings by Kamat et al. who have also observed this trend [49]. UV–vis spectra (Figure 2A and Additional file 1) of gold nanoparticles electrophoretically deposited into TiO2 films have shown increasing plasmonic intensity with the growing concentration of nanoparticles in the deposition solution. As expected, the deposition of gold nanoparticles resulted in a very large increase in the optical absorption of the TiO2 films when studied with UV–vis spectroscopy and visually (see Additional file 1). The presence of a large plasmon band was also observed in the UV–vis spectra, indicative of the presence of gold nanoparticles in the TiO2 films. The plasmon peak position of the gold nanoparticles embedded in TiO2 closely matched that of the plasmon position for the gold particles in the liquid phase, confirming that after the EPD, the particles are still in the nanoparticulate form and have not coalesced into a bulk gold film.Figure 1

Bottom Line: The composite film demonstrates a significant increase in the short circuit current (I sc) compared to unmodified TiO2 when excited at or close to the plasmon resonance of the gold nanoparticles.Photo-electrochemical investigations revealed that the increase in photocurrent is attributed to the generation and separation of plasmonically generated hot electrons at the gold/TiO2 interface and also the inter-band generation of holes in gold nanoparticles by photons with λ < 520 nm.Theoretical modelling outputs perfectly match our results obtained from photo-physical studies of the processes leading to enhanced photocurrent.

View Article: PubMed Central - PubMed

Affiliation: School of Chemistry and CRANN Institute, Trinity College Dublin, Dublin 2, Ireland.

ABSTRACT
In this manuscript, for the first time, we report a combination of electrophoretic and sintering approaches for introducing gold nanoparticles into nanoporous TiO2 films to generate 'hot' electrons resulting in a strong enhancement of photocurrent. The Au-TiO2 nanocomposite material was prepared by the electrophoretic deposition of gold nanoparticles into a porous nanoparticulate titanium dioxide film, creating a photoactive electrode. The composite film demonstrates a significant increase in the short circuit current (I sc) compared to unmodified TiO2 when excited at or close to the plasmon resonance of the gold nanoparticles. Then, we employed a thermal ripening process as a method of increasing the I sc of these electrodes and also as a method of tuning the plasmon peak position, with a high degree of selectivity. Photo-electrochemical investigations revealed that the increase in photocurrent is attributed to the generation and separation of plasmonically generated hot electrons at the gold/TiO2 interface and also the inter-band generation of holes in gold nanoparticles by photons with λ < 520 nm. Theoretical modelling outputs perfectly match our results obtained from photo-physical studies of the processes leading to enhanced photocurrent.

No MeSH data available.


Related in: MedlinePlus