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Ag2S/CdS/TiO2 Nanotube Array Films with High Photocurrent Density by Spotting Sample Method.

Sun H, Zhao P, Zhang F, Liu Y, Hao J - Nanoscale Res Lett (2015)

Bottom Line: The X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectrum (XPS) results demonstrated that the Ag2S/CdS/TNTs prepared by SSM and other films were successfully prepared.The cycles of local deposition have great influence on their photoelectric properties.The photocurrent density of Ag2S/CdS/TNTs by SSM with optimum deposition cycles of 6 was about 37 times that of TNTs without modification, demonstrating their great prospective applications in solar energy utilization fields.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Colloid and Interface Chemistry & Key Laboratory of Special Aggregated Materials, Shandong University, Ministry of Education, Jinan, 250100, People's Republic of China.

ABSTRACT
Ag2S/CdS/TiO2 hybrid nanotube array films (Ag2S/CdS/TNTs) were prepared by selectively depositing a narrow-gap semiconductor-Ag2S (0.9 eV) quantum dots (QDs)-in the local domain of the CdS/TiO2 nanotube array films by spotting sample method (SSM). The improvement of sunlight absorption ability and photocurrent density of titanium dioxide (TiO2) nanotube array films (TNTs) which were obtained by anodic oxidation method was realized because of modifying semiconductor QDs. The CdS/TNTs, Ag2S/TNTs, and Ag2S/CdS/TNTs fabricated by uniformly depositing the QDs into the TNTs via the successive ionic layer adsorption and reaction (SILAR) method were synthesized, respectively. The X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectrum (XPS) results demonstrated that the Ag2S/CdS/TNTs prepared by SSM and other films were successfully prepared. In comparison with the four films of TNTs, CdS/TNTs, Ag2S/TNTs, and Ag2S/CdS/TNTs by SILAR, the Ag2S/CdS/TNTs prepared by SSM showed much better absorption capability and the highest photocurrent density in UV-vis range (320~800 nm). The cycles of local deposition have great influence on their photoelectric properties. The photocurrent density of Ag2S/CdS/TNTs by SSM with optimum deposition cycles of 6 was about 37 times that of TNTs without modification, demonstrating their great prospective applications in solar energy utilization fields.

No MeSH data available.


Related in: MedlinePlus

A, B The photocurrent density (I-V) curves of different array films to evaluate their photoelectric properties. C, D The EIS Nyquist plots. TNTs (a), CdS/TNTs (b), Ag2S/TNTs (c), Ag2S/CdS/TNTs by SSM (d), and Ag2S/CdS/TNTs via SILAR (e). All the QDs are deposited 6 cycles (A and C), Ag2S/CdS/TNTs by SSM at different deposition cycles (B and D), the number in the parenthesis is the deposition cycles. The experiments were carried out under irradiation of visible light (λ > 420 nm).
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Fig7: A, B The photocurrent density (I-V) curves of different array films to evaluate their photoelectric properties. C, D The EIS Nyquist plots. TNTs (a), CdS/TNTs (b), Ag2S/TNTs (c), Ag2S/CdS/TNTs by SSM (d), and Ag2S/CdS/TNTs via SILAR (e). All the QDs are deposited 6 cycles (A and C), Ag2S/CdS/TNTs by SSM at different deposition cycles (B and D), the number in the parenthesis is the deposition cycles. The experiments were carried out under irradiation of visible light (λ > 420 nm).

Mentions: Figure 7a, b shows the photocurrent density (I-V) curves of different array films to evaluate their photoelectric properties. As shown in Fig. 7a, under visible light illumination, TNTs, Ag2S/TNTs, and Ag2S/CdS/TNTs via SILAR exhibit low photocurrent density, while high photocurrent density values were recorded for CdS/TNTs and Ag2S/CdS/TNTs by SSM. Clearly, Ag2S/CdS/TNTs by SSM exhibits the highest photocurrent density among the five array films of TNTs, CdS/TNTs, Ag2S/TNTs, Ag2S/CdS/TNTs by SSM, and Ag2S/CdS/TNTs via SILAR method. The photocurrent density of Ag2S/CdS/TNTs by SSM (2.83 mA/cm2 at 0 V vs. SCE) is much higher than that of TiO2 array films (0.59 mA/cm2). In addition, the onset potentials of all the array films are read directly from the instrument. The onset potentials of TiO2, CdS/TiO2, Ag2S/TiO2, Ag2S/CdS/TNTs via SILAR, and Ag2S/CdS/TNTs by SSM are −0.85, −1.09, −0.89, −0.90, and −1.21 V, respectively. The negative shift in onset potential values indicates the decreased surface state densities of the electrodes and increased charge transfer rates at the interface [33], suggesting that Ag2S/CdS/TNTs by SSM has improved photoelectric properties compared with other array films. As shown in Fig. 7b, Ag2S/CdS/TNTs by SSM with 6 deposition cycles exhibits the largest photocurrent density, and the onset potentials of Ag2S/CdS/ TNTs by SSM with 3, 6, 9, and 12 deposition cycles are −0.96, −1.21, −1.09, and −1.05 V, respectively. In order to investigate the photoelectric properties of the five nanotube array films further, electrochemical impedance spectra (EIS) measurements were carried out using the five films respectively as the working electrodes in 0.20 M Na2S/Na2SO3 aqueous solution at the open-circuit potential of the system under visible illumination (λ > 420 nm) with an AC amplitude of 5 mV and frequency range from 100 kHz to 0.1 Hz. The EIS Nyquist plots were shown in Fig. 7c, d. As depicted in Fig. 7c, the diameters of the impedance arcs of CdS/TNTs and Ag2S/CdS/TNTs by SSM are smaller than those of TNTs, Ag2S/TNTs, and Ag2S/CdS/TNTs via SILAR. In the EIS Nyquist plots, the smaller semicircle diameter indicates an effective separation of photogenerated electron-hole pairs and fast interfacial charge transfer to the electron donor or acceptor. Obviously, the impedance arc of Ag2S/CdS/TNTs by SSM is the smallest among the five films of TNTs, CdS/TNTs, Ag2S/TNTs, Ag2S/CdS/TNTs via SILAR, and Ag2S/CdS/TNTs by SSM, confirming that the synergy of Ag2S, CdS, and TiO2 may decrease the interfacial resistance and increase the separation capability of photogenerated electron-hole pairs of Ag2S/CdS/TNTs by SSM. However, Ag2S/TNTs and Ag2S/CdS/TNTs via SILAR have larger semicircle diameters despite a higher absorption capability of visible light. This suggests that uniformly deposited Ag2S on the whole TNTs may increase the recombination capability of photogenerated electron-hole pairs and block the electron transfer to Ti substrate. In addition, as shown in Fig. 7d, the deposition cycles of CdS and Ag2S affect the impedance arc of Ag2S/CdS/TNTs by SSM. Ag2S/CdS/TNTs by SSM with 6 deposition cycles has the smallest semicircle diameter, which suggests that an optimal number of deposition cycles may improve its photoelectric properties obviously. Too much QD deposition will increase interfacial resistance and the recombination possibility of the photogenerated electron-hole pairs. The EIS results of the different array films correspond to the changing trends of photocurrents and the onset potentials (Fig. 7a, b).Fig. 7


Ag2S/CdS/TiO2 Nanotube Array Films with High Photocurrent Density by Spotting Sample Method.

Sun H, Zhao P, Zhang F, Liu Y, Hao J - Nanoscale Res Lett (2015)

A, B The photocurrent density (I-V) curves of different array films to evaluate their photoelectric properties. C, D The EIS Nyquist plots. TNTs (a), CdS/TNTs (b), Ag2S/TNTs (c), Ag2S/CdS/TNTs by SSM (d), and Ag2S/CdS/TNTs via SILAR (e). All the QDs are deposited 6 cycles (A and C), Ag2S/CdS/TNTs by SSM at different deposition cycles (B and D), the number in the parenthesis is the deposition cycles. The experiments were carried out under irradiation of visible light (λ > 420 nm).
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Fig7: A, B The photocurrent density (I-V) curves of different array films to evaluate their photoelectric properties. C, D The EIS Nyquist plots. TNTs (a), CdS/TNTs (b), Ag2S/TNTs (c), Ag2S/CdS/TNTs by SSM (d), and Ag2S/CdS/TNTs via SILAR (e). All the QDs are deposited 6 cycles (A and C), Ag2S/CdS/TNTs by SSM at different deposition cycles (B and D), the number in the parenthesis is the deposition cycles. The experiments were carried out under irradiation of visible light (λ > 420 nm).
Mentions: Figure 7a, b shows the photocurrent density (I-V) curves of different array films to evaluate their photoelectric properties. As shown in Fig. 7a, under visible light illumination, TNTs, Ag2S/TNTs, and Ag2S/CdS/TNTs via SILAR exhibit low photocurrent density, while high photocurrent density values were recorded for CdS/TNTs and Ag2S/CdS/TNTs by SSM. Clearly, Ag2S/CdS/TNTs by SSM exhibits the highest photocurrent density among the five array films of TNTs, CdS/TNTs, Ag2S/TNTs, Ag2S/CdS/TNTs by SSM, and Ag2S/CdS/TNTs via SILAR method. The photocurrent density of Ag2S/CdS/TNTs by SSM (2.83 mA/cm2 at 0 V vs. SCE) is much higher than that of TiO2 array films (0.59 mA/cm2). In addition, the onset potentials of all the array films are read directly from the instrument. The onset potentials of TiO2, CdS/TiO2, Ag2S/TiO2, Ag2S/CdS/TNTs via SILAR, and Ag2S/CdS/TNTs by SSM are −0.85, −1.09, −0.89, −0.90, and −1.21 V, respectively. The negative shift in onset potential values indicates the decreased surface state densities of the electrodes and increased charge transfer rates at the interface [33], suggesting that Ag2S/CdS/TNTs by SSM has improved photoelectric properties compared with other array films. As shown in Fig. 7b, Ag2S/CdS/TNTs by SSM with 6 deposition cycles exhibits the largest photocurrent density, and the onset potentials of Ag2S/CdS/ TNTs by SSM with 3, 6, 9, and 12 deposition cycles are −0.96, −1.21, −1.09, and −1.05 V, respectively. In order to investigate the photoelectric properties of the five nanotube array films further, electrochemical impedance spectra (EIS) measurements were carried out using the five films respectively as the working electrodes in 0.20 M Na2S/Na2SO3 aqueous solution at the open-circuit potential of the system under visible illumination (λ > 420 nm) with an AC amplitude of 5 mV and frequency range from 100 kHz to 0.1 Hz. The EIS Nyquist plots were shown in Fig. 7c, d. As depicted in Fig. 7c, the diameters of the impedance arcs of CdS/TNTs and Ag2S/CdS/TNTs by SSM are smaller than those of TNTs, Ag2S/TNTs, and Ag2S/CdS/TNTs via SILAR. In the EIS Nyquist plots, the smaller semicircle diameter indicates an effective separation of photogenerated electron-hole pairs and fast interfacial charge transfer to the electron donor or acceptor. Obviously, the impedance arc of Ag2S/CdS/TNTs by SSM is the smallest among the five films of TNTs, CdS/TNTs, Ag2S/TNTs, Ag2S/CdS/TNTs via SILAR, and Ag2S/CdS/TNTs by SSM, confirming that the synergy of Ag2S, CdS, and TiO2 may decrease the interfacial resistance and increase the separation capability of photogenerated electron-hole pairs of Ag2S/CdS/TNTs by SSM. However, Ag2S/TNTs and Ag2S/CdS/TNTs via SILAR have larger semicircle diameters despite a higher absorption capability of visible light. This suggests that uniformly deposited Ag2S on the whole TNTs may increase the recombination capability of photogenerated electron-hole pairs and block the electron transfer to Ti substrate. In addition, as shown in Fig. 7d, the deposition cycles of CdS and Ag2S affect the impedance arc of Ag2S/CdS/TNTs by SSM. Ag2S/CdS/TNTs by SSM with 6 deposition cycles has the smallest semicircle diameter, which suggests that an optimal number of deposition cycles may improve its photoelectric properties obviously. Too much QD deposition will increase interfacial resistance and the recombination possibility of the photogenerated electron-hole pairs. The EIS results of the different array films correspond to the changing trends of photocurrents and the onset potentials (Fig. 7a, b).Fig. 7

Bottom Line: The X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectrum (XPS) results demonstrated that the Ag2S/CdS/TNTs prepared by SSM and other films were successfully prepared.The cycles of local deposition have great influence on their photoelectric properties.The photocurrent density of Ag2S/CdS/TNTs by SSM with optimum deposition cycles of 6 was about 37 times that of TNTs without modification, demonstrating their great prospective applications in solar energy utilization fields.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Colloid and Interface Chemistry & Key Laboratory of Special Aggregated Materials, Shandong University, Ministry of Education, Jinan, 250100, People's Republic of China.

ABSTRACT
Ag2S/CdS/TiO2 hybrid nanotube array films (Ag2S/CdS/TNTs) were prepared by selectively depositing a narrow-gap semiconductor-Ag2S (0.9 eV) quantum dots (QDs)-in the local domain of the CdS/TiO2 nanotube array films by spotting sample method (SSM). The improvement of sunlight absorption ability and photocurrent density of titanium dioxide (TiO2) nanotube array films (TNTs) which were obtained by anodic oxidation method was realized because of modifying semiconductor QDs. The CdS/TNTs, Ag2S/TNTs, and Ag2S/CdS/TNTs fabricated by uniformly depositing the QDs into the TNTs via the successive ionic layer adsorption and reaction (SILAR) method were synthesized, respectively. The X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectrum (XPS) results demonstrated that the Ag2S/CdS/TNTs prepared by SSM and other films were successfully prepared. In comparison with the four films of TNTs, CdS/TNTs, Ag2S/TNTs, and Ag2S/CdS/TNTs by SILAR, the Ag2S/CdS/TNTs prepared by SSM showed much better absorption capability and the highest photocurrent density in UV-vis range (320~800 nm). The cycles of local deposition have great influence on their photoelectric properties. The photocurrent density of Ag2S/CdS/TNTs by SSM with optimum deposition cycles of 6 was about 37 times that of TNTs without modification, demonstrating their great prospective applications in solar energy utilization fields.

No MeSH data available.


Related in: MedlinePlus