Sequential Chemical Bath Deposition Research Articles

Interfacial competing interaction eliminates voids in the buried interface for efficient and stable perovskite solar modules on bare NiOX

Perovskite solar cells (PSCs) with impressive efficiency is promising for commercialization. However, when scaling up PSCs to large-area perovskite solar modules (PSMs), the rapid degradation of performance and stability still remains a grand challenge. One of the main causes of the degradation is the presence of local voids in the buried interface for large-area films, which we find could be attributed to the unbalanced interfacial interaction between precursor solvent and substrate. Here we improve a scalable and low-temperature sequential two-step chemical bath deposition process aiming for high quality NiOX. Further with the modulation of A-site cations to enhance the interaction between DMSO and perovskite precursor, the potential for DMSO absorbing on the NiOX could be eliminated. This strategy can inhibit the delay movement of DMSO on NiOX and improve the buried interfacial quality, with compact morphology and absent of voids. The inverted structured PSCs and PSMs based on the bare NiOX and modified perovskite precursor reach a champion efficiency of 22.40% and 19.09%, respectively, which are both among the highest reported values. The highly efficient PSMs also exhibit a long-term operational stability, which retain 84% of the initial performance after 1056 h operating under one-sun illumination.

Tin Oxide/Vertically Aligned Graphene Hybrid Electrodes Prepared by Sonication-Assisted Sequential Chemical Bath Deposition for High-Performance Supercapacitors.

Hybrid electrodes comprising metal oxides and vertically aligned graphene (VAG) are promising for high-performance supercapacitor applications because they enhance the synergistic effect owing to the large contact area between the two constituent materials. However, it is difficult to form metal oxides (MOs) up to the inner surface of a VAG electrode with a narrow inlet using conventional synthesis methods. Herein, we report a facile approach to fabricate SnO2 nanoparticle-decorated VAG electrodes (SnO2@VAG) with excellent areal capacitance and cyclic stability using sonication-assisted sequential chemical bath deposition (S-SCBD). The sonication treatment during the MO decoration process induced a cavitation effect at the narrow inlet of the VAG electrode, allowing the precursor solution to reach the inside of the VAG surface. Furthermore, the sonication treatment promoted MO nucleation on the entire VAG surface. Thus, the SnO2 nanoparticles uniformly covered the entire electrode surface after the S-SCBD process. SnO2@VAG exhibited an outstanding areal capacitance (4.40 F cm-2) up to 58% higher than that of VAG electrodes. The symmetric supercapacitor with SnO2@VAG electrodes showed an excellent areal capacitance (2.13 F cm-2) and a cyclic stability of 90% after 2000 cycles. These results suggest a new avenue for sonication-assisted fabrication of hybrid electrodes in the field of energy storage.

Chemical Preparation of Metallic Cu Layer on Glass Substrate Using Intermediate Cu(OH)2/Cu(O, S) Bilayer

A metallic Cu layer with a sheet resistance of 0.19 Ω was chemically prepared on a glass substrate by chemical reduction of the intermediate Cu(OH)2/Cu(O,S) bilayers using dimethylamine-borane (DMAB), while Cu(OH)2, and Cu(O,S) layers were fabricated by a sequential chemical bath deposition (CBD) in aqueous solutions containing copper (II) nitrate hydrate and ammonium nitrate with urea and thiourea. The thickness of the Cu(OH)2 and resultant Cu layers were strongly affected by the structure under the Cu(O, S) layer, and a metallic Cu layer was formed mainly from the Cu(OH)2 layer. The reduction reactions of Cu(OH)2 and Cu(O, S) were discussed based on thermodynamics.

Self-rectifying threshold resistive switching based non-volatile memory of CBD/CBD grown vertical n-ZnO nanowire/p-Si heterojunction diodes

Vertically oriented ZnO nanowires are grown on p-Si substrate by employing two-step sequential chemical bath deposition technique. The ZnO nanowire exhibits n-type doping due to the presence of oxygen vacancies. The electrical characterizations of n-ZnO NWs/p-Si heterojunction diodes exhibit a self-rectifying, threshold resistive switching behavior. Such switching behavior is explained by oxygen vacancy assisted conducting filament formation mechanism. The relevant charge transport is governed by TC-SCLC and multistep recombination-tunneling processes through the interface traps. Threshold-voltage for resistive switching is observed to be increasing with increasing bias sweep rate. The device shows superior memory endurance for forward and reverse voltage sweep of 50 cycles in fast sweep mode. The ratio of HRS to LRS resistances shows one order of difference. The retention time of such resistive switching memory is recorded to be 4000 seconds, suggesting its non-volatile functionality. Thus, the n-ZnO NWs/p-Si heterojunction can be employed for fabricating promising non-volatile memory devices with excellent endurance and retentions. Copyright © 2018 VBRI Press.

Chemically synthesized Bi2S3, CuS and Bi2S3/CuS heterostructure materials as counter electrode: Dye sensitized solar cell application

In the present work, we have successfully synthesized Bi2S3, CuS, and its heterojunction Bi2S3/CuS thin film on fluorine doped tin oxide (FTO) coated glass as counter electrodes. These depositions are done by simple, cost effective, and simply executable sequential chemical bath deposition (S-CBD) method. Well optimized preparative parameters led to the formation of good quality thin films of Bi2S3 and CuS films and heterojunction. The structural validation Bi2S3, CuS, and its heterojunction were achieved by X-ray diffraction and Raman scattering, surface morphological study observed through Scanning Electron Microscopy (SEM) and topology was confirmed by Atomic Force Microscopy (AFM). We have employed Bi2S3/CuS heterostructure as a counter electrode (CE) in dye-sensitized solar cell (DSSC). We have observed different parameters like short circuit current density (Jsc), open circuit voltage (Voc), Fill Factor (FF) and efficiency (n) by Current–voltage (J-V) characteristics. Though we do not achieve an anticipated outcome for heterostructure compared with conventional Platinum and Carbon black counter electrode, CuS separately found worthy as Counter electrode (CE) in DSSC.

Enhanced photoelectrocatalytic activity of Bi2S3–TiO2 nanotube arrays hetero-structure under visible light irradiation

Constructing heterosystems by sensitizing a wide band gap semiconductor with a narrow band gap semiconductor is an effective way to improve photocatalytic performance. Bismuth sulfide (Bi2S3) has a direct band gap of 1.38 eV and shows great potential in capturing visible light, which makes it a good candidate for photocatatlytic applications. In this work, Bi2S3 nanoparticles were efficiently deposited on TiO2 nanotube arrays (Bi2S3-TNTAs) by sequential chemical bath deposition (CBD) method to enhance visible light response of the photocatalytic system. Notably, a high-throughput screening method of scanning photoelectrochemical microscopy (SPECM) was exploited to evaluate photoelectrochemical response of the as-prepared composites and to find out the optimized photocatatlytic system. The effects of Bi2S3 nanoparticles on visible light absorption and photoelectrocatalytic hydrogen production rate of the TiO2-system were investigated in detail. When adopted as photoanode, the optimized heteroelectrode exhibited a more than 13-fold enhancement in hydrogen production rate. The result of electrochemical impedance spectroscopy (EIS) and photoluminescence (PL) shows that photo-generated charges excited under visible light in Bi2S3-TNTAs composites are efficiently separated, which gives rise to the superior photoelectrocatalytic performance of the Bi2S3-TNTAs photoanodes.

Photoelectrochemical activity of Ag loaded TiO2 nanotube arrays produced by sequential chemical bath deposition for water splitting

We report on remarkable improvement of photoelectrochemical (PEC) properties of TiO2 nanotubes by loading of Ag nanoparticles into them. The silver nanoparticles were loaded on the nanotubes by sequential chemical bath deposition (S-CBD) with different number of deposition cycles. Various characterizations including field emission scanning electron microscopy, X-ray diffraction, and energy dispersive X-ray analysis (EDX), all confirm that the silver nanoparticles were deposited inside and outside of TiO2 nanotubes. In addition, the PEC properties of the samples were investigated using linear sweep voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. The PEC analyses clearly show that the photo-electrochemical activity of the Ag-loaded samples are considerably higher than the bare TiO2 nanotubes (about 3 times). This mostly originates from the improvement of light absorption due to the plasmonic effects in addition to better separation and transport of electron–hole pairs in the Ag-loaded samples relative to the bare TiO2 nanotubes. All results indicate that the maximum efficiency were obtained for the 8-cycle of S-CBD Ag-loading on the bare TiO2 nanotubes.

A competitive photoelectrochemical immunosensor for the detection of diethylstilbestrol based on an Au/UiO-66(NH2)/CdS matrix and a direct Z-scheme Melem/CdTe heterojunction as labels

A novel photoelectrochemical (PEC) bioassay protocol for diethylstilbestrol (DES) was systematically proposed. The Au/UiO-66(NH2) hybrid with countless active sites was fabricated using an in situ reduction strategy and was subsequently decorated with CdS nanoparticles (NPs) by a sequential chemical bath deposition process. The resulting Au/UiO-66(NH2)/CdS composites were exploited as a sensing matrix for the first time. The excellent photocurrent response of the as-prepared hybrid under visible light is attributed to its improved photo-electric conversion efficiency due to the local surface plasma resonance (LSPR) effect of Au and the matching energy-level structure between UiO-66(NH2) and CdS. In addition, the competitive strategy for the detection of DES was devised by employing the direct Z-scheme Melem/CdTe heterojunction covalently conjugated with bovine serum albumin (BSA)-DES as signal tags. As a consequence, a cascade-like band-edge level was obtained, which could effectively promote the transfer of photogenerated charges and markedly improve the photocurrent. On the basis of the above strategy, the concentrations of DES could be detected through the competitive binding of DES antibodies (Anti-DES) with either Melem/CdTe/BSA-DES or free DES. Under optimal conditions, the linear range for the detection of DES was 0.1 pg mL−1 to 20 ng mL−1. The detection limit was as low as 0.06 pg mL−1 (S/N = 3). Furthermore, the designed PEC DES-sensing approach has acceptable selectivity, reproducibility, and stability and offers great promise for the detection of small molecules in biomedical, food and environmental samples.

Solution‐Processed Transparent Self‐Powered p‐CuS‐ZnS/n‐ZnO UV Photodiode

Transparent diodes formed by a heterojunction between p‐type CuS–ZnS and n‐type ZnO thin films were fabricated by sequential chemical bath deposition and sol‐gel spin coating. The diodes are transparent in the visible (≈70% at 550 nm) and exhibit a good rectifying characteristics, with If/Ir ratios of up to 800 at ±1 V, higher than most of the reported solution‐processed diodes measured at a similar bias. More importantly, when operated as a self‐powered (zero bias) UV photodetector, they show stable and fast (<1 s) photoresponse with a maximum responsivity of 12 mA W−1 at 300 nm. Both the response time and responsivity of the p‐CuZnS/n‐ZnO UV photodiode are comparable or superior to similar solution‐processed devices reported in the literature.

(Invited) Enhanced Photoelectrocatalytic Activity for Splitting Water Based on Heterostructured TiO2 Nanotube Arrays

Photoelectrocatalytic water splitting is widely recognized as one of the most promising strategies to large-scale production of hydrogen for renewable energy. To further enhance the photoelectrocatalytic efficiency, severalheterostructures based on TiO2 nanotube arrays were developed in this work. (1) TiO2 nanotube arrays (TNTAs) were decorated with NiO nanoparticles via a sequential chemical bath deposition (CBD) approach to yield NiO@TNTA photoanodes. It demonstrated that the incident-photon-to-current-conversion efficiency (IPCE) and hydrogen production rate of the optimized NiO@TNTA reached 62.8% and 37.8 μmol.h-1.cm-2, respectively, approximately 5.0 times higher than pure TNTAs, which was attributed primarily to the efficient separation of photogenerated charge carriers at the p–n junction of p-type NiO and n-type TiO2. (2) CuxZn1-xIn2S4 ultrathin nanosheets on TiO2 nanotube arrays (CZIS@TNTAs) was successfully synthesized by solvothermal reaction. It found that the CuxZn1-xIn2S4 ultrathin nanosheets on TNTAs significantly enhanced visible light absorption and and a near 8.0-fold increase in photoelectrocatalytic hydrogen production rate was achieved compared to that of the blank TNTAs. The superior photoelectrocatalytic activity of CZIS@TNTAs heterostructured composite electrode was mainly due to enhanced light absorption and separation of photo-generated charges, and facilitating electron transport along the 1D TiO2 structure. (3) TiO2 nanotube arrays (TNTAs) sensitized by palladium quantum dots (Pd QDs) by a modified hydrothermal reaction. When Pd@TNTA nanocomposites were used as both photoanode and cathode in water splitting, the photon-to-current conversion efficiency of nearly 100% atλ=330 nm and a greatly promoted photocatalytic hydrogen production rate of 592 μmol·h−1·cm−2 under 320 mW·cm−2 irradiation were achieved. The synergy between nanotubular structures of TiO2 and uniformly dispersed Pd QDs on TiO2 facilitated the charge transfer from TiO2 nanotubes to Pd QDs and the high activity of Pd QDs catalytic center, thereby leading to high-efficiency photoelectrocatalytic hydrogen generation.

Synthesis of α-Bi2Mo3O12/TiO2 Nanotube Arrays for Photoelectrochemical COD Detection Application.

One-dimensional anodic TiO2 nanotube arrays hold great potential as a photoelectrochemical sensor for the determination of chemical oxygen demand (COD). In this work, we report a warm synthesis of modified TiO2 nanotube arrays with enhanced photoelectrochemical determination performance. Herein, a bismuth-based semiconductor (α-Bi2Mo3O12) was introduced into TiO2 nanotube arrays by sequential chemical bath deposition (CBD) at room temperature. Field-emission scanning electron microscopy, X-ray diffraction, Raman, and X-ray photoelectron spectroscopy were used to investigate the morphologies, structures, and elemental analysis of the products. The photoelectrochemical properties of TiO2 and α-Bi2Mo3O12/TiO2 NTAs were measured by amperometry and cyclic votammetry methods. The α-Bi2Mo3O12/TiO2 nanotube arrays decrease the background photocurrent and increase the current response to organics at the same time, both of which are beneficial to enhancing the photoelectrochemical detection performance. The optimized α-Bi2Mo3O12/TiO2 NTAs with enhanced photoelectrochemical detection performance can achieve a detection sensitivity of 2.05 μA·cm-2/(mg·L-1) and a COD detection range of 0.366-208.9 mg/L respectively. With the α-Bi2Mo3O12 modification, the surface electrochemical reactions of TiO2 NTAs were regulated, the mechanisms of which were also further studied.

Bi2S3 modified single crystalline rutile TiO2 nanorod array films for photoelectrochemical cathodic protection

A combined hydrothermal reaction and sequential chemical bath deposition method is developed for fabricating a Bi2S3 modified single crystalline rutile TiO2 nanorod array film on transparent conductive glass. The results indicate that the modification of Bi2S3 nanoparticles extends the photoresponse of the Bi2S3/TiO2 composite film into the visible light region, and enhances its photoactivity. The Bi2S3/TiO2 film can serve as a photoanode in a photoelectrochemical cell and provide more effective photogenerated cathodic protection for 403 stainless steel in a corrosion cell with a 0.5M NaCl solution under white or visible light illumination compared with the pure TiO2 film.

Photoelectrochemical sensitive detection of insulin based on CdS/polydopamine co-sensitized WO3 nanorod and signal amplification of carbon nanotubes@polydopamine

An ultrasensitive photoelectrochemical sandwich immunosensor was designed for detection of insulin based on WO3/CdS/polydopamine (WO3/CdS/PDA) co-sensitized and PDA@carbon nanotubes (PDA@CNT) conjugates for signal amplification. The CdS nanoparticles were first deposited on the WO3 nanorods via sequential chemical bath deposition to form the WO3/CdS structure to enhance photocurrent. Then equipped with PDA to form the WO3/CdS/PDA photosensitive structure. The PDA was used not only to reduce the toxicity of CdS but also adsorb insulin primary antibodies (Ab1). Meanwhile, insulin secondary antibodies (Ab2) were decorated by PDA@CNT conjugates for signal amplification and further enhance photocurrent. Different photocurrent intensities were obtained by the photoelectrochemical workstation at applied bias of 0V due to the different amount of the PDA@CNT conjugates introduced by the different concentrations of insulin. A good linear relationship was obtained between the increased photocurrent and insulin concentrations range from 0.01ngmL−1 to 50ngmL−1. And a detection limit of 2.8pgmL−1 was obtained. The proposed sensor was applied to the determination of the insulin in human serum sample, and satisfactory results were obtained. The sensor presented good specificity, reproducibility and stability, thus it might find application in the clinical diagnosis of insulin or other biomarkers in the near future.

Novel multi-heterostructured Pt-BiOBr/TiO2 nanotube arrays with remarkable visible-light photocatalytic performance and stability

Unique multiple heterojunction of Pt-BiOBr/TiO2 nanotube arrays (Pt-BiOBr/TNTAs) was achived by successively loading both Pt nanoparticles (NPs) and BiOBr nanoflkes (NFs) on surface of ordered and spaced TiO2 nanotubes (NTs) using anodization followed by solvothermal and sequential chemical bath deposition (S-CBD) method. The fabricated Pt-BiOBr/TNTAs were fully characterized, and the photocatalytic (PC) activity and stability of Pt-BiOBr/TNTAs toward degradation of methyl orange (MO) under visible-light irradiation (λ>400 nm) were evaluated. The results reveal that multiple heterostructures of Pt/TiO2, Pt/BiOBr and BiOBr/TiO2 are constructed among TNTAs substrate, Pt NPs and BiOBr NFs, and the hybrid Pt-BiOBr/TNTAs catalyst exhibits remarkable visible-light PC activity, favourable reusability and long-term stability. The combined effect of several factors may contribute to the remarkable PC performance, including strong visible-light absorption by both Pt NPs and BiOBr NFs, lower recombination rate of photo-generated electrons and holes attributed to the multiple heterojunction, microstructures for facile light injection and adsorption as well as efficient mass transport, and larger specific surface area for enhancing light absorption, increasing the effective contact area between the absorbed dye molecules and catalyst and benefiting the molecule transport of reactants or products.

Photoelectrochemical performance of cadmium sulfide quantum dots modified titania nanotube arrays

The cadmium sulfide quantum dots modified titania nanotube arrays (CdS QDs/TiO2 NTAs) were prepared through a sequential sonication-assisted chemical bath deposition (CBD) process. The morphology and microstructure of CdS QDs/TiO2 NTAs were characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectroscopy, energy-dispersive X-ray spectroscopy, Raman spectroscopy and UV–vis diffuse reflectance spectroscopy. The photoelectrochemical performance of CdS QDs/TiO2 NTAs was investigated under solar light illumination. The affecting parameters were studied including the nanotube length of TiO2 NTAs, CBD cycles of CdS QDs and the annealing treatment of CdS QDs/TiO2 NTAs. CdS QDs synthesized through 8 CBD cycles could uniformly cover on the tube walls of TiO2 NTAs to form unique CdS QDs/TiO2 NTAs with an open pore mouth. The appropriate annealing treatment at 400°C for 60min in N2 atmosphere could improve the crystallinity of CdS QDs, and accordingly enhance the photovoltaic properties of CdS QDs/TiO2 NTAs. Significantly, the nanotube length was the predominant factor affecting photoelectrochemical performance of CdS QDs/TiO2 NTAs. The unannealed CdS QDs/TiO2 NTAs with an optimal nanotube length of 12μm achieved a short-circuit photocurrent density of 4.37mAcm−2, an open circuit photovoltage of 1.10V and a top photoconversion efficiency of 3.56%. Comparatively, the annealed CdS QDs/TiO2 NTAs with an optimal nanotube length of 4μm achieved a short-circuit photocurrent density of 6.31mAcm−2, an open circuit photovoltage of 1.23V and a top photoconversion efficiency of 4.18%. The suitable modification of crystalline CdS QDs could well improve the photoelectrochemical performance of TiO2 NTAs photoanode.

Efficient visible light-induced photoelectrocatalytic hydrogen production using CdS sensitized TiO2 nanorods on TiO2 nanotube arrays

CdS/TNRs/TNTs were synthesized by combining a hydrothermal method with a sequential-chemical bath deposition method and displayed enhanced visible light-induced photoelectrocatalytic hydrogen production activity compared with TNTs, TNRs/TNTs and CdS/TNTs.

Enhanced electrochemical performance of manganese dioxide spheres deposited on a titanium dioxide nanotube arrays substrate

The deposition of MnO2 spheres on a TiO2 nanotube arrays substrate are achieved via a sequential chemical bath deposition (SCBD) method for an application of anode materials in supercapacitors. The electrochemical performance of the MnO2–TiO2 composite electrode is observed to show a strong dependence on the MnO2 loading mass, which could be adjusted by repeating the SCBD treatment for several cycles. The optimized doses of MnO2 loaded MnO2–TiO2 and MnO2–Ti samples are compared in terms of their areal capacitance studies and the former is of 175 and 101 mF cm−2 at a scan rate of 10 and 100 mV s−1, respectively, which are 1.52-fold and 1.51-fold of that of the latter sample at corresponding scan rates. The enhancement in areal capacitance has been accounted to the progressive effect of the TiO2 tubular substrate on the capacitive behavior of the loaded MnO2 rather than the different MnO2 loading mass on these two substrates. Impedance analysis reveals this enhanced electrochemical activity is owing to the tubular structure of the TiO2 substrate provides an increased reaction area and facilitates the contact of electrolyte with the active MnO2 material. This work justified the suitability of using the TiO2 nanotube arrays for constructing high-performance supercapacitors.

CdS-TiO2 photoelectrodes Formed through Pulsed Electrodeposition of Cadmium on TiO2 Nanotube Films and Treatment with H2s for Application in Solar Cells

TiO2 nanotubes films (TNAs), compared with classic nanocrystalline photoanodes, can accelerate electron transport and diminish the recombination probability, making it suitable for use as a photoelectrode in solar cells [1]. However, one of the critical drawbacks of TiO2 is its wide band gap (3.0 and 3.2 eV for the rutile and anatase phases, respectively). That means, only ultraviolet region of the solar spectrum (about 7%) can be utilized by pure TiO2. Therefore, different methods were developed to extend the light harvesting region of TiO2, including dye sensitization and coupling with low band gap semiconductors. Coupled CdS/TNAs photoelectrode has been considered to be an important technique because CdS has a narrow band gap (2.4 eV) and its conduction band level is higher than that of TiO2. Upon illumination, the excited electrons from CdS can be rapidly transferred to TNAs, arriving at the electron collectors through the nanotube microstructure [1]. Different methods have been reported to couple CdS with TNAs, being the most commonly used: sequential chemical bath deposition (SCBD) and electrochemical deposition. However, with these methods the CdS is obtained for precipitation reactions between ions Cd2+ and S2- located in the interface electrode-electrolyte, therefore, no direct contact is ensured among CdS and TNAs. In this way, to guarantee direct contact between CdS and TNAs, an electrochemical/chemical (E/C) process was proposed in this work. This process is similar as that developed by Penner and his group to deposit CdS nanocrystals on HOPG substrates. TiO2 nanotube films were grown by potentiostatic anodization of titanium foils at 30 V during 2 hours in 0.05 M NH4F in ethylene glycol (10% water) electrolyte [2]. As-prepared films were rinsed with ethanol and water, left to air dry, and heat treated in ambient air at 450º C for 30 min (slope rate 10 ºCmin-1). E/C method consists of three steps [3]: (1) Cd nanoparticles were deposited in heat treated TNAs by pulsed electrodeposition to different reduction potentials [4] and varying on and off times; (2) the modified films were annealing at 400ºC for 30 min (slope rate 10 ºCmin-1) to form CdO/TNAs; (3) finally, the CdO/TNAs were heated in H2S atmosphere at 300º C for 30 min (slope rate 10 ºCmin-1) to convert CdO into CdS. The CdS/TNAs photoelectrodes were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and UV-Vis diffuse reflectance absorption spectra (DRS). We also investigated the photoelectrochemical behavior of the CdS/TNAs photoelectrodes under visible illumination. Acknowledgements.The authors are indebted to the CONACyT (Mexico) for their financial support to carry out this work (Projects CB-2008/105655 and INFR-2011-1-163250). J.E. Carrera-Crespo is grateful to CONACyT for the PhD fellowship granted. The authors thank to LDRX (T 128) UAM-I for XRD measurements. References. [1] X. Ma, Y. Shen, G. Wu, Q. Wu, B. Pei, M. Cao, F. Gu, “Sonication-assisted sequential chemical bath deposition of CdS nanoparticles into TiO2 nanotube arrays for application in solar cells”, J Alloy Compd (2012) 538: 61-65 [2] P. Acevedo-Peña, L. Lartundo-Rojas, I. González, “Effect of water and fluoride content on morphology and barrier layer properties of TiO2 nanotubes grown in ethylene glycol-based electrolytes”, J Solid State Electr (2013) 17: 2939-2947 [3] R. M. Penner, “Hybrid electrochemical/chemical synthesis of quantum dots”, Acc Chem Res (2000) 33: 78-86 [4] J. E. Carrera-Crespo, P. Acevedo-Peña, M. Miranda-Hernández, I. González, “Electrocrystallization of cadmium on anodically formed titanium oxide”, J Solid State Electr (2013) 17: 445-457

How CdS nanoparticles can influence TiO2 nanotube arrays in solar energy applications?

In this study, titanium dioxide (TiO2) nanotube array (TNA) films are fabricated via anodization of titanium (Ti) sheet. After annealing, the films consisted of well ordered, vertically oriented TNAs of 125±6nm diameter, 38±3nm wall thickness, and 2.9±0.3μm in length. Cadmium sulfide (CdS) nanoparticles are deposited on the synthesized TNAs by sequential-chemical bath deposition (S-CBD) method with different immersion cycle (n) to produce heterogeneous TNA/CdS-n (n=10, 20 and 30) nanostructures. UV–visible absorption spectra of the samples revealed that the absorption edge of CdS modified TNAs was shifted to a higher wavelength with respect to the pure TNAs indicating band gap reduction of the TNA/CdS-n. Photocurrent response of the samples was changed with n, and the maximum photocurrent density (at steady state) of 28±1mA/cm2 (or 70±2mA/W) was obtained for the TNA/CdS-20 photoanode which is about 30 times higher than one for the pure TNA under similar condition.

Hydrothermal growth of TiO2 nanowire membranes sensitized with CdS quantum dots for the enhancement of photocatalytic performance.

In this paper, TiO2 nanowires (NWs) on Ti foils were prepared using a simple hydrothermal approach and annealing treatment. CdS quantum dots (QDs) were assembled onto the crystallized TiO2 NWs by sequential chemical bath deposition. Ultraviolet-visible absorption spectra showed that CdS adds bands in the visible to the TiO2 absorption and exhibited a broad absorption band in the visible region, which extended the scope of absorption spectrum and helped improve the photocatalytic degradation efficiency. The results of photocatalytic experiment revealed that CdS-TiO2 NWs possessed higher photocatalytic activities toward methyl orange than pure TiO2 nanowires. The degradation efficiency of 96.32% after ten cycles indicated that the as-prepared CdS-TiO2 composite exhibited excellent long-time recyclable ability and can be reused for the degradation of contaminants.