2S3 Nanorods - ACS Publications - American Chemical Society

Research Article www.acsami.org

Cite This: ACS Appl. Mater. Interfaces 2018, 10, 7334−7343

Composition-Dependent Aspect Ratio and Photoconductivity of Ternary (BixSb1−x)2S3 Nanorods Junli Wang,* Hongsong Yu, Tingting Wang, Yajie Qiao, Ying Feng, and Kangmin Chen School of Materials Science & Engineering, Jiangsu University, Zhenjiang 212013, P. R. China S Supporting Information *

ABSTRACT: The chemical composition, size and shape, and surface engineering play key roles in the performance of electronic, optoelectronic, and energy devices. V2VI3 (V = Sb, Bi; VI = S, Se) group materials are actively studied in these fields. In this paper, we introduce a colloidal method to synthesize uniform ternary (BixSb1−x)2S3 (0 < x < 1) nanorods. These nanorods show composition-dependent aspect ratios, enabling their composition, size, and shape control by varying Bi/Sb precursor ratios. It is found that the surface passivation by various thiols (L−SH) efficiently enhances the photoconductivity and optical responsive capability of (BixSb1−x)2S3 nanorods when used as active materials in indium tin oxide (ITO)/(BixSb1−x)2S3/ITO optoelectronic devices. Meanwhile, the increase of Sb content causes a gradual deterioration of photoconductivity of thiolpassivated nanorods. We propose that the thiol passivation is able to reduce the number of S vacancies, which act as the recombination centers (trapped states) for photogenerated electrons and holes, and thus boosts the carrier transport in (BixSb1−x)2S3 nanorods, and in particular that the composition-related conductivity deterioration is attributed to the increase of unpassivated S vacancies and surface oxidation due to the rise of Sb content. KEYWORDS: ternary nanorods, colloidal synthesis, photoconductivity, thiol passivation, S vacancies, surface oxidation, optoelectronic devices plasmon resonance absorption in BiSbS3 nanorods.24 Ternary Bi0.94Sb1.06S3 nanorod clusters/graphite composite anode displayed much improved charge/discharge cycle stability in sodium-ion batteries compared to its Bi2S3−graphite and Sb2S3−graphite counterparts.25 Interestingly, these four compounds V2VI3 (V = Sb, Bi; VI = S, Se) share a common crystal structure, that is, the orthorhombic structure,1−4,26−30 which is called the isostructure. Such a structural characteristic facilitates the formation of ternary solid solutions over a wide range of compositions by an equivalent cation (Sb3+, Bi3+) or anion (S2−, Se2−) substitution mechanism.1−3,6,23−25,29,30 This mechanism is found to occur not only in large crystals of V2VI3 natural minerals1−3 or thin films29,30 but also in artificially synthetic nanocrystals, such as (Sb1−xBix)2Se3 nanowires,6 Sb2Se3−xSx (0 < x < 3) nanotubes,23

1. INTRODUCTION Group V2VI3 (V = Sb, Bi; VI = S, Se) compounds are important natural minerals1−4 and can be extracted as a kind of inherently earth-abundant, environmentally friendly materials for the optoelectronic and energy applications.5−19 These compounds display a number of excellent optical and electronic characteristics, including the suitable band structures/gap energies, high electrical (photo)conductivity, and strong visible light adsorption,5−19 and especially, when the dimensions reduced to the nanoscale size, they find their widespread use in optical detection/switch devices,6−9 solar cells (photovoltaics),10−13 lithium/sodium-ion batteries,14−17 as well as thermoelectrics.18,19 Such fundamental physical properties and applications are highly composition-dependent, which motivates many researchers to modulate and optimize material performance by means of tuning chemical compositions.6,9−13,20−25 For example, Se variations in Sb−Se−S nanotubes led to the band gap energy varying from the visible to near-infrared region.23 The replacement of Sb for Bi generated a localized surface © 2018 American Chemical Society

Received: November 13, 2017 Accepted: January 31, 2018 Published: January 31, 2018 7334

DOI: 10.1021/acsami.7b17253 ACS Appl. Mater. Interfaces 2018, 10, 7334−7343

Research Article

ACS Applied Materials & Interfaces and (BixSb1−x)2S3 nanorods.24,25 Clearly, the isostructural substitution is a promising strategy for composition regulation of a variety of nanomaterials. A series of continuous substitutional solid solutions of (BixSb1−x)2S3 with different Sb/Bi ratios are formed between isostructural Sb2S3 and Bi2S3.1,2,22,24,25,29,30 In contrast to the two endmembers Sb2S3 and Bi2S3, however, the concerns and research studies are limited on ternary (BixSb1−x)2S3 (0 < x < 1) nanocrystals on the aspects of preparation, size, morphology and composition control, and physical property.24,25 In this paper, we present a colloidal synthetic route to uniform ternary (BixSb1−x)2S3 nanorods (0 < x < 1) in the mixed solution of long-chain alkylamines. This method, which was previously employed to prepare Bi2S3 nanorods,31 is effective for the composition regulation of ternary (BixSb1−x)2S3 nanorods by varying Bi/Sb precursor ratios. It is particularly interesting that the as-obtained (BixSb1−x)2S3 nanorods display composition-dependent aspect ratios as well as compositiondependent optoelectronic responsive characteristic after surface-passivated by organic thiols including 1-dodecanethiol (DDT), 1-octanethiol (OT), and 1-butanethiol (BT): the aspect ratio increases whereas the photoconductivity decreases with the Sb proportion rising. Our work reveals that the surface modification by thiols is able to enhance the photoconductivity and photoresponsive ability of (BixSb1−x)2S3 nanorods. An atomic model is proposed to explain the reasons for the conductivity enhancement, in which the chemical interaction of thiols with the exposed, unsaturated Sb ions at the nanorod surface can effectively reduce S vacancies (i.e., recombination centers) and boost the carrier transport. We also explain the reasons for composition-dependent optoelectronic characteristic of thiol-passivated (BixSb1−x)2S3 nanorods from the aspects of S vacancies and surface oxidation.

photoelectron spectroscopy (XPS) measurements were performed on an ESCALAB250Xi X-ray photoelectron spectrometer with an Al Kα excitation source (ThermoFisher Scientific). 2.3. Photoelectric Measurements. A simple photoelectronic device based on (BixSb1−x)2S3 nanorods were fabricated on indium tin oxide (ITO)-coated glass substrates. The resistance of ITO film is 15 Ω. In detail, a concentrated n-hexane solution of (BixSb1−x)2S3 nanorods was drop-cast on ITO films, and then, two pieces of ITO coated with the nanorods were assembled together and some of ITO films were set aside to serve as conductive electrodes, that is, the ITO/ (BixSb1−x)2S3/ITO device is as shown in the inset of Figure 6f. A xenon lamp (300 W) equipped with a cutoff filter of 400 nm is used as a white light source with an output wavelength range of 400−780 nm. Current−voltage (I−V) characteristic and the time-dependent current (I−t curves) of the device were recorded with a two-probe method using an electrochemical workstation (CHI660e) in ambient conditions.

3. RESULTS AND DISCUSSION The products prepared from different Bi/Sb precursor ratios (typically, 5:0, 7:1, 4:1, 3:2, 2:3, 1:4, 1:7, and 0:5) were characterized by powder XRD(Figure 1). For comparison, the

2. EXPERIMENTAL SECTION 2.1. Synthesis of (BixSb1−x)2S3 Nanorods. Bismuth chloride (BiCl3, AR), antimony trichloride (SbCl3, AR), sulfur powder (S, 99.95%), oleylamine (OLA, 80−90%, technical grade), dodecylamine (DA, n-C12H25NH2, 98%), DDT (1-C12H25SH, 98%), OT (1C8H17SH, 98%), and BT (1-C4H9SH, 97%) were purchased from Aladdin Chemistry Co. Ltd. All chemicals were used as received without further treatments. In a typical synthetic procedure, 8 mL of OLA, 1 g of DA, and BiCl3 and SbCl3 with different ratios (total amount: 0.5 mmol) were loaded into a three-necked flask. It was heated to 130 °C in an oil bath and kept at this temperature for 30 min under stirring, followed by the swift addition of 3 mmol of S powder (0.096 g). The temperature was increased to 180 °C and the reaction continued for 1 h for the synthesis of (BixSb1−x)2S3 nanorods. For the thiol-passivated (BixSb1−x)2S3 nanorods, the difference in the synthesis is that 2 mL of DDT (BT or OT) was injected into the flask at the time of 10 min before the synthesis is terminated. The products of (BixSb1−x)2S3 nanorods were precipitated by centrifuging, washed with dichloromethane or n-hexane three to four times, and finally dried at 50 °C. 2.2. Characterization. Powder X-ray diffraction (XRD) patterns of the samples were obtained on a D8 ADVANCE diffractometer with graphite-monochromatized Cu Kα radiation (λ = 1.54178 Å, BrukerAXS). The analysis softwares of MDI Jade 6.0 and Pcpdfwin 2.3 were employed to index the XRD data. Transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) images were conducted on a JEM-2100 electron microscope operated at an accelerating voltage of 200 kV. Energy-dispersive X-ray spectroscopy (EDS) line scanning and mapping were carried out on a JEM-2100F microscope equipped with a GENESIS system (EDAX Inc.). UV−visible absorption spectra of powder samples of (BixSb1−x)2S3 nanorods were recorded on Shimadzu UV-2450 spectrophotometers. X-ray

Figure 1. XRD patterns of (BixSb1−x)2S3 samples prepared from different Bi/Sb precursor ratios as labeled in the figure. The standard XRD lines of orthorhombic Bi2S3 (top) and Sb2S3 (bottom) from JCPDS are included for reference.

XRD patterns of pure Bi2S3 and Sb2S3 samples are also shown. All the results are in good agreement with the diffraction pattern for the orthorhombic structure of a space group (SG) Pnma: at the high Bi/Sb precursor ratios (5:0 to 2:3), the XRD patterns of the products are well-indexed to Bi2S3 (a = 11.29 Å, b = 3.978 Å, c = 11.150 Å, JCPDS no. 65-2431), whereas at the low Bi/Sb precursor ratios (1:4 to 0:5), the XRD patterns accord with Sb2S3 (a = 11.30 Å, b = 3.834 Å, c = 11.221 Å, JCPDS no. 65-2434). The increase of Sb with the decrease of Bi in the ternary (BixSb1−x)2S3 solid solution series leads to a transition from Bi2S3 to Sb2S3. For the group VA elements, the Sb3+ ion is isovalent to the 3+ Bi ion but has a smaller ionic radius (0.76 vs 1.03 Å), and consequently, the lattice parameters will gradually decrease with the transition from Bi2S3, (BixSb1−x)2S3 (0 < x < 1) to Sb2S3. 7335


Research Article

ACS Applied Materials & Interfaces

Figure 2. TEM images of (BixSb1−x)2S3 nanorods prepared from different Bi/Sb precursor ratios: (a) 5:0 (Bi2S3), (b) 7:1, (c) 4:1, (d) 3:2, (e) 2:3, (f) 1:4, (g) 1:7, and (h) 0:5 (Sb2S3).

Table 1. Aspect Ratios and Average Lengths/Diameters of (BixSb1−x)2S3 Nanorods (0 < x < 1) Obtained at Different Bi/Sb Precursor Ratios Bi/Sb ratio length × diameter (nm) aspect ratio

7:1 49.1 × 19.3 2.54

4:1 52.3 × 19.6 2.67

3:2 80.1 × 23.7 3.38

2:3 84.0 × 19.7 4.26

1:4 115.5 × 17.5 6.60

1:7 203.8 × 23.9 8.53

formation of ternary (BixSb1−x)2S3 nanorods, through which the aspect ratios (lengths and diameters) can be tuned by Bi/Sb ratios. EDS was further employed to examine the Bi/Sb ratio and distribution of the as-obtained ternary (BixSb1−x)2S3 nanorods. The results of EDS point analyses in Figure 3a clearly reflect the difference in the Bi/Sb contents and ratios of the asprepared ternary nanorods. The measured Bi and Sb contents and their ratios are proportional to the added amounts of Bi/Sb precursors in the synthesis of Bi2S3, (BixSb1−x)2S3 (0 < x < 1) to Sb2S3. Figure 3b,c displays the EDS line scanning results of the

This tendency is detected in our XRD studies. The enlarged XRD parts within the 2θ window of 20−30°, displayed in Figure S1 in the Supporting Information, demonstrate the change of the peak position as the compositions transform. The d-values for the peak (marked with #) of the (112) plane from (BixSb1−x)2S3 gradually decline, ranging from 3.1094 Å (Bi2S3) to 3.0456 Å (Sb2S3). Accordingly, the d-value difference of (112) planes between Bi2S3 and Sb2S3 can be calculated to be 2.05%. This is consistent with the previous reports, which showed that the volumes of orthorhombic unit cells differ by 3.5% at most between Bi2S3 and Sb2S3.1,2 The gradual decrease in the lattice parameters with the Bi/Sb precursor ratios, along with no detection of mixed Bi2S3 and Sb2S3 phases in the XRD results, is indicative of the production of a single phase of solid solution (BixSb1−x)2S3. Figure 2 shows the TEM images of the (BixSb1−x)2S3 products. All the samples exhibit a one-dimensional (1D) rodlike shape. An obvious change in the aspect ratios (length and diameter) is detected with the alternation of Bi/Sb precursor ratios (more images are shown in Figure S2). Uniform Bi2S3 nanorods are produced without adding the Sb precursor (Bi/Sb = 5:0, Figure 2a),31 whereas without the Bi precursor (Bi/Sb = 0:5), sheaflike Sb2S3 nanorod bundles with a relatively large size are obtained (Figure 2h). The sheaflike nanostructures8,24,32,33 are often observed in the V2VI3 (V = Sb, Bi; VI = S, Se) crystals because of the crystal split growth.32,33 Compared to Bi2S3 nanorods, the introduction of Sb ions induces the length reduction and diameter increase of ternary (BixSb1−x)2S3 nanorods (0 < x < 1) (Figure 2a,b), and compared to sheaflike Sb2S3 nanorod bundles, the introduction of Bi produces separate nanorods with a reduced size (Figure 2g,h). For the intermediate ternary (BixSb1−x)2S3 (0 < x < 1) nanorods, however, the length and aspect ratio is increased with the increase of Sb proportion relative to Bi (Figure 2b−g). Such a tendency is summarized in Table 1, which is opposite to the case described in Pradhan’s work.24 These results indicate that a composition-dependent growth characteristic occurs during the

Figure 3. EDS spectra of (BixSb1−x)2S3 nanorods prepared at different Bi/Sb precursor molar ratios as marked in the figures: (a) point analysis and (b,c) line scan. 7336


Research Article


crystal structural characteristics of orthorhombic Bi2S3 and Sb2S3 and prefer to grow into 1D nanostructures, for example, the nanorods. At the same time, it can be predicted that, like the endmembers Bi2S3 and Sb2S3,7,9,31−33 these (BixSb1−x)2S3 (0 < x < 1) solid solution nanorods should possess the crystallographic feature that they grow along the b axis direction ([010]). Our results of HRTEM imaging confirm such a judgment. Figure 5a shows a typical HRTEM image taken on the (BixSb1−x)2S3 nanorods obtained at the Bi/Sb precursor ratio of 4:1, with its corresponding fast Fourier transformation (FFT) pattern shown in Figure 5a1. Clear two-dimensional lattice fringes are observed and the lattice spaces with intervals of 0.395 and 0.194 nm are measured, corresponding to the characteristic interplanar distances of the (202) and (020) planes of orthorhombic (BixSb1−x)2S3, respectively. It can be assigned that the reflection spots of these planes are projected from the [−101] zone axis, as indicated in the FFT pattern (Figure 5a1). For the orthorhombic structure, the crystallographic direction vertical to the (020) plane is the [020] direction, which exactly corresponds to the elongated direction of the (BixSb1−x)2S3 nanorod, thus confirming that this (BixSb1−x)2S3 nanorod is grown along the [020] direction (i.e., [010]). Moreover, the results of HRTEM images and the corresponding FFT patterns recorded on the (BixSb1−x)2S3 nanorods prepared at 3:2, 1:4, and 1:7 Bi/Sb precursor ratios all reveal such a growth feature (Figure 5b−d). Shown in Figure 5b,b1 are the HRTEM image and FFT pattern for the nanorods prepared at the 3:2 Bi/Sb ratio. The assignment demonstrates that the nanorod is oriented with its [001] zone axis vertical to the substrate with the lattice spacings determined to be 0.565 and 0.392 nm, which respectively correspond to that of the (200) and (010) planes of orthorhombic (BixSb1−x)2S3. Obviously, it can be confirmed that this nanorod is grown along the [010] direction. Similarly, the growth direction of ternary (BixSb1−x)2S3 nanorods prepared at 1:4 and 1:7 Bi/Sb ratios is also proved to be the [010] crystallographic orientation, although the corresponding HRTEM images and FFT patterns are recorded from different zone axes (Figure 5c,d). Bi2S3 and Sb2S3 are both important semiconductive materials with the bulk band gap energies of about 1.37,10,31 and 1.7 eV,5,12,34,35 respectively, corresponding to 954 and 775 nm in wavelength. Such suitable band gaps, along with their high absorption coefficient and long-term stability make Bi2S3 and Sb2S3 (stibnite) promising candidates for visible-light-sensitive photodetectors, solar cells (photovoltaics), and photo(electro)catalysts.9−12,24,30,31,34,35 The ternary (BixSb1−x)2S3 solid solutions will resemble the two endmembers Bi2S3 and Sb2S3 in crystal structures and physical properties. The UV−visible absorption spectra of the as-prepared ternary (BixSb1−x)2S3 nanorods were recorded, in which a strong broad-spectrum absorption is present within the wavelength range of 300−900 nm for all the samples (Figure S3). In general, the absorption edge of (BixSb1−x)2S3 nanorods is blue-shifted with the increase of Sb ratio. Such a tendency is in good agreement with the fact that Sb2S3 has a larger band gap than Bi2S3. Consequently, it is expected that the ternary (BixSb1−x)2S3 nanorods should exhibit excellent optoelectronic performance within the visible spectrum in the fields mentioned above, although a composition alternation occurs in (BixSb1−x)2S3. We construct an ITO/(BixSb1−x)2S3/ITO photodetector, like the ITO/Bi2S3/ ITO photodetection device in our previous work,31 to evaluate

(BixSb1−x)2S3 nanorods prepared at 4:1 and 1:4 Bi/Sb precursor ratios. S Kα, Bi Mα, and Sb Lα signals as well as the Bi/Sb relative ratios are evidently detected. Bi has a high content in (BixSb1−x)2S3 nanorods that were prepared at the 4:1 Bi/Sb precursor ratio, whereas Sb has a high content in the products prepared at the 1:4 Bi/Sb precursor ratio. Importantly, the signal intensities of these three elements rise and drop simultaneously along the scanning trajectories, indicating a uniform distribution of S, Bi, and Sb in (BixSb1−x)2S3 nanorods.25 Furthermore, EDS mapping analyses were also conducted to probe the elemental distribution and variation of nanorods. Figure 4 presents the results of bight-

Figure 4. Bight- and dark-field TEM images and EDS mappings of Sb, Bi, and S elements of (BixSb1−x)2S3 nanorods prepared at the Bi/Sb precursor ratios of (a,b) 4:1 and (c,d) 3:2.

and dark-field TEM images and EDS mappings of Sb, Bi, and S elements of (BixSb1−x)2S3 nanorods prepared at 4:1 and 2:3 Bi/ Sb precursor ratios. Despite that the signal of Sb is weak in the sample prepared at the 4:1 Bi/Sb ratio (Figure 4b), all the elemental distribution mappings are well-consistent with the profiles of nanorods, demonstrating a uniform, homogeneous distribution of these elements. These EDS characterizations confirm the formation of pure, single phase of ternary solid solutioned (BixSb1−x)2S3 nanorods, rather than the phaseseparate core−shell or dimer structure. As is known, the orthorhombic structure (SG: Pnma) of both Bi2S3 and Sb2S3 consist of the specific 1D ribbonlike [V4S6]n (V = Bi, Sb) polymers (see Figure 7 below), which are formed through strong V−S covalent bonds and extend along the b axis direction (defined as the short axis, [010]) but are linked with each other by intermolecular van der Waals force between V and S atoms in the a and c axis directions.4,5,7,9,26−28,31−33 It has been shown that such a highly anisotropic ribbonlike structure enables Bi2S3 and Sb2S3 nanoscale crystals to preferentially grow into 1D nanostructures along the [V4S6]n extending direction.7,9,31−33 The ternary (BixSb1−x)2S3 solid solutions are formed by means of the isostructural cation replacement between Bi and Sb ions.1,2,24,30 Therefore, they retain the 7337


Research Article


Figure 5. HRTEM images and their corresponding FFT patterns recorded on the (SbxBi1−x)2S3 nanorods prepared at different Sb/Bi precursor ratios: (a,a1) 4:1, (b,b1) 3:2, (c,c1) 1:4, and (d,d1) 1:7.

which are expected to offer reactive ligand atoms (S) to coordinate to unsaturated Sb ions at the nanorod surface and accordingly reduce S vacancies and the number of surface recombination centers (trapped states). As a result, the thiol-passivated ternary (BixSb1−x)2S3 (0 < x < 1) nanorods exhibit an obviously enhanced photoelectric responsive performance and a composition-dependent photoconductivity, while keeping their shape and structure unchanged compared with their unpassivated counterparts (see XRD and TEM results shown in Figures S4 and S5). Figure 6a presents the I−V curves measured for the samples prepared at 4:1 Bi/Sb ratio. The unpassivated nanorods show a low electric conductivity and a very weak increase in the photocurrent when exposed to light, and especially, their I−t curves were not detectable. As compared, a large enhancement in the photocurrent is detected in all of the passivated (BixSb1−x)2S3 nanorods by different thiols (Figure 6a). At the same time, these thiol-passivated nanorods are highly responsive to the white light and the visible light of specific wavelengths (blue: 450 nm, green: 550 nm, and red: 650 nm), exhibiting superior photoresponsive repeatability and stability with the light on/off, as measured in the I−t curves (Figure 6b,c). Similarly, the photocurrent improvement is determined in the thiol-passivated (BixSb1−x)2S3 nanorods obtained at other Bi/Sb ratios (7:1, 3:2, 2:3, and 1:4, Figure 6d) while their unpassivated counterparts show poor photoconductivity (not shown). As shown in Figure 6e,f, a promising photoelectric responsive capability and stability is readily present in the OTpassivated (BixSb1−x)2S3 nanorods that were prepared at the 1:4 Bi/Sb precursor ratio, as exposed to the white light or visible light of specific wavelengths. On the basis of a number of repeated control experiments, we notice that the photoconductivity of DDT-passivated (BixSb1−x)2S3 nanorods is statistically downgraded with the increase of Sb content based on the difference in photocurrent intensity (Figure 6d). For example, the photocurrent of (BixSb1−x)2S3 nanorods prepared at the 4:1 Bi/Sb ratio is measured to be higher than

the optoelectronic effect of the as-obtained ternary (BixSb1−x)2S3 nanorods. Compared to the ITO/Bi2S3/ITO device,31 however, it is found that the ITO/(BixSb1−x)2S3/ITO (0 < x < 1) and ITO/Sb2S3/ITO photodetectors are not sensitive to the simulated sunlight (white) or the visible light of specific wavelengths (450, 550, and 650 nm): the enhancement of photocurrent is not obvious in the I−V curves and the timedependent photocurrent (I−t curves) change cannot be detected with the light on/off. A similar case was reported by Ito et al., in which the introduction of Bi into Sb2S3 (Bi-doping Sb2S3) resulted in photocurrent deterioration for the Sb2S3 extremely thin absorber solar cells.36 The associated reasons and how to improve the optoelectronic activity of ternary (BixSb1−x)2S3 are required to be explored. Theoretically, there are some factors that suppress the photogenerated carriers (electron/hole) separation and transport, which reduce the photoconductivity (photocurrent), for example, (i) the absence of suitable electron or hole conduction agents that couple with the active materials (absorbers or sensitizers);9−12,24,37−39 (ii) the large recombination loss of photoexcited electrons and holes due to the existence of surface trapped states;12,38−41 and (iii) the surface or interface barrier induced by surfactants or boundaries.41−46 Some of recent studies revealed that S vacancies at the surface of Sb2S3 often act as recombination centers (trapped states) and lead to the photocurrent and power conversion efficiency deterioration for Sb2S3-sensitized solar cells.12,39,40,47 To improve the solar cell performance, a surface sulfurization process was introduced to minimize or even eliminate S vacancies through the chemical binding of external S atoms with surface unsaturated Sb ions.39,40 On the other hand, organic thiol (L−SH), such as DDT, was found to have a highly active S atom to form coordination bonds (S−M bonds) or metal sulfides with metal ions at elevated temperatures.48,49 These studies inspire us to improve the photoconductivity (photocurrent) of ternary (BixSb1−x)2S3 (0 < x < 1) nanorods through the surface passivation of organic thiols, including DDT, OT, and BT, 7338


Research Article


Figure 6. (a) I−V curves of unpassivated and thiol-passivated (BixSb1−x)2S3 nanorods prepared at the 4:1 Bi/Sb ratio. (b,c) I−t curves of DDTpassivated (BixSb1−x)2S3 nanorods prepared at the 4:1 Bi/Sb ratio under the on/off illumination of white light and visible light of different wavelengths. (d) I−V curves of DDT-passivated (BixSb1−x)2S3 nanorods prepared at different Bi/Sb ratios as labeled in the figure. (e,f) I−V and I−t curves of OT-passivated (BixSb1−x)2S3 nanorods prepared at the Bi/Sb ratio of 1:4. All the I−t curves were recorded at an applied bias of 1 V.

Figure 7. Schematic illustration: (a,b) crystal structure of orthorhombic (BixSb1−x)2S3 viewed from the [010] and [001] directions, respectively; (c) thiol passivation process of the (BixSb1−x)2S3 (100) surface. Brown circles in panel (c) denote S vacancies (VS).

(BixSb1−x)2S3 nanorods prepared at the 1:7 Bi/Sb ratio do not display the measurable photocurrent enhancement under the light irradiation in our experiments.

that of the nanorods prepared at the 1:4 Bi/Sb ratio by 1−2 orders of magnitude (Figure 6c−f); the DDT-passivated Sb2S3 sheaflike nanostructures as well as the DDT-passivated 7339


Research Article


conductivity. A similar case is reported for the Sb2S3 film serving as absorber layers in Sb2S3-sensitized solar cells.12,40 It was also found that Sb2S3 is easy to be oxidized during the Raman spectrum collection even using a low intensity of laser illumination in a short time.50 In our work, XPS spectra were collected for the characterization of surface oxidation of thiolpassivated (BixSb1−x)2S3 nanorods typically prepared at 4:1 and 1:4 Bi/Sb precursor ratios. As shown in Figure 8a, the pair

Undoubtedly, the thiol passivation improves the photoconductivity of ternary (BixSb1−x)2S3 (0 < x < 1) nanorods in the ITO/(BixSb1−x)2S3/ITO optoelectronic device. The main reason can be ascribed to the fact that such a passivation process is able to minimize the dangling bonds and the surface recombination centers through the coordination binding of S atoms with surface unsaturated Sb atoms.39,40 Figure 7 illustrates the crystal structure and thiol passivation mechanism of (BixSb1−x)2S3 nanorods. Because the growth direction of the as-obtained nanorods ([010], as confirmed in Figure 5) is the extending direction of ribbonlike [V4S6]n (V = Bi, Sb) polymers (Figure 7a,b), the surface of (BixSb1−x)2S3 nanorods can be simply seen as the surface of 1D ribbonlike [V4S6]n (V = Bi, Sb) building blocks (Figure 7b). On the basis of structural and growth characteristics revealed by HRTEM images and structural models (Figures 5 and 7a,b), it is known that the exposed surfaces of (BixSb1−x)2S3 nanorods are mainly the (100), (101), (201), and (001) facets. Figure 7c demonstrates the atomic configuration evolution at the (100) face of orthorhombic (BixSb1−x)2S3 before and after thiol passivation. Like Sb2S3,39,40,47 the unsaturated, dangling bonds are present because of the breakage of Sb−S (major) and Bi−S (minor) covalent bonds, resulting in the presence of S vacancies at the surface of (BixSb1−x)2S3 nanorods (Figure 7c, marked with brown circles). S vacancies introduces defect states as recombination centers and thus suppresses the separation and transport of charged carriers and the (photo)conductivity of (BixSb1−x)2S3 nanorods. As illustrated in Figure 7c, the addition of thiols (DDT, OT, or BT = L−SH) can either release free S atoms (pink balls) or take advantage of L−S− groups (red balls) to form the coordination bonds with surface unsaturated Sb atoms, which is able to decrease the number of S vacancies and therefore reduce the surface trapped states or recombination centers for photogenerated electrons and holes. At the same time, it is considered that the thiol passivation can also decrease the amount of surfactants absorbed on the surface of nanorods, because of the relatively strong binding ability of S atoms in comparison with N atoms from OLA and DA. The decrease of the amount of surfactants will increase the mobility of carriers on the surface of nanomaterials and across grain boundaries.43−46 As such, the thiol passivation leads to the obvious improvement in photoconductivity and optical responsive capability of (BixSb1−x)2S3 nanorods. It is considered that there are two main factors, that is, the increased S vacancies and surface oxidation, that contribute to the composition-dependent photoconductivity in thiol-passivated (BixSb1−x)2S3 nanorods (0 < x < 1). On one hand, with the increase of Sb proportion in (BixSb1−x)2S3, the number of exposed, unsaturated Sb atoms increases at the nanorod surface. Therefore, an increased part of S vacancies and the surface trapped states (recombination centers) caused by unsaturated Sb atoms cannot be eliminated during the thiol passivation process in our experiments. This may be one reason that can explain why the thiol-passivated (BixSb1−x)2S3 nanorods with high Sb contents (those prepared at 1:7 Bi/Sb and pure Sb2S3) do not exhibit a satisfied photoconductivity enhancement. On the other hand, ternary (BixSb1−x)2S3 nanorods with high Sb contents are easier to be oxidized. All of the as-obtained (BixSb1−x)2S3 nanorods possess rather small sizes (ranging 10− 30 nm in diameter and 30−250 nm in length, see Figure 2) and have high surface area-to-volume ratios. Thus, these nanorods are sensitive to oxygen and easy to be oxidized as exposed to air. The surface oxidation probably induces the deterioration of

Figure 8. (a) Bi 4f and (b,c) Sb 3d high-resolution XPS spectra of (BixSb1−x)2S3 nanorods prepared at 4:1 and 1:4 Bi/Sb precursor ratios with/without DDT-passivation as labeled in the figure.

peaks with binding energies of 158.0 and 163.3 eV, corresponding to trivalent Bi 4f7/2 and Bi 4f5/2 in bismuth chalcogenides,7,51,52 are detected for two samples. Bi 4f peaks exhibit a highly symmetric profile, which can preclude the existence of trivalent Bi from Bi2O3 or other oxides. In contrast, the high-resolution XPS spectra for Sb 3d core levels show a detectable shoulder peak neighboring the major peak (Figure 8b,c), revealing the coexistence of Sb2O3 (Sb 3d5/2: 530.1 eV and 3d3/2: 539.7 eV) and Sb2S3 (Sb 3d5/2: 529.2 eV and 3d3/2: 538.5 eV).12,40 The difference in the XPS peak intensities further demonstrates that the thiol-passivated (BixSb1−x)2S3 nanorods prepared at 4:1 Bi/Sb has less Sb2O3 than those prepared at 1:4 Bi/Sb (Figure 8b,c). Such a result indicates that Sb−S bonds (or Sb2S3) are more easily oxidized than Bi−S 7340


Research Article


(BixSb1−x)2S3 nanorods that were prepared at low Bi/Sb precursor ratios (Bi/Sb = 1:7 and pure Sb2 S3 ). The conductivity deterioration is correlated with the increased number of S vacancies that cannot be eliminated by thiol passivation as well as to the surface oxidation arising from the higher Sb content. Our work offers an effective strategy and thought for improving the photoconductivity and optoelectronic response of semiconductive nanomaterials. We believe that this work will inspire more concerns and insightful efforts on the tunable synthesis, surface engineering, and optoelectronic performance of V2VI3 (V = Sb, Bi; VI = S, Se) binary and ternary materials.

bonds (or Bi2S3) and accordingly that the increase of Sb content results in more Sb 2 O 3 . More Sb 2 O 3 induces conductivity deterioration and will contribute to the phenomenon that the photoconductivity of (BixSb1−x)2S3 nanorods is dependent on the content of Sb. In comparison with the unpassivated nanorods, the XPS studies also reveal that the content and ratio of Sb from Sb2O3 increases in the thiol-passivated (BixSb1−x)2S3 nanorods (Figure 8b,c), that is, from 13.6 to 48.3% and 19.8 to 23.3% for the both samples obtained at 1:4 and 4:1 Bi/Sb precursor ratios, respectively. This provides a hint for that the amount of surfactants absorbed on the surface of nanorods is declined after the thiol passivation, which leads to more oxide but facilitates the charge transport of photoelectronic devices. Though the passivated (BixSb1−x)2S3 nanorods are relatively easily oxidized, the enhancement function of thiol passivation in the improvement of photoconductivity overwhelms the deterioration effect of the oxidation process. In general, the thiol passivation results in an enhanced optical responsive ability and a composition-related photoconductivity in ternary (BixSb1−x)2S3 nanorods. Finally, the enhanced photoconductive gain and optoelectronic response in thiol-passivated (BixSb1−x)2S3 nanorods are considered to originate from the oxygen-related shallow-level hole-trap conduction mechanism. This mechanism has been widely adopted for photoconductors and photodetectors made of nanoscale metal oxides (e.g., ZnO)53−56 or metal chalcogenides (e.g., CdS, Sb2S3, and Bi2S3),7,9,31,54 in which the oxygen adsorption and desorption on the surfaces of nanomaterials plays a key role. In brief, the absorbed O2 molecules on the surface of (BixSb1−x)2S3 nanorods can capture the free electrons from (BixSb1−x)2S3 to generate oxygen ions O2− (O2(g) + e− → O2−(ad)). Upon exposure to the light with photon energy larger than the band gap, the electron−hole pairs are created (hν → e− + h+). The photogenerated holes migrate to the nanorod surface and discharge the adsorbed oxygen ions by surface e−h recombination (h+ + O2−(ad) → O2(g)), wherein oxygen is photodesorbed from the surface of nanorods. Such a process traps the photoexcited holes and delays the photoexcited e−h recombination, leading to the release of free electrons and the enhanced photocurrent in the external circuit. The O2 adsorption/desorption is highly repeatable on the nanorod surfaces, which endows (BixSb1−x)2S3 nanorods with good photoelectronic responsive capability to follow the fast switch of light. In the XPS spectra, an increased amount of surface oxidation and oxygen species57 (binding energy of O 1s at 530.6−531.2 eV, cyan lines in Figure 8b,c) is supportive of the oxygen-related hole-trap conduction process for the thiol-passivated (BixSb1‑x)2S3 nanorods.

■

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsami.7b17253. Enlarged XRD patterns within the 2θ window of 20−30°, additional TEM images, and UV−visible absorption spectra of (BixSb1−x)2S3 nanorods prepared at different Bi/Sb precursor ratios; XRD patterns and TEM images of thiol-passivated (BixSb1−x)2S3 nanorods prepared at 4:1 and 1:4 Bi/Sb ratios (PDF)

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected], [email protected]. ORCID

Junli Wang: 0000-0002-3775-539X Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This work was supported by the NSFC (21571086 and 21201086), the China Postdoctoral Science Foundation (2014M550267 and 2015T80501), the Natural Science Foundation of Jiangsu Province (BK20141297), and the Cultivating Project of Young Academic Leader and the Research Foundation of Jiangsu University (11JDG071).

■

REFERENCES

(1) Springer, G.; Laflamme, J. H. G. The System Bi2S3-Sb2S3. Can. Mineral. 1971, 10, 847−853. (2) Kyono, A.; Kimata, M. Structural Variations Induced by Difference of the Inert Pair Effect in the Stibnite-Bismuthinite Solid Solution Series (Sb,Bi)2S3. Am. Mineral. 2004, 89, 932−940. (3) Liu, J.; Liu, J.; Li, J.; Xie, H.; Wang, J.; Deng, J.; Feng, C.; Qi, F.; Zhang, N. Experimental Synthesis of the Stibnite-Antimonselite Solid Solution Series. Int. Geol. Rev. 2008, 50, 163−176. (4) Caruso, F.; Filip, M. R.; Giustino, F. Excitons in OneDimensional van der Waals Materials: Sb2S3 Nanoribbons. Phys. Rev. B: Condens. Matter Mater. Phys. 2015, 92, 125−134. (5) Carey, J. J.; Allen, J. P.; Scanlon, D. O.; Watson, G. W. The Electronic Structure of the Antimony Chalcogenide Series: Prospects for Optoelectronic Applications. J. Solid State Chem. 2014, 213, 116− 125. (6) Huang, R.; Zhang, J.; Wei, F.; Shi, L.; Kong, T.; Cheng, G. Ultrahigh Responsivity of Ternary Sb-Bi-Se Nanowire Photodetectors. Adv. Funct. Mater. 2014, 24, 3581−3586. (7) Chen, G.; Yu, Y.; Zheng, K.; Ding, T.; Wang, W.; Jiang, Y.; Yang, Q. Fabrication of Ultrathin Bi2S3 Nanosheets for High-Performance, Flexible, Visible−NIR Photodetectors. Small 2015, 11, 2848−2855.

4. CONCLUSIONS In summary, ternary (BixSb1−x)2S3 nanorods with tunable aspect ratios and Bi/Sb ratios have been prepared through a simple colloidal synthetic route in the mixed long-chain alkylamines. The aspect ratio is generally increased with the increase of Sb content. As measured in the ITO/(BixSb1−x)2S3/ ITO photoelectronic devices, the photoconductivity and optoelectronic responsiveness of the as-prepared (BixSb1−x)2S3 nanorods are boosted by the surface passivation of thiols, which is considered to minimize the S vacancies (recombination centers or trapped states) and therefore enhance the carrier transport. Meanwhile, it is found that the increase of Sb ratio results in damping of photoconductivity of thiol-passivated 7341


Research Article


(26) Caracas, R.; Gonze, X. First-Principles Study of the Electronic Properties of A2B3 Minerals, with A=Bi,Sb and B=S, Se. Phys. Chem. Miner. 2005, 32, 295−300. (27) Filip, M. R.; Patrick, C. E.; Giustino, F. GW Quasiparticle Band Structures of Stibnite, Antimonselite, Bismuthinite, and Guanajuatite. Phys. Rev. B: Condens. Matter Mater. Phys. 2013, 87, 205125. (28) Tumelero, M. A.; Faccio, R.; Pasa, A. A. Unraveling the Native Conduction of Trichalcogenides and Its Ideal Band Alignment for New Photovoltaic Interfaces. J. Phys. Chem. C 2016, 120, 1390−1399. (29) Nayak, B. B.; Acharya, H. N.; Mitra, G. B.; Mathur, B. K. Structural Characterization of Bi2−xSbxS3 Films Prepared by the DipDry Method. Thin Solid Films 1983, 105, 17−24. (30) Rajalakshmi, P. U.; Oommen, R.; Sanjeeviraja, C. Improved Photoelectrochemical Performance of (Bi1−xSbx)2S3 Photoanodes. Thin Solid Films 2013, 531, 76−80. (31) Yu, H.; Wang, J.; Wang, T.; Yu, H.; Yang, J.; Liu, G.; Qiao, G.; Yang, Q.; Cheng, X. Scalable Colloidal Synthesis of Uniform Bi2S3 Nanorods as Sensitive Materials for Visible-Light Photodetectors. CrystEngComm 2017, 19, 727−733. (32) Tang, J.; Alivisatos, A. P. Crystal Splitting in the Growth of Bi2S3. Nano Lett. 2006, 6, 2701−2706. (33) Chen, G.-Y.; Dneg, B.; Cai, G.-B.; Zhang, T.-K.; Dong, W.-F.; Zhang, W.-X.; Xu, A.-W. The Fractal Splitting Growth of Sb2S3 and Sb2Se3 Hierarchical Nanostructures. J. Phys. Chem. C 2008, 112, 672− 679. (34) Zhong, M.; Wang, X.; Liu, S.; Li, B.; Huang, L.; Cui, Y.; Li, J.; Wei, Z. High-Performance Photodetectors Based on Sb2S3 Nanowires: Wavelength Dependence and Wide Temperature Range Utilization. Nanoscale 2017, 9, 12364−12371. (35) Wang, X.; Li, J.; Liu, W.; Yang, S.; Zhu, C.; Chen, T. A Fast Chemical Approach Towards Sb2S3 Film with a Large Grain Size for High-Performance Planar Heterojunction Solar Cells. Nanoscale 2017, 9, 3386−3390. (36) Ito, S.; Tsujimoto, K.; Nguyen, D.-C.; Manabe, K.; Nishino, H. Doping Effects in Sb2S3 Absorber for Full-Inorganic Printed Solar Cells with 5.7% Conversion Efficiency. Int. J. Hydrogen Energy 2013, 38, 16749−16754. (37) Bera, A.; Mahapatra, A. D.; Mondal, S.; Basak, D. Sb2S3/SpiroOMeTAD Inorganic−Organic Hybrid p−n Junction Diode for High Performance Self-Powered Photodetector. ACS Appl. Mater. Interfaces 2016, 8, 34506−34512. (38) Boix, P. P.; Larramona, G.; Jacob, A.; Delatouche, B.; MoraSeró, I.; Bisquert, J. Hole Transport and Recombination in All-Solid Sb2S3-Sensitized TiO2 Solar Cells Using CuSCN As Hole Transporter. J. Phys. Chem. C 2012, 116, 1579−1587. (39) Im, S. H.; Lim, C.-S.; Chang, J. A.; Lee, Y. H.; Maiti, N.; Kim, H.-J.; Nazeeruddin, M. K.; Grätzel, M.; Seok, S. I. Toward Interaction of Sensitizer and Functional Moieties in Hole-Transporting Materials for Efficient Semiconductor-Sensitized Solar Cells. Nano Lett. 2011, 11, 4789−4793. (40) Choi, Y. C.; Lee, D. U.; Noh, J. H.; Kim, E. K.; Seok, S. I. Highly Improved Sb2S3 Sensitized-Inorganic−Organic Heterojunction Solar Cells and Quantification of Traps by Deep-Level Transient Spectroscopy. Adv. Funct. Mater. 2014, 24, 3587−3592. (41) Zhou, Y.; Wang, L.; Chen, S.; Qin, S.; Liu, X.; Chen, J.; Xue, D.J.; Luo, M.; Cao, Y.; Cheng, Y.; Sargent, E. H.; Tang, J. Thin-Film Sb2Se3 Photovoltaics with Oriented One-Dimensional Ribbons and Benign Grain Boundaries. Nat. Photonics 2015, 9, 409−415. (42) Moseley, J.; Metzger, W. K.; Moutinho, H. R.; Paudel, N.; Guthrey, H. L.; Yan, Y.; Ahrenkiel, R. K.; Al-Jassim, M. M. Recombination by Grain-Boundary Type in CdTe. J. Appl. Phys. 2015, 118, 025702. (43) Crisp, R. W.; Callahan, R.; Reid, O. G.; Dolzhnikov, D. S.; Talapin, D. V.; Rumbles, G.; Luther, J. M.; Kopidakis, N. Photoconductivity of CdTe Nanocrystal-Based Thin Films: Te2− Ligands Lead to Charge Carrier Diffusion Lengths Over 2 μm. J. Phys. Chem. Lett. 2015, 6, 4815−4821. (44) Boles, M. A.; Ling, D.; Hyeon, T.; Talapin, D. V. The Surface Science of Nanocrystals. Nat. Mater. 2016, 15, 141−153.

(8) Chen, G.; Wang, W.; Wang, C.; Ding, T.; Yang, Q. Controlled Synthesis of Ultrathin Sb2Se3 Nanowires and Application for Flexible Photodetectors. Adv. Sci. 2015, 2, 1500109. (9) Zhang, K.; Luo, T.; Chen, H.; Lou, Z.; Shen, G. AuNanoparticles-Decorated Sb2S3 Nanowire-based Flexible Ultraviolet/ Visible Photodetectors. J. Mater. Chem. C 2017, 5, 3330−3335. (10) Martinez, L.; Bernechea, M.; de Arquer, F. P. G.; Konstantatos, G. Near IR-Sensitive, Non-toxic, Polymer/Nanocrystal Solar Cells Employing Bi2S3 as the Electron Acceptor. Adv. Energy Mater. 2011, 1, 1029−1035. (11) Christians, J. A.; Kamat, P. V. Trap and Transfer. Two-Step Hole Injection Across the Sb2S3/CuSCN Interface in Solid-State Solar Cells. ACS Nano 2013, 7, 7967−7974. (12) Gödel, K. C.; Choi, Y. C.; Roose, B.; Sadhanala, A.; Snaith, H. J.; Seok, S. I.; Steiner, U.; Pathak, S. K. Efficient Room Temperature Aqueous Sb2S3 Synthesis for Inorganic−organic Sensitized Solar Cells with 5.1% Efficiencies. Chem. Commun. 2015, 51, 8640−8643. (13) Wang, L.; Li, D.-B.; Li, K.; Chen, C.; Deng, H.-X.; Gao, L.; Zhao, Y.; Jiang, F.; Li, L.; Huang, F.; He, Y.; Song, H.; Niu, G.; Tang, J. Stable 6%-Efficient Sb2Se3 Solar Cells with a ZnO Buffer Layer. Nat. Energy 2017, 2, 17046. (14) Yu, D. Y. W.; Prikhodchenko, P. V.; Mason, C. W.; Batabyal, S. K.; Gun, J.; Sladkevich, S.; Medvedev, A. G.; Lev, O. High-capacity Antimony Sulphide Nanoparticle-Decorated Graphene Composite as Anode for Sodium-ion Batteries. Nat. Commun. 2013, 4, 2922. (15) Xiong, X.; Wang, G.; Lin, Y.; Wang, Y.; Ou, X.; Zheng, F.; Yang, C.; Wang, J.-H.; Liu, M. Enhancing Sodium Ion Battery Performance by Strongly Binding Nanostructured Sb2S3 on Sulfur-Doped Graphene Sheets. ACS Nano 2016, 10, 10953−10959. (16) Yao, S.; Cui, J.; Lu, Z.; Xu, Z.-L.; Qin, L.; Huang, J.; Sadighi, Z.; Ciucci, F.; Kim, J.-K. Unveiling the Unique Phase Transformation Behavior and Sodiation Kinetics of 1D van der Waals Sb2S3 Anodes for Sodium Ion Batteries. Adv. Energy Mater. 2017, 8, 1602149. (17) Luo, W.; Calas, A.; Tang, C.; Li, F.; Zhou, L.; Mai, L. Ultralong Sb2Se3 Nanowire-Based Free-Standing Membrane Anode for Lithium/ Sodium Ion Batteries. ACS Appl. Mater. Interfaces 2016, 8, 35219− 35226. (18) Liufu, S.-C.; Chen, L.-D.; Yao, Q.; Wang, C.-F. Assembly of One-Dimensional Nanorods into Bi2S3 Films with Enhanced Thermoelectric Transport Properties. Appl. Phys. Lett. 2007, 90, 112106. (19) Liu, W.; Guo, C. F.; Yao, M.; Lan, Y.; Zhang, H.; Zhang, Q.; Chen, S.; Opeil, C. P.; Ren, Z. Bi2S3 Nanonetwork as Precursor for Improved Thermoelectric Performance. Nano Energy 2014, 4, 113− 122. (20) Chen, B.; Uher, C.; Iordanidis, L.; Kanatzidis, M. G. Transport Properties of Bi2S3 and the Ternary Bismuth Sulfides KBi6.33S10 and K2Bi8S13. Chem. Mater. 1997, 9, 1655−1658. (21) Hor, Y. S.; Williams, A. J.; Checkelsky, J. G.; Roushan, P.; Seo, J.; Xu, Q.; Zandbergen, H. W.; Yazdani, A.; Ong, N. P.; Cava, R. J. Superconductivity in CuxBi2Se3 and its Implications for Pairing in the Undoped Topological Insulator. Phys. Rev. Lett. 2010, 104, 057001. (22) Shang, M.-H.; Zhang, J.; Wei, S.; Zhu, Y.; Wang, L.; Hou, H.; Wu, Y.; Fujikawa, T.; Ueno, N. Bi-Doped Sb2S3 for Low Effective Mass and Optimized Optical Properties. J. Mater. Chem. C 2016, 4, 5081− 5090. (23) Deng, Z.; Mansuripur, M.; Muscat, A. J. Simple Colloidal Synthesis of Single-Crystal Sb−Se−S Nanotubes with Composition Dependent Band-Gap Energy in the Near-Infrared. Nano Lett. 2009, 9, 2015−2020. (24) Patra, B. K.; Khilari, S.; Bera, A.; Mehetor, S. K.; Pradhan, D.; Pradhan, N. Chemically Filled and Au-Coupled BiSbS3 Nanorod Heterostructures for Photoelectrocatalysis. Chem. Mater. 2017, 29, 1116−1126. (25) Zhao, Y.; Manthiram, A. Bi0.94Sb1.06S3 Nanorod Cluster Anodes for Sodium-Ion Batteries: Enhanced Reversibility by the Synergistic Effect of the Bi2S3−Sb2S3 Solid Solution. Chem. Mater. 2015, 27, 6139−6145. 7342


Research Article

ACS Applied Materials & Interfaces (45) Dolzhnikov, D. S.; Zhang, H.; Jang, J.; Son, J. S.; Panthani, M. G.; Shibata, T.; Chattopadhyay, S.; Talapin, D. V. CompositionMatched Molecular “Solders” for Semiconductors. Science 2015, 347, 425−428. (46) Zhang, H.; Son, J. S.; Dolzhnikov, D. S.; Filatov, A. S.; Hazarika, A.; Wang, Y. Y.; Hudson, M. H.; Sun, C.-J.; Chattopadhyay, S.; Talapin, D. V. Soluble Lead and Bismuth Chalcogenidometallates: Versatile Solders for Thermoelectric Materials. Chem. Mater. 2017, 29, 6396−6404. (47) Yuan, S.; Deng, H.; Yang, X.; Hu, C.; Khan, J.; Ye, W.; Tang, J.; Song, H. Postsurface Selenization for High Performance Sb2S3 Planar Thin Film Solar Cells. ACS Photonics 2017, 4, 2862−2870. (48) Zhuang, Z.; Lu, X.; Peng, Q.; Li, Y. A Facile “DispersionDecomposition” Route to Metal Sulfide Nanocrystals. Chem.Eur. J. 2011, 17, 10445−10452. (49) Nørby, P.; Johnsen, S.; Iversen, B. B. In Situ X-ray Diffraction Study of the Formation, Growth, and Phase Transition of Colloidal Cu2−xS Nanocrystals. ACS Nano 2014, 8, 4295−4303. (50) Makreski, P.; Petruševski, G.; Ugarković, S.; Jovanovski, G. Laser-Induced Transformation of Stibnite (Sb2S3) and Other structurally Related Salts. Vib. Spectrosc. 2013, 68, 177−182. (51) Xiao, C.; Xu, J.; Cao, B.; Li, K.; Kong, M.; Xie, Y. SolidSolutioned Homojunction Nanoplates with Disordered Lattice: A Promising Approach toward “Phonon Glass Electron Crystal” Thermoelectric Materials. J. Am. Chem. Soc. 2012, 134, 7971−7977. (52) Rahman, A. A.; Huang, R.; Whittaker-Brooks, L. Distinctive Extrinsic Atom Effects on the Structural, Optical, and Electronic Properties of Bi2S3‑xSex Solid Solutions. Chem. Mater. 2016, 28, 6544− 6552. (53) Soci, C.; Zhang, A.; Xiang, B.; Dayeh, S. A.; Aplin, D. P. R.; Park, J.; Bao, X. Y.; Lo, Y. H.; Wang, D. ZnO Nanowire UV Photodetectors with High Internal Gain. Nano Lett. 2007, 7, 1003− 1007. (54) Zhai, T.; Li, L.; Wang, X.; Fang, X.; Bando, Y.; Golberg, D. Recent Developments in One-Dimensional Inorganic Nanostructures for Photodetectors. Adv. Funct. Mater. 2010, 20, 4233−4248. (55) Bayan, S.; Mohanta, D. ZnO nanorod-based UV photodetection and the role of persistent photoconductivity. Philos. Mag. 2012, 92, 3909−3919. (56) Ji, L. W.; Peng, S. M.; Su, Y. K.; Young, S. J.; Wu, C. Z.; Cheng, W. B. Ultraviolet photodetectors based on selectively grown ZnO nanorod arrays. Appl. Phys. Lett. 2009, 94, 203106. (57) Sutthiumporn, K.; Kawi, S. Promotional Effect of Alkaline Earth over Ni−La2O3 Catalyst for CO2 Reforming of CH4: Role of Surface Oxygen Species on H2 Production and Carbon Suppression. Int. J. Hydrogen Energy 2011, 36, 14435−14446.

7343


2S3 Nanorods - ACS Publications - American Chemical Society

Recommend Documents