Localized Surface Plasmon Resonances in Plasmonic Molybdenum

Subscriber access provided by University of Virginia Libraries & VIVA (Virtual Library of Virginia)

Article

Localized Surface Plasmon Resonances in Plasmonic Molybdenum Tungsten Oxide Hybrid for Visible-Light-Enhanced Catalytic Reaction Haibo Yin, Yasutaka Kuwahara, Kohsuke Mori, Hefeng Cheng, Meicheng Wen, Yuning Huo, and Hiromi Yamashita J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.7b08403 • Publication Date (Web): 02 Oct 2017 Downloaded from http://pubs.acs.org on October 2, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

The Journal of Physical Chemistry C is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

The Journal of Physical Chemistry

Localized Surface Plasmon Resonances in Plasmonic Molybdenum Tungsten Oxide Hybrid for Visible-Light-Enhanced Catalytic Reaction Haibo Yin,† Yasutaka Kuwahara,†,‡ Kohsuke Mori,†,‡,§ Hefeng Cheng,† Meicheng Wen,† Yuning Huo,¥ and Hiromi Yamashita†,‡,* †

Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871,

Japan ‡

Unit of Elements Strategy Initiative for Catalysts & Batteries, Kyoto University, Kyoto 615-

8520, Japan §

JST, PRESTO, 4-1-8 HonCho, Kawaguchi, Saitama 332-0012, Japan

¥

Shanghai Key Laboratory of Rare Earth Functional Materials, Shanghai Normal University,

Shanghai 200234, China Corresponding Author *Hiromi Yamashita [email protected]

ACS Paragon Plus Environment

1


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 34

ABSTRACT: A well-crystallized plasmonic MoxW1-xO3-y hybrid was obtained by a nonaqueous method. Detailed characterization by means of XRD, TEM, Raman, UV-Vis, N2 physisorption, and XPS measurements revealed that the synthesized plasmonic MoxW1-xO3-y hybrid showed strong localized surface plasmon resonance (LSPRs). It was demonstrated that such strong LSPRs was generated from crystal vacancies, mainly including mutual doping vacancies of molybdenum ions and tungsten ions and oxygen vacancies. More importantly, the LSPR absorption intensity of MoxW1-xO3-y was almost 20, 16, and 8 times larger than that of assynthesized MoO3-x, WO3-x, and our previously reported MoO3-x nanosheets (NS), respectively. To the best of our knowledge, such materials exhibiting strong LSPR absorption intensity have never been reported elsewhere. We also demonstrated that such plasmonic MoxW1-xO3-y could be used as a highly efficient catalyst that dramatically enhanced the dehydrogenation activity from ammonia borane (NH3BH3; AB) under visible light irradiation.


2

Page 3 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


INTRODUCTION Since the pioneering work of Zhao et al. in 2009 demonstrated that copper sulfide (Cu2-xS) nanocrystals (NCs) show localized surface plasmon resonances (LSPRs) in the near infrared, plasmonic properties of doped semiconductor NCs have been studied extensively.1-10 Essentially any semiconductor NC with appreciable free carrier concentrations can support LSPRs, which has been demonstrated by Luther et al.8 LSPRs from the visible through the terahertz can be achieved by modifying the size and doping level of the nanostructure.8 Strategies to deliberately inject dopant atoms to the crystal of a semiconductor nanostructure have seen rapid, effective processes and various doped semiconductor NCs have recently been synthesized, including aluminum, germanium, indium doped zinc oxide, phosphorous and boron-doped silicon NCs and indium doped tin oxide (ITO) NCs.11-13 The above all NCs have intense resonances ranging from the mid to near infrared (NIR) owing to the LSPRs effect. It is well known that copper chalcogenides are important class of doped semiconductors. The high density of free carriers is a result of copper vacancies in the structure, which leads to strong LSPRs in the NIR. Meanwhile, the exact position of the LSPR is determined by a variation of the copper to sulfide stoichiometry.1,8-10 Similarly, the nonstoichiometric composition in Cu3-xP NCs and Cu2-xSe generates free charge carriers that lead to plasmonic response in the NIR.14-16 Another prominent case of doped semiconductors are doped metal oxides. For instance, WO3-x nanorods show strong NIR absorption with an LSPR peak at approximately 900 nm.17 Among all doped metal oxides, the heavily doped non-stoichiometric molybdenum oxide (MoO3-x) is typical and primary member.4,18-20 As an n-type semiconducting material, MoO3 has found important applications in a large number of catalysis, optoelectronics, and gas sensors. However, MoO3 only response to UV light due to the wide bandgap (3.05 eV), which accounts for less than 5% of


3


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 34

the solar energy.21-22 In consideration of the sunlight utilization, photocatalytic reactions under visible light are more promising due to a major proportion (about 43%) of all solar spectrum. As compared with stoichiometric MoO3, plasmonic MoO3-x displays LSPR absorption in a wide solar spectrum range.23-24 For example, well-defined 2D MoO3-x NS show intense and tunable plasmonic resonance across the visible and NIR region and dramatically enhance the dehydrogenation activity from ammonia borane (NH3BH3; AB) under visible light irradiation.4,1819

In heterogeneous photocatalysis, single-component materials are usually restricted due to their intrinsic features, such as weak light absorption and low catalytic efficiency, and consequently, they could not meet the functional requirements.18,25 Recently, bimetallic hybrid catalysts have been extensively developed because of their excellent performance for many reactions including oxidation, oxygen reduction reaction, hydrogenation and hydrogen evolution.26-28 For example, some hybrid catalysts, such as Co-Mo-N, Fe-Ni-P and Ni-Mo-S, were found to show a superior hydrogen evolution reaction (HER) activity from water or hydrogen storage materials than the corresponding single component owing to the synergistic effect of different components,29-35 which can either change the surface morphology of hybrids to expose more active sites, or tune the intrinsic electric properties of hybrids. On the other hand, though single plasmonic doped semiconductor NCs, such as MoO3-x, Cu2-xS, have been studied extensively during recent years,36-40 dual-plasmonic hybrid nanometerials, which is defined as a material synthesized by mutual doping of two different plasmonic semiconductors, has rarely been reported.37 Motivated by the above situations, we expected that the LSPRs effect can be enhanced by coupling MoO3-x with another plasmonic metal oxides, which ultimately boost the photocatalytic performance. Tungsten (W) element and molybdenum (Mo) are classified into group VI element in the periodic table, which usually have the same electrons number in outermost layer.41 Meanwhile,


4

Page 5 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


metallic phases of WO3-x show a strong and tunable LSPRs, which opens up the possibility of rationally designing plasmonic WO3-x for light harvesting, bioimaging, and sensing.16-17,42-48 Coupling of MoO3-x and WO3-x is expected to reinforce the optical property, which would allow the synthesis of new class of plasmonic nanomaterial with intense light absorption property. Herein, we report a facile nonaqueous solvothermal method to synthesize plasmonic MoxW1O3-y hybrid without adding any surfactants, which exhibits strong LSPRs in the visible light

x

region. It was found that the experimental parameters, such as reaction solvent and synthetic temperatures, were found to play a crucial role in the crystallinity and morphology evolution of MoxW1-xO3-y hybrid, which were strongly associated with LSPR response intensity from the visible light region to the NIR. The plasmonic MoxW1-xO3-y under optimized conditions could be used as a highly efficient catalyst that dramatically enhanced the dehydrogenation activity from ammonia borane under visible light irradiation (λ > 420 nm), especially under visible light irradiation with a longer wavelength (λ > 450 nm). The above excellent properties of dualplasmonic MoxW1-xO3-y hybrid nanomaterial open up a new frontier for acquiring better optical property to boost specific chemical reactions.2,7,36

EXPERIMENTAL SECTION Synthesis of plasmonic MoxW1-xO3-y: In a typical synthetic procedure, 2 mmol of molybdenum metal powder and 2 mmol of tungsten metal powder (molar ratio of Mo:W = 1:1) were added to a Teflon vessel (45 mL) containing 30 mL of 2-propanol under magnetically stirred. Then 5 mL of H2O2 was injected and continued stirring for 1 hour (h) to obtain the yellow suspension. The Teflon vessel was then sealed in stainless steel autoclave, heated and maintained at 160 oC for 12 h. After naturally cooling down to room temperature, the sample was collected by centrifugation,


5


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 6 of 34

rinsed with ethanol for three times and finally dried at vacuum. Instead of 2-propanol, some other solvents such as 1-butanol and ethanol were also used as the solvents to prepare MoxW1O3-y nanostructures. For comparison, pure MoO3-x and pure WO3-x were also synthesized in the

x

same manner without the addition of the tungsten powder and molybdenum powder, respectively. Different molar rate of Mo/W (2:1, 1:2), solvothermal temperature (140 oC, 180 oC), and amount of H2O2 (1 mL, 10 mL) were also used to prepare MoxW1-xO3-y nanostructure. Synthesis of plasmonic reported MoO3-x NS: The synthesis of reported MoO3-x followed a previous method published by Cheng.19 In a typical synthetic procedure, 2 mmol of molybdenum metal powder were added to a Teflon vessel (45 mL) containing 24 mL of ethanol under magnetically stirred. Then 3 mL of H2O2 was injected and continued stirring for 0.5 h to obtain the yellow suspension. The Teflon vessel was then sealed in stainless steel autoclave, heated and maintained at 160 oC for 12 h. After naturally cooling down to room temperature, the sample was collected by centrifugation, rinsed with ethanol for three times and finally dried at vacuum. And “WO3-x-H2O2 reduction” was also synthesized in the same manner by adding tungsten metal powder instead of molybdenum metal powder. Synthesis of “MoO3-x-NaBH4 reduction”, “WO3-x-NaBH4 reduction”, Au/SiO2, and Ag/SiO2: The synthesis of above catalysts followed another previous report.18 Taking “MoO3-xNaBH4 reduction”, for example, firstly, MoO3 were prepared by thermal decomposition of (NH4)6Mo7O24.4H2O at 450 oC for 4 h in air with the ramping rate of 1 oC min-1. MoO3 (0.2 g) was dispersed in 100 mL of distilled water and then the freshly prepared NaBH4 aqueous solution was added to the suspension. The molar ratio for NaBH4 to MoO3 was 10:1. The suspension was further stirred for 1 h. The samples were obtained by centrifugation, rinsed with


6

Page 7 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


water, and finally dried in vacuum. Likewise, “WO3-x-NaBH4 reduction”, Au/SiO2, and Ag/SiO2 were synthesized by the same method. Characterization: The X-ray diffraction (XRD) patterns were recorded using a Rigaku Ultima IV diffractometer with Cu kα radiation (λ = 1.5406 Å). Transmission electron microscopy (TEM) images were measured with a Hitachi H-800 electron microscope equipped with an energy dispersive X-ray detector operated at 200 kV. UV-Vis-NIR diffuse reflectance spectra were collected on a Shimadzu UV 2600 recording spectrophotometer equipped with an integrating sphere at room temperature and the fixed amount of sample (60 mg) was used for each measurement. The reference was BaSO4 and the absorption spectra were obtained using the Kubelka-Munk function. XPS measurements were carried out using a Shimadzu ESCA 3200 photoelectron spectrometer with Mg Kα radiation, and C 1s (284.6 eV) was used to calibrate the peak positions of the elements. Mo K-edge and W L3-edge XAFS spectra were measured at room temperature in fluorescence mode at the beam line 01B1 station with an attached Si (311) monochromator at SPring-8 (JASRI, Harima, Japan) and at the beam line BL-9C with an Si(111) monochromator at PhotonFactory (KEK, Tsukuba, Japan), respectively. Nitrogen adsorption measurements (BET) were performed using BELSORP-max system (MicrotracBEL Corp.) at 196 oC. Samples were degassed under vacuum at 200 oC for 24 h prior to data collection. Raman experiment was conducted using a Portable Stabilized R. Laser Analyzer with an arrow line width diode laser at 633 nm with an adjustable power of the maximum at 300 mW. NH3-TPD measurement was carried out on a BELCAT-II (MicrotracBEL Corp.) apparatus. The samples were mounted in a quartz tube, and were reduced in a flow of 5 vol% NH3/He (30 mL/min). The heating rate of 5 oC/min, and the consumption of ammonia was monitored by the thermal conductive detector (TCD).


7


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 34

Catalytic performances evaluation: The catalytic performances of the molybdenum tungsten oxide hybrid nanostructures were measured by dehydrogenation of NH3BH3 in aqueous suspensions at room temperature (25 oC). Typically, MoxW1-xO3-y sample (20 mg) was suspended in 5 mL distilled water in a test tube. 200 µL of NH3BH3 (0.1 M, 20 mmol) solution was injected into the above solution through a rubber septum after bubbling with Argon gas for 30 min. The reaction was conducted with magnetically stirred in the dark condition and under visible light irradiation with cutoff filter. The amount of H2 in gas phase was determined by a Shimadzu GC8A gas chromatograph with MS-5A column by TCD detector.

RESULTS AND DISCUSSION MoxW1-xO3-y hybrid was synthesized by solvothermal treatment of mixture solution of 2-propanol and hydrogen peroxide (H2O2, 30%) at 160 oC for 12 h (see the Experimental Section). Scheme 1 shows the designed synthetic route of MoxW1-xO3-y in this study. First, pure Mo and W powder were added to a 2-propanol solution containing 5 mL of H2O2 (30 %). All Mo powder and some W powder were dissolved and a yellow solution was obtained after magnetic stirring for 30 min. In this process, the solution-soluble precursor compound MoO2(OH)(OOH) and WO2(OH)(OOH) could form easily.19-20,40 In the subsequent growth stage, tiny MoxW1-xO3 nuclei were generated by dehydration of the dissolved yellow Mo-W-complex. Due to the layered crystal structure of orthorhombic MoO3 and WO3 composed of MoO6 octahedra and WO6 octahedra sharing edges and corners, respectively,19-20 the intrinsic anisotropic crystal growth with the help of 2-propanol leads to the preferential formation of MoxW1-xO3-y nanowires.19


8

Page 9 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Scheme 1. Schematic illustration of the plausible formation process of plasmonic MoxW1-xO3-y. As shown in Figure 1a, the collected products exhibit intense black color. Such black molybdenum and tungsten oxide species are quite stable in air and can sustain this original color for several months. It has been well documented that the black color of transition oxides derives from the characteristic outer d-shell electrons of transition metal atom, such as deficient TiO2-x,49 WO3-x,17 and Cu2-xS.1 From the X-ray diffraction pattern (XRD; Figure 1b), the sample showed typical peaks of WO3 with a peak assignable to (002) plane of WO3 stronger than that of other peaks, which should be caused by its preferred orientation with the effect of Mo atom.25,50 It is interesting that the typical XRD patterns of MoO3 were not observed, which may be because crystal structure of MoO3 is significantly perturbed by the insertion of WO6 octahedra with longer W-O bond length (see Table S2 and Table S3 for the bond length calculation based on Raman spectra).51-54 The peaks located at 2θ ≈ 40.3o, 58.3o, and 73.2o are assigned to the W0 state (JCPDS No.04-0806), which demonstrates that W powders were not oxidized completely by H2O2. Figure S1a-d shows the morphology and the structure of as-prepared MoxW1-xO3-y hybrids. It is clear that MoxW1-xO3-y is composed of interconnected nanowires with average diameter of 10 nm. The energy-dispersive X-ray (EDX) elemental mapping images (Figure S1c-d) verify that Mo and W elements are homogeneously distributed throughout the whole nanowires.


9


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 34

Figure 1. (a) A photograph of as-synthesized MoxW1-xO3-y hybrid dispersed in ethanol. (b) XRD pattern of MoxW1-xO3-y hybrid. Figure 2 shows the UV/Vis-NIR spectra of plasmonic MoxW1-xO3-y hybrid, as-synthesized MoO3-x, WO3-x, and our previously reported MoO3-x NS. A strong absorption peak located at approximately 630 nm connected with LSPRs is clearly observed in the spectra of MoxW1-xO3-y. It is worth noticing that such a strong LSPR peak is seldom appeared in the plasmonic semiconductor nanostructures in visible light range, even in the NIR-mid infrared (MIR) region, such as plasmonic MoO3-x, WO3-x, Cu2-xS and so on.54 The absorption peak position (630 nm) of MoxW1-xO3-y is shorter than that of as-synthesized MoO3-x (920 nm), WO3-x (> 1400 nm), and our previously reported MoO3-x NS (680 nm). Most importantly, the LSPR absorption intensity of MoxW1-xO3-y was almost 20, 16, and 8 times larger than that of as-synthesized MoO3-x, WO3-x, and our previously reported MoO3-x NS, respectively. On the other hand, commercial MoO3 and commercial WO3 samples show only a UV-light response compared with plasmonic MoxW1-xO3-y


10

Page 11 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


in Figure S2, with the respective absorption edge at about 400 nm and 463 nm, which corresponds to their wide band gaps (ca 3.1 eV and 2.6 eV, respectively).

Figure 2. (a) UV-Vis-NIR diffuse reflectance spectra of MoxW1-xO3-y, MoO3-x, WO3-x, and our previously reported MoO3-x nanosheets. (b) Magnified UV-Vis-NIR diffuse reflectance spectra of MoO3-x, WO3-x, and our previously reported MoO3-x nanosheets in (a). The experimental parameters (e.g., solvothermal temperatures, H2O2 volumes, molar ratios of Mo/W, and solvents) play important roles in determining plasmonic properties of the samples (Table S1). Three samples synthesized with different molar ratio (Mo:W) show the similar XRD patterns (Figure S3a). However, MoxW1-xO3-y hybrid (1:1) presents a lower absorption peak position and stronger absorption intensity in UV-Vis-NIR spectra as compared to other samples (Figure S3b). When the molar ratio of Mo/W was changed from 1:1 to 2:1 and 1:2, the corresponding LSPR wavelength was both red-shifted to about 655 and 642 nm with decreased absorption peak intensity, which indicates that MoxW1-xO3-y hybrid (1:1) has more crystal vacancies and larger carrier density than MoxW1-xO3-y with disproportionate Mo/W ratios (1:2 or 2:1). When the solvothermal temperature was changed from 160 oC to 140 oC or 180 oC (Figure S4a), plasmonic MoxW1-xO3-y hybrid retained its original crystalline structure. Raising the


11


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 34

synthesis temperature from 140 oC to 160 oC led to the formation of MoxW1-xO3 with more doping vacancies and oxygen vacancies, which could generate deficient MoxW1-xO3-y with sufficient free carriers to support the stronger LSPR (Figure S4b). MoxW1-xO3-y synthesized at 180 oC still remains the original structure of nanowires (Figure S4c). When the amount of H2O2 in the initial reaction solution was decreased to 1 mL, characteristic peaks assigned to W metal were apparently observed in XRD pattern (Figure S5a), which meant that majority of W powder was not oxidized. A small number of MoO3 nanosheets were obtained after the solvothermal reaction (Figure S5c), which resulted in a weak absorption peak located at 821 nm in Figure S5b. On the other hand, when excess amount of H2O2 was added (10 mL), the majority of Mo metal and W metal was oxidized to MoO3 and WO3, respectively, while the sample still kept morphology of nanowires (Figure S5d). The choice of solvents was also crucial factor in tailoring the plasmonic wavelength of MoxW1O3-y. Instead of 2-propanol, other kinds of alcohols, such as ethanol and 1-butanol, could also

x

afford black-colored samples. When ethanol and 1-butanol were used as the solvents, the absorption bands assigned to LSPR were red-shifted to 817 and 780 nm, respectively (Figure S6b). The samples synthesized with ethanol or 1-butanol also remained morphology of nanowires (Figure S6c-d). The peak of W metal at 2θ ≈ 40.3o disappeared when using 1-butanol, indicating majority of W metal was oxidized to WO3 (Figure S6a). On the basis of the control experiments, it indicates that the synergistic effect of synthetic temperature, amount of H2O2 and choice of solvent is crucial to prepare plasmonic MoxW1-xO3-y with stronger LSPRs. In order to elucidate the oxidation state of Mo and W in the plasmonic MoxW1-xO3-y nanostructures, X-ray photoelectron spectroscopy (XPS) measurements were implemented. Mo 3d and W 4f XPS core spectra of the as-prepared MoxW1-xO3-y, commercial MoO3, and


12

Page 13 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


commercial WO3 are displayed in Figure 3a and Figure 3b, respectively. For commercial MoO3, two peaks (236.15 and 233.05 eV) are assigned to the 3d3/2 and 3d5/2 of Mo6+ species, respectively. The two peaks (38.75 and 36.65 eV) observed for commercial WO3 represents W6+ state. On the contrary, for MoxW1-xO3-y, the peaks of Mo 3d5/2 and 3d3/2 shift to lower binding energies. The peaks at 235.95 and 233.05 eV are assigned to Mo6+, and those centered at 234.5 and 231.06 eV correspond to Mo5+. W 4f XPS spectra also show a similar tendency, the peaks of W 4f5/2 and W 4f7/2 shift to lower binding energies. The peaks at 38.75 and 36.65 eV correspond to W6+, and other two peaks (37.65 and 35.60 eV) are assigned to W5+. According to the XPS peak area of Mo 3d and W 4f, the Mo6+ and Mo5+ cations in MoxW1-xO3-y account for 46.2 % and 52.8 % of the total Mo state, respectively, and the proportion of W6+ and W5+ cations of MoxW1O3-y is estimated to be 20.6 % and 79.4 %, respectively. The average oxidation state of Mo and

x

W is thus calculated to be 5.46 and 5.20, which manifests the mixed-valence state resulting from the oxygen vacancies. In addition, two subtle peaks (33.6 and 32.2 eV) of W0 state were found after etching process (Figure S7), indicating that a small quantity of W metal exists in the samples, which is consistent with XRD results (Figure 1b).


13


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 34

Figure 3. (a) Mo 3d and (b) W 4f XPS spectra of as-prepared MoxW1-xO3-y, commercial MoO3, and commercial WO3, respectively. It has been proposed that doping could lead to the generation of crystal defect and crystal structure distortion in doped semiconductor crystals.55 To further understand the crystal defects and crystal structure distortion in MoxW1-xO3-y nanostructures, Raman spectra of MoxW1-xO3-y samples were measured. For commercial MoO3, the vibration modes appearing in the frequency ranges of 1000-600 cm-1 and 600-200 cm-1 correspond to the stretching and deformation modes in Figure S8, respectively. The narrow band at 994 cm-1 is assignable to the antisymmetric v(Mo=O1) stretching. The strong band at 819 cm-1 represents the symmetric v(Mo-O1-Mo) stretching with the bond aligning along the a axis direction. The weak and broad bands at 666 and 470 cm-1 are ascribable to the antisymmetric v(Mo-O2-Mo) stretching and bending, respectively.21 For commercial WO3, the two main intense peaks at 806 and 718 cm-1 correspond to the stretching and bending vibrations of the bridging tungsten and oxygen atoms. They are assigned to the W-O stretching, W-O bending and O-W-O deformation modes, respectively.43 Nevertheless, tiny variations in peak width and location of Mo-O1-Mo (819 cm-1), W-O (806 cm1

), and O-W-O (718 cm-1) stretching motions were observed in Figure S9a and Figure S9b. It is

found that low wavenumber shift occurs with an increase in the amount of tungsten. In addition, to investigate the degree of crystal distortion, the empirical equations of RMo-O = 0.48239 ln (32895/v) and RW-O = 0.52576 ln (25823/v) were used to calculate the Mo-O and W-O bond length,56-57 respectively, where v is the Raman stretching frequency in wavenumbers and R is the metal-oxygen length in angstroms. The calculated results of Mo-O and W-O bond lengths are given in Table S2 and Table S3 in the Supporting Information, suggesting that all MoxW1-xO3-y samples shows distinct distortion and symmetry breaking of MoO6 octahedron and WO6


14

Page 15 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


octahedron compared with commercial MoO3, commercial WO3, pure MoO3-x and pure WO3-x, which mainly results from mutual doping of molybdenum ions and tungsten ions. Especially for MoxW1-xO3-y (1:1), the bond length of Mo-O and W-O changes dramatically after doping, and peak at around 664-704 (cm-1) has disappeared, which will finally result in the generation of crystal defects. X-ray absorption fine structure (XAFS) measurements were conducted to check the structural information. Figure S10a shows the normalized X-ray absorption near-edge structure (XANES) spectra at the W L3-edge for MoxW1-xO3-y and reference samples (commercial WO3 and W powder). The pre-edge peaks position of three samples follow the order of commercial WO3 (10207.8 eV) > MoxW1-xO3-y (10206.8 eV) > W powder (10204.9 eV). This small shift to lower energies indicates that W species of MoxW1-xO3-y present between W6+ and W0,58-59 which corresponds to the XPS result shown in Figure 3b. From the Fourier transform (FT) k3-weighed extended X-ray absorption fine structure (EXAFS, Figure S10b), a peak at around 2.7 Å due to the W-W bond was observed in W powder and commercial WO3. However, for MoxW1-xO3-y hybrid, this peak was shifted to longer interatomic distance around 3.0 Å compared to commercial WO3 owing to different local atomic arrangement, which indicates that Mo ions are inserted into the structure of WO3.50 The above conclusion corresponds to the results shown in Figure 1b (XRD spectra).25 The NH3 temperature-programmed desorption (NH3-TPD) technique was used to determine the strength of the acid sites presented on the surface of catalyst, as well as the total acidity. Not only the strength of the acid sites but also the total acidity amount of MoxW1-xO3-y (1.55 mmol/g) increase dramatically compared with as-synthesized MoO3-x (0.50 mmol/g) and WO3-x (0.30 mmol/g) (Figure S11). This result confirms that the doping of Mo and W strongly influences the


15


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 34

acidic properties of MoxW1-xO3-y sample. According to the above discussion, it is concluded that acid sites will be formed around the crystal vacancies during the formation process of crystal vacancies, and free carriers induced by visible light can be easily transferred to acid sites of catalytic active center. Based on the discussion of the above data, possible formation process of crystal defects in plasmonic MoxW1-xO3-y structure was illustrated in Scheme 2. MoxW1-xO3 nuclei possesses unique layered structure composed of MoO6 octahedron and WO6 octahedron by corner- and edge-sharing. Mo doping and W doping process could result in different types of crystal defects, such as symmetry disturbances, and redox couples. At the beginning of doping process, Mo ions and W ions inserted into WO6 octahedron and MoO6 octahedron, respectively, which could lead to huge variation in WO6 octahedron and MoO6 octahedron and drastic changes of electronic structures. On the other hand, intercalation of hydrogen atoms of H2O2 or 2-propanol during synthetic process also disturbed the charge balance of MoxW1-xO3 system, resulting in the generation of Mo5+ and W5+ for charge compensation as confirmed by XPS data and the formation of oxygen vacancies. With corner- and edge-sharing MoO6 octahedron and WO6 octahedron, orthorhombic MoO3 and WO3 host material with the layered structure allowed an insertion of a mass of H atoms at interlayer positions, which could coordinate strongly with terminal oxygen atoms and then lead to the distortion of MoO6 octahedron and WO6 octahedron and the generation of the acid sites. Subsequently, the terminal oxygen atoms transferred charges to the coordinating Mo and W atoms, resulting in partial reduction of molybdenum and tungsten ions, respectively.4,18-19 Meanwhile, the reduction property of H2O2 and alcohols could also produce oxygen vacancies during the synthetic process.20 Therefore, both the ion substitution and formation process of oxygen vacancies could destroy the corner-sharing and edge-sharing


16

Page 17 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


octahedral structure for the lack of equatorial oxygen and low coordination of molybdenum ions and tungsten ions, which could increase carrier density dramatically and eventually lead to the strong LSPRs.

Scheme 2. Illustration of the possible formation process of crystal defects in plasmonic MoxW1xO3-y

structure.

Ammonia borane has emerged as a candidate of hydrogen storage materials because of its low molecular weight (30.87 g mol-1), nontoxicity, high stability in solid form under ambient conditions and high theoretical hydrogen gravimetric capacity (19.6 wt%).60-61 The hydrolysis of AB can be attained under mild reaction condition with suitable catalysts according to the following equation. +

−

NH 3 BH 3 + 2 H 2O Catalyst  → NH 4 + BO2 + 3H 2

(1)

Recently, many noble metal nanostructures, such as Pd, Au, Ru, and Rh, have been already demonstrated to show high activity for dehydrogenation of AB solutions.61-62 Plasmonic MoO3-x nanosheets that we have reported previously have shown relatively high H2 evolution from


17


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 34

NH3BH3 solution, which motivated us to continuously investigate dehydrogenation of AB solutions by MoxW1-xO3-y with strong LSPRs. We firstly investigated dehydrogenation activities of samples in the dark condition. H2 could be produced from AB over MoxW1-xO3-y and commercial MoO3 under dark condition (Figure S12a). Initial reaction rates of as-synthesized MoxW1-xO3-y was 2.58 µmol/min, which was much faster than the rate of commercial MoO3 (0.44 µmol/min) and commercial WO3 (0.06 µmol/min). After reaction for 60 min, only 30.5 and 6.3 mol% conversion of AB was yielded by commercial MoO3 and commercial WO3, respectively. In contrast, almost 67.0 mol% conversion of AB was obtained by MoxW1-xO3-y. The higher H2 production performance of MoxW1-xO3-y is probably due to its’ larger surface area (Figure S13) and more acid sites. Interestingly, when the dehydrogenation reaction was implemented under visible light irradiation (Figure S12b), H2 evolution was dramatically improved. MoxW1-xO3-y could give 52.7 mol% conversion of AB in the first 10 min, whose initial reaction rate (3.16 µmol/min) was 3.4 and 2.8 times higher that of commercial MoO3 (0.92 µmol/min) and commercial WO3 (1.12 µmol/min), respectively. After reaction for 50 min, MoxW1-xO3-y obtained 100 mol% conversion of AB, which was much higher than those of commercial MoO3 (63.3 mol%) and commercial WO3 (10.0 mol%) after reaction for 50 min. Table S4 shows the summary of catalytic activities in the dehydration of AB over some reported plasmonic noble metal and doped-semiconductor catalysts. Under visible light irradiation, the plasmonic MoxW1-xO3-y displayed a 24.3 and 12.2 times higher initial reaction rate than Ag/SiO2 and Au/SiO2 samples, respectively (for reaction kinetics data, see Figure S14d), which shows typical LSPR absorption wavelengths located at 385 and 560 nm, respectively (for UV-vis-NIR spectra, see Figure S14a-b). In contrast to the reaction carried out in dark condition (Figure S14c), MoxW1-xO3-y can produce H2 more rapidly under visible light irradiation, which


18

Page 19 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


far outperformed than Ag/SiO2 and Au/SiO2. Figure S15a shows UV-Vis-NIR diffuse reflectance spectra of plasmonic doped-semiconductor MoO3-x with different preparation methods, e.g., MoO3-x was prepared by solvothermal method with H2O2 as reductant and 2-propanol as solvent, “Reported MoO3-x NS” was prepared by solvothermal method with H2O2 as reductant and ethanol as solvent, and “MoO3-x-NaBH4 reduction” was prepared with NaBH4 as reductant (see the Experimental Section). Compared with these plasmonic MoO3-x, the LSPR absorption intensity of MoxW1-xO3-y was at least 8 times stronger than that of MoO3-x, and the corresponding LSPR wavelength was blue shift to about 630 nm. Although the dehydrogenation activity of AB did not show much difference in the dark (Figure S15b), MoxW1-xO3-y with strong LSPRs could afford 100% conversion of AB within 50 min under visible light irradiation. However, MoO3-x synthesized with different preparation methods (corresponding to Table S4) could only achieve approximately 80 mol% conversion of AB within 50 min and did not show any catalytic performance in the subsequent 10 min (Figure 4a) due to weaker intensity of LSPRs and relatively low-concentration AB. Plasmonic WO3-x samples with different preparation methods were also used to compare with MoxW1-xO3-y, e.g., WO3-x was prepared by solvothermal method with H2O2 as reductant and 2-propanol as solvent, “WO3-x-H2O2 reduction” was prepared by solvothermal method with H2O2 as reductant and ethanol as solvent, and “WO3-x-NaBH4 reduction” was prepared with NaBH4 as reductant (see the Experimental Section). As shown in Figure S15c, all plasmonic WO3-x samples show a certain absorption intensity under Vis-NIR region. However, these samples usually displayed much lower dehydrogenation activities than MoxW1-xO3-y both in dark condition (Figure S15d) and under visible light irradiation (Figure 4b) owing to weaker intensity of light absorption.


19


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 34

Figure 4. (a) H2 evolution from AB at room temperature of as-prepared MoxW1-xO3-y and reference materials: (a) MoO3-x, and (b) WO3-x under visible light irradiation (λ > 420 nm). Under visible-light irradiation with a longer wavelength (λ > 450 nm), photocatalytic dehydrogenation activity for plasmonic MoxW1-xO3-y does not change compared with the activity under λ > 420 nm visible-light irradiation, while dehydrogenation activity of as-synthesized MoO3-x decreased by about 28.3 mol% under the identical conditions (Figure S16). This is due to the contribution of strong LSPRs, which can eliminate the possible effect of band-gap excitation. Because of the wide infrared-light absorption of the plasmonic MoxW1-xO3-y, the temperature of the suspension was detected to increase by approximately 15 oC under visible light irradiation. A control experiment at 40 oC was carried out with MoxW1-xO3-y in order to investigate the contribution of photothermal effect (Figure 5a). The initial H2 yield rate at 40 oC in the dark was 2.7 µmol/min, which was a little higher than that at room temperature (25 oC, 2.5 µmol/min). Similarly, under visible light irradiation (λ > 420 nm), the initial H2 yield rate at 40 oC (3.2 µmol/min) was almost the same as the rate at 25 oC (3.4 µmol/min), indicating that the


20

Page 21 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


contribution by LSPR is greater than that given by photothermal effect. The wavelengthdependence for H2 production enhancement was also surveyed by using LED lamp (λ = 470, 530, and 650 nm) (Figure 5b). The improvement of reaction rate fairly corresponds to the light absorption of MoxW1-xO3-y, indicating that the improvement of dehydrogenation activity can be assigned to the LSPRs effect of MoxW1-xO3-y. Red LED light irradiation (λ = 650 nm) provided the maximum activity enhancement of which initial H2 production rate (2.64 µmol/min) was 1.06 times higher than that in the dark condition. To understand the mechanism of activity enhancement under visible light irradiation, NaHCO3 (as a positive charge scavenger), Na2S2O8 (as negative charge scavenger), and 2-propanol (as hydroxyl radicals (.OH) scavenger) were added to the suspension of MoxW1-xO3-y sample under visible light irradiation condition for dehydrogenation of AB. As shown in Figure 5c, dehydrogenation activity was dramatically decreased in the presence of NaHCO3. MoxW1-xO3-y could be excited by visible light irradiation and generate positive charge and negative charge pairs, and then HCO3- can easily react with a positive charge (4HCO3- + 4h+ → 2H2O + 4CO2+ O2),18,63 thus resulting in appreciable activity reduction under visible light irradiation. However, catalytic activity has only decreased marginally (5.8 µmol within 60 min) after adding Na2S2O8 under visible light condition, which means only a small part of LSPR-induced hot electrons participate in dehydrogenation reaction of AB. According to the above study, we propose the possible dehydrogenation mechanism of AB molecules. Firstly, MoxW1-xO3-y effectively adsorbs of AB molecule owing to its large surface area. Then, plasmonic MoxW1-xO3-y can be excited due to the strong LSPRs under visible light irradiation and generate positive charge and negative charge pairs on the surface of MoxW1-xO3-y. Positive charge as main active species can directly react with the absorbed AB to facilitate the dissociation of the B-N bond. The formed BH3 finally


21


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 34

hydrolyzes to form H2 and generates a BO2- ion.20,62 The catalytic stability of MoxW1-xO3-y was also investigated by repeated use. As shown in Figure 5d, MoxW1-xO3-y still displayed a similar catalytic performance. Furthermore, XRD spectra, UV/Vis-NIR diffuse spectra further ascertained the original structure and optical property of MoxW1-xO3-y (Figure S17a-b) even after multiple recycling experiments, which means efficient and stable property of plasmonic MoxW1O3-y with high potential application prospect.

x

Figure 5. (a) The comparison of the initial H2 yield rate on MoxW1-xO3-y in dark conditions (25 and 40 oC) and under visible light irradiation (λ > 420 nm). (b) Wavelength-dependent initial H2


22

Page 23 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


yield rate enhancement of MoxW1-xO3-y samples upon irradiation by LED light. (blue light λ = 470 nm, 33.3 mW cm-2, green light λ = 530 nm, 17.0 mW cm-2, red light λ = 650 nm, 23.5 mW cm-2). (c) The comparison of H2 production activity within 60 min under visible light irradiation (λ > 420 nm) from AB solution with or without NaHCO3 (100 µmol) as positive charge scavenger, 2-propanol (100 µmol) as .OH scavenger, and Na2S2O8 (100 µmol) as negative charge scavenger over plasmonic MoxW1-xO3-y sample. (d) The five recycling experiments for NH3BH3 dehydrogenation under visible light irradiation.

CONCLUSIONS In summary, plasmonic MoxW1-xO3-y was prepared by a nonaqueous method via a solvothermal process. The prepared MoxW1-xO3-y shows strong LSPR in the visible region because of crystal vacancies, including mutual doping vacancies of molybdenum ions and tungsten ions and oxygen vacancies, which can be tuned by varying the synthesis temperature, amount of H2O2 and the kind of solvent. Under visible light irradiation (λ > 420 nm and λ > 450 nm), such plasmonic MoxW1-xO3-y showed higher H2 evolution from aqueous NH3BH3 solutions compared with the conventional plasmonic MoO3-x and WO3-x synthesized by the same preparation method owing to strong LSPR, which outperformed our previously reported MoO3-x NS. This study offers a promising strategy in exploring stable and efficient plasmonic semiconductor photocatalysts with strong LSPR properties for harvesting and utilizing abundant solar light into specific catalytic reactions.

ASSOCIATED CONTENT


23


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 34

Supporting Information. TEM images, XRD, UV-Vis-NIR, XPS, Raman, XAFS spectra, and catalytic results of the related materials. These materials are available free of charge via the Internet at http://pubs.acs.org. AUTHOR INFORMATION Corresponding Author *[email protected] Notes The authors declare no competing financial interest. ACKNOWLEDGMENT The present work was supported by the Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan (16K14478, 26620194 and 26220911). Part of this work was performed under a management of “Elements Strategy Initiative for Catalysts and Batteries (ESICB)” supported by MEXT program, Japan. The synchrotron radiation experiments were performed at the BL01B1 beamline in SPring-8 with the approval of JASRI (Nos. 2016A1057 and 2017A1063) and at the BL-9C beamline in PhotonFactory with the approval of KEK (No. 2016G006). Y.H. would like to acknowledge the National Nature Science Foundation of China (21577092). REFERENCES (1) Zhao, Y.; Pan, H.; Lou, Y.; Qiu, X.; Zhu, J.; Burda, C. Plasmonic Cu2-xS Nanocrystals: Optical and Structural Properties of Copper-Deficient Copper(I) Sulfides. J. Am. Chem. Soc. 2009, 131, 4253-4261.


24

Page 25 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(2) Comin, A.; Manna, L. New Materials for Tunable Plasmonic Colloidal Nanocrystals. Chem. Soc. Rev. 2014, 43, 3957-3975 (3) Faucheaux, J.; Stanton, A.; Jain, P. Plasmon Resonances of Semiconductor Nanocrystals: Physical Principles and New Opportunities. J. Phys. Chem. Lett. 2014, 5, 976-985. (4) Cheng, H.; Wen, M.; Ma, X.; Kuwahara, Y.; Mori, K.; Dai, Y.; Huang, B.; Yamashita, H. Hydrogen Doped Metal Oxide Semiconductors with Exceptional and Tunable Localized Surface Plasmon Resonances. J. Am. Chem. Soc. 2016, 138, 9316-9324. (5) Wang, G.; Chen, X.; Liu, S.; Wong, C.; Chu, S. Mechanical Chameleon through Dynamic Real-Time Plasmonic Tuning. ACS Nano 2016, 10, 1788-1794. (6) Zhou, Y.; Li, W.; Zhang, Q.; Yan, S.; Cao, Y.; Dong, F.; Wang, F. Non-Noble Metal Plasmonic Photocatalysis in Semimetal Bismuth Films for Photocatalytic NO Oxidation. Phys. Chem. Chem. Phys. 2017, 19, 25610-25616. (7) Zhao, Y.; Burda, C. Development of Plasmonic Semiconductor Nanomaterials with Copper Chalcogenides for A Future with Sustainable Energy Materials. Energy Environ. Sci. 2012, 5, 5564-5576. (8) Luther, J. M.; Jain, P. K.; Ewers, T.; Alivisatos, A. P. Localized Surface Plasmon Resonances Arising from Free Carriers in Doped Quantum Dots. Nature Mater. 2011, 10, 361-366. (9) Kriegel, I.; Jiang, C.; Rodriguez-Fernandez, J.; Schaller, R. D.; Talapin, D. V.; Como, E. D.; Feldmann, J. Tuning the Excitonic and Plasmonic Properties of Copper Chalcogenide Nanocrystals. J. Am. Chem. Soc. 2012, 134, 1583-1590.


25


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 34

(10) Dorfs, D.; Hartling, T.; Miszta, K.; Bigall, N. C.; Kim, M. R.; Genovese, A.; Falqui, A.; Povia, M.; Manna, L. Reversible Tunability of the Near-Infrared Valence Band Plasmon Resonance in Cu2-xSe Nanocrystals. J. Am. Chem. Soc. 2011, 133, 1117511180. (11) Kramer, N.; Schramke, K. S.; Kortshagen, U. R. Plasmonic Properties of Silicon Nanocrystals Doped with Boron and Phosphorus. Nano Lett. 2015, 15, 5597-5603. (12) Zhou, S.; Ni, Z.; Ding, Y.; Sugaya, M.; Pi, X.; Nozaki, T. Ligand-Free, Colloidal, and Plasmonic Silicon Nanocrystals Heavily Doped with Boron. ACS Photonics 2016, 3, 415-422. (13) Gaspera, E. D.; Chesman, A. S. R.; Embden, J. V.; Jasieniak, J. Non-injection Synthesis of Doped Zinc Oxide Plasmonic Nanocrystals. ACS Nano 2014, 8, 91549163. (14) Zhang, S.; Sun, C.; Zeng, J.; Sun, Q.; Wang, G.; Wang, Y.; Wu, Y.; Dou, S.; Gao, M.; Li, Z. Ambient Aqueous Synthesis of Ultrasmall PEGylated Cu2-xSe Nanoparticles as a Multifunctional Theranostic Agent for Multimodal Imaging Guided Photothermal Therapy of Cancer. Adv. Mater. 2016, 28, 8927-8936. (15) Trizio, L. D.; Gaspari, R.; Bertoni, G.; Kriegel, I.; Moretti, L.; Scotognella, F.; Maserati, L.; Zhang, Y.; Messina, G. C.; Prato, M.; Marras, S.; Cavalli, A.; Manna, L. Cu3-xP Nanocrystals as a Material Platform for Near-Infrared Plasmonics and Cation Exchange Reactions. Chem. Mater. 2015, 27, 1120-1128. (16) Manna, G.; Pradhan, N. Semiconducting and Plasmonic Copper Phosphide Platelets. Angew. Chem. Int. Ed. 2013, 52, 6762-6766.


26

Page 27 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(17) Manthiram, K.; Alivisatos, A. P. Tunable Localized Surface Plasmon Resonances in Tungsten Oxide Nanocrystals. J. Am. Chem. Soc. 2012, 134, 3995-3998. (18) Cheng, H.; Qian, X.; Kuwahara, Y.; Mori, K.; Yamashita, H. A Plasmonic Molybdenum Oxide Hybrid with Reversible Tunability for Visible-Light-Enhanced Catalytic Reactions. Adv. Mater. 2015, 27, 4616-4621. (19) Cheng, H.; Kamegawa, T.; Mori, Kohsuke.; Yamashita, H. Surfactant-Free Nonaqueous Synthesis of Plasmonic Molybdenum Oxide Nanosheets with Enhanced Catalytic Activity for Hydrogen Generation from Ammonia Borane under Visible Light. Angew. Chem. Int. Ed. 2014, 53, 2910-2914. (20) Yin, H.; Kuwahara, Y.; Mori, K.; Cheng, H.; Wen, M.; Yamashita, H. High-SurfaceArea Plasmonic MoO3-x: Rational Synthesis and Enhanced Ammonia Borane Dehydrogenation Activity. J. Mater. Chem. A 2017, 5, 8946-8953. (21) Chen, D.; Liu, M.; Yin, L.; Li, T.; Yang, Z.; Li, X.; Fan, B.; Wang, H.; Zhang, R.; Li, Z.; Xu, H.; Lu, H.; Yang, D.; Sun, J.; Gao, L. Single-Crystalline MoO3 Nanoplates: Topochemical Synthesis and Enhanced Ethanol-Sensing Performance. J. Mater. Chem. 2011, 21, 9332-9342. (22) Chen, Z.; Cummins, D.; Reinecke, B. N.; Clark, E.; Sunkara, M. K.; Jaramillo, T. F. Coreshell MoO3-MoS2 Nanowires for Hydrogen Evolution: A Functional Design for Electrocatalytic Materials. Nano Lett. 2011, 11, 4168-4175. (23) Alsaif, M.; Latham, K.; Field, M. R.; Yao, D. D.; Medehkar, N. V.; Beane, G. A.; Kaner, R. B.; Russo, S. P.; Ou, J. Z; Kalantar-zadeh, K. Tunable Plasmon Resonances in Two-Dimensional Molybdenum Oxide Nanoflakes. Adv. Mater. 2014, 26, 39313937.


27


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 28 of 34

(24) Vasilopoulou, M.; Douvas, A. M.; Georgiadou, D. G.; Palilis, L. C.; Kennou, S.; Sygellou, L.; Soultati, A.; Kostis, I.; Papadimitropoulos, G.; Davazoglous, D.; Argitis, P. The Influence of Hydrogenation and Oxygen Vacancies on Molybdenum Oxides Work Function and Gap States for Application in Organic Optoelectronics. J. Am. Chem. Soc. 2012, 134, 16178-16187. (25) Wang, X.; Xu, Y.; Rao, H.; Xu, W.; Chen, H.; Zhang, W.; Kuang, D.; Su, C. Novel Porous Molybdenum Tungsten Phosphide Hybrid Nanosheets on Carbon Cloth for Efficient Hydrogen Evolution. Energy Environ. Sci. 2016, 9, 1468-1475. (26) Peng, X.; Pan, Q.; Rempel, G. Bimetallic Dendrimer-Encapsulated Nanoparticles as Catalysts: a Review of the Research Advances. Chem. Soc. Rev. 2008, 37, 1619-1628. (27) Yu, L.; Xia, B.; Wang, X.; Lou, X. General Formation of M-MoS3 (M = Co, Ni) Hollow Structures with Enhanced Electrocatalytic Activity for Hydrogen Evolution. Adv. Mater. 2016, 28, 92-97. (28) Hermans, S.; Raja, R.; Thomas, J. M.; Johnson, B.; Sankar, G.; Gleeson, D. SolventFree, Low-Temperature, Selective Hydrogenation of Polyenes using a Bimetallic Nanoparticle Ru-Sn Catalyst. Angew. Chem. Int. Ed. 2001, 40, 1211-1215. (29) Cao, B.; Veith, G. M.; Neuefeind, J. C.; Adzic, R. R.; Khalifah, P. Mixed ClosePacked Cobalt Molybdenum Nitrides as Non-noble Metal Electrocatalysts for the Hydrogen Evolution Reaction. J. Am. Chem. Soc. 2013, 135, 19186-19192. (30) Miao, J.; Xiao, F.; Yang, H.; Khoo, S.; Chen, J.; Fan, Z.; Hsu, Y.; Chen, H.; Zhang, H.; Liu, B. Hierarchical Ni-Mo-S Nanosheets on Carbon Fiber Cloth: a Flexible Electrode for Efficient Hydrogen Generation in Neutral Electrolyte. Sci. Adv. 2015, 1, 1-14.


28

Page 29 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(31) Hitihami-Mudiyanselage, A.; Arachchige, M. P.; Seda, T.; Lawes, G.; Brock, S. L. Synthesis and Characterization of Discrete FexNi2-xP Nanocrystals (0 < x < 2): Compositional Effects on Magnetic Properties. Chem. Mater. 2015, 27, 6592-6600. (32) Tran, P.; Nguyen, M.; Pramana, S. S. Bhattacharjee, A.; Chiam, S.; Fize, J.; Field, M. J.; Artero, V.; Wong, L. H.; Loo, J.; Barber, J. Copper Molybdenum Sulfide: a New Efficient Electrocatalyst for Hydrogen Production from Water. Energy Environ. Sci. 2012, 5, 8912-8916. (33) Chen, W.; Sasaki, K.; Ma, C.; Frenkel, A. I.; Marinkovis, N.; Muckerman, J. T.; Zhu, Y.; Adzic, R. R. Hydrogen-Evolution Catalysts Based on Non-Noble Metal NickelMolybdenum Nitride Nanosheets. Angew. Chem. Int. Ed. 2012, 51, 6131-6135. (34) Mendoza-Garcia, A.; Zhu, H.; Yu, Y.; Li, Q.; Zhou, L.; Su, D.; Kramer, M. J.; Sun, S. Controlled Anisotropic Growth of Co-Fe-P from Co-Fe-O Nanoparticles. Angew. Chem. Int. Ed. 2015, 54, 9642-9645. (35) Xiao, P.; Ge, X.; Wang, H.; Liu, Z.; Fisher, A.; Wang, X. Novel Molybdenum Carbide-Tungsten Carbide Composite Nanowires and Their Electrochemical Activation for Efficient and Stable Hydrogen Evolution. Adv. Funct. Mater. 2015, 25, 1520-1526. (36) Kriegel, I.; Scotognella, F.; Manna, L. Plasmonic Doped Semiconductor Nanocrystals: Proper-ties, Fabrication, Applications and Perspectives. Phys Rep. 2017, 674, 1-52. (37) Muhammed, M.; Doblinger, M.; Rodriguez-Fernandez, J. Switching Plasmons: Gold Nanorod-Copper Chalcogenide Core-Shell Nanoparticle Clusters with Selectable Metal/Semiconductor NIR Plasmon Resonances. J. Am. Chem. Soc. 2015, 137, 1166611677.


29


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 30 of 34

(38) Marin, B. C.; Hsu, S.; Chen, L.; Lo, A.; Zwissler, D. W.; Liu, Z.; Tao, A. R. PlasmonEnhanced Two-Photon Absorption in Photoluminescent Semiconductor Nanocrystals. ACS Photonics 2016, 3, 526-531. (39) Li, W.; Zamani, R.; Gil, P. R.; Pelaz, B.; Ibanez, M.; Cadavid, D.; Shavel, A.; AlvarezPuebla, R.; Parak, W.; Arbiol, J.; Cabot, A. CuTe Nanocrystals: Shape and Size Control, Plasmonic Properties, and Use as SERS Probes and Photothermal Agents. J. Am. Chem. Soc. 2013, 135, 7098-7101. (40) Schimpf, A. M.; Thakkar, N.; Gunthardt, C. E.; Masiello, D. J.; Gamelin, D. R. Charge-Tunable Quantum Plasmons in Colloidal Semiconductor Nanocrystals. ACS Nano 2014, 8, 1065-1072. (41) Dinoi, C.; Poli, R.; Perrin, L.; Maron, L. Mechanistic insights into β-oxygen atom transfer in olefin epoxidation mediated by W(VI) complexes and H2O2. Dalton Trans. 2012, 41, 1131-1133. (42) Kim, J.; Ong, G. K.; Wang, Y.; LeBlanc, G.; Williams, T. E.; Mattox, T. M.; Helms, B. A.; Milliron, D. J. Nanocomposite Architecture for Rapid, Spectrally-Selective Electrochromic Modulation of Solar Transmittance. Nano Lett. 2015, 15, 5574-5579. (43) Qadri, M. U.; Diaz, A. F.; Cittadini, M.; Martucci, A.; Pujol, M.; Ferre-Borrull, J.; Llobet, E.; Aguilo, M.; Diaz, F. Effect of Pt Nanoparticles on the Optical Gas Sensing Properties of WO3 Thin Films. Sensors 2014, 14, 11427-11443. (44) Zheng, H.; Ou, J.; Strano, M.; Kaner, R.; Mitchell, A.; Kalantar-zadeh, K. Nanostructured Tungsten Oxide-Properties, Synthesis, and Applications. Adv. Funct. Mater. 2011, 21, 2175-2196.


30

Page 31 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(45) Mattox, T.; Ye, X.; Manthiram, K.; Schuck, P. J.; Alivisatos, A. P.; Urban, J. J. Chemical Control of Plasmons in Metal Chalcogenide and Metal Oxide Nanostructures. Adv. Mater. 2015, 27, 5830-5837. (46) Castro, I.; Datta, R.; Ou, J.; Castellanos-Gomez, A.; Sriram, S.; Daeneke, T.; Kalantarzadeh, K. Molybdenum Oxides-From Fundamentals to Functionality. Adv. Mater. 2017, 1701619, 1-31. (47) Brezesinski, T.; Wang, J.; Tolbert, S. H.; Dunn, B. Ordered Mesoporous α-MoO3 with Iso-Oriented Nanocrystalline Walls for Thin-Film pseudocapacitors. Nature Mater. 2010, 9, 146-151. (48) Tian, B.; Liu, X.; Tu, B.; Yu, C.; Fan, J.; Wang, L.; Xie, S.; Stucky, G. D.; Zhao, D. Self-Adjusted Synthesis of Ordered Stable Mesoporous Minerals by Acid-Base Pairs. Nature Mater. 2003, 2, 159-163. (49) Gordon, T. R.; Cargnello, M.; Paik, T.; Mangolini, F.; Weber, R. T.; Fornasiero, P.; Murray, C. B. Nonaqueous Synthesis of TiO2 Nanocrystals Using TiF4 to Engineer Morphology, Oxygen Vacancy Concentration, and Photocatalytic Activity. J. Am. Chem. Soc. 2012, 134, 6751-6761. (50) Song, X.; Yang, E.; Liu, G.; Zhang, Y.; Liu, Z.; Chen, H.; Wang, Y. Preparation and Photocatalytic Activity of Mo-Doped WO3 Nanowires. J. Nanopart. Res. 2010, 28132819. (51) Alsaif, M.; Field, M. R.; Daeneke, T.; Chrimes, A. F.; Zhang, W.; Carey, B. J.; Berean, K. J.; Walia, S.; Embden, J.; Zhang, B.; Latham, K.; Kalantar-zadeh, K.; Ou, J. Exfoliation Solvent Dependent Plasmon Resonances in Two-Dimensional Sub-


31


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 32 of 34

Stoichiometric Molybdenum Oxide Nanoflakes. ACS Appl. Mater. Interfaces 2016, 8, 3482-3493. (52) Tan, X.; Wang, L.; Cheng, C.; Yan, X.; Shen, B.; Zhang, J. Plasmonic MoO3-x@MoO3 Nanosheets for Highly Sensitive SERS Detection through Nanoshell-Isolated Electromagnetic Enhancement. Chem. Commun. 2016, 52, 2893-2896. (53) Ye, X.; Hickey, D. R.; Fei, J.; Diroll, B.; Paik, T.; Chen, J.; Murray, C. B. Seeded Growth of Metal-Doped Plasmonic Oxide Heterodimer Nanocrystals and Their Chemical Transformation. J. Am. Chem. Soc. 2014, 136, 5106-5115. (54) Naik, G.; Shalaev, V. M.; Boltasseva, A. Alternative Plasmonic Materials: Beyond Gold and Silver. Adv. Mater. 2013, 25, 3264-3294. (55) Dai, Z.; Qin, F.; Zhao, H.; Ding, J.; Liu, Y.; Chen, R. Crystal Defect Engineering of Aurivillius Bi2MoO6 by Ce Doping for Increased Reactive Species Production in Photocatalysis. ACS Catal. 2016, 6, 3180-3192. (56) Hardcastle, F. D.; Wachs, I. E. Molecular Structure of Molybdenum Oxide in Bismuth Molybdates by Raman Spectroscopy. J. Phys. Chem. 1991, 95, 10763-10772. (57) Hardcastle, F. D.; Wachs, I. E. Determination of the Molecular Structures of Tungstates by Raman Spectroscopy. J. Raman Spectrosc. 1995, 26, 397-405. (58) Oakton, E.; Siddiqi, G.; Fedorov, A.; Coperet, C. Tungsten Oxide by Non-Hydrolytic Sol-Gel: Effect of Molecular Precursor on Morphology, Phase and Photocatalytic Performance. New J. Chem. 2016, 40, 217-222. (59) Wen, M.; Kuwahara, Y.; Mori, K.; Zhang, D.; Li, H.; Yamashita, H. Synthesis of Ce Ions Doped Metal-Organic Framework for Promoting Catalytic H2 Production from


32

Page 33 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Ammonia Borane under Visible Light Irradiation. J. Mater. Chem. A, 2015, 3, 1413414141. (60) Li, L.; Yao, X.; Sun, C.; Du, A.; Cheng, L.; Zhu, Z.; Yu, C.; Zou, J.; Smith, S.; Wang, P.; Cheng, H.; Frost, R.; Lu, G. Lithium-Catalyzed Dehydrogenation of Ammonia Borane within Mesoporous Carbon Framework for Chemical Hydrogen Storage. Adv. Funct. Mater. 2009, 19, 265-271. (61) Fuku, K.; Hayashi, R.; Takakura, S.; Kamegawa, T.; Mori, K.; Yamashita, H. The Synthesis of Size- and Color-Controlled Silver Nanoparticles by Using Microwave Heating and their Enhanced Catalytic Activity by Localized Surface Plasmon Resonance. Angew. Chem. Int. Ed. 2013, 52, 7446-7450. (62) Mori, K.; Miyawaki, K.; Yamashita, H. Ru and Ru-Ni Nanoparticles on TiO2 Support as Extremely Active Catalysts for Hydrogen Production from Ammonia-Borane. ACS Catal. 2016, 6, 3128-3135. (63) Hu, C.; Peng, T.; Hu, X.; Nie, Y.; Zhou, X.; Qu, J.; He, H. Plasmon-Induced Photodegradation of Toxic Pollutants with Ag-AgI/Al2O3 under Visible-Light Irradiation. J. Am. Chem. Soc. 2010, 132, 857-862.


33


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 34 of 34

TOC GRAPHICS


34

Localized Surface Plasmon Resonances in Plasmonic Molybdenum

Recommend Documents