1
|
Cheong IT, Yang Szepesvari L, Ni C, Butler C, O'Connor KM, Hooper R, Meldrum A, Veinot JGC. Not all silicon quantum dots are equal: photostability of silicon quantum dots with and without a thick amorphous shell. NANOSCALE 2024; 16:592-603. [PMID: 38058198 DOI: 10.1039/d3nr04478e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/08/2023]
Abstract
Luminescent colloidal silicon quantum dots (SiQDs) are sustainable alternatives to metal-based QDs for various optical applications. While the materials are reliant on their photoluminescence efficiency, the relationship between the structure and photostability of SiQDs is yet to be well studied. An amorphous silicon (a-Si) shell was recently discovered in SiQDs prepared by thermally-processed silicon oxides. As a-Si is known as a source of defects upon UV irradiation, the disordered shell could potentially have an adverse effect on the optical properties of nanoparticles. Herein, the photostability of ∼5 nm diameter SiQDs with an amorphous shell was compared with that of over-etched SiQDs of equivalent dimensions that bore an a-Si shell of negligible thickness. An UV-induced degradation study was conducted by subjecting toluene solutions of SiQDs to 365 nm light-emitting diodes (LEDs) under an inert atmosphere for predetermined times up to 72 hours. The structure, composition, and optical responses of the exposed SiQDs were evaluated.
Collapse
Affiliation(s)
- I Teng Cheong
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada.
| | | | - Chuyi Ni
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada.
| | - Cole Butler
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada.
| | - Kevin M O'Connor
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada.
| | - Riley Hooper
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada.
| | - Alkiviathes Meldrum
- Department of Physics, University of Alberta, Edmonton, Alberta T6G 2E1, Canada
| | - Jonathan G C Veinot
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada.
| |
Collapse
|
2
|
Ono T, Xu Y, Sakata T, Saitow KI. Designing Efficient Si Quantum Dots and LEDs by Quantifying Ligand Effects. ACS APPLIED MATERIALS & INTERFACES 2022; 14:1373-1388. [PMID: 34967610 DOI: 10.1021/acsami.1c18779] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The impact of colloidal silicon quantum dots (SiQDs) on next-generation light sources is promising. However, factors determining the efficiency of SiQDs, such as the photoluminescence (PL) wavelength, PL quantum yield (PLQY), and the SiQD LED performance based on the type of ligand, ligand coverage, stress, and dangling bonds, have not been quantified. Characterizing these variables would accelerate the design and implementation of SiQDs. Herein, colloidal SiQDs were synthesized by pyrolyzing hydrogen silsesquioxane and their surfaces were terminated with 1-decene by either thermal hydrosilylation (HT-SiQDs) or room-temperature hydrosilylation using PCl5 (RT-SiQD). As a result, PL, PL-excitation, and ultraviolet-visible absorption spectra were similar, but their PLQYs were significantly different: 54% (RT-SiQDs) vs 19% (HT-SiQDs). To understand their similarities and differences, surface coverages (dangling bonds, Si-H (≡Si-H1, ═Si-H2, and -Si-H3), Si-O-Si, Si-C, Si-Cl) were determined. A core stress analysis established that a single ligand terminated to a SiQD bond site stretched the Si-Si bond length by 0.3%. From the two well-defined SiQDs, the PLQY and SiQD LED efficiency were attributed to four factors: low coverage of insulator ligands, the Cl ligand effect on radiative and nonradiative rates, negligible dangling bonds, and a SiQD core with low tensile stress. The PLQY of the RT-SiQDs in toluene was 80%. In addition, the 20× electroluminescence intensity difference of the LEDs originated from a 10× difference in current density and a 2× difference in Auger recombination. The concepts demonstrated here can be applied to further improve the PLQY and LED efficiencies of SiQDs with other ligands.
Collapse
Affiliation(s)
- Taisei Ono
- Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan
| | - Yuping Xu
- Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan
| | - Toshiki Sakata
- Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan
| | - Ken-Ichi Saitow
- Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan
- Natural Science Center for Basic Research and Development (N-BARD), Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan
- Graduate School of Advanced Science and Engineering, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan
| |
Collapse
|
3
|
Sakamoto M, Terada S, Mizutani T, Saitow KI. Large Field Enhancement of Nanocoral Structures on Porous Si Synthesized from Rice Husks. ACS APPLIED MATERIALS & INTERFACES 2021; 13:1105-1113. [PMID: 33332080 DOI: 10.1021/acsami.0c14248] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Silicon (Si) is a highly abundant, environmentally benign, and durable material and is the most popular semiconductor material; and it is used for the field enhancement of dielectric materials. Porous Si (PSi) exhibits high functionality due to its specific structure. However, the field enhancement of PSi has not been clarified sufficiently. Herein, we present the field enhancement of PSi by the fluorescence intensity enhancement of a dye molecule. The raw material used for producing PSi was rice husk, a biomass material. A nanocoral structure, consisting of spheroidal structures on the surface of PSi, was observed when PSi was subjected to chemical processes and pulsed laser melting, and it demonstrated large field enhancement with an enhancement factor (EF) of up to 545. Confocal microscopy was used for EF mapping of samples before and after laser melting, and the maps were superimposed on nanoscale scanning electron microscope images to highlight the EF effect as a function of microstructure. Nanocoral Si with high EF values were also evaluated by analyzing the porosity from gas adsorption measurements. Nanocoral Si was responsible for the high EF, according to thermodynamic calculations and agreement between experimental and calculation results as determined by Mie scattering theory.
Collapse
Affiliation(s)
- Masanori Sakamoto
- Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan
| | - Shiho Terada
- Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan
| | - Tomoya Mizutani
- Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan
| | - Ken-Ichi Saitow
- Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan
- Natural Science Center for Basic Research and Development (N-BARD), Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan
- Graduate School of Advanced Science and Engineering, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan
| |
Collapse
|
4
|
Tang J, Sakamoto M, Ohta H, Saitow KI. 1% defect enriches MoS 2 quantum dot: catalysis and blue luminescence. NANOSCALE 2020; 12:4352-4358. [PMID: 31808769 DOI: 10.1039/c9nr07612c] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Defects in solids are typically recognized as unfavorable, leading to degradation of the structure and properties of the material. However, defects occasionally provide extraordinary benefits as the active sites of catalysts and chemical reactions, and can result in the creation of new electronic states. In particular, a low-dimensional material can become a defect-rich material due to the unique ratio of surface area to volume, giving many dangling bonds. Herein, we report the rapid (20 min) synthesis of MoS2 quantum dots (QDs) with a diameter of 4 nm at room temperature using nanosecond pulsed laser ablation in a binary solvent. The MoS2 QDs are crystalline particles composed of 3-5 layers and contain sulfur vacancies at an atomic concentration of 1% acting as a functional defect. The MoS2 QDs exhibit excellent electrocatalytic performance (Tafel slope = 49 mV dec-1) for the hydrogen evolution reaction and high quantum yield blue photoluminescence with a large Stokes shift.
Collapse
Affiliation(s)
- Jingmin Tang
- Department of chemistry, Graduate school of science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japan.
| | | | | | | |
Collapse
|
5
|
Wakatsuki Y, Ishikawa Y, Koshizaki N. Hydrofluoric acid pretreatment effect on the formation of silicon submicrometer particles by pulsed laser melting in liquid and their optical scattering property. NANOTECHNOLOGY 2020; 31:095601. [PMID: 31809268 DOI: 10.1088/1361-6528/ab5617] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Recently, the optical properties of silicon (Si) submicrometer spherical particles have been investigated to understand the dielectric nano-photonic function. Herein, we fabricated Si submicrometer spherical particles with high scattering efficiency using pulsed laser melting in deionized water or ethanol by irradiating laser at 66 mJ pulse-1 cm-2 via third harmonic of Nd:YAG laser. Hydrofluoric acid pretreatment was effective to remove surface oxide of raw Si particles; the laser fluence to obtain well crystallized spherical particles was lowered to 20 mJ pulse-1 cm-2 and the crystallinity of particles obtained were greatly improved without forming unwanted byproducts. The amount of particles was much more than those obtained by conventional fabrication technique. The particle size can be controlled by changing the laser fluence, and the scattering wavelength of colloidal solution can be controlled from visible to the near infrared range by increasing the laser fluence.
Collapse
Affiliation(s)
- Yuya Wakatsuki
- Graduate School of Engineering, Hokkaido University, Kita 13, Nishi 8, Kita-ku, Sapporo, Hokkaido 060-8628, Japan
| | | | | |
Collapse
|
6
|
Saitow KI, Okamoto Y, Suemori H. Size-Selected Submicron Gold Spheres: Controlled Assembly onto Metal, Carbon, and Plastic Substrates. ACS OMEGA 2019; 4:14307-14311. [PMID: 31508555 PMCID: PMC6733168 DOI: 10.1021/acsomega.9b01999] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Accepted: 08/02/2019] [Indexed: 06/10/2023]
Abstract
Size-selected submicron spheres become very useful building blocks if the spheres could be synthesized and integrated at any desired position. In particular, spheres having a similar size to visible-light wavelength have attracted much attention. Here, we show the synthesis and assembly of size-selected submicron gold spheres using pulsed laser ablation of a gold plate in a supercritical fluid. Four findings were obtained in the study. Submicron spheres with a narrow size distribution were generated, and the polydispersity was ≈ 6%. The average diameter was controlled from 600 to 1000 nm. A thermodynamic condition for scalable synthesis was found. The assembly of spheres onto a metal, carbon, or plastic substrate was accomplished.
Collapse
Affiliation(s)
- Ken-Ichi Saitow
- Natural Science Center for Basic Research and Development (N-BARD), and Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-hiroshima 739-8526, Japan
| | - Yoshinori Okamoto
- Natural Science Center for Basic Research and Development (N-BARD), and Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-hiroshima 739-8526, Japan
| | - Hidemi Suemori
- Natural Science Center for Basic Research and Development (N-BARD), and Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-hiroshima 739-8526, Japan
| |
Collapse
|