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Size-confined Si nanorods (NRs) have gained notable interest because of their tunable photophysical properties that make them attractive for optoelectronic, charge storage, and sensor technologies. However, established routes for fabrication of Si NRs use well-defined substrates and/or nanoscopic seeds as promoters that cannot be easily removed, hindering the investigation of their true potential and physical properties. Herein, we report a facile, one-step route for the fabrication of Si NRs via thermal disproportionation of hydrogen silsesquioxane (HSQ) in the presence of a molecular tin precursor (SnCl4) at a substantially lower temperature (450 ºC) compared to those used in the synthesis of size-confined Si nanocrystals (>1000 ºC). The use of these precursors allows the facile isolation of phase pure Si NRs via HF etching and subsequent surface passivation with 1-dodecene via hydrosilylation. The diameters (7.7–16.5 nm) of the NRs can be controlled by varying the amount of SnCl4 (0.2–3.0%) introduced during the HSQ synthesis. Physical characterization of the NRs suggests that the diamond cubic structure is not affected by the SnCl4, HF etching, and hydrosilylation. Surface analysis of NRs indicates the presence of Si0 and Sin+ species, which can be attributed to core Si and surface Si species bonded to dodecane ligands, respectively, and a systematic variation of Si0: Si-C ratio with the NR diameter. The NRs show strong size confinement effects with solid-state absorption onsets (2.51–2.80 eV) and solution-state (Tauc) indirect energy gaps (2.54–2.70 eV) that can be tuned by varying the diameters (16.5–7.7 nm), respectively. Photoluminescence (PL) and time-resolved PL (TRPL) studies reveal size-dependent emission (1.95–2.20 eV) with short, nanosecond lifetimes across the visible spectrum which trend closely to absorption trends seen in solid-state absorption data. The facile synthesis developed for size-confined Si NRs with high crystallinity and tunable optical properties will promote their application in optoelectronic, charge storage, and sensing studies.
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Correlation of solid-state order to optoelectronic behavior in heterocyclic oligomers
A longstanding challenge in the field of optoelectronic materials, the effects of solid-state arrangement and morphology are still a prominent factor associated with small-molecule and polymer-based device performance. Here, mixed heterocyclic aromatic oligomers containing thiophene, furan and pyrazine are prepared alongside their methylated congeners. Their solution and solid-phase properties were studied via spectroscopic, electrochemical and single-crystal X-ray diffraction (XRD) analysis. Comparative analysis between solid-state packing arrangements and photophysical properties revealed optical band gaps as low as 1.7 eV with Stokes-shifts up to 130 nm and quantum yields of 12%. Results of the study aid in further understanding the effects of molecular and solid-state arrangements that give rise to unique optical and photophysical properties critical to enhancing optoelectronic behavior.
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- PAR ID:
- 10345438
- Date Published:
- Journal Name:
- CrystEngComm
- Volume:
- 24
- Issue:
- 25
- ISSN:
- 1466-8033
- Page Range / eLocation ID:
- 4564 to 4572
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D2CE00560C
