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A wet chemical method for black phosphorus thinning and passivation
摘要： Layered black phosphorus (BP) has been expected to be a promising material for future electronic and optoelectronic applications since its discovery. However, the difficulty in mass fabricating layered air-stable BP severely obstructs its potential industry applications. Here, we report a new BP chemical modification method to implement all-solution based mass production of layered air-stable BP. This method uses the combination of two electron-deficient reagents of 2,2,6,6-tetramethylpiperidinyl-N-oxyl (TEMPO) and triphenylcarbenium tetrafluorobor ([Ph3C]BF4) to accomplish thinning and/or passivation of BP in organic solvent. The field effect transistor and photo detection devices constructed from the chemically modified BP flakes exhibit enhanced performances with environmental stability up to four months. A proof-of-concept BP thin film transistor fabricated through the all-solution based exfoliation and modification displays air-stable and typical p-type transistor behavior. This all-solution based method improves the prospects of BP for industry applications.
关键词： triphenylcarbenium tetrafluorobor,black phosphorus,TEMPO,chemical thinning,covalent functionalization
更新于2025-11-14 17:04:02
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N-hydroxyphthalimide-TiO2 complex visible light photocatalysis
摘要： TiO2 is the most established semiconductor photocatalyst. The prominence of TiO2 is becoming increasingly obvious because its interfacial redox reactions have implication on a wide range processes such as energy conversion and environmental remediation. Herein, we exploited the surface complex created by the interaction between organic molecules with binding sites and accommodating surface of TiO2 for visible light-driven selective aerobic oxidation reactions. A novel surface complex formed between N-hydroxyphthalimide (NHPI) and TiO2 was discovered. The NHPI-TiO2 complex turned out to be an outstanding visible light photocatalyst and was successfully used in the selective oxidation of amines into imines with atmosphere O2 under blue LED irradiation. The stability of the NHPI-TiO2 complex was preserved by 3 mol% of (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) acted as a cooperative catalyst. Moreover, selectivities for the imine products were also prompted by TEMPO. Superoxide radicals (O2?-) were evidenced to be the primary reactive oxygen species (ROS) to execute the oxidative conversions. This work suggests that TiO2 surface complexes can be robust photocatalysts for visible light-driven selective aerobic reactions, provided that an appropriate cooperative redox catalyst exists to channel the photocatalytic electron transfer.
关键词： titanium dioxide,surface complex,N-hydroxyphthalimide,molecular oxygen,TEMPO
更新于2025-09-23 15:22:29
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Cellulose nanofiber nanocomposites with aligned silver nanoparticles
摘要： Celluloses have attracted much attention as sustainable and abundant materials. Herein, we focus on nanocomposites based on the oxidation-treated nano-sized fibrillated celluloses, namely TOCNs. The silver nanoparticles (AgNPs) were prepared in TOCN aqueous dispersion. Generally, the AgNPs are quickly agglomerated after preparation. For the inhibition of the agglomeration of AgNPs, it is required that AgNPs were prepared under the chelation of TOCN, followed by reduction therein. Therefore, AgNPs possessed the nano-scaled radii and aligned along the TOCN from the atomic force microscopic measurements. The thermal stabilities and mechanical properties were increased. The anisotropic thermal conductivities originated from the orientation of TOCN in nanocomposites were observed. The loading of the large amounts of AgNP fillers led to the drastic increase of the thermal and electrical conductivities. The conductive paths of heat and electron were formed by the contact of AgNP with each other. We functionalized the TOCN papers through the loading of AgNPs and the obtained nanocomposites sheets served as conductors.
关键词： Cellulose nanofiber,mechanical property,TEMPO-mediated oxidation,silver nanoparticle,thermal conductivity
更新于2025-09-19 17:15:36
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Ultrafast hole extraction from photoexcited colloidal CdSe quantum dots coupled to nitroxide free radicals
摘要： Organic free radicals related to the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical are known as photoluminescence-quenchers when coupled to group II-chalcogenide colloidal quantum dots (QDs), but the mechanism responsible for this phenomenon has so far remained unresolved. Using a combination of time-resolved photoluminescence and transient absorption spectroscopies, we demonstrate that photoexcited colloidal CdSe QDs coupled to 4-amino-TEMPO undergo highly efficient reductive quenching, that is, hole transfer from the valence band of the quantum dot to the organic paramagnetic species. Interestingly, the process is shown to occur on a subpicosecond time scale for bound 4AT; such a large rate constant for the extraction of holes from photoexcited CdSe QD by a molecular species is rare and underlines the potential that TEMPO derivatives can play in mediating efficient redox processes involving colloidal CdSe QDs.
关键词： TEMPO,photoluminescence quenching,ultrafast spectroscopy,colloidal quantum dots,hole transfer
更新于2025-09-12 10:27:22
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Nitroxide-radicals–modified gold nanorods for in vivo CT/MRI-guided photothermal cancer therapy
摘要： This article presents a report of the synthesis, characterization, and biomedical application of nitroxide-radicals–modified gold nanorods (Au-TEMPO NRs) for imaging-guided photothermal cancer therapy. Patients and methods: Au nanorods were synthesized through seed-mediated growth method, 4-Amino-TEMPO was added and the reaction proceeded under magnetic stirring. Results: With a mean length of 39.2 nm and an average aspect ratio of approximately 3.85, Au-TEMPO NRs showed good photothermal ability when they were irradiated by 808-nm laser. Au-TEMPO NRs could be stored in PBS for more than 1 month, showed no cytotoxicity against both tumor and normal cells at a concentration of up to 3 mg/mL, and functioned as a dual-mode contrast agent for CT/magnetic resonance (MR) imaging in vitro and in vivo, due to their high X-ray attenuation of Au and good r1 relaxivity of nitroxide radicals. Further, they had a long retention time (~4 hours) in the main organs, which enabled a long CT/MR imaging time window for diagnosis. Bio-distribution results revealed that these Au-TEMPO NRs passively aggregated in the liver and spleen. After irradiation by 808-nm laser, Au-TEMPO NRs could ablate the solid tumor in 4T1 tumor-bearing mice, which implied they were a potential theranostic agent for dual-mode imaging and photothermal cancer therapy. Conclusion: This type of Au-TEMPO NRs with the abilities of CT/MR imaging and photothermal therapy, can play an active role in imaging-guided photothermal cancer therapy.
关键词： TEMPO,magnetic resonance imaging,PTT,Au NRs,computed tomography
更新于2025-09-10 09:29:36