Near-infrared (NIR) photoinduced
chemical processes are highly
attractive for specific applications owing to the deep penetration
of NIR into the nontransparent materials including biological and
synthetic materials. Robust NIR photoinduced atom transfer radical
polymerization (photoATRP) was achieved using upconversion nanoparticles
(UCNPs) as an internal light converter to turn a 980 nm NIR light
to the wavelength of UV/vislight. This NIR photoATRP was capable of
polymerizing both hydrophobic and hydrophilic monomers at a low loading
of ppm concentrations of the CuBr2/tris(2-pyridylmethyl)amine
catalyst under the irradiation of a 980 nm NIR light (4 W/cm2) and UCNPs with reusable performance, providing well-defined polymers
with predetermined molecular weight, low dispersity, and excellent
chain-end fidelity. The switching of light “on/off”
showed an excellent temporal control of the polymerization. The NIR
photoATRP exhibited excellent penetrations through several visible
light-proof barriers using NIR light, and it may provide future directions
of photopolymerization in nontransparent systems, especially biological
systems containing photosensitive moieties.
A facile fabrication
strategy of transparent and upconversion photoluminescent
nylon 6 (PA6) nanofiber mats was developed based on PA6 nanofiber
mats, carboxylic acid-functionalized upconversion nanoparticles (UCNP-COOH),
and poly(methyl methacrylate) (PMMA) solution. UCNP-COOH were prepared
by a solvothermal method, followed by the ligand exchange process.
The electrospinning method and the spin-coating process were employed
to combine PA6 nanofiber mats with UCNP-COOH and PMMA to introduce
upconversion photoluminescent properties and transparency into the
nanocomposite mats, respectively. The prepared UCNP-COOH/PA6/PMMA
nanofiber mats are transparent and exhibit green emission, which are
similar to UCNP-COOH when they were excited under 980 nm laser. The
upconversion luminescent intensity of the functional nanofiber mats
can be tailored by adjusting the weight fraction of UCNP-COOH as fillers.
This facile strategy can be readily used to other types of intriguing
nanocomposites for diverse applications.
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