Preparation of Multishell-Structured NaYF₄:Yb,Tm,Nd@NaYF₄:Yb,Nd@SiO₂@ZnO Nanospheres with Effective NIR-Induced Photocatalytic Activity

Abstract

The multishell-structured NaYF 4 :Yb,Tm,Nd@NaYF 4 :Yb,Nd@ SiO 2 @ZnO nanospheres were synthesized for the first time by combining active-core/active-shell structured upconversion nanoparticles (UCNPs) with ZnO semiconductor. The composite nanospheres can be used as an efficient NIR-induced photocatalyst. Design of core/shell structure for the lanthanidedoped UCNPs (NaYF 4 :Yb,Tm,Nd@NaYF 4 :Yb,Nd) greatly improved their upconversion luminescence (UCL) efficiency which was attributed to the increase of NIR absorption at 808 nm based on Nd 3+ /Yb 3+ cascade-sensitized UC process and the efficient energy migration from active-shell to active-core. The composite photocatalyst used the enhanced NIR-to-UV upconverted light from UCNPs to realize dye photodegradation and photosterilization. On the basis of the results of the scavenger test, we confirm that the hydroxyl radicals (•OH) were considered as the main reactive species produced in the charge transfer and played a key role in the photocatalytic reaction process, while the superoxide radicals (•O 2 − ) and holes (h + ) as secondary active species also participated in the reaction. As measured by MTT assay, the composite photocatalyst exhibited low cytotoxicity for cells. The possible working mechanism can help us to improve the design and photochemical properties of the multishell-structured photocatalyst with NIR light response.

Intensifying Upconverted Ultraviolet Emission towards Efficient Reactive Oxygen Species Generation

“…In stark contrast, only ∼32% degradation was observed in G Tm GGG@SiO 2 @ZnO nanocomposite solution (Figures 6a, S13 and S14). Moreover, calculated reaction rate results suggest that the GG Tm YGG@SiO 2 @ZnO nanocomposites had a superior photocatalytic performance, by comparison with previously reported upconversion‐ZnO photocatalysts [44–46] . (Table S1 and Figure S15).…”

“…Moreover, calculated reaction rate results suggest that the GG Tm YGG@SiO 2 @ZnO nanocomposites had a superior photo-catalytic performance, by comparison with previously reported upconversion-ZnO photocatalysts. [44][45][46] (Table S1 and Figure S15). To gain more insight into the photocatalysis process, we probed various types of reactive radical species by adding different scavengers into photochemical reaction solution.…”

“…Photocatalytic activity measurements : In a typical experiment, [45] GG Tm YGG@SiO 2 @ZnO nanoparticles (10 mg) were mixed with Rhodamine B water solution (RhB, 8 mg/L), and then stirred in a dark room for 1 h until it reached the adsorption‐desorption equilibrium. The mixture was then exposed to 808‐nm laser irradiation (10 W/cm 2 ).…”

Facile Realization of Boosted Near‐Infrared‐Visible Light Driven Photocatalytic Activities of BiOF Nanoparticles through Simultaneously Exploiting Doping and Upconversion Strategy

“…[27] Qiao et al stated that the photodegradation of RhB dye was impossible by using ZnO nanoparticles upon 808 nm irradiation, while it became available when the NaYF 4 :Yb 3+ /Tm 3+ /Nd 3+ @NaYF 4 :Yb 3+ /Nd 3+ @ SiO 2 @ZnO nanospheres were adopted. [28] Notably, with the introduction of UC emissions, more energy of sunlight can be utilized by photocatalysts, leading to the enhanced photocatalytic activity. Consequently, it would be a facile route to modulate the photocatalytic properties of semiconductors through exploiting the UC emissions of rare-earth ions.…”

Enhanced TiO2 Broadband Photocatalytic Activity Based on Very Small Upconversion Nanosystems

“…Moreover, a sensitizer-incorporated shell (active shell) enables more NIR photon absorption and subsequent energy transfer to the activator ions positioned in the core . The upconversion/semiconductor heterostructures realize the NIR photocatalytic activity on account of the fact that the upconverted UV or visible light triggered by NIR light can photoexite the semiconductor leading to ROS generation. ,,− Additionally, these hybrid structures are widely employed in various biomedical applications such as phototherapy, − drug delivery, and biosensing , due to the ability of NIR excitation to penetrate into deeper tissue layers. The development of an NIR-activated photosensitizer is highly desirable for photodynamic therapy (PDT) in order to treat deeper-seated tumors and prevent excessive heat production and irradiation-induced photodamage to living tissue, two major obstacles for the clinical applications. , …”