| 1. |
- Bergstrand, Jan, et al.
(författare)
-
On the decay time of upconversion luminescence
- 2019
-
Ingår i: Nanoscale. - : Royal Society of Chemistry. - 2040-3364 .- 2040-3372. ; 11:11, s. 4959-4969
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, we systematically investigate the decay characteristics of upconversion luminescence (UCL) under anti-Stokes excitation through numerical simulations based on rate-equation models. We find that a UCL decay profile generally involves contributions from the sensitizer's excited-state lifetime, energy transfer and cross-relaxation processes. It should thus be regarded as the overall temporal response of the whole upconversion system to the excitation function rather than the intrinsic lifetime of the luminescence emitting state. Only under certain conditions, such as when the effective lifetime of the sensitizer's excited state is significantly shorter than that of the UCL emitting state and of the absence of cross-relaxation processes involving the emitting energy level, the UCL decay time approaches the intrinsic lifetime of the emitting state. Subsequently, Stokes excitation is generally preferred in order to accurately quantify the intrinsic lifetime of the emitting state. However, possible cross-relaxation between doped ions at high doping levels can complicate the decay characteristics of the luminescence and even make the Stokes-excitation approach fail. A strong cross-relaxation process can also account for the power dependence of the decay characteristics of UCL.
|
|
| 2. |
- Guo, Xin, et al.
(författare)
-
Achieving low-power single-wavelength-pair nanoscopy with NIR-II continuous-wave laser for multi-chromatic probes
- 2022
-
Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 13:1
-
Tidskriftsartikel (refereegranskat)abstract
- The authors introduce stimulated-emission induced excitation depletion (STExD) nanoscopy using a single pair of low-power, near-infrared, continue-wave lasers. Emission of multichromatic probes is inhibited by cascade amplified depletion in lanthanide upconversion systems induced by manipulating their common sensitizer. Stimulated emission depletion (STED) microscopy is a powerful diffraction-unlimited technique for fluorescence imaging. Despite its rapid evolution, STED fundamentally suffers from high-intensity light illumination, sophisticated probe-defined laser schemes, and limited photon budget of the probes. Here, we demonstrate a versatile strategy, stimulated-emission induced excitation depletion (STExD), to deplete the emission of multi-chromatic probes using a single pair of low-power, near-infrared (NIR), continuous-wave (CW) lasers with fixed wavelengths. With the effect of cascade amplified depletion in lanthanide upconversion systems, we achieve emission inhibition for a wide range of emitters (e.g., Nd3+, Yb3+, Er3+, Ho3+, Pr3+, Eu3+, Tm3+, Gd3+, and Tb3+) by manipulating their common sensitizer, i.e., Nd3+ ions, using a 1064-nm laser. With NaYF4:Nd nanoparticles, we demonstrate an ultrahigh depletion efficiency of 99.3 +/- 0.3% for the 450 nm emission with a low saturation intensity of 23.8 +/- 0.4 kW cm(-2). We further demonstrate nanoscopic imaging with a series of multi-chromatic nanoprobes with a lateral resolution down to 34 nm, two-color STExD imaging, and subcellular imaging of the immunolabelled actin filaments. The strategy expounded here promotes single wavelength-pair nanoscopy for multi-chromatic probes and for multi-color imaging under low-intensity-level NIR-II CW laser depletion.
|
|
| 3. |
|
|
| 4. |
- Huang, Fuhua, et al.
(författare)
-
Suppression of Cation Intermixing Highly Boosts the Performance of Core-Shell Lanthanide Upconversion Nanoparticles
- 2023
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 145:32, s. 17621-17631
-
Tidskriftsartikel (refereegranskat)abstract
- Lanthanide upconversion nanoparticles (UCNPs) have beenextensivelyexplored as biomarkers, energy transducers, and information carriersin wide-ranging applications in areas from healthcare and energy toinformation technology. In promoting the brightness and enrichingthe functionalities of UCNPs, core-shell structural engineeringhas been well-established as an important approach. Despite its importance,a strong limiting issue has been identified, namely, cation intermixingin the interfacial region of the synthesized core-shell nanoparticles.Currently, there still exists confusion regarding this destructivephenomenon and there is a lack of facile means to reach a delicatecontrol of it. By means of a new set of experiments, we identify andprovide in this work a comprehensive picture for the major physicalmechanism of cation intermixing occurring in synthesis of core-shellUCNPs, i.e., partial or substantial core nanoparticle dissolutionfollowed by epitaxial growth of the outer layer and ripening of theentire particle. Based on this picture, we provide an easy but effectiveapproach to tackle this issue that enables us to produce UCNPs withhighly boosted optical properties.
|
|
| 5. |
- Huang, Fuhua, et al.
(författare)
-
Transient energy trapping as a size-conserving surface passivation strategy for producing bright ultrasmall upconversion nanoprobes
- 2023
-
Ingår i: Nano Energy. - : Elsevier BV. - 2211-2855 .- 2211-3282. ; 105
-
Tidskriftsartikel (refereegranskat)abstract
- Lanthanide-doped upconversion nanoparticles (UCNPs) have been widely exploited as nanoprobes or energy transducers in traditional as well as emerging biological applications, such as bioimaging, photodynamic ther-apy, optogenetics, gene editing. However, the breadth and depth of their utility in the biomedical areas are still not comparable to conventional luminescent probes, such as fluorescent dyes and semiconductor quantum dots. Their application is largely limited by their large size, typically > 20 nm, to ensure a sufficient luminescence brightness. In order to enhance the brightness of UCNPs without exceeding the critical size limitations for biomedical applications, we employ here a transient energy trapping effect as a nanoprobe surface passivation strategy to prevent deleterious distant energy migration in the host lattice, which is particularly prevalent in ultrasmall UCNPs and leads to luminescence quenching. We demonstrate this strategy by incorporating Tm3+ ions as energy trapping centers near the surface of sub-10 nm NaYF4: Yb, Er UCNPs and obtain an emission enhancement by almost one order of magnitude without any increment on the nanoparticle size. Our work presents a promising strategy for the preparation of ultrasmall and bright upconversion nanoprobes that are less vulnerable to surface quenching and that potentially minimize the interference with the object. This facilitates their biomedical applications as here demonstrated by unprecedented high-quality cell labeling and imaging, featured with very uniform nanoparticle distribution in the outer nuclear region.
|
|
| 6. |
|
|
| 7. |
- Li, Nana, et al.
(författare)
-
Yb3+-enhanced UCNP@SiO2 nanocomposites for consecutive imaging, photothermal-controlled drug delivery and cancer therapy
- 2016
-
Ingår i: Optical Materials Express. - : Optical Society of America. - 2159-3930 .- 2159-3930. ; 6:4, s. 1161-1171
-
Tidskriftsartikel (refereegranskat)abstract
- UCNP-based drug delivery systems commonly rely on stimulisensitive auxiliaries, lacking a straightforward manipulation strategy. Here we designed Yb3+-enhanced upconversion/ mesoporous silica nanocomposites (UCNP@SiO2) for consecutive cell imaging, photothermal drug delivery and cancer therapy. Core UCNPs (NaYbF4: 2% Er3+) were synthesized and coated with mesoporous silica, whose high-efficiency photothermal properties were verified in vitro. Then doxorubicin hydrochloride (DOX) was loaded on the UCNP@SiO2 and successfully triggered to release by a 975 nm laser of 150 mW or 300 mW. Before the therapy, we used a much lower laser power of 15 mW (which would cause little DOX release) for UCNP-probed fluorescence imaging of Hela cells and affirmed a favorable cell uptake of nanocomposites. Subsequently, cell viability assay and PI stain have demonstrated that the 300 mW laser could manipulate drug delivery of UCNP@SiO2-DOX and cause a severe loss of cell viability. The Yb3+-enhanced UCNP@SiO2 shows a great potential in simultaneous biomedical imaging and photothermal-triggered on-site drug delivery for chemotherapy of cancer. (C) 2016 Optical Society of America
|
|
| 8. |
- Li, Xin, et al.
(författare)
-
Study on enhancement of fluorescence with gold nanorods
- 2008
-
Ingår i: Asia Optical Fiber Communication and Optoelectronic Exposition and Conference 2008. - : Optical Society of America. - 9781557528636
-
Konferensbidrag (refereegranskat)abstract
- Enhancement of fluorescence of streptavidin conjugated with gold nanorods (GNRs) was observed. The impact of GNRs with different surface plasmon resonance bands and different concentrations to the efficiency of the fluorescence enhancement was studied.
|
|
| 9. |
- Liang, Yusen, et al.
(författare)
-
Migrating photon avalanche in different emitters at the nanoscale enables 46th-order optical nonlinearity
- 2022
-
Ingår i: Nature Nanotechnology. - : Springer Nature. - 1748-3387 .- 1748-3395. ; 17:5, s. 524-530
-
Tidskriftsartikel (refereegranskat)abstract
- A photon avalanche (PA) effect that occurs in lanthanide-doped solids gives rise to a giant nonlinear response in the luminescence intensity to the excitation light intensity. As a result, much weaker lasers are needed to evoke such PAs than for other nonlinear optical processes. Photon avalanches are mostly restricted to bulk materials and conventionally rely on sophisticated excitation schemes, specific for each individual system. Here we show a universal strategy, based on a migrating photon avalanche (MPA) mechanism, to generate huge optical nonlinearities from various lanthanide emitters located in multilayer core/shell nanostructrues. The core of the MPA nanoparticle, composed of Yb3+ and Pr3+ ions, activates avalanche looping cycles, where PAs are synchronously achieved for both Yb3+ and Pr3+ ions under 852 nm laser excitation. These nanocrystals exhibit a 26th-order nonlinearity and a clear pumping threshold of 60 kW cm−2. In addition, we demonstrate that the avalanching Yb3+ ions can migrate their optical nonlinear response to other emitters (for example, Ho3+ and Tm3+) located in the outer shell layer, resulting in an even higher-order nonlinearity (up to the 46th for Tm3+) due to further cascading multiplicative effects. Our strategy therefore provides a facile route to achieve giant optical nonlinearity in different emitters. Finally, we also demonstrate applicability of MPA emitters to bioimaging, achieving a lateral resolution of ~62 nm using one low-power 852 nm continuous-wave laser beam.
|
|
| 10. |
- Liu, Haichun, et al.
(författare)
-
Photon Upconversion Kinetic Nanosystems and Their Optical Response
- 2018
-
Ingår i: Laser & Photonics reviews. - : John Wiley & Sons. - 1863-8880 .- 1863-8899. ; 12:1
-
Forskningsöversikt (refereegranskat)abstract
- Lanthanide-doped photon upconversion nanoparticles (UCNPs) are capable of converting low-intensity near-infrared light to UV and visible emission through the synergistic effects of light excitation and mutual interactions between doped ions. UCNPs have attracted strong interest as unique spectrum converters and found a multitude of applications in areas like biomedical imaging, energy harvesting and information technology. UCNPs are distinct from many other types of luminescent materials in terms of the involvement of a host lattice and multiple optical centers, i.e., trivalent lanthanide ions with manyfolds of accessible long-lived energy states, in individual nanoparticles. The mutual interactions between these optical centers, i.e., sequential energy transfers, make them operate as an integrated unit and co-determine the luminescence kinetics and other optical properties of the individual nanoparticle. Thus, each nanoparticle consititutes a kinetic optical system. In this work, we explore UCNPs from the outset of being such kinetic optical systems and review their physical formation, the underlying photophysics, macroscopic statistical description, and their response to various optical stimuli in the spectral, polarization, intensity, temporal and frequency domains, and demonstrate ways that their optical output can be optimized by manipulating the excitation schemes. Our review highlights upconversion nanotechnology as an interdisciplinary field across chemistry, physics and biomedical engineering, with great future possibilities, flexibility and ramifications. We outline some of the potential directions of upconversion nanoparticle research.
|
|
