scholarly journals Effect of dopant concentration and excitation intensity on the upconversion and downconversion emission of $\beta$-NaYF$_4$:Yb$^{3+}$,Er$^{3+}$ nanoparticles

2021 ◽  
Author(s):  
Vivian Torres Vera ◽  
Diego Méndez González ◽  
Diego J. Ramos ◽  
Asmae Igalla ◽  
Marco Laurenti ◽  
...  
Keyword(s):  
Dopant Concentration ◽  
Excitation Intensity ◽  
Lanthanide Ions ◽  
Upconversion Nanoparticles ◽  
Application Development ◽  
Key Points

The dopant concentration of lanthanide ions in photon-upconversion nanoparticles (UCNPs) remains one of the key points to boost these nanomaterials' brightness and, therefore, their application development. Here, we analyzed the...

scholarly journals Anisotropic Energy Migration: An Excitation Navigating Energy Migration of Lanthanide Ions in Upconversion Nanoparticles (Adv. Mater. 9/2020)

2020 ◽  
Vol 32 (9) ◽  
pp. 2070068
Author(s):  
Zhendong Lei ◽  
Xiao Ling ◽  
Qingsong Mei ◽  
Shuai Fu ◽  
Jing Zhang ◽  
...  
Keyword(s):  
Energy Migration ◽  
Lanthanide Ions ◽  
Upconversion Nanoparticles ◽  
Anisotropic Energy

scholarly journals Porous upconversion nanostructures as bimodal biomedical imaging contrast agents

2019 ◽  
Author(s):  
Ziqing Du ◽  
Abhishek Gupta ◽  
Christian Clarke ◽  
Matt Cappadana ◽  
David Clases ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Contrast Agent ◽  
Imaging Techniques ◽  
Fluorescent Imaging ◽  
Lanthanide Ions ◽  
Great Promise ◽  
Upconversion Nanoparticles ◽  
Porous Shell ◽  
The Core ◽  
Surface Areas

AbstractLanthanide ions doped upconversion nanoparticles (UCNPs) hold great promise as the imaging contrast agent for multimodal medical imaging techniques for diagnosis, including fluorescent bioimaging, magnetic resonance imaging, and computed tomography. However, the maximized signal values of fluorescence and MRI cannot be achieved simultaneously from the same upconversion nanoparticles structures because high specific surface areas can benefit the signal gaining of MRI while big size can induce brighter fluorescent imaging. In this work, we designed and fabricated novel core-porous shell structures for UCNPs with much-enhanced signal values for both fluorescent imaging and MRI. The core-porous shell UCNPs were synthesized via a post-treatment process after an inert shell was coated onto the core UCNPs. The formation mechanism was carefully investigated. The fluorescent and magnetic resonance properties have been detailed characterized and compared from core, core-shell and core-porous UCNPs. Large and bright UCNPs in fluorescence and MRI have been achieved and great potential as the dual-modal contrast agent.

scholarly journals Effect of Different Silica Coatings on the Toxicity of upconversion nanoparticles on RAW 264.7 macrophage cells

2020 ◽  
Author(s):  
Cynthia E Kembuan ◽  
Helena Oliveira ◽  
Christina Graf
Keyword(s):  
Inductively Coupled Plasma ◽  
Charged Particles ◽  
Silica Shell ◽  
Lanthanide Ions ◽  
Raw 264.7 Cells ◽  
Emission Spectrometry ◽  
Upconversion Nanoparticles ◽  
Raw 264.7 ◽  
Silica Layer ◽  
Functionalized Particles

Upconversion nanoparticles (UCNP) consisting of NaYF₄ doped with 18% Yb and 2% Er were coated with microporous silica shells of 7±2 nm and 21±3 nm thickness. Subsequently, the initially negatively charged particles were optionally functionalized with N-(6-aminohexyl)-aminopropyltrimethoxysilane (AHAPS), providing a positive charge onto the nanoparticle surface. Inductively coupled plasma optical emission spectrometry (ICP-OES) measurements revealed that the particles with the thicker shells release fewer lanthanide ions in 24 h than particles with a thinner shell but that even a 21±3 nm thick silica layer does not entirely block the disintegration process of the UCNP. MTT tests and cell cytometry measurements with macrophages (RAW 264.7 cells) indicate that the cells treated with amino-functionalized particles with a thicker silica shell have higher viability than those incubated with UCNP with a thinner silica shell even if more particles with a thicker shell are taken up. This effect is less significant for negatively charged particles. A cell cycle analysis with amino-functionalized particles also confirms that a thicker silica shell reduces the cytotoxicity. Thus, growing silica shells of sufficient thickness is a simple approach to minimize the cytotoxicity of UCNP.

An Excitation Navigating Energy Migration of Lanthanide Ions in Upconversion Nanoparticles

2020 ◽  
Vol 32 (9) ◽  
pp. 1906225 ◽  
Author(s):  
Zhendong Lei ◽  
Xiao Ling ◽  
Qingsong Mei ◽  
Shuai Fu ◽  
Jing Zhang ◽  
...  
Keyword(s):  
Energy Migration ◽  
Lanthanide Ions ◽  
Upconversion Nanoparticles

Dynamics of Energy Transfer by Singlet Excitons in Naphthalene Crystals as Studied by Time-Resolved Spectroscopy

1979 ◽  
Vol 34 (6) ◽  
pp. 761-772 ◽  
Author(s):  
H. Auweter ◽  
A. Braun ◽  
U. Mayer ◽  
D. Schmid
Keyword(s):  
Energy Transfer ◽  
Transfer Rate ◽  
Functional Form ◽  
Dopant Concentration ◽  
Excitation Intensity ◽  
Picosecond Pulse ◽  
Pulse Excitation ◽  
Energy Transfer Rate ◽  
Time Resolved ◽  
Sensitized Fluorescence

Abstract The time-resolved sensitized fluorescence of anthracene-doped naphthalene crystals following picosecond-pulse excitation was investigated experimentally as a function of dopant concentration and temperature. The influence of the excitation intensity on the decay of pure naphthalene crystals is studied and yields an almost temperature-independent annihilation constant, yss ≈ 4 x 10-11 cm3 s-1 . The analysis of the time-resolved host and guest fluorescence shows that the energy transfer rate, kHG > changes its functional form with the guest concentration. The temperature dependence of the energy transfer rate is explained tentatively in terms of phonon relaxation and phonon promotion processes.

scholarly journals Effect of different silica coatings on the toxicity of upconversion nanoparticles on RAW 264.7 macrophage cells

2021 ◽  
Vol 12 ◽  
pp. 35-48
Author(s):  
Cynthia Kembuan ◽  
Helena Oliveira ◽  
Christina Graf
Keyword(s):  
Inductively Coupled Plasma ◽  
Charged Particles ◽  
Silica Shell ◽  
Lanthanide Ions ◽  
Raw 264.7 Cells ◽  
Emission Spectrometry ◽  
Upconversion Nanoparticles ◽  
Raw 264.7 ◽  
Silica Layer ◽  
Functionalized Particles

Upconversion nanoparticles (UCNPs), consisting of NaYF4 doped with 18% Yb and 2% Er, were coated with microporous silica shells with thickness values of 7 ± 2 and 21 ± 3 nm. Subsequently, the negatively charged particles were functionalized with N-(6-aminohexyl)-3-aminopropyltrimethoxysilane (AHAPS), which provide a positive charge to the nanoparticle surface. Inductively coupled plasma optical emission spectrometry (ICP-OES) measurements revealed that, over the course of 24h, particles with thicker shells release fewer lanthanide ions than particles with thinner shells. However, even a 21 ± 3 nm thick silica layer does not entirely block the disintegration process of the UCNPs. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays and cell cytometry measurements performed on macrophages (RAW 264.7 cells) indicate that cells treated with amino-functionalized particles with a thicker silica shell have a higher viability than those incubated with UCNPs with a thinner silica shell, even if more particles with a thicker shell are taken up. This effect is less significant for negatively charged particles. Cell cycle analyses with amino-functionalized particles also confirm that thicker silica shells reduce cytotoxicity. Thus, growing silica shells to a sufficient thickness is a simple approach to minimize the cytotoxicity of UCNPs.

scholarly journals Microlens array enhanced upconversion luminescence at low excitation irradiance

Nanoscale ◽  
2019 ◽  
Vol 11 (29) ◽  
pp. 14070-14078 ◽  
Author(s):  
Qingyun Liu ◽  
Haichun Liu ◽  
Deyang Li ◽  
Wen Qiao ◽  
Guanying Chen ◽  
...  
Keyword(s):  
Nonlinear Response ◽  
Upconversion Luminescence ◽  
Microlens Array ◽  
Excitation Intensity ◽  
Spatial Light Modulators ◽  
Upconversion Nanoparticles ◽  
Microlens Arrays ◽  
Excitation Light ◽  
Light Modulators ◽  
Intensity Threshold

Microlens arrays are applied as spatial light modulators to manipulate the distribution of excitation light fields in order to overcome the high excitation-intensity threshold of upconversion nanoparticles, taking advantage of their nonlinear response to excitation irradiance.

Construction of a near-infrared responsive upconversion nanoplatform against hypoxic tumors via NO-enhanced photodynamic therapy

Nanoscale ◽  
2020 ◽  
Vol 12 (14) ◽  
pp. 7875-7887 ◽  
Author(s):  
Ying Lan ◽  
Xiaohui Zhu ◽  
Ming Tang ◽  
Yihan Wu ◽  
Jing Zhang ◽  
...  
Keyword(s):  
Photodynamic Therapy ◽  
Near Infrared ◽  
Upconversion Nanoparticles

A near-infrared (NIR) activated theranostic nanoplatform based on upconversion nanoparticles (UCNPs) is developed in order to overcome the hypoxia-associated resistance in photodynamic therapy by photo-release of NO upon NIR illumination.

Autism and Neurodiversity: Addressing Concerns and Offering Implications for the School-Based Speech-Language Pathologist

2020 ◽  
pp. 1-7
Author(s):  
Laura S. DeThorne ◽  
Kelly Searsmith
Keyword(s):  
Service Provision ◽  
Individualized Education Program ◽  
Institutional Constraints ◽  
Individualized Education ◽  
Existing Structures ◽  
Eligibility Determination ◽  
Speech Language Pathologist ◽  
School Based ◽  
Key Points ◽  
C Center

Purpose The purpose of this article is to address some common concerns associated with the neurodiversity paradigm and to offer related implications for service provision to school-age autistic students. In particular, we highlight the need to (a) view first-person autistic perspectives as an integral component of evidence-based practice, (b) use the individualized education plan as a means to actively address environmental contributions to communicative competence, and (c) center intervention around respect for autistic sociality and self-expression. We support these points with cross-disciplinary scholarship and writings from autistic individuals. Conclusions We recognize that school-based speech-language pathologists are bound by institutional constraints, such as eligibility determination and Individualized Education Program processes that are not inherently consistent with the neurodiversity paradigm. Consequently, we offer examples for implementing the neurodiversity paradigm while working within these existing structures. In sum, this article addresses key points of tension related to the neurodiversity paradigm in a way that we hope will directly translate into improved service provision for autistic students. Supplemental Material https://doi.org/10.23641/asha.13345727

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