Hollow Upconversion Research Articles

Hollow upconversion nanoparticles: Synthesis and luminescence in comparison with their solid counterparts

Upconversion nanoparticles (UCNPs) have attracted a lot of interest in recent years due to their unique optical properties and potential for use in many different applications. However, direct synthesis of UCNPs with hollow structure at room temperature remains challenging. Here, ultra-facile one-pot synthesis of hollow Yb/Er co-doped NaBiF4 UCNPs at room temperature is reported. The NaBiF4:Yb,Er nanoparticles exhibit bright upconversion luminescence (UCL) upon near infrared excitation at 980 nm. Benefiting from the inherent advantages of the hollow structure (large surface permeability and large internal surface area), NaBiF4:Yb,Er hollow nanoparticles have superior luminescence properties than their solid counterparts. The UCL intensity of NaBiF4:Yb,Er hollow nanoparticles is 6.8 times that of solid counterparts, and its upconverison quantum efficiency is almost 10 times that of solid counterparts. Successful synthesis of these hollow UCNPs at room temperature in one-pot makes large-scale production possible due to the simplicity and low temperature nature of the synthesis and opens new ways to load sensitizer dyes or other materials for enhanced upconversion emission or multiplexed assays/imaging, or loading of photosensitive drugs for therapeutic applications. These finding will encourage researchers to further explore hollow structural materials with excellent UCL properties in the future.

A Novel Strategy to Obtain Hollow NaBiF₄:Yb3+/Er3+ Upconversion Nanospheres by One Step Coprecipitation.

Hollow upconversion luminescence nanomaterials have widespread applications in drug delivery, high efficiency catalysis, as well as energy storage owes to super-large specific surface area, cavity volume, and fluorescence properties. However, a series of complex processes and high temperature is required for the synthesis of these materials. Herein, a facile template-free coprecipitation route based on the Kirkendall diffusion process at room temperature had been developed to synthesize hollow NaBiF₄:Yb3+/Er3+ nanospheres with upconversion luminescence. X-ray diffraction (XRD), nitrogen adsoption/desorption isotherms, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and upconversion emission spectra demonstrated the successful preparation of NaBiF₄:Yb3+/Er3+ nanospheres with pervasive hollow morphology, relatively high specific surface area, and excellent upconversion luminescence properties. Moreover, the influence of some reaction parameters on the morphology and structure of the obtained samples were systematically explored. Additionally, the evolution mechanism of the hollow structure nanospheres was analyzed on account of the Kirkendall diffusion process related to the solid-liquid interfacial ion migration. It is expected that these hollow upconversion NaBiF₄:Yb3+/Er3+ nanospheres with upconversion luminescence prepared by this type of synthetic strategy will have widespread medical, environmental, and energy applications.

Peasecod-Like Hollow Upconversion Nanocrystals with Excellent Optical Thermometric Performance.

Trivalent lanthanide (Ln3+)‐doped hollow upconversion nanocrystals (UCNCs) usually exhibit unique optical performance that cannot be realized in their solid counterparts, and thus have been receiving tremendous interest from their fundamentals to diverse applications. However, all currently available Ln3+‐doped UCNCs are solid in appearance, the preparation of hollow UCNCs remains nearly untouched hitherto. Herein, a class of UCNCs based on Yb3+/Er3+‐doped tetralithium zirconium octafluoride (Li4ZrF8:Yb/Er) featuring 2D layered crystal lattice is reported, which makes the fabrication of hollow UCNCs with a peasecod‐like shape possible after Ln3+ doping. By employing the first‐principle calculations, the unique peasecod‐like hollow nanoarchitecture primarily associated with the hetero‐valence Yb3+/Er3+ doping into the 2D layered crystal lattice of Li4ZrF8 matrix is revealed. Benefiting from this hollow nanoarchitecture, the resulting Li4ZrF8:Yb/Er UCNCs exhibit an abnormal green upconversion luminescence in terms of the population ratio between two thermally coupled states (2H11/2 and 4S3/2) of Er3+ relative to their solid Li2ZrF6:Yb/Er counterparts, thereby allowing to prepare the first family of hollow Ln3+‐doped UCNCs as supersensitive luminescent nanothermometer with almost the widest temperature sensing range (123–800 K). These findings described here unambiguously pave a new way to fabricate hollow Ln3+‐doped UCNCs for numerous applications.

Construction of a Dual Drug Carrier on the Basis of Hollow Structured Upconversion Nanoparticles for pH‐Responsive Drug Delivery and UCL/MRI Dual Mode Imaging

AbstractA series of Gd3+ doping hollow upconversion nanoparticles NaYF4:Yb,Gd,Tm (h‐UNCP) are prepared successfully. The hollow NaYF4:Yb,Gd,Tm possess excellent upconversion luminescence (UCL) and large longitudinal relativity (r1 = 128.3 mm−1 s−1), which can be potentially used for UCL/magnetic resonance imaging (MRI) dual mode imaging. On the basis of the optimal h‐UCNP, doxorubicin hydrochloride (DOX) and methotrexate (MTX) are used as drug models to prepare a dual drug carrier. After the encapsulation of DOX on the h‐UCNP, chitosan (CS) is further wrapped and then used to load MTX to obtain a dual drug carrier h‐UCNPs/DOX/CS/MTX. The pH responsive release of DOX and MTX is discussed. The MTX release climbs from 33% to 100% by regulating the pH from 5.8 to 7.4. The DOX release is different at different pH conditions. The synergistic effect of DOX and MTX on the cancer cells is confirmed by cell viability. The h‐UCNPs/DOX/CS/MTX are tracked by cells UCL imaging and vivo MRI imaging. The excellent performance of UCL imaging and positive MRI images demonstrates that h‐UCNPs/DOX/CS/MTX can be used for UCL/MRI dual mode imaging. All the results show the potential application of h‐UCNPs/DOX/CS/MTX in pH responsive release and UCL/MRI dual imaging.

A Hollow NaGdF4/AFn Nanosystem Based on “Relay Race” Release for Therapy

To develop a multifunctional nanomaterial for dual-mode imaging and synergetic chemotherapy, curcumin (CUR) was physically entrapped into hollow upconversion NaGdF4 nanomaterial, then apoferritin (AFn) loaded with doxorubicin (DOX) was attached to the NaGdF4 surface. Subsequent modification with the targeting reagent folic acid (FA) led to generation of the CUR/NaGdF4 -DOX/AFn-FA conjugate for cancer treatment. X-ray diffraction, scanning (SEM) and transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) spectroscopy demonstrated the successful preparation of hexagonal-phase NaGdF4 and NaGdF4 -AFn-FA. Moreover, no toxicity was observed for NaGdF4 -AFn-FA. In vitro and in vivo experiments demonstrated that the two drugs are sequentially released from the nanocomposites. This two-drug system showed strong growth inhibitory effects on MCF-7 cells. Upconversion luminescence imaging and magnetic resonance (MR) imaging of NaGdF4 -AFn-FA were carried out. The results of this study show that NaGdF4 -AFn-FA can be used for targeted anticancer drug delivery as well as imaging, a novel multi-pronged theranostic system for tumor treatment.

Multifunctional hollow CaF2:Yb3+/Er3+/Mn2+-poly(2-Aminoethyl methacrylate) microspheres for Pt(IV) pro-drug delivery and tri-modal imaging

Combining the multi-modal medical imaging with cancer therapy in one single system has attracted the great interests for theranostic purpose. In this paper, CaF2:Yb3+/Er3+/Mn2+-poly(2-Aminoethyl methacrylate) (UCHNs-PAMA) hybrid microspheres were successfully fabricated. The synthetic route to the nanocomposite based on a facile hydrothermal method for fabrication of hollow upconversion (UC) nanospheres at first and then post-filling the PAMA interiorly through photo-initiated polymerization. The UCHNs showed orange fluorescence under 980 nm near infrared (NIR) laser excitation, which provided the upconverting luminescence (UCL) imaging modality. Meanwhile, the presence of functional Mn2+ and Yb3+ offered the enhanced T1-weighted magnetic resonance (MR) and computed tomography (CT) imaging, respectively. Thanks to introducing amine groups-containing PAMA inside the hollow nanospheres, the Pt(IV) pro-drug, c,c,t-Pt(NH3)2Cl2(OOCCH2CH2COOH)2 (DSP), can be conveniently bonded on the polymer network to construct a nanoscale anti-cancer drug carrier. The UCHNs-PAMA-Pt(IV) nanocomposite shows effective inhibition for Hela cell line via MTT assay. In contrast, Pt(IV) pro-drug and UCHNs-PAMA microspheres behave little cytotoxicity to Hela cells. This should be attributed the fact that the anti-cancer ability can be recovered only when Pt(IV) pro-drug was reduced to Pt(II)-drug in cellular environment. Furthermore, the in vivo experiments on small mice also confirm that the hybrid microspheres have relatively low toxic side effects and high tumor inhibition rate. These findings show that the multifunctional hybrid microspheres have potential to be used as UCL/MR/CT tri-modal imaging contrast agent and anti-cancer drug carriers.

DNA‐mediated Construction of Hollow Upconversion Nanoparticles for Protein Harvesting and Near‐Infrared Light Triggered Release

A simple DNA-mediated solvothermal method has been developed for the construction of well-defined hollow UNPs that can be used for a new paradigm to realize NIR light-controlled non-invasive protein release. In vitro studies show that the UNPs are capable of the transportation of enzyme into living cells. Intracellular NIR triggers the release of enzymes with high spatial and temporal precision and the released enzyme also retains its biological activity.

Correction to Formation of Hollow Upconversion Rare-Earth Fluoride Nanospheres: Nanoscale Kirkendall Effect During Ion Exchange

ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionORIGINAL ARTICLEThis notice is a correctionCorrection to Formation of Hollow Upconversion Rare-Earth Fluoride Nanospheres: Nanoscale Kirkendall Effect During Ion ExchangeFan Zhang, Yifeng Shi, Xiaohong Sun, Dongyuan Zhao, and Galen D. Stucky*Cite this: Chem. Mater. 2012, 24, 13, 2619Publication Date (Web):June 25, 2012Publication History Published online25 June 2012Published inissue 10 July 2012https://doi.org/10.1021/cm301856pCopyright © 2012 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views1098Altmetric-Citations1LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (104 KB) Get e-Alerts Get e-Alerts