Responsive Upconversion Research Articles

Multiple wavelengths excitation of NaYF4:Tm/Er microcrystals for multicolor anti-counterfeiting and temperature sensing

Multicolor luminescence and optical thermometry hold charming potential applications in many fields, which are likely to be achieved in one rationally designed unit. Herein, a triple-wavelength (980 nm, 1550 nm and 808 nm) responsive upconversion microcrystal, using Er3+ ions as sensitizers, is proposed, which can generate tunable emission color from red to yellow and then to green. The modulated population route and energy transfer process of Er3+ are perceived to be the reason for tunable luminescence color upon excitation-wavelength. In addition, based on thermally coupled energy levels (TCLs), i.e., 2H11/2/4S3/2 and non-thermally coupled energy levels (NTCLs), i.e., 2H11/2/4F9/2 of Er3+ ions, the temperature-dependent upconversion properties were investigated. The maximum relative sensing sensitivity (Sr) of NaYF4:0.5%Tm/20%Er was found to be 1.373 % K−1 at 313 K, outperforming the majority of the same type thermometers. The results indicate that the NaYF4:0.5%Tm/20%Er microcrystals serve as a promising candidate for multicolor anticounterfeiting and optical thermometry applications.

High-efficiency decontamination of pharmaceutical wastewater: Synergistic effects from NaGdF4:Tm,Yb@Mn-MOFs composite photocatalysts

Water pollution caused by antibiotics poses a serious threat to human health and ecosystems. Rapid and efficient removal of antibiotic pollution in water by photocatalysts is one of the effective means to protect the environment and public health. Herein, a wide-spectral responsive upconversion NaGdF4:Yb,Tm@Mn-MOFs core-shell nanostructures were built by coating hexagonal NaGdF4:Yb,Tm cores with amino-functionalized manganese carboxylate MOFs (Mn-MOFs) shells, which exhibited good water dispersibility. Mn-MOFs catalysts is mainly concentrated in the ultraviolet region, while NaGdF4:Yb,Tm nanoparticles can transform infrared light into visible light or even higher energy ultraviolet light, which is harvested by the Mn-MOFs. The optimized nanostructures were tested under simulated solar light (After 120 min irradiation) in the degradation of tetracycline, oxytetracycline hydrochloride and tetracycline hydrochloride, while their degradation rates reached 70%, 72% and 75%, respectively. The better photocatalytic mechanism for antibiotics than its individual components was elucidated, which provides a potential strategy to broaden the full spectrum absorption of the wide bandgap semiconductors and apply for the field of environmental remediation.

Near-infrared-responsive nanoplatforms integrating dye-sensitized upconversion and heavy-atom effect for enhanced photodynamic therapy efficacy

The development of near-infrared (NIR)-responsive upconversion nanoplatforms for photodynamic therapy (PDT) has attracted considerable attention in recent years, but is still limited by the low PDT efficacy. Herein, we designed and synthesized a NIR-responsive nanoplatform through the integration of lanthanide-doped upconversion nanoparticles (UCNPs), Pt-decorated porphyrin metal-organic frameworks (PMOFs) and NIR dye IR808 into a core-shell structure for highly efficient antibacterial PDT. The PMOF shell can function not only as a photosensitizer to absorb the upconversion luminescence (UCL) of UCNPs for singlet oxygen (1O2) generation, but also as a porous host material for loading of IR808. Remarkably, we demonstrated that the heavy-atom effect of Pt(II) can simultaneously enhance the intersystem crossing (S1→T1) efficiencies of the IR808 and the porphyrin ligand Pt-TCPP, resulting in the enhancement of dye-triplet-sensitized UCL of UCNPs and 1O2 production capacity of the photosensitizer. As a result, the proposed nanoplatform exhibited excellent 1O2 production and a significant bactericidal activity against methicillin-resistant Staphylococcus aureus (MRSA) with 5.27 log10 (> 99.999%) killing efficacy. These findings will pave the way for designing highly efficient PDT nanoplatforms and accelerate their biomedical applications.

Preparation of near-infrared light responsive upconversion nanoparticles TiO2/(Ca,Y)F2:Tm,Yb for photodynamic antitumor therapy

Preparation of near-infrared light responsive upconversion nanoparticles TiO2/(Ca,Y)F2:Tm,Yb for photodynamic antitumor therapy

Hydrophobicity Regulation of Energy Acceptors Confined in Mesoporous Silica Enabled Reversible Activation of Optogenetics for Closed-Loop Glycemic Control.

Optogenetics-based synthetic biology holds great promise as a cell-based therapy strategy for many clinical incurable diseases; however, precise control over genetic expression strength and timing through disease state-related closed-loop regulation remains a challenge due to the lack of reversible probes to indicate real-time metabolite fluctuations. Here, based on a novel mechanism of analyte-induced hydrophobicity regulation of energy acceptors confined in mesoporous silica, we developed a smart hydrogel platform comprising glucose reversible responsive upconversion nanoprobes and optogenetic engineered cells, in which the upconverted blue light strength was adaptively tuned through blood glucose levels to control optogenetic expressions for insulin secretion. The intelligent hydrogel system enabled convenient maintenance of glycemic homeostasis through simple near-infrared illuminations without any additional glucose concentration monitoring, which efficiently avoided genetic overexpression-induced hypoglycemia. This proof-of-concept strategy efficiently combines diagnostics with optogenetics-based synthetic biology for mellitus therapy, opening up a new avenue for nano-optogenetics.

Sensitive and responsive upconversion nanoprobes for fluorescence turn-on detection of glucose concentration

Various approaches for detecting glucose concentration in real time are emerging at a breakneck pace. Glucose metabolism is closely linked to severe pathological events, which would either cause or predispose many progressive diseases in human. Herein, hydrophilic upconversion nanoprobes NaGdF4: Yb3+, Er3+@Ag anchored with glucose oxidase (GOx) for glucose detection with lower detection limits have been efficaciously constructed. In the upconversion nanoprobes, NaGdF4: Yb3+, Er3+ cores, and Ag layers act as energy donors and effective quenchers, respectively, through energy transfer. Moreover, the layer of Ag may disintegrate by H2O2 in the presence of glucose when glucose oxidase anchoring on the exterior of NaGdF4: Yb3+, Er3+@Ag nanoprobes, which leads to the phenomenon of upconverting emission recovery. Additionally, NaGdF4: Yb3+, Er3+@Ag-GOx has an ultralow detection limit of 1.77 μmol L−1 on glucose detection, and it can achieve optical bioimaging to distinguish cancer cells from normal cells. As a result, the NaGdF4: Yb3+, Er3+@Ag nanoprobes could be expanded to detect diverse H2O2-involved analytes. Overall, this nanoprobe has promising potential to be a compelling tool for the biomedical applications.

NIR-II Responsive Upconversion Nanoprobe with Simultaneously Enhanced Single-Band Red Luminescence and Phase/Size Control for Bioimaging and Photodynamic Therapy.

Lanthanide based upconversion (UC) nanoprobes have emerged as promising agents for biological applications. Extending the excitation light to the second near-infrared (NIR-II), instead of the traditional 980/808 nm light, and realizing NIR-II responsive single-band red UC emission is highly demanded for bioimaging application, which has not yet been explored. Here, a new type of NIR-II (1532nm) light responsive UC nanoparticles (UCNPs) with enhanced single-band red UC emission and controllable phase and size is designed by introducing Er3+ as sensitizer and utilizing Mn2+ as energy manipulator. Through tuning the content of Mn2+ in NaLnF4 :Er/Mn, the crystal phase, size, and emitting color are readily controlled, and the red-to-green (R/G) ratio is significantly increased from ≈20 to ≈300, leading to NIR-II responsive single band red emission via efficient energy transfer between Er3+ and Mn2+ . In addition, the single band red emitting intensity can be further improved by coating shell to avoid the surface quenching effect. More importantly, NIR-II light activated red UC bioimaging and photodynamic therapy through loading photosensitizer of zinc phthalocyanine are successfully achieved for the first time. These findings provide a new strategy of designing NIR-II light responsive single-band red emissive UCNPs for biomedical applications.

Frenkel Defect Responsive Upconversion Through High‐Energy Radiation

AbstractNear‐infrared light excitable upconversion nanocrystals are extensively applied in anticounterfeiting, optical imaging, and biomedicine, wherein many mechanistic endeavors are made to manipulate energy transfer through chemical engineering. However, how external stimuli such as high‐energy radiation (X‐ray) influence the energy transfer of these upconversion nanoparticles remains poorly understood. Here a new strategy for energy transfer modulation through X‐ray irradiation in Yb3+ and Tm3+ co‐doped nanoparticles is reported. Mechanistic studies indicate that X‐ray induced Frenkel defects in crystal lattices, other than the variation of lanthanide valence or crystal symmetry, lead to energy mismatch between adjacent Yb3+ sensitizers and the resultant inefficient energy transfer from sensitizers to activators. Based on these findings, high‐contrast X‐ray imaging and long‐term information storage (over 50 days) using nanoparticle‐containing flexible films are demonstrated. This work offers insights into the understanding of light‐matter interaction by high‐energy radiation and provides a promising methodology for long‐term information storage and X‐ray imaging.

Multilayer core-shell nanostructures for enhanced 808 nm responsive upconversion

The construction of core-shell structure is an effective strategy for promoting the emission efficiency of upconversion nanocrystals (UCNCs). In this work, the UCNCs based on Nd-doping with a multilayer core-shell nanostructure are fabricated toward achieving efficient upconversion for 808 nm excitation, which have great potential for optical applications, especially photobiological applications.

PH Responsive Upconversion Mesoporous Silica Nanoparticles for Targeted Photodynamic and Photothermal Cancer Therapy

pH Responsive Upconversion Mesoporous Silica Nanoparticles for Targeted Photodynamic and Photothermal Cancer Therapy

The pH responsive upconversion fluorescence and photothermal conversion properties of NaYF4:Yb3+/Er3+@NaYF4@MnO2@Au.

While photothermal therapy is widely applied in phototherapy, there are still challenges in developing new generation phototherapy materials with precise diagnostic functions. Here we report the construction of a pH responsive upconversion fluorescence imaging precisely guided photothermal therapy system, namely NaYF4:Yb3+/Er3+@NaYF4@MnO2@Au nanocomposites, which can effectively avoid light damage to non-target tissues. Owing to the fluorescence resonance energy transfer between the upconversion nanocrystal donor and MnO2 and Au acceptor, the upconversion fluorescence is completely quenched. However, in pH 5.3 PBS buffer, MnO2 is gradually broken down, and the upconversion fluorescence is partially recovered, which could be used for upconversion fluorescence imaging to precisely guide photothermal therapy under 980 nm excitation. Simultaneously, due to the absorption of 980 nm excitation light and the emission bands of Er3+ (2H11/2→4I15/2 and 4S3/2→4I15/2 transition), temperature increment of core@shell@MnO2@Au could reach 35.5 °C under 980 nm excitation at 0.8 W cm-2. The core@shell@MnO2@Au nanocomposites are supposed to contribute significantly in the biological applications of photoluminescence imaging and photothermal therapy.

Near-infrared responsive upconversion glass-ceramic@BiOBr heterojunction for enhanced photodegradation performances of norfloxacin

An efficient luminous and electronic energy transmission BiOBr based near-infrared (NIR) responsive heterojunction photocatalyst was successfully fabricated through growing BiOBr nanosheets on the superficial layer of the SrF2–Bi2O3–B2O3/Yb3+,Tb3+ (SBBF) upconversion glass-ceramic (GC) via a facile in-situ etching GC method (FIEG). A high norfloxacin (NOR) degradation rate of 56% was obtained under 180 min NIR light irradiation for the NIR GC photocatalyst (SBBF/BiOBr-10), and it possesses much enhanced photocatalytic activity compared with that of pure BiOBr under UV–vis–NIR light irradiation. Wherein six intermediate products were identified in the NOR photodegradation process and the possible degradation pathways were proposed. B3+, Yb3+ and Tb3+ ions in GC can be doped into BiOBr layer during the FIEG process. The core–shell structure of the GC@BiOBr heterojunction photocatalyst is in favor of increasing charge transport and reducing the recombination rate of excited carriers, and it efficiently harvests NIR photons to emit UV and visible light upconversion emissions, which can be utilized during the photocatalysis process. The photocatalyst can be facilely regenerated via HBr etching again, moreover, the low-cost and less time requirement promote the possibility of large-scale fabrication of the efficient photocatalysts.

PH Responsive Upconversion Mesoporous Silica Nanoparticles for Targeted Photodynamic and Photothermal Cancer Therapy

pH Responsive Upconversion Mesoporous Silica Nanoparticles for Targeted Photodynamic and Photothermal Cancer Therapy

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

Photodynamic therapy (PDT) has been extensively used to treat cancer and other malignant diseases because it can offer many unique advantages over other medical treatments such as less invasive, fewer side effects, lower cost, etc. Despite great progress, the efficiency of PDT treatment, as an oxygen-dependent therapy, is still limited by the hypoxic microenvironment in the human tumor region. In this work, we have developed a near-infrared (NIR) activated theranostic nanoplatform based on upconversion nanoparticles (UCNPs), which incorporates PDT photosensitizer (curcumin) and NO donor (Roussin's black salt) in order to overcome hypoxia-associated resistance by reducing cellular respiration with NO presence in the PDT treatment. Our results suggest that the photo-released NO upon NIR illumination can greatly decrease the oxygen consumption rate and hence increase singlet oxygen generation, which ultimately leads to an increased number of cancer cell deaths, especially under hypoxic condition. It is believed that the methodology developed in this study enables to relieve the hypoxia-induced resistance in PDT treatment and also holds great potential for overcoming hypoxia challenges in other oxygen-dependent therapies.

Excitation-power responsive upconversion logic operations based on the multiphoton process of a praseodymium ion

Controlling the spectral regulation properties of Pr3+ion doped material can realize by the excitation power due to the unique multiphoton processes, which could be utilized to design elementary logic operations and integrative logic operations.

Bi20TiO32 Nanoparticles Doped with Yb3+ and Er3+ as UV, Visible, and Near-Infrared Responsive Photocatalysts

In this work, we employed Yb3+ and Er3+ ions doped in a narrow bandgap oxide Bi20TiO32 to fabricate Bi20TiO32:Yb,Er, which can achieve near-infrared (NIR) responsive upconversion (UC) photocatalysi...

Understanding the Role of Yb3+ in the Nd/Yb Coupled 808-nm-Responsive Upconversion.

The realization of upconversion at 808 nm excitation has shown great advantages in advancing the broad bioapplications of lanthanide-doped nanomaterials. In an 808 nm responsive system, Nd3+ and Yb3+ are both needed where Nd3+ acts as a sensitizer through absorbing the excitation irradiation. However, few studies have been dedicated to the role of Yb3+. Here, we report a systemic investigation on the role of Yb3+ by designing a set of core-shell-based nanostructures. We find that energy migration over the ytterbium sublattice plays a key role in facilitating the energy transportation, and moreover, we show that the interfacial energy transfer occurring at the core-shell interface also has a contribution to the upconversion. By optimizing the dopant concentration and surface anchoring the infrared indocyanine green dye, the 808 nm responsive upconversion is markedly enhanced. These results present an in-depth understanding of the fundamental interactions among lanthanides, and more importantly, they offer new possibilities to tune and control the upconversion of lanthanide-based luminescent materials.

Responsive Upconversion Nanoprobe for Background-Free Hypochlorous Acid Detection and Bioimaging.

Responsive nanoprobes play an important role in bioassay and bioimaging, early diagnosis of diseases and treatment monitoring. Herein, a upconversional nanoparticle (UCNP)-based nanoprobe, Ru@UCNPs, for specific sensing and imaging of hypochlorous acid (HOCl) is reported. This Ru@UCNP nanoprobe consists of two functional components,, i.e., NaYF4 :Yb, Tm UCNPs that can convert near infrared light-to-visible light as the energy donor, and a HOCl-responsive ruthenium(II) complex [Ru(bpy)2 (DNCH-bpy)](PF6 )2 (Ru-DNPH) as the energy acceptor and also the upconversion luminescence (UCL) quencher. Within this luminescence resonance energy transfer nanoprobe system, the UCL OFF-ON emission is triggered specifically by HOCl. This triggering reaction enables the detection of HOCl in aqueous solution and biological systems. As an example of applications, the Ru@UCNPs nanoprobe is loaded onto test papers for semiquantitative HOCl detection without any interference from the background fluorescence. The application of Ru@UCNPs for background-free detection and visualization of HOCl in cells and mice is successfully demonstrated. This research has thus shown that Ru@UCNPs is a selective HOCl-responsive nanoprobe, providing a new way to detect HOCl and a new strategy to develop novel nanoprobes for in situ detection of various biomarkers in cells and early disgnosis of animal diseases.

Responsive upconversion nanoprobe for monitoring and inhibition of EBV-associated cancers via targeting EBNA1.

Non-responsive emission enhancement is the disadvantage of upconversion nanomaterials (UCNM) when compared with conventional organic based agents for molecular imaging. We herein show a new strategy by conjugating NaGdF4:Yb3+,Er3+@NaGdF4 (UCNP) with peptides to achieve responsive UC emission enhancement upon binding to a targeted protein - EBNA1. EBNA1 is a well-known viral latent protein for the EBV-associated cancer. Peptide-coating of the functionalized core-shell nanoparticle diminishes upconverted emission intensity drastically. However, the peptide-coated UCNP shows selective and responsive UC emission enhancement via aggregation with the targeted protein. This phenomenon paves a new way for UCNM in molecular imaging.

Construction of a hypoxia responsive upconversion nanosensor for tumor imaging by fluorescence resonance energy transfer from carbon dots to ruthenium complex.

In this work, we synthesized a hypoxia responsive upconversion nanosensor by the conjugation of oxygen insensitive upconversion carbon dots (CDs) with an oxygen sensitive ruthenium(ii) complex (Rud2b). The CD-Rud2b conjugate was then PEGylated to mediate the formation of nano-sized assemblies of the resultant polymer probe (CD-Ru-mPEG) in aqueous solution. The strategy allows the oxygen sensitive probe (Rud2b) to be excited by NIR irradiation and achieve upconverted emission through the Förster resonance energy transfer process from the CDs. The oxygen sensitivity of the ruthenium moiety was well-preserved in the polymeric aggregates because the PEG chains could prohibit the occurrence of self-quenching that may occur due to the close packing of the probes. Such an upconversion photoluminescence property makes the CD-Ru-mPEG nanosensor work as a biocompatible imaging system to monitor the oxygen level in cells and the hypoxic condition in vivo.