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In this work, Gd-based coordination polymer (GdCP) hollow spheres have been synthesized by a general, facile and template-free solvothermal strategy. The products were well characterized and analyzed. Results indicate that the uniform hollow nanospheres have diameters of 160–260 nm. Influential factors such as reaction temperature, time, and dosage...
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... One of the most common ways of synthesizing coordination polymers is heating the precursors and solvents mixture inside a sealed vial using an autoclave. Most reported spherical ICPs have been produced by using this method [22,[45][46][47][48][49][50][51][52]. The solvothermal synthesis can lead to either crystalline MOFs or amorphous ICPs depending on the reaction temperature and time, concentration of reactants, surfactant, solvent and pH values. ...
... The calculated pore volumes are usually average values since the amorphous structure leads to the formation of different sized pores. Rare-earth based ICPs typically exhibits even lower values, due to the high coordination numbers and multiple geometries in the same structure closing the pore access [48]. ...
Since Alfred Werner published his work on coordination compounds in 1893, much progress has been made regarding this class of materials. Further studies evolved to the coordination polymers, among which the Metal-Organic Frameworks (MOFs), which are two- or three-dimensional coordination networks containing potentially empty cavities. Frequently, MOFs are crystalline materials with the coordination units repeating itself in an ordered manner in the structure, thus creating different topologies. However, synthetic parameters (pH, temperature, solvent) directly influence the kinetics and thermodynamics of the nucleation and growth of MOF crystals. In some cases, a material of low crystallinity may be formed, with short-range order. Most authors classify these compounds as Infinite Coordination Polymers (ICPs), Coordination Polymer Particles (CPPs) or Nanoscale Coordination Polymers (NCPs). Although not yet standardized by IUPAC, several articles, including recent review articles, name low-crystalline coordination polymers as ICPs. ICPs can show high tailorability regarding the particle size and morphology. They are usually obtained as micro- or nanoparticles, with spherical (mainly), cubic, rod-like and ring-like morphologies being reported. The major challenge in the study of ICPs lies in the structural elucidation, often performed by single crystal X-ray diffraction in crystalline MOFs. In this chapter, the synthetic routes, formation mechanisms, characterization techniques and potential applications of spherical ICP particles, such as in sensing, light-emitting devices, biomedicine, catalysis, gas sorption and separation, will be discussed.
Rapid and accurate monitoring of food freshness to provide consumers with high-quality meat continues to be of tremendous importance to the food industry. In this report, an efficient Fe-doped polydopamine (Fe-PDA) nanozyme with peroxidase-mimicking activity was synthesized by a high-temperature hydrothermal method, and was applied to a spectrophotometric sensing system, which successfully reports the concentration of hypoxanthine (Hx) related to meat freshness. The Fe-PDA nanozyme showed excellent peroxidase simulation activity, which was primarily verified by steady-state kinetics experiments. In the presence of xanthine oxidase (XOD), Hx can react quantitatively with dissolved O2 to generate H2O2, which can be further catalyzed and produce hydroxyl radicals (•OH) under acidic conditions via the Fe-PDA nanozyme and oxidize colorless TMB to blue oxTMB with absorbance at 653 nm. The absorbance at 653 nm expressed a clear linear relationship with hypoxanthine concentration in the range of 5.13-200 μM, and the detection limit was 1.54 μM. This method was further assessed by measuring the recovery of Hx added to meat samples, which showed promising accuracy. Overall, the developed Fe-PDA nanozyme with excellent peroxidase-mimicking activity is cost-effective, high-performance and easy to produce, offering an efficient and low-cost sensing system based on spectrophotometry for meat freshness determination as an alternative to conventional methods.
Coordination polymers have been extensively studied in recent years. Some of these materials can exhibit several properties such as permanent porosity, high surface area, thermostability and light emission, as well as open sites for chemical functionalization. Concerning the fact that this kind of compounds are usually solids, the size and morphology of the particles are important parameters when an application is desired. Inside this context, there is a subclass of coordination polymers, named infinite coordination polymers (ICPs), which auto‐organize as micro‐ or nanoparticles with low crystallinity. Specifically, the particles exhibiting spherical shapes and reduced sizes can be better dispersed, enter cells much easier than bulk crystals and be converted to inorganic materials by topotactic transformation. Luminescent ICPs, in particular, can find applications in several areas, such as sensing probes, light‐emitting devices and bioimaging. In this review, we present the state‐of‐the‐art of ICP‐based spherical particles, including the growth mechanisms, some applications for luminescent ICPs and the challenges to overcome in future commercial usage of these materials.
Daunorubicin is a common antineoplastic agent used for the treatment of lymphoma and acute leukemia. Here, we report an 808 nm-excited, citric acid coated, core–shell upconversion fluorescent sensor for daunorubicin (DAU) detection in aqueous solutions. The designed Nd³⁺ doped core–shell structure significantly raises the upconversion fluorescence intensity, while the presence of citric acid ligands helps to reduce the surface quenching effect exerted by water and improve the dispersibility. The upconversion fluorescence of nanoparticles is efficiently quenched in the presence of DAU via a fluorescence resonance energy transfer mechanism. The dynamic quenching constant was 1.58 × 10⁴ M⁻¹. The fluorescence intensity ratio showed a good linear response to DAU concentration in the range of 0.1 μM to 70 μM with a detection limit of 0.06 μM. The sensing method was simple, rapid, and low-cost and was further applied to determine the levels of DAU in urine with spike recoveries from 97.3% to 101.5%. The proposed fluorescent sensor holds great potential for in vivo imaging and detection of DAU.
Bioactive metal–organic frameworks (bio‐MOFs) built from biofunctional metal ions and linkers show a new strategy to construct multifunctional theranostic platforms. Herein, a bio‐MOF is synthetized via the self‐assembling of Fe³⁺ ions and doxorubicin hydrochloride (DOX) molecules. Then, through a stepwise assembly strategy, another bio‐MOFs structure consisting of Gd³⁺ ions and 1,3,5‐benzenetricarboxylic acid (H3BTC) is wrapped on the surfaces of Fe‐DOX nanoparticles, followed by adsorbing photosensitizer indocyanine green (ICG). Specifically, the Gd‐MOF shell structure can not only act as a contrast agent for magnetic resonance imaging (MRI), but also provides protection for Fe‐DOX cores, controlling the release of DOX. The photoacoustic and photothermal imaging (PAI and PTI) methods are successfully introduced to the platform by loading ICG, providing potential applications for multimodal biological imaging. The in vitro and in vivo outcomes indicate that the Fe‐DOX@Gd‐MOF‐ICG nanoplatform exhibits outstanding synergistic antitumor performance via MR/PA/PT imaging guided chemotherapy, photothermal and photodynamic combination therapy. The work may encourage further exploration of bio‐MOFs based multifunctional theranostic platforms for multimodal imaging guided compound antitumor therapy, which will open an avenue of MOFs toward biological applications.
Infinite Coordination Polymers (ICPs) are compounds usually obtained as spherical particles exhibiting amorphous phases in the powder X-ray diffraction patterns. In the present work, we report an ICP system based on rare-earth ions with pyrazole-3,5-dicarboxylate as linker and malonate as coordination modulator. The compounds exhibit a 2D MOF structure. Three different synthetic routes were used, namely microwave-assisted, solvothermal and gel diffusion. The syntheses yield single-phase spherical particles, which were characterized by PXRD, ¹H NMR, CHN, FTIR, TGA, SEM and TEM. Photoluminescence spectroscopy was carried out to study the luminescent properties of the Eu³⁺ and Tb³⁺-based samples. With the different-sized particles obtained, we could elucidate the intricate microstructure of the spheres and propose a reason behind the observed amorphous phases in the PXRD patterns.
Traditional tumor treatments suffer from severe side effects on account of their invasive process and inefficient outcomes. Featuring unique physical microenvironment, the tumor microenvironment (TME) provides a new research direction for designing more efficient and safer treatment paradigm. In this study, we fabricated a polydopamine (PDA)-based TME-responsive nanosystem, which successfully integrate glucose degradation, Fenton reaction and photothermal therapy for efficient cancer therapy. Through a convenient hydrothermal method, Fe2+ doped Fe(Ⅱ)-PDA nanoparticle was successfully fabricated, which shows excellent photothermal effect and interesting reactivity for Fenton reaction. Instead of introducing of toxic anticancer agents, natural glucose oxidase (GOD) was grafted on the Fe(Ⅱ)-PDA, forming a cascade catalytic nanomedicine for specific response to the glucose in TME. The GOD grafted on the Fe(Ⅱ)-PDA-GOD is ought to catalyze rich glucose in TME into gluconic acid and H2O2. The concomitant generation of H2O2 can enhance the efficiency of sequential Fenton reaction, producing abundant hydroxyl radicals (OH) for cancer therapy. Besides, the extra consumption of intratumoral glucose also could inhibit tumor growth by reducing the energy supply. Taken together, the in vitro and in vivo anti-tumor studies of such TME-based Fe(Ⅱ)-PDA-GOD nanosystems displayed a favorable synergistic potency of glucose degradation, Fenton reaction and photothermal therapy against tumor growth. Our design expands the biological application of multifunctional PDA, while provides novel strategies toward effective anti-tumor treatment with minimal side effects.
In this work, we have developed a general, simple and template-free solvothermal strategy to prepare Yb³⁺ and Er³⁺ codoped Gd-based coordination polymer (GdCP) hollow spheres with glycylglycine as a ligand. Scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, energy dispersive X-ray spectroscopy, infrared and thermogravimetric analysis were used to characterize the hollow spheres. The GdCP hollow spheres are with a size of about 200 nm and the thickness of the shell was about 30 nm. Upconversion emission with 832 nm being the strongest was realized in the hollow spheres when excited with 980 nm laser. Magnetic measurement reveals that the GdCP hollow sphere is paramagnetic. The relaxation information was measured and the product is subjected to T1 weighted imaging. These prepared GdCP hollow spheres may be applied to multimodal imaging.
