The Influence of Rhenium Content on Helium Desorption Behavior in Tungsten-Rhenium Alloy.

To investigate the influence of different rhenium contents on the helium desorption behavior in tungsten-rhenium alloys, pure tungsten and tungsten-rhenium alloys were irradiated with helium under the same conditions. All irradiated samples were characterized using TDS and DBS techniques. The results indicate that the addition of rhenium can reduce the total helium desorption quantity in tungsten-rhenium alloys and slightly accelerate the reduction in the concentration of vacancy-type defects accompanying helium dissociation. The desorption activation energy of helium is approximately 2 eV at the low-temperature peak (~785 K) and about 4 eV at the high-temperature peak (~1475 K). An increase in rhenium content causes the desorption peak to shift towards higher temperatures (>1473 K), which is attributed to the formation of the stable complex structures between rhenium and vacancies. Besides, the migration of He-vacancy complexes towards traps and dynamic annealing processes both lead to the recovery of vacancy-type defects, resulting in a decrease in the positron annihilation S parameters.

Analysis of the utilization value of different tissues of Taxus×Media based on metabolomics and antioxidant activity.

BACKGROUND: Taxaceae, is a class of dioecious and evergreen plant with substantial economic and ecology value. At present many phytochemical analyses have been performed in Taxus plants. And various biological constituents have been isolated from various Taxus species. However, the difference of compounds and antioxidant capacity of different tissues of T. media is not clear. RESULTS: In the present study, we investigated the metabolites and antioxidant activity of four tissues of T. media, including T. media bark (TB), T. media fresh leaves (TFL), T. media seeds (TS), T. media aril (TA). In total, 808 compounds, covering 11 subclasses, were identified by using UPLC-MS/MS. Paclitaxel, the most popular anticancer compound, was found to accumulate most in TS, followed by TB, TFL and TA in order. Further analysis found that 70 key differential metabolites with VIP > 1.0 and p < 0.05, covering 8 subclasses, were screened as the key differential metabolites in four tissues. The characteristic compounds of TFL mainly included flavonoids and tanninsis. Alkaloids and phenolic acids were major characteristic compounds of TS and TB respectively. Amino acids and derivatives, organic acids, saccharides and lipids were the major characteristic compounds of TA. Additionally, based on FRAP and ABTS method, TS and TFL exhibited higher antioxidant activity than TB and TA. CONCLUSION: There was significant difference in metabolite content among different tissues of T. media. TFL and TS had higher metabolites and antioxidant capacity than other tissues, indicating that TFL and TS were more suitable for the development and utilization of T. media in foods and drinks.

TiO2-Modified Montmorillonite-Supported Porous Carbon-Immobilized Pd Species Nanocomposite as an Efficient Catalyst for Sonogashira Reactions.

In this study, a combination of the porous carbon (PCN), montmorillonite (MMT), and TiO2 was synthesized into a composite immobilized Pd metal catalyst (TiO2-MMT/PCN@Pd) with effective synergism improvements in catalytic performance. The successful TiO2-pillaring modification for MMT, derivation of carbon from the biopolymer of chitosan, and immobilization of Pd species for the prepared TiO2-MMT/PCN@Pd0 nanocomposites were confirmed using a combined characterization with X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N2 adsorption-desorption isotherms, high-resolution transition electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. It was shown that the combination of PCN, MMT, and TiO2 as a composite support for the stabilization of the Pd catalysts could synergistically improve the adsorption and catalytic properties. The resultant TiO2-MMT80/PCN20@Pd0 showed a high surface area of 108.9 m2/g. Furthermore, it exhibited moderate to excellent activity (59-99% yield) and high stability (recyclable 19 times) in the liquid-solid catalytic reactions, such as the Sonogashira reactions of aryl halides (I, Br) with terminal alkynes in organic solutions. The positron annihilation lifetime spectroscopy (PALS) characterization sensitively detected the development of sub-nanoscale microdefects in the catalyst after long-term recycling service. This study provided direct evidence for the formation of some larger-sized microdefects during sequential recycling, which would act as leaching channels for loaded molecules, including active Pd species.

Using Herbal-Cake-Separated Moxibustion for the Treatment of Rats with Chronic Renal Failure.

In the process of moxibustion in clinical practice, subjects need to be in a stable mood and comfortable posture to avoid problems such as moxa ash falling, scalding skin, and poor curative effect. Such problems also exist in the rat moxibustion experiment. To simulate clinical practice, it is necessary to introduce an experimental instrument in animal experiments, that is, a moxibustion device with fixed rats and moxibustion treatment synchronization, which can make experimental rats receive moxibustion treatment quietly and comfortably under non-anesthesia. Our research group designed a rat moxibustion experimental platform. The device was framed by a wooden board with a supporting base plate, multiple fixed components, and partitioned components. The device can achieve the operation mode of moxibustion in rats without binding, avoiding anesthesia and scalding and simultaneously exposing multiple acupoints on the back. This operation can avoid physical and mental injury to rats and operators, which improves the research efficiency and further promotes the development and research of moxibustion animal experiments. The device has a simple structure, is easy to operate and popularize, is comprehensively and innovatively designed, reusable, and is suitable for rat experiments mainly based on moxibustion. This article mainly introduces the structure of the experimental platform device for rat moxibustion, the basic procedure of herbal-cake-separated-moxibustion in experimental rats using the device and describes the establishment of a rat model of chronic renal failure (CRF) and representative experimental results.

HS-SPME/GC-MS Reveals the Season Effects on Volatile Compounds of Green Tea in High-Latitude Region.

This study investigates the volatile compounds of green tea produced with different leaves from spring, summer, and autumn in high-latitude region. A total of 95 volatile compounds were identified by gas chromatography-mass spectrometry (GC-MS). Spring, summer and autumn green tea contained 68, 72 and 82 volatile compounds, respectively. Principal component analysis (PCA), partial least squares-discrimination analysis (PLS-DA), and hierarchical cluster analysis (HCA) classified the samples and showed the difference. And 32 key characteristic components were screened out based on variable importance in the projection (VIP) values higher than 1.0. The characteristic volatile compounds of spring green tea including 18 components, such as geranylacetone, phenethyl alcohol, geraniol, ß-ionone, jasmone, 1-octen-3-ol and longifolene. 13 components such as 2-methylfuran, indole, 1-octanol, D-limonene and ethanethiol were the key compounds in summer green tea. And 2,4,6-trimethylstyrene was the major differential volatile compounds in autumn green tea. The results increase our knowledge of green tea in different seasons and provide a theoretical basis for production control of green tea.

Efficacy of Wen-Luo-Tong on Peripheral Neuropathy Induced by Chemotherapy or Target Therapy: A Randomized, Double-Blinded, Placebo-Controlled Trial.

OBJECTIVE: To evaluate the efficacy of Wen-Luo-Tong Granules (WLT) local administration in the treatment of patients with peripheral neuropathy (PN) induced by chemotherapy or target therapy. METHODS: This study is a randomized, double-blinded, and placebo-controlled trial. Seventy-eight patients with PN induced by chemotherapy or target therapy were enrolled from China-Japan Friendship Hospital between July 2019 and January 2020. They were randomly assigned to WLT (39 cases) and control groups (39 cases) using a block randomization method. The WLT group received WLT (hand and foot bath) plus oral Mecobalamin for 1 week, while the control group received placebo plus oral Mecobalamin. The primary endpoint was PN grade evaluated by the National Cancer Institute-Common Toxicity Criteria for Adverse Events (NCI-CTCAE). The secondary endpoints included quantitative touch-detection threshold, neuropathy symptoms, Quality of Life Questionnaire-Chemotherapy Induced Peripheral Neuropathy (QLQ-CIPN20), and Quality of Life Questionnaire-Core30 (QLQ-C30). RESULTS: After treatment, the PN grade in the WLT group was significantly lower than that in the control group (1.00 ± 0.29 vs. 1.75 ± 0.68, P<0.01). The total effective rate in the WLT group was significantly higher than that in the control group (82.05% vs. 51.28%, P<0.01). Compared with the control group, the touch-detection thresholds at fingertips, neuropathy symptom score, QLQ-CIPN 20 (sensory scale, motor scale, autonomic scale, and sum score), and QLQ-C30 (physical functioning, role functioning, emotional functioning, and global health) in the WLT group significantly improved after treatment (P<0.01 or P<0.05). CONCLUSION: WLT local administration was significantly effective in the treatment of patients with PN induced by chemotherapy or target therapy. (Trial registration No. ChiCTR1900023862).

Polyvinyl pyrrolidone-coordinated ultrathin bismuth oxybromide nanosheets for boosting photoreduction of carbon dioxide via ligand-to-metal charge transfer.

Photoreduction of CO2 to useful ingredients remains a great challenge due to the high energy barrier of CO2 activation and poor product selectivity. Herein, Polyvinyl pyrrolidone (PVP) coordinated BiOBr was synthesized by a facile chemical precipitation method at room temperature. The CO2 photoreduction behaviors of PVP coordinated BiOBr were evaluated with H2O without sacrificial agent under the simulated sunlight. The evolution rates of CO and CH4 are 263.2 µmol g-1h-1 and 3.3 µmol g-1h-1, which are 8 times and 2 times higher than those of pure BiOBr respectively. Furthermore, the coordination of PVP on BiOBr surface enhances greatly the selectivity of product CO, which is close to 100%. Loading PVP onto BiOBr could not only induce and stabilize the oxygen vacancy, but also increase the charge density of BiOBr via the ligand to metal charge transfer (LMCT), which could be beneficial to the adsorption and activation of CO2 molecule. The photoreduction mechanism of CO2 for PVP coordinated BiOBr was proposed based on the improved charge density of BiOBr by the experimental results and Density functional theory (DFT) calculations. This finding provides a new pathway to boost the conversion efficiency and selectivity for the activation of CO2 photoreduction and new molecule insights into the role of PVP in photocatalysis.

Effect of Vacancy Behavior on Precipitate Formation in a Reduced-Activation V-Cr-Mn Medium-Entropy Alloy.

In this work, we studied the evolution of vacancy-like defects and the formation of brittle precipitates in a reduced-activation V-Cr-Mn medium-entropy alloy. The evolution of local electronic circumstances around Cr and Mn enrichments, the vacancy defects, and the CrMn3 precipitates were characterized by using scanning electron microscopy with energy-dispersive spectroscopy, X-ray diffraction, and positron annihilation spectroscopy. The microstructure measurements showed that the Mn and Cr enrichments in the as-cast sample significantly evolved with temperature, i.e., from 400 °C, the Cr/Mn-segregated regions gradually dissolved into the matrix and then disappeared, and from 900 °C to 1000 °C, they existed as CrMn3 precipitates. The crystallite size of the phase corresponding to CrMn3 precipitates was about 29.4 nm at 900 °C and 43.7 nm at 1000 °C. The positron annihilation lifetime results demonstrated that the vacancies mediated the migration of Cr and Mn, and Cr and Mn segregation finally led to the formation of CrMn3 precipitates. The coincidence Doppler broadening results showed that the characteristic peak moved to the low-momentum direction, due to an increase in the size of the vacancy defects at the interface and the formation of CrMn3 precipitates.

Effects of He-D Interaction on Irradiation-Induced Swelling in Fe9Cr Alloys.

The atomic-scale defects such as (deuterium, helium)-vacancy clusters in nuclear energy materials are one of the causes for the deterioration of the macroscopic properties of materials. Unfortunately, they cannot be observed by transmission electron microscopy (TEM) before they grow to the nanometer scale. Positron annihilation spectroscopy (PAS) has been proven to be sensitive to open-volume defects, and could characterize the evolution of the size and concentration of the vacancy-like nanoclusters. We have investigated the effects of He-D interaction on the formation of nanoscale cavities in Fe9Cr alloys by PAS and TEM. The results show that small-sized bubbles are formed in the specimen irradiated with 5 × 1016 He+/cm2, and the subsequent implanted D-ions contribute to the growth of these helium bubbles. The most likely reason is that helium bubbles previously formed in the sample captured deuterium injected later, causing bubbles to grow. In the lower dose He-irradiated samples, a large number of small dislocations and vacancies are generated and form helium-vacancy clusters with the helium atoms.

Sox9 Is Crucial for Mesenchymal Stem Cells to Enhance Cutaneous Wound Healing.

BACKGROUND AND OBJECTIVES: Human umbilical cord mesenchymal stem cells (HUC-MSCs) are promising candidates for cell-based therapy in regenerative medicine or other diseases due to their superior characteristics, including higher proliferation, faster self-renewal ability, lower immunogenicity, a noninvasive harvest procedure, easy expansion in vitro, and ethical access, compared with stem cells from other sources. METHODS AND RESULTS: In the present study, we knocked down the expression of SOX9 in HUC-MSCs by lentivirus interference and found that knockdown of SOX9 inhibited the proliferation and migration of HUC-MSCs and influenced the expression of cytokines (IL-6 and IL-8), growth factors (GM-CSF and VEGF) and stemness-related genes (OCT4 and SALL4). In addition, the repair effect of skin with burn injury in rats treated with HUC-MSCs transfected with sh-control was better than that rats treated with HUC-MSCs transfected with shSOX9 or PBS, and the accessory structures of the skin, including hair follicles and glands, were greater than those in the other groups. We found that knockdown of the expression of SOX9 obviously inhibited the expression of Ki67, CK14 and CK18. CONCLUSIONS: In conclusion, this study will provide a guide for modifying HUC-MSCs by bioengineering technology in the future.

Study of Interaction Mechanism between Positrons and Ag Clusters in Dilute Al-Ag Alloys at Low Temperature.

The microstructural evolution of dilute Al-Ag alloys in its early aging stage and at low temperatures ranging from 15 K to 300 K was studied by the combined use of Positron annihilation lifetime spectroscopy (PALS), high resolution transmission electron microscopy (HRTEM), and positron annihilation Coincidence Doppler broadening (CDB) techniques. It is shown that at low temperatures below 200 K, an Ag-vacancy complex is formed in the quenched alloy, and above 200 K, it decomposes into Ag clusters and monovacancies. Experimental and calculation results indicate that Ag clusters in Al-Ag alloys can act as shallow trapping sites, and the positron trapping rate is considerably enhanced by a decreasing measurement temperature.

Oxygen vacancy-rich hierarchical BiOBr hollow microspheres with dramatic CO2 photoreduction activity.

Conversion of carbon dioxide into useful chemicals has attracted great attention. However, the significant bottlenecks facing in the field are the poor conversion efficiency of CO2 and low selectivity of products. Herein, hierarchical BiOBr hollow microspheres are fabricated by a solvothermal method using ethylene glycol (EG) as solvent in presence of polyvinyl pyrrolidone (PVP). The hollow BiOBr microspheres prepared at 120 °C exhibit the best performance for CO2 photoreduction. The evolution rates of product CO and CH4 are up to 88.1 µmol g-1h-1 and 5.8 µmol g-1h-1, which are 8.8 times and 5.8 times higher than that of plate-like BiOBr respectively. The hollow microspheres possess larger specific area and generate multiple reflections of light in the cavity, thus enhancing the utilization efficiency of light. The modulated electronic structure by oxygen vacancy (OVs) is beneficial to the transfer of photogenerated electrons and holes. Especially, the enriched charge density of BiOBr by OVs is conductive to the adsorption and activation of CO2, which could lower the overall activation energy barrier of CO2 photoreduction. In summary, the synergistic effect of the hollow structure with OVs plays a vital role in boosting the photoreduction of CO2 for BiOBr. This work provides a new opportunity for designing the high efficiency catalyst by morphology engineering with defects at the atomic level for CO2 photoreduction.

Chitosan modified Ti-PILC supported PdOx catalysts for coupling reactions of aryl halides with terminal alkynes.

Biopolymer of chitosan (CS) and titanium pillared clays (Ti-PILCs) have been combined in a hybrid as advanced supports for immobilization of PdOx=0,1 species to prepare novel PdOx=0,1@Ti-PILC/CS nano-composite catalysts. The Ti-PILC materials showed high specific surface areas and abundant meso-porous structure with many irregular pore channels caused by collapses of layered structure of clay during Ti pillaring process. Both CS chains and sub-nano sized PdOx particles were successfully incorporated into the pore channels of Ti-PILC, resulting in a decrease in both the specific surface areas and uniform distribution of pore size. Besides conventional methods characterizations, the strong interactions between PdOx species and Ti-PILC/CS support were further evidenced with positron annihilation lifetime spectroscopy studies. The resultant PdOx@Ti-PILC/CS catalyst was highly active for the coupling reactions of aryl halides with phenyl acetylenes. It was recyclable and gave excellent yield up to 13 runs with low leaching of Pd species.

Synergistic effect of internal electric field and oxygen vacancy on the photocatalytic activity of BiOBrxI1-x with isomorphous fluorine substitution.

Recently, bismuth oxyhalide photocatalysts have attracted much attention owing to their unique layered structure. In this paper, fluorine isomorphously substituted BiOBrxI1-x solid solution was synthesized by controlling the molar ratios of F, Br and I elements by the chemical precipitation method at room temperature. It was found that BiOF0.4Br0.5I0.1 exhibited excellent photocatalytic activity for the degradation of methyl orange, which was 10.1, 5.0 and 4.3 times higher than that of BiOI, BiOBr and BiOBr0.9I0.1 under visible light irradiation, respectively. It could be inferred that fluorine substitution is favorable to enhance the internal electric field (IEF) for BiOBrxI1-x with layered structure, which could improve the separation efficiency of the photogenerated holes and electrons and thus enhance the photocatalytic activity. On the other hand, the concentration of oxygen vacancies (OVs) rose with the increase of fluorine content, which could facilitate the adsorption of pollutants and serve as trapping sites for photo-induced carriers to improve the photocatalytic activity. The finding provides new insights into the synergistic effect of IEF and OVs toward the construction of high efficient photocatalysts.

Microstructure and catalytic performances of chitosan intercalated montmorillonite supported palladium (0) and copper (II) catalysts for Sonogashira reactions.

In this study, an efficient heterogeneous catalytic material including Pd0 nanoparticles and Cu2+ cations supported on montmorillonite/chitosan (MMT/CS) composite was prepared by solution intercalation and complexion methods. The valence states of Pd (both Pd(0) and Pd(II) coexisting) and Cu (mainly Cu(II)) of the Pd0/Cu2+@MMT/CS catalyst were confirmed by the X-ray photoelectron spectroscopy (XPS) characterization. The d001 spacing was enlarged from 1.25nm (MMT) to 1.94nm (Pd0/Cu2+@MMT/CS). Pd0/Cu2+@MMT/CS catalyst had obviously bigger specific surface area (SBET) and total pore volume (Vp) than pure MMT. High resolution transmission electron microscopy (HR-TEM) observation of the Pd0/Cu2+@MMT/CS catalyst showed that separated Pd0 nanoparticles sized below 3nm dispersed well both in the interlayer space and surface of MMT layers. The positron annihilation lifetime spectroscopy (PALS) was very sensitive to the microstructure changes caused by the formation of nano particles Pd0 after reduction of Pd2+/Cu2+@MMT/CS to Pd0/Cu2+@MMT/CS. The prepared Pd0/Cu2+@MMT/CS catalysts are highly active for the Sonogashira reactions of aromatic halides and alkynes in H2O/ether solution, and can be recycled 6 times. The leaching of Cu species is much quicker than Pd species during recycling, which should be the main reason for the decrease in efficiency of the recycled Pd0/Cu2+@MMT/CS catalysts.

Insightful understanding of the correlations of the microstructure and catalytic performances of Pd@chitosan membrane catalysts studied by positron annihilation spectroscopy.

In this study, the catalytic performances of palladium supported on chitosan (Pd@CS) membrane heterogeneous catalysts have been studied from the aspects of free volume by positron annihilation lifetime spectroscopy (PALS). The results showed that the variation in free volume hole size of the Pd@CS membrane catalyst was closely associated with microstructure evolutions, such as increase of Pd content, valence transition of Pd by reduction treatment, solvent swelling, physical aging during catalyst recycling, and so on. The PALS results showed that both the mean free volume hole size of the Pd0@CS membrane in the dry or swollen state (analyzed by the LT program) and its distribution (analyzed by the MELT program) are smaller than the molecule size of the reactants and products in the catalysis reaction. However, the results showed that the Pd0@CS membrane catalyst has excellent catalytic activity for the Heck coupling reaction of all the reactants with different molecule size. It was revealed that the molecule transport channels of the Pd0@CS membrane catalyst in the reaction at high temperature was through a number of instantaneously connected free volume holes rather than a single free volume hole. This hypothesis was powerfully supported by the catalytic activity assessment results of the CS layer sealed Pd0@CS membrane catalyst. Meanwhile, it was confirmed that the leaching of Pd0 nanoparticles of the reused Pd0@CS membrane catalyst during the recycling process was also through such instantaneously connected free volume holes.

Oxygen vacancy clusters essential for the catalytic activity of CeO2 nanocubes for o-xylene oxidation.

Catalytic oxidation of o-xylene was investigated on CeO2 nanocubes calcined at 350, 450, 550, and 650 °C, among which the samples calcined at 550 °C exhibited the highest activity and long durability. Positron annihilation spectroscopy measurements revealed that the size and distribution of oxygen vacancies for CeO2 nanocubes could be tuned by carefully controlling the calcination temperature. An excellent linear correlation between a factor related to size and density of oxygen vacancy clusters and reaction rate of o-xylene oxidation was revealed on ceria nanocubes. This means that oxygen vacancy clusters with suitable size and distribution are responsible for catalytic reaction via simultaneous adsorption and activation of oxygen and o-xylene. Electron spin resonance spectra revealed that over the CeO2 cubes, water vapor significantly promoted the formation of ∙OH radicals with a sharp decrease in the signals relating to oxygen vacancies, accelerating the transformation of o-xylene to the intermediate benzoate species, resulting in an enhancement of catalytic activity. Water thus serves as a "smart" molecule; its introduction into the feed mixture further confirmed the key role of oxygen vacancies in the catalytic performance of CeO2 nanocubes. A possible mechanism of oxygen vacancy formation during the calcination process was also proposed.

Probing sub-nano level molecular packing and correlated positron annihilation characteristics of ionic cross-linked chitosan membranes using positron annihilation spectroscopy.

Chitosan, CS, cross-linked with bivalent palladium has shown enhanced mechanical and thermal properties depending on the transformation of the structure at a microscopic scale. In the present study, CS directly cross-linked by palladium cation membranes (CS-cr-PM) was prepared through a solution-casting method. Mobility of chitosan chains were greatly reduced after crosslinking, making a great reduction in the swelling ratio studied by a water-swelling degree measurement, which led to an improvement in molecular chain rigidity. In order to investigate the chain packing at the molecular level in the ionic cross-linked CS system, the structure of chemically-crosslinked CS is investigated by means of the combined use of wide angle X-ray diffraction (WAXD) and infrared measurements, and a combination of positron annihilation lifetime spectroscopy (PALS) and simultaneous coincidence Doppler broadening (CDB) spectroscopy offers coherent information on both the free-volume related sub-nano level molecular packing and the chemical surrounding of free volume nanoholes in CS-cr-PM as a function of palladium salt loading. The variations in the free volume size and size distribution have been determined through the ortho-positronium (o-Ps) lifetime and its lifetime distribution. The studies showed that a strong interaction between CS molecules and palladium cations results in the change in crystallinity in formed CS-cr-PM leading to variational chain packing density. Meanwhile, significant inhibition effects on positronium formation due to doping are observed, which could be interpreted in terms of the existence of chloride ions. Applications of positron annihilation spectroscopy to study the microstructure and correlated positron annihilation characteristics of an ionic cross-linked CS system are systematically discussed.

Encaging Palladium Nanoparticles in Chitosan Modified Montmorillonite for Efficient, Recyclable Catalysts.

Metal nanoparticles, once supported by a suitable scaffolding material, can be used as highly efficient heterogeneous catalysts for numerous organic reactions. The challenge, though, is to mitigate the continuous loss of metals from the supporting materials as reactions proceed, so that the catalysts can be recycled multiple times. Herein, we combine the excellent chelating property of chitosan (CS) and remarkable stability of montmorillonite (MMT) into a composite material to support metal catalysts such as palladium (Pd). The in situ reduction of Pd2+ into Pd0 in the interstices of MMT/CS composites effectively encages the Pd0 nanoparticles in the porous matrices, while still allowing for reactant and product molecules of relatively small sizes to diffuse in and out the matrices. The prepared Pd0@MMT/CS catalysts are highly active for the Heck reactions of aromatic halides and alkenes, and can be recycled 30 times without significant loss of activities. Positron annihilation lifetime analysis and other structural characterization methods are implemented to elucidate the unique compartmentalization of metal catalysts in the composite matrices. As both CS and MMT are economical and abundant materials in nature, this approach may facilitate a versatile platform for developing highly recyclable, heterogeneous catalysts containing metal nanoparticles.