Ultrasmall Particles Research Articles

Room-Temperature Synthesis of Sub-2 nm Ultrasmall Platinum-Rare-Earth Metal Nanoalloys for Hydrogen Evolution Reaction.

To tune the activity of Pt alloy electrocatalysts and reduce the Pt loading, researchers have intensively studied alloys of Pt with late transition metals. However, Pt alloy formation with rare-earth (RE) elements through the traditional chemical route is still a challenge due to the vastly different standard reduction potentials. Here, we report a universal chemical method to prepare a series of Pt/RE (RE = La, Ce, Pr, Nd, Eu, Gd, Tb, Dy, Lu) nanoalloys with tunable compositions and ultrasmall particle sizes (sub-2 nm). These Pt-RE nanoalloys were synthesized by a strong liquid metal reduction with high-speed shearing assistance at room temperature. Among the nine Pt-RE alloy catalysts, the PtNd/C shows the best hydrogen evolution reaction (HER) activity, stability, and durability compared to commercial Pt/C. The PtNd/C shows an overpotential of 25.9 mV at the current density of 10 mA/cm2 with a Tafel slope of 19.5 mV/dec and excellent stability in the acidic medium. This work not only provides a general and scalable strategy for synthesizing noble metal-RE alloys but also highlights noble metal-RE alloys as sufficiently advanced catalysts and accelerates the research of noble metal-RE alloy in energy-related applications.

Is there a common reaction pathway for chromium sulfides as anodes in sodium-ion batteries? A case study about sodium storage properties of MCr2S4 (M = Cr, Ti, Fe)

We present new insights into the electrochemical properties of three metal sulfides MCr2S4 (M = Cr, Ti, Fe) probed as anode materials in sodium-ion batteries for the first time. The electrodes deliver decent reversible capacities and good long-term cycle stability, e.g., 470, 375, and 524 mAh g−1 are obtained after 200 cycles applying 0.5 A g−1 for M = Cr, Ti, and Fe, respectively. The reaction mechanisms are investigated via synchrotron-based X-ray powder diffraction and pair distribution function analyses. The highly crystalline educts are decomposed into Na2S nanoparticles and ultra-small metal particles during initial discharge without formation of intermediate NaCrS2 domains as previously reported for CuCrS2 and NiCr2S4. After a full cycle, the structural integrity of MCr2S4 (M = Cr, Ti, Fe) is not recovered. Thus, the Na storage properties are attributed to redox reactions between nanoscopic to X-ray amorphous conversion products with only local atomic correlations M···S/S···S in the charged and M···M/Na···S in the discharged state.Graphical

Electrochemical sensing of indole in plasma using Pd nanoparticles modified metal-organic framework Cr-MIL-101/ionic liquid sensor

Herein, an electrochemical sensor for detection of indole was fabricated based on Pd nanoparticles modified Metal-Organic Framework Cr-MIL-101 (Pd@Cr-MOF) and ionic liquid (IL). The electrochemical behavior of indole was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) at the surface of the modified electrode. The sensor was developed by incorporating of ultra-small nano-sized palladium particles stabilized on metal–organic framework Cr-MIL-101 and 1-hexyl-3-methylimidazolium chloride in the carbon paste electrode (CPE). The synthesized Pd nanoparticles modified Metal-Organic Framework Cr-MIL-101 (Pd@Cr-MOF) was characterized using Brunauer-Emmett-Teller (BET), EDS, XRD, SEM and TEM techniques. The Pd@Cr-MOF/IL/CPE exhibited the good sensitivity towards indole compared to the unmodified electrode. The linear range for determination of indole by this sensor was found to be 1 to 1100 nM with a detection limit of 0. 3 nM. Also, the proposed sensor was successfully applied for monitoring of indole in human serum sample and satisfactory results were obtained. Ultimately, high performance liquid chromatography (HPLC) method was applied for the validation of the electrochemical method for the determination of indole in human serum sample.

Two Physical Levels of Fundamental Particles That Determine Essence and Natural Independence of Electricity and Magnetism

The experiments of F. Ehrenhaft, as well as the experimental and theoretical studies of the author, showed that it is the magnetic elementary particles (magnetic charges) that are the direct sources of the magnetic field and all magnetic manifestations in Nature. Eddy currents of magnetic charges (the rotating magnetic dipoles), which actually exist in the structures of a substance and are untwisted by means of an electric current in conductors, are direct sources of the well-known eddy magnetic field rotH. Together with electric charges, magnetic charges make up the shells of atoms, which are actually electromagnetic not electronic. It is the electromagnetic shells of atoms that are the sources of the vortex electromagnetic (gravitational) field, which is described by the vortex vector rot[E – H]. The main reason for ignoring magnetic charges, as well as true anti-electrons in physical science, is the harsh conditions for their retention in atoms and matter, which are fundamentally different from the retention of electrons.     The introduction of magnetic charges into basic physics showed that the real Physical World is formed by three global phases: Matter, Antimatter and Energo-medium which make up the world Physical Triad. Each of the noted phases is formed by its own fundamental particles. The material phase or Matter is formed by spinor (charged) particles of electrical and magnetic nature with a negative charge. The antimaterial phase or Antimatter is formed by magnetic and electric particles with a positive charge. The third phase of the Physical Triad is a super-dense Energo- medium (Energo-ether), which fills the entire space of the real World and consists of its own ultra-small elementary particles, which received the author's name - energions. Energions are massless and spinless particles moving in all directions at near-light speeds. The author showed that particles-energions in the composition of the Energo-medium are divided into two natural groups: Electro-energions and Magneto-energions. In addition, the energions in each of the marked groups differ in the direction of their own rotation which can be either left or right. Thus, the particles of the Energo-medium are doubly degenerate which, together with the discovered magnetic charges and true anti-electrons, determines the physical essence of electricity and magnetism, as well as their natural independence. The vector character of the gravitational field is in many respects similar to the vortex magnetic field, which has been known for hundreds of years, but no one has come up with the version of spatial magnetic waves. Therefore, the version of gravitational waves, according to the author, is another fake, inspired by crooked physics, in which real magnetic charges are ignored and, as a result, there is no representation of the real physics of the gravitational field.

A Preclinical Validation of Iron Oxide Nanoparticles for Treatment of Perianal Fistulizing Crohn's Disease.

Fistulizing anoperineal lesions are severe complications of Crohn’s disease (CD) that affect quality of life with a long-term risk of anal sphincter destruction, incontinence, permanent stoma, and anal cancer. Despite several surgical procedures, they relapse in about two-thirds of patients, mandating innovative treatments. Ultrasmall particles of iron oxide (USPIO) have been described to achieve in vivo rapid healing of deep wounds in the skin and liver of rats thanks to their nanobridging capability that could be adapted to fistula treatment. Our main purpose was to highlight preclinical data with USPIO for the treatment of perianal fistulizing CD. Twenty male Sprague Dawley rats with severe 2,4,6-trinitrobenzenesulfonic acid solution (TNBS)-induced proctitis were operated to generate two perianal fistulas per rat. At day 35, two inflammatory fistulas were obtained per rat and perineal magnetic resonance imaging (MRI) was performed. After a baseline MRI, a fistula tract was randomly drawn and topically treated either with saline or with USPIO for 1 min (n = 17 for each). The rats underwent a perineal MRI on postoperative days (POD) 1, 4, and 7 and were sacrificed for pathological examination. The primary outcome was the filling or closure of the fistula tract, including the external or internal openings. USPIO treatment allowed the closure and/or filling of all the treated fistulas from its application until POD 7 in comparison with the control fistulas (23%). The treatment with USPIO was safe, permanently closed the fistula along its entire length, including internal and external orifices, and paved new avenues for the treatment of perianal fistulizing Crohn’s disease.

Ultrasmall Superparamagnetic Particles of Iron Oxide and Cardiac Magnetic Resonance: Novel Imaging in Everyday Conditions

Myocardial inflammation has been hypothesised to be the common underlying mechanism through which several cardiovascular diseases develop and progress. Cardiac magnetic resonance (CMR) has become a powerful non-invasive tool that enables the direct visualisation of the myocardium. The emerging use of ultrasmall superparamagnetic particles of iron oxide (USPIO) and their magnetic properties is gaining a lot of research interest. USPIO-enhanced CMR can provide valuable information, as it allows for the identification of active inflammation in the myocardium, a process that has been hypothesised to be the substrate for adverse remodelling and, eventually, heart failure. In this review, we summarise the properties of USPIO and their role in cardiac magnetic resonance imaging as well as their clinical applications.

Optimization, characterization and in vivo evaluation of mupirocin nanocrystals for topical administration

Treatment of infectious skin conditions resulting from wounds and burns with topical antibiotics is challenging, particularly those caused by methicillin-resistant Staphylococcus aureus bacteria (MRSA). This is due to the formation of bacterial biofilms characterized by antimicrobial resistance. Mupirocin (MP), a widely used topical antibiotic, is active against gram-positive bacteria including MRSA. However, MP suffers from sub-optimal therapeutic efficacy due to its poor water-solubility and the significant rise in MP-resistant S. aureus. In this study, the physico-chemical characteristics of MP were modified through nanocrystallization to improve its therapeutic efficacy for the treatment of skin infections. Mupirocin-nanocrystals (MP-NC) were prepared using a nanoprecipitation technique and optimized using a D-optimal response surface design. The optimization of MP-NC produced ultra-small monodisperse spherical particles with a mean diameter of 70 nm and a polydispersity index of 0.2. The design resulted in two optimal MP-NC formulations that were evaluated by performing series of in vitro, ex vivo, microbiological, and in vivo studies. In-vitro results showed a 10-fold increase in the saturation solubility and a 9-fold increase in the dissolution rate of MP-NC. Ex vivo permeation studies, using pig ears skin, showed a 2-fold increase in the dermal deposition of MP-NC with the highest drug deposition occurring at 500-µm skin depth. Moreover, the optimal MP-NC formulations were lyophilized and incorporated into a 2% w/w cream. Microbiological studies revealed a 16-fold decrease in the minimum inhibitory concentration and the minimum bactericidal concentration of MP-NC. In vivo studies, using a rat excision burn wound model, demonstrated rapid and complete healing of infected burn wounds in rats treated with MP-NC cream in comparison to marketed Avoban ointment. Our results suggest that nanocrystallization of MP may provide an avenue through which higher levels of a topically applied MP can be permeated into the skin to reach relevant infectious areas and exert potential local antibacterial effects.

Continuous-Flow Reactor Synthesis for Homogeneous 1 nm-Sized Extremely Small High-Entropy Alloy Nanoparticles.

High-entropy alloy nanoparticles (HEA NPs) emerged as catalysts with superior performances that are not shown in monometallic catalysts. Although many kinds of synthesis techniques of HEA NPs have been developed recently, synthesizing HEA NPs with ultrasmall particle size and narrow size distribution remains challenging because most of the reported synthesis methods require high temperatures that accelerate particle growth. This work provides a new methodology for the fabrication of ultrasmall and homogeneous HEA NPs using a continuous-flow reactor with a liquid-phase reduction method. We successfully synthesized ultrasmall IrPdPtRhRu HEA NPs (1.32 ± 0.41 nm), theoretically each consisting of approximately 50 atoms. This average size is the smallest ever reported for HEA NPs. All five elements are homogeneously mixed at the atomic level in each particle. The obtained HEA NPs marked a significantly high hydrogen evolution reaction (HER) activity with a very small 6 mV overpotential at 10 mA/cm-2 in acid, which is one-third of the overpotential of commercial Pt/C. In addition, although mass production of HEA NPs is still difficult, this flow synthesis can provide high productivity with high reproducibility, which is more energy efficient and suitable for mass production. Therefore, this study reports the 1 nm-sized HEA NPs with remarkably high HER activity and establishes a platform for the production of ultrasmall and homogeneous HEA NPs.

Mn-doped Ru/RuO2 nanoclusters@CNT with strong metal-support interaction for efficient water splitting in acidic media

Preparation of low-cost, highly activity and stable bifunctional electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in acidic media has great challenges. Here, a series of M-Ru/RuO2@CNT (M = Mn, Cd, Cu) bifunctional catalysts were synthesized by doping and strong metal-support interaction (SMSI) strategies to improve the activity and stability of the catalysts. The experiment results show that the optimized Mn–Ru/RuO2@CNT catalyst with ultra-small particle size (2.5 nm) has the best catalytic performance, and the OER and HER tests at 10 mA cm−2 in 0.5 M H2SO4 solution show excellent overpotentials of 177 mV and 30 mV respectively, which are better than most of the catalysts reported recently. In addition, current densities of 10 mA cm−2 and 100 mA cm−2 can be obtained at 1.43 V and 1.51 V when measuring water splitting and can last up to 100 h at a current density of 100 mA cm−2. And this is the first time to achieve the stability of acid water splitting of Ru-based catalyst under large current density. Density functional theory (DFT) calculations show that after manganese doping, the electronic structure is changed by charge redistribution between doped ions and ruthenium-based catalysts containing heterojunctions, and the binding energy of intermediates is optimized to improve the catalytic activity; the stability of the catalyst is improved by increasing the formation energy of ruthenium vacancy and preventing the formation of ruthenium vacancy.

7．結晶性複合酸化物の超微粒子化と助触媒への応用

7．結晶性複合酸化物の超微粒子化と助触媒への応用

Stability of Polyethylene Glycol-Coated Copper Nanoparticles and Their Optical Properties

Oxidation is a corrosion reaction where the corroded metal forms an oxide. Prevention of oxidation at the nanoscale is critically important to retain the physicochemical properties of metal nanoparticles. In this work, we studied the stability of polyethylene glycol (PEG) coated copper nanoparticles (PEGylated CuNPs) against oxidation. The freshly-prepared PEGylated CuNPs mainly consist of metallic Cu which are quite stable in air although their surfaces are typically covered with a few monolayers of cuprous oxide. However, they are quickly oxidized in water due to the presence of protons that facilitate oxidation of the cuprous oxide to cupric oxide. PEG with carboxylic acid terminus could slightly delay the oxidation process compared to that with thiol terminus. It was found that a solvent with reducing power such as ethanol could greatly enhance the stability of PEGylated CuNPs by preventing further oxidation of the cuprous oxide to cupric oxide and thus retain the optical properties of CuNPs. The reducing environment also assists the galvanic replacement of these PEGylated CuNPs to form hollow nanoshells; however, they consist of ultra-small particle assemblies due to the co-reduction of gold precursor during the replacement reaction. As a result, these nanoshells do not exhibit strong optical properties in the near-infrared region. This study highlights the importance of solvent effects on PEGylated nonprecious metal nanoparticles against oxidation corrosion and its applications in preserving physicochemical properties of metallic nanostructures.

Preparation of fluorescent bimodal probe coupled with ultra-small superparamagnetic iron oxide particles

To prepare USPIO-PEG-Cy5.5 targeted bimodal probe for noninvasive diagnosis of thyroid cancer. The characterization was verified, and the physical and chemical properties were discussed. Fe3O4 was used as the carrier. Fluorescent Cy5.5 was linked with polyethylene glycol (PEG). A small amount of Cy5.5-NHS fluorescent powder were dissolved in dimethyl sulfoxide solution. PEG-Fe3O4 nanoparticles were centrifuged and ultra-filtrated. The nanoparticles were resuspended with phosphate buffer to change the pH. The Cy5.5 fluorescence was added to the Fe3O4 particles and incubated at 37 °C for 2 h. Characterization test of Cy5.5-PEG-Fe3O4 and relaxation rate measurement were performed. Fro cells were used to perform cell imaging experiment. CCK-8 assay was carried out to detect the cytotoxicity. The bimodal molecular probe Cy5.5-PEG-Fe3O4 was synthesized successfully. Transmission electron microscopy showed that the particle size of the probe was 18.8 ± 3.5 nm, the water and particle size of the nanoparticles was 35.7 ± 18.6 nm, and the zeta potential was −18.0 mv. The relaxation rate was 0.044 and the slope was 0.97. The cytotoxicity test showed that the bimodal molecular probe had slight toxicity to fro cells with a concentration-dependent manner. The synthesized Cy5.5-PEG-Fe3O4 probe has low toxicity, good biocompatibility, stable particle size, which can be used for cell imaging for noninvasive diagnosis of thyroid cancer.

ZSM-5@Rh amphiphilic nanoreactor: Efficient reduction of nitrobenzene under mild conditions

An amphiphilic ZSM-5 loaded with the metal Rh nanoreactor was synthesized for the first time, which realized the hydrotreating of nitroaromatic hydrocarbons under green conditions. Specifically, ZSM-5 is modified with the amino group on the outside and the octyl group on the inside. The amphiphilic ZSM-5 nanoreactor was loaded with the metal Rh with ultra-small particle size, due to the ability of amino groups to fix metal. And the octyl groups enhances the enrichment of ZSM-5 for organic matter.

Preparation, biocompatibility and imaging performance of ultrasmall iron oxide magnetic fluids for T1/T2-weighted MRI

In order to further improve the stability and biocompatibility of magnetic fluids (MFs), we report a one-step protocol for the preparation of ultrasmall superparamagnetic iron oxide MFs. Four kinds of MFs (n %L-Cysteine-S-branched polymethacrylic acid-coated Fe3O4 nanoparticles MFs, n %Cys-PMAA@Fe3O4 MFs) with ultrasmall particle size (< 5 nm) were obtained using the different molecular weight of polymer ligands as the outer layer. Among them, 2 %Cys-PMAA@Fe3O4 MFs show the best performance in the apparent particle size (4.10 ± 0.90 nm), hydrodynamic size (< 50 nm), and magnetic weight gain (67 mg), and stability index (I = 99 %). In addition, 2 %Cys-PMAA@Fe3O4 MFs exhibit excellent stability for 180 days under different salt concentrations (up to 3 mol/L) and pH (2−12). Importantly, the 2 %Cys-PMAA@Fe3O4 MFs show good biocompatibility in vitro that HEK293T and MCF-7 cells viability are higher than 90 % in 24 h when the iron concentration is 250 μg·mL−1. Furthermore, the hemolysis test and H&E tissue section staining demonstrate that the MFs are non-toxic in vivo. Finally, the value of 2 %Cys-PMAA@Fe3O4 MFs at 1.5 T (r2 = 57.48 mM−1·s−1, r1 = 8.61 mM−1·s−1, r2/r1 = 6.68) is slightly less than Combidex for r2 (r2 = 65 mM−1·s−1), and 2.5-folds higher than Gd-DTPA for r1 (r1 = 3.5 mM−1·s−1), so the tumor area can be clearly observed with dual-mode imaging at 3.0 T in vivo by the tail vein injection. This study contributes to the rationalized design and development of a clinical dual-modulus contrast agent.

Smart hypoxia-responsive transformable and charge-reversible nanoparticles for the deep penetration and tumor microenvironment modulation of pancreatic cancer

The compact extracellular matrix (ECM) of pancreatic ductal adenocarcinoma (PDAC) is the major physical barrier that hinders the delivery of anti-tumor drugs, leading to strong inherent chemotherapy resistance as well as establishing an immunosuppressive tumor microenvironment (TME). However, forcibly destroying the stroma barrier would break the balance of delicate signal transduction and dependence between tumor cells and matrix components. Uncontrollable growth and metastasis would occur, making PDAC more difficult to control. Hence, we design and construct an aptamer-decorated hypoxia-responsive nanoparticle s(DGL)n@Apt co-loading gemcitabine monophosphate and STAT3 inhibitor HJC0152. This nanoparticle can reverse its surficial charge in the TME, and reduce the size triggered by hypoxia. The released ultra-small DGL particles loading gemcitabine monophosphate exhibit excellent deep-tumor penetration, chemotherapy drugs endocytosis promotion, and autophagy induction ability. Meanwhile, HJC0152 inhibits overactivated STAT3 in both tumor cells and tumor stroma, softens the stroma barrier, and reeducates the TME into an immune-activated state. This smart codelivery strategy provides an inspiring opportunity in PDAC treatment.

Nickel encapsulated in silicalite-1 zeolite catalysts for steam reforming of glycerol (SRG) towards renewable hydrogen production

Valorisation of crude glycerol via steam reforming, i.e., SRG, is a promising method to produce sustainable hydrogen. However, catalyst deactivation under harsh SRG conditions is still a main challenge which hinders the further development of practical SRG. In this work, the encapsulated Ni catalyst in siliceous silicalite-1 zeolite (Ni@Si-1) were developed to show the improved performance and enhanced anti-deactivation potentials in catalytic SRG as compared with the conventional impregnated Ni catalysts (i.e., Ni/Si-1). Importantly, the post-synthetic treatment of Ni@Si-1 using TPAOH solution formed the encapsulated Ni catalyst with the mesoporous hollow structure (i.e., Ni@HolSi-1), which demonstrate even better performance in SRG with glycerol conversion of >95%, H2 yield of ~70%, H2/CO2 molar ratio of >2.33 and CO/CO2 molar ratio of <1 at 750 °C. Specifically, highly dispersed ultrasmall encapsulated Ni particles were retained within the hollow crystals of siliceous silicalite-1, as confirmed by XPS and HRTEM characterisation. The activation energy for glycerol conversion over Ni@HolSi-1 (i.e., Ea = ~ 19 kJ mol−1) was much lower than that of Ni/Si-1 and Ni@Si-1. 100-h longevity tests over the three catalysts were investigated at 750 °C, and the Ni@HolSi-1 catalyst exhibited an excellent stability and activity, as well as insignificant coke deposition, which could be due to the enhancement of highly dispersed yet accessible Ni NPs within the hollow Si-1 crystals. The findings of the work show the promise of the encapsulation strategy and mesoporous zeolites for developing the future reforming catalysts.

Structural design and optimization of metal-organic framework-derived FeO @C/rGO anode materials for constructing high-performance hybrid supercapacitors

Hybrid supercapacitors are promising energy storage devices that bridge the performance gap between conventional capacitors and batteries. However, the backward development of anode materials is a key issue that hinders the performance improvement of the hybrid supercapacitors. Therefore, this study proposes a strategy to fabricate reliable FeOx-based (Fe2O3 or Fe3O4) anode materials using the Fe-based metal-organic framework (Fe-MOF) as a template. Polyvinyl pyrrolidone (PVP) was used to stabilize and regulate the morphology of the Fe-MOF template to ensure a desirable microstructure of the final product. A series of FeOx@Carbon nanocages/reduced graphene oxide (FeOx@C/rGO) nanocomposites were obtained by calcinating the templates. The optimized Fe2O3@C/rGO–2 nanocomposite possesses considerable specific surface area and pore volume, with ultrasmall Fe2O3 particles (<5 nm) stably embedded in the carbon nanocages. The unique microstructure of the Fe2O3@C/rGO–2 electrode results in improved ion/electron accessibility that ensures an admirable specific capacity (713 C g−1 at 1 A g−1) and rate capability (67.3% retention at 50 A g−1). Meanwhile, the impressive cycling stability (104% retention after 20000 cycles) originates from the dual protection of Fe2O3 particles by the carbon nanocages and rGO. Furthermore, a hybrid supercapacitor constructed from a Fe2O3@C/rGO–2 anode and a nickel foam-supported NiCo2O4 nanoneedles (NiCo2O4–NF) cathode exhibited a maximum energy density of 101.9 Wh kg−1, suggesting that the delicately designed anode material is a promising candidate for constructing advanced energy storage devices.

Structure of allophanes with varied Si/Al molar ratios and implications to their differentiation on Mars

Allophane occurs ubiquitously in soils of volcanic origin on Earth and is also a probable constituent on martian surface, serving as a natural adsorbent and/or an environmental indicator. It remains to be one of the few minerals whose structure has not been unequivocally defined, as a result of its ultrasmall particle size, extremely low structural order and highly variable Si/Al molar ratios. To gain insights into the structure and probably also the formation processes of allophane, we hydrothermally synthesized allophanes at varied initial Si/Al molar ratios (0.5, 0.57, 0.66, 0.75, and 1.0), followed by characterizing their structure using a combination of advanced techniques. X-ray diffraction (XRD) patterns, Fourier transform infrared (FTIR) spectra, and 27Al/29Si magic-angle-spinning nuclear magnetic resonance (MAS NMR) spectra show that bayerite was obtained at initial Si/Al molar ratios of 0.5 and 0.57. FTIR and 29Si/27Al MAS NMR spectra also suggest the presence of oligomeric silicates in all the products and the significant amount of AlIV occurring invariably in both natural and synthetic allophanes is located in these oligomeric silicates. A possible explanation for the presence of oligomeric silicates is that the formation of imogolite local structure (ImoLS, which constitutes the skeleton of allophane) and the attachment of oligomeric silicates to it occur simultaneously. The scanning transmission electron microscopy (STEM) and atomic force microscopy (AFM) images showed that these products exhibited different aggregation states, probably resulting from formation of byproducts such as bayerite and proto-allophanes. The visible and near-infrared (VNIR) spectra exhibited little obvious differences resulting from Si/Al molar ratios, indicative of the weakness of this technique in detecting the geochemistry of Al and Si in poorly ordered aluminosilicate components at Mars' surface. Instead, the significant increases of intensity ratios observed in the FTIR bands (1043 cm−1 / 972 cm−1) and the 27Al/29Si MAS NMR signals (60 ppm / 7.6 ppm and (−80 ppm − −110 ppm) / −79 ppm, respectively) with increase of the Si/Al molar ratio of allophane indicate FTIR and MAS NMR could be used in combination with VNIR on future Mars orbiters/rovers.

Hypoxia-Responsive Azobenzene-Linked Hyaluronate Dot Particles for Photodynamic Tumor Therapy

In this study, we developed ultra-small hyaluronate dot particles that selectively release phototoxic drugs into a hypoxic tumor microenvironment. Here, the water-soluble hyaluronate dot (dHA) was covalently conjugated with 4,4′-azodianiline (Azo, as a hypoxia-sensitive linker) and Ce6 (as a photodynamic antitumor agent), producing dHA particles with cleavable Azo bond and Ce6 (dHA-Azo-Ce6). Importantly, the inactive Ce6 (self-quenched state) in the dHA-Azo-Ce6 particles was switched to the active Ce6 (dequenched state) via the Azo linker (–N=N–) cleavage in a hypoxic environment. In vitro studies using hypoxia-induced HeLa cells (treated with CoCl2) revealed that the dHA-Azo-Ce6 particle enhanced photodynamic antitumor inhibition, suggesting its potential as an antitumor drug candidate in response to tumor hypoxia.

Controlled Synthesis of Perforated Oxide Nanosheets with High Density Nanopores Showing Superior Water Purification Performance.

A method for creating genuine nanopores in high area density on monolayer two-dimensional (2D) metallic oxides has been developed. By use of the strong reduction capability of hydroiodic acid, active metal ions, such as FeIII and CoIII, in 2D oxide nanosheets can be reduced to a divalent charge state (2+). The selective removal of FeO2 and CoO2 metal oxide units from the framework can be tuned to produce pores in a range of 1-4 nm. By monitoring of the redox reaction kinetics, the pore area density can be also tuned from ∼0.9 × 104 to ∼3.3 × 105 μm-2. The universality of this method to produce much smaller pores and higher area density than the previously reported ones has been proven in different oxide nanosheets. To demonstrate their potential applications, ultrasmall metal organic framework particles were grown inside the pores of perforated titania oxide nanosheets. The optimized hybrid film showed ∼100% rejection of methylene blue (MB) from the water. Its water permeance reached 4260 L m-2 h-1 bar-1, which is 1-3 orders of that for reported 2D membranes with good MB rejections.