Ionized acrylamide-based copolymer / terpolymer hydrogels for recovery of positive and negative heavy metal ions.

In this study, we explored the effective capture of both cations and anions onto a single adsorbent. Acrylamide (AAm) served as the polymer backbone, onto which co-monomers sodium p-styrenesulfonate (SS) and N,N-dimethylaminopropyl acrylamide (DMAPAA) were grafted, creating ionized polymer hydrogel adsorbents. These adsorbents were engineered for the synergistic separation and recovery of heavy metal cations and anions from concentrated solutions, focusing specifically on industrially significant ions such as Ni2+-, Cu2+, Zn2+ and (Cr2O7)2-. The adsorption and desorption behaviors of the AAm terpolymer hydrogels were investigated across various pH solutions, considering the competition and concentrations of these specific metal ions. Moreover, the study delved into the effects of the internal pH environment within the hydrogel adsorbents, determining its impact on the type of metal adsorbed and the adsorption capacity. Our findings indicated that the adsorption of cations was enhanced with a higher proportion of SS relative to DMAPAA in the hydrogel. In contrast, significant anion capture occurred when the concentration of DMAPAA exceeded that of SS. However, equal ratios of SS and DMAPAA led to a noticeable reduction in the adsorption of both types of substrates, attributed to the counteractive nature of these co-monomers. To enhance the adsorption efficiency, it may be necessary to consider methods for micro-scale separation of the two types of monomers. Additionally, the adsorption capacity was observed to be directly proportional to the swelling capacity of the hydrogels. For complete desorption and separation of the cations and anions from the adsorbent, the application of concentrated NaOH solutions followed by HNO3 was found to be essential. Given the varying concentrations of cation and anion pollutants, often present in heavy metal factory effluents, it is crucial to fine-tune the ratios of DMAPAA and SS during the synthesis process. This adjustment ensures optimized efficiency in the decontamination and recovery of these significant heavy metal ions.

Local electronic structure of interstitial hydrogen in MgH2inferred from muon study.

Magnesium hydride has great potential as a solid hydrogen (H) storage material because of its high H storage capacity of 7.6 wt%. However, its slow hydrogenation and dehydrogenation kinetics and the high temperature of 300 ∘C required for decomposition are major obstacles to small-scale applications such as automobiles. The local electronic structure of interstitial H in MgH2is an important fundamental knowledge in solving this problem, which has been studied mainly based on density functional theory (DFT). However, few experimental studies have been performed to assess the results of DFT calculations. We have therefore introduced muon (Mu) as pseudo-H into MgH2and investigated the corresponding interstitial H states by analyzing their electronic and dynamical properties in detail. As a result, we observed multiple Mu states similar to those observed in wide-gap oxides, and found that their electronic states can be attributed to relaxed-excited states associated with donor/acceptor levels predicted by the recently proposed 'ambipolarity model'. This provides an indirect support for the DFT calculations on which the model is based via the donor/acceptor levels. An important implication of the muon results for improved hydrogen kinetics is that dehydrogenation, serving as areductionfor hydrides, stabilises the interstitial H-state.

Conjugation monitoring of gold nanoparticles with alkanedithiols by capillary zone electrophoresis.

Alkanedithiols were used for the conjugation of gold nanoparticles (AuNP) prepared by a solution plasma process. Capillary zone electrophoresis was utilized for the monitoring of the conjugated AuNP. When 1,6-hexanedithiol (HDT) was used as a linker, a resolved peak from the AuNP was detected in the electropherogram; the resolved peak was attributed to the conjugated AuNP. The resolved peak was developed with increasing concentrations of HDT, while the peak of the AuNP decreased complementary. The resolved peak also tended to develop along with the standing time at least up to 7 weeks. The electrophoretic mobility of the conjugated AuNP was almost identical over the HDT concentrations examined, suggesting that the conjugation of the AuNP did not proceed further, such as aggregate/agglomerate formation. The conjugation monitoring was also examined with some dithiols and monothiols. Resolved peak of the conjugated AuNP was also detected with 1,2-ethanedithiol and 2-aminoethanethiol.

Highly stable gold nanoparticles in an aqueous solution without any stabilizer prepared by a solution plasma process evaluated through capillary zone electrophoresis.

Gold nanoparticles (AuNP) were prepared by a solution plasma process in the presence of H2O2, and they were dispersed in an aqueous solution without any stabilizer generally used. The dispersion stability of the AuNP in an aqueous solution was evaluated by capillary zone electrophoresis (CZE). An anionic broad peak was detected with the AuNP by CZE based on its wide variations in size and net charge. The broad peak also suggests that the AuNP were well dispersed in an aqueous solution. The dispersion stability of AuNP was evaluated from the viewpoints of long-term dispersion, salt concentration, and organic co-solvent. The anionic broad peak attributed to the dispersed AuNP was successfully detected for at least 55 weeks from the preparation with less shot signals of the aggregates. The AuNP was also well dispersed in aqueous NaCl solutions with its concentrations up to 30 mmol L-1, as well as with ethanol co-solvent up to 40%(v/v). The AuNP prepared by the solution plasma process was proved to be highly stable in an aqueous solution.

Organic molecular dynamics and charge-carrier lifetime in lead iodide perovskite MAPbI3.

The long charge carrier lifetime of the hybrid organic-inorganic perovskites (HOIPs) is the key for their remarkable performance as a solar cell material. The microscopic mechanism for the long lifetime is still in debate. Here, by using a muon spin relaxation technique that probes the fluctuation of local magnetic fields, we show that the muon depolarization rate (Δ) of a prototype HOIP methylammonium lead iodide (MAPbI3) shows a sharp decrease with increasing temperature in two steps above 120 K and 190 K across the structural transition from orthorhombic to tetragonal structure at 162 K. Our analysis shows that the reduction of Δ is quantitatively in agreement with the expected behavior due to the rapid development of methyl ammonium (MA) jumping rotation around the C 3 and C 4 symmetry axes. Our results provide direct evidence for the intimate relation between the rotation of the electric dipoles of MA molecules and the charge carrier lifetime in HOIPs.

Dimensional reduction by geometrical frustration in a cubic antiferromagnet composed of tetrahedral clusters.

Dimensionality is a critical factor in determining the properties of solids and is an apparent built-in character of the crystal structure. However, it can be an emergent and tunable property in geometrically frustrated spin systems. Here, we study the spin dynamics of the tetrahedral cluster antiferromagnet, pharmacosiderite, via muon spin resonance and neutron scattering. We find that the spin correlation exhibits a two-dimensional characteristic despite the isotropic connectivity of tetrahedral clusters made of spin 5/2 Fe3+ ions in the three-dimensional cubic crystal, which we ascribe to two-dimensionalisation by geometrical frustration based on spin wave calculations. Moreover, we suggest that even one-dimensionalisation occurs in the decoupled layers, generating low-energy and one-dimensional excitation modes, causing large spin fluctuation in the classical spin system. Pharmacosiderite facilitates studying the emergence of low-dimensionality and manipulating anisotropic responses arising from the dimensionality using an external magnetic field.

Gapless spin liquid in a square-kagome lattice antiferromagnet.

Observation of a quantum spin liquid (QSL) state is one of the most important goals in condensed-matter physics, as well as the development of new spintronic devices that support next-generation industries. The QSL in two dimensional quantum spin systems is expected to be due to geometrical magnetic frustration, and thus a kagome-based lattice is the most probable playground for QSL. Here, we report the first experimental results of the QSL state on a square-kagome quantum antiferromagnet, KCu6AlBiO4(SO4)5Cl. Comprehensive experimental studies via magnetic susceptibility, magnetisation, heat capacity, muon spin relaxation (µSR), and inelastic neutron scattering (INS) measurements reveal the formation of a gapless QSL at very low temperatures close to the ground state. The QSL behavior cannot be explained fully by a frustrated Heisenberg model with nearest-neighbor exchange interactions, providing a theoretical challenge to unveil the nature of the QSL state.

Quantum magnetisms in uniform triangular lattices Li2AMo3O8 (A = In, Sc).

Molecular based spin-1/2 triangular lattice systems such as LiZn2Mo3O8 have attracted research interest. Distortions, defects, and intersite disorder are suppressed in such molecular-based magnets, and intrinsic geometrical frustration gives rise to unconventional and unexpected ground states. Li2AMo3O8 (A = In or Sc) is such a compound where spin-1/2 Mo3O13 clusters in place of Mo ions form the uniform triangular lattice. Their ground states are different according to the A site. Li2InMo3O8 undergoes conventional 120° long-range magnetic order below TN = 12 K whereas isomorphic Li2ScMo3O8 exhibits no long-range magnetic order down to 0.5 K. Here, we report exotic magnetisms in Li2InMo3O8 and Li2ScMo3O8 investigated by muon spin rotation (µSR) and inelastic neutron scattering (INS) spectroscopies using polycrystalline samples. Li2InMo3O8 and Li2ScMo3O8 show completely different behaviors observed in both µSR and INS measurements, representing their different ground states. Li2InMo3O8 exhibits spin wave excitation which is quantitatively described by the nearest neighbor anisotropic Heisenberg model based on the 120° spin structure. In contrast, Li2ScMo3O8 undergoes short-range magnetic order below 4 K with quantum-spin-liquid-like magnetic fluctuations down to the base temperature. Origin of the different ground states is discussed in terms of anisotropies of crystal structures and magnetic interactions.

In Situ Observation of Desorption and Direct Electron Transfer Reaction of Cytochrome c on Bare ITO Electrode with Electrochemical Slab Optical Waveguide Spectroscopy.

Cyclic voltammograms (CVs) of cytochrome c (cytc) on the bare ITO were measured with every 10 times of the continuous the solution exchange (SE) processes at the same time of slab optical waveguide (SOWG) spectral observation, and it was proved that direct electron transfer (DET) reaction functionality of cytc adsorbed on the bare ITO electrode was kept after 100 times SE processes. The existence of three kinds of cytc molecules which were weakly adsorbed, strongly adsorbed and immobilized on the bare ITO electrode below a monolayer coverage was indicated from the change in the Soret band absorbance at 408 nm due to the desorption reaction of cytc with In Situ observation by electrochemically controlled SOWG spectroscopy. As the actual procedure, 100 times of the SE process in the SOWG cell by hands induced the gradual decrease of the absorbance due to cytc desorption, and with every 10 times of the SE process SOWG absorption spectra were obtained. The SOWG absorbance decay curve was well fitted with two components exponential equation depending on the SE process numbers showing that around 31.6% of the cytc molecules adsorbed on bare ITO electrode were finally immobilized.

Equilibrium and kinetic studies for silver removal from aqueous solution by hybrid hydrogels.

Hybrid hydrogels were prepared by blending Carboxymethyl chitosan (CMCts), Carboxymethyl cellulose (CMC) with Sodium sulfonate styrene (SSS) by 60-kGy gamma rays. The prepared hydrogels were utilized as silver-ion (Ag) sorbent under non- and competitive cases. Batch adsorption experiments were conducted in functional conditions including contact time, ratios of (CMC:CMCts) and SSS, pH value, temperature and adsorbent weight. Equilibrium contact time of 10 h. was obtained by the adsorption material. The optimal 4:2 ratio of (CMC:CMCts):SSS showed the Ag highest adsorption efficiency. The maximum percentage of Ag+ removal was achieved at the pH 5. The temperature effect on the adsorption ability of hybrid hydrogel indicated the Ag adsorption process was endothermic and spontaneous. The Langmuir isotherm model fitted Ag adsorption data well, assuming a monolayer adsorption with predicted maximum adsorption capacity of 451.74 × 10-3 mg. g-1. From the kinetic data, the process of Ag adsorption had higher agreement with the pseudo-2nd order model, predicting the amount of Ag+ uptake at different contact time intervals and at equilibrium.

Radiation synthesis and characterization of super-absorbing hydrogel from natural polymers and vinyl monomer.

This article exploits a new approach for synthesis of polysaccharide-based grafted sodium styrene sulfonate (SSS) super absorbent hydrogels (SAHs) in aqueous solution by γ-radiation under ambient conditions. Important optimal conditions for preparation of hydrogels with the best swelling ratio, such as gamma irradiation dose and the ratio of feed composition have been discussed. Characterization techniques such as the SEM/EDS, FTIR and DSC were used in describing the newly prepared hydrogels. The FTIR gave characteristic peaks for -SO3Na group at 1042 and 988 cm-1, showing successful grafting of SSS onto the polysaccharide base material. The dependence of swelling behaviors in various pH solutions and salts solutions were investigated in detail. The prepared hybrid hydrogel showed most optimum swelling capacity at neutral pH whereas equilibrium swelling of SAHs was achieved within 5 h. The swelling of SAHs influenced obviously to metal ion removal percentage in solution.

Totally synthetic microperoxidase-11.

A totally synthetic microperoxidase-11 (MP-11) is reported. Accordingly, the undecapeptide (VQKCAQCHTVE) was synthesized by solid-phase peptide synthesis followed by the thiol-ene click reaction with haemin for reconstitution. High-speed atomic force microscopy measurement conducted in water confirmed the protein reconstitution by visualizing the morphological differences as animated molecular images. The synthetic MP-11 showed a considerable magnitude of catalytic activity (27%) against the natural MP-11 in the oxidation of 3,3',5,5'-tetramethylbenzidine by hydrogen peroxide, whereas it showed very low (2.7%) activity of a synthetic variant with a point mutation (VQKCAQC M TVE, H8M). Slab waveguide spectroscopic measurements revealed that the ferrous/ferric redox reaction occurred by the direct electron transfer with specific spectral changes. Indeed, if hydrogen peroxide existed in the solution phase, the peroxidase-modified electrode showed catalytic current-voltage behaviour regardless of whether it was prepared using natural MP-11 or the synthetic MP-11. If a substrate recycling reaction was assumed, computer simulation well reproduced the experimental curves to give a global set of electrocatalytic reaction parameters. In any of the experiments, the synthetic MP-11 and natural MP-11 gave almost identical results. Our approach will be a convenient means of preparing MP-11, as well as its mutants, that does not rely on nature.

Synthesis and Characterization of Poly(1,4,7-Trioxacycloundecane-8,11-dione) Macrocyclic Functionalized Hydrogel for High Selectivity Adsorption and Complexation of Bismuth Ion.

Macrocyclic functional hydrogels incorporating new poly cyclic active sites (1,4,7-trioxacycloundecane-8,11-dione) within their entire network, have been synthesized. Using the high-dilution coupling of the bi-functional monomers maleic acid and bis(chloroethyl)ether in a sol-gel chemistry synthesis, 11-membered chelate rings infused with three oxygen donor atoms were created and characterized, and their structures confirmed using Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopic analyses. The macrocyclic gel, designed for selective host-guest adsorption and complexation of metal substrates, was initially tested against an aqueous set of 14 metal competitive solutions, where it demonstrated exclusive selectivity for Bi3+aq, with the other metals exhibiting zero adsorption. Further analysis using binary and single ion Bi3+-containing solutions showed a near-complete removal of Bi3+ using this polycyclic hydrogel, with 98% extraction efficiency and q = 9.80 mg/g. These results clearly confirm that the 1,4,7-trioxacycloundecane-8,11-dione cyclic sites are most suitable for high selectivity and capture of Bi. The metal substrates were entrapped within the 1,4,7-trioxacycloundecane-8,11-dione cyclic sites. Evidently, by exploiting the host-guest complexation chemistry of macrocycles, we were able to design hydrogel adsorbents whose networks were comprised entirely of macrocyclic active groups for possible purification works of copper involving bismuth impurities, and/or for efficient selective uptake and recovery of bismuth trace ions existing in highly competitive environments such as sea water.

Possible Tomonaga-Luttinger spin liquid state in the spin-1/2 inequilateral diamond-chain compound K3Cu3AlO2(SO4)4.

K3Cu3AlO2(SO4)4 is a highly one-dimensional spin-1/2 inequilateral diamond-chain antiferromagnet. Spinon continuum and spin-singlet dimer excitations are observed in the inelastic neutron scattering spectra, which is in excellent agreement with a theoretical prediction: a dimer-monomer composite structure, where the dimer is caused by strong antiferromagnetic (AFM) coupling and the monomer forms an almost isolated quantum AFM chain controlling low-energy excitations. Moreover, muon spin rotation/relaxation spectroscopy shows no long-range ordering down to 90 mK, which is roughly three orders of magnitude lower than the exchange interaction of the quantum AFM chain. K3Cu3AlO2(SO4)4 is, thus, regarded as a compound that exhibits a Tomonaga-Luttinger spin liquid behavior at low temperatures close to the ground state.

In situ Observation of Desorption Reaction of Cytochrome c from Solid/Liquid Interfaces with Slab Optical Waveguide Spectroscopy.

An automated solution exchange (SE) mechanism has been introduced to slab optical waveguide spectroscopy to estimate the protein immobilizing ability of a slab optical waveguide (SOWG) surface. In each SE process, SOWG spectral change in absorbance at peak position of cytochrome c (cyt.c) Soret band at 409 nm was observed to analyze the desorption ratio of cyt.c adsorbed on SOWG surface. Continuous SE processes for 100 times have successfully brought us a kind of master desorption curve of cyt.c, which was well fitted by a double exponential equation, indicating the existence of three kinds of adsorbed states, including weakly adsorbed, strongly adsorbed, and immobilized cyt.c. The present results showed that around 30 times SE processes were enough to anticipate the ratio of desorbed and immobilized amounts of cyt.c adsorbed on SOWG surface.

In situ Observation of Direct Electron Transfer Reaction of Cytochrome c Immobilized on ITO Electrode Modified with 11-{2-[2-(2-Methoxyethoxy)ethoxy]ethoxy}undecylphosphonic Acid Self-assembled Monolayer Film by Electrochemical Slab Optical Waveguide Spectroscopy.

To immobilize cytochrome c (cyt.c) on an ITO electrode while keeping its direct electron transfer (DET) functionality, the ITO electrode surface was modified with 11-{2-[2-(2-methoxyethoxy)ethoxy]ethoxy}undecylphosphonic acid (CH3O (CH2CH2O)3C11H22PO(OH)2, M-EG3-UPA) self-assembled monolayer (SAM) film. After a 100-times washing process to exchange a phosphate buffer saline solution surrounding cyt.c and ITO electrode to a fresh one, an in situ observation of visible absorption spectral change with slab optical waveguide (SOWG) spectroscopy showed that 87.7% of the cyt.c adsorbed on the M-EG3-UPA modified ITO electrode remained on the ITO electrode. The SOWG absorption spectra corresponding to oxidized and reduced cyt.c were observed with setting the ITO electrode potential at 0.3 and -0.3 V vs. Ag/AgCl, respectively, while probing the DET reaction between cyt.c and ITO electrode occurred. The amount of cyt.c was evaluated to be about 19.4% of a monolayer coverage based on the coulomb amount in oxidation and reduction peaks on cyclic voltammetry (CV) data. The CV peak current maintained to be 83.4% compared with the initial value for a M-EG3-UPA modified ITO electrode after 60 min continuous scan with 0.1 V/s between 0.3 and -0.3 V vs. Ag/AgCl.

Removal of metal ions from aqueous solutions using carboxymethyl cellulose/sodium styrene sulfonate gels prepared by radiation grafting.

Sodium Carboxymethyl Cellulose (CMCNa)/Sodium Styrene Sulfonate (SSS) hydrogels with grafted and crosslinked polymeric networks were prepared by γ-radiation at atmosphere condition. The obtained hydrogels were characterized by gel fraction, swelling ratio, TGA and FTIR spectroscopy. The results showed the ratio of CMC and SSS 1:0 gave the highest gel fraction, compared with other ratios. The swelling capacity increased by increasing SSS content due to the presence of SO3Na, OH groups in gel structure. The FTIR spectrum of CMC/SSS gel showed the new absorption peaks at 1034 and 1012cm-1 corresponds to SO3Na group. The metal ion adsorption capacity of CMC/SSS gel was investigated. The grafted gel effectively removed metal ions, especially Cr and Pb. The effects of hydrogel composition, contact time, and initial concentration on the adsorption capacity of the grafted hydrogels were studied. The adsorption kinetics and equilibrium isotherms were investigated using pseudo-second-order model and Langmuir model.

Relaxation with long-period oscillation in defect turbulence of planar nematic liquid crystals.

Through experiments, we studied defect turbulence, a type of spatiotemporal chaos in planar systems of nematic liquid crystals, to clarify the chaotic advection of weak turbulence. In planar systems of large aspect ratio, structural relaxation, which is characterized by the dynamic structure factor, exhibits a long-period oscillation that is described well by a combination of a simple exponential relaxation and underdamped oscillation. The simple relaxation arises as a result of the roll modulation while the damped oscillation is manifest in the repetitive gliding of defect pairs in a local area. Each relaxation is derived analytically by the projection operator method that separates turbulent transport into a macroscopic contribution and fluctuations. The analysis proposes that the two relaxations are not correlated. The nonthermal fluctuations of defect turbulence are consequently separated into two independent Markov processes. Our approach sheds light on diversity and universality from a unified viewpoint for weak turbulence.

Responses of spatiotemporal chaos to oscillating forces.

The responses of soft-mode turbulence, a kind of spatiotemporal chaos seen in electroconvection of a nematic liquid crystal, to alternating-current magnetic fields is investigated to uncover the dynamical properties of spatiotemporal chaos. The dynamical responses can be measured by an order parameter, M(p)(t), which indicates ordering in the convective roll pattern induced by the magnetic field. Determined by properties of the liquid crystal in a magnetic field, M(p)(t) oscillates in accordance with the square of the magnetic field. The relaxation time of the system was obtained by fitting the frequency dependence of the complex susceptibility for the pattern obtained from the oscillation of M(p)(t) to the Debye-type relaxation spectra. However, for the high-frequency regime, the susceptibility deviates from the spectra because slow and large fluctuations of M(p)(t) contribute to the oscillation. The properties of this type of fluctuation were investigated by introducing a dynamic ordering parameter defined as the period average of M(p)(t).

Biophoton emission induced by heat shock.

Ultraweak biophoton emission originates from the generation of reactive oxygen species (ROS) that are produced in mitochondria as by-products of cellular respiration. In healthy cells, the concentration of ROS is minimized by a system of biological antioxidants. However, heat shock changes the equilibrium between oxidative stress and antioxidant activity, that is, a rapid rise in temperature induces biophoton emission from ROS. Although the rate and intensity of biophoton emission was observed to increase in response to elevated temperatures, pretreatment at lower high temperatures inhibited photon emission at higher temperatures. Biophoton measurements are useful for observing and evaluating heat shock.