Photoreduced Ag+/sodium alginate supramolecular hydrogel as a sensitive SERS membrane substrate for rapid detection of uranyl ions.

BACKGROUND: In the fields of environmental monitoring and nuclear emergency, in order to obtain the relevant information of uranyl-induced environmental pollution and nuclear accident, it is necessary to establish a rapid quantitative analytical technique for uranyl ions. As a new promising technique, surface-enhanced Raman scattering (SERS) is hopeful to achieve this goal. However, uranyl ions are easily desorbed from SERS substrates under acidic conditions, and the structures of SERS substrates will be destroyed in the strong acidic aqueous solutions. Besides, the quantitative detection ability of SERS for uranyl ions needs to be promoted. Hence, it is necessary to develop new SERS substrates for accurate quantitative detection of trace uranyl in environmental water samples, especially in acidic solutions. RESULTS: In this work, we prepared silver ions/sodium alginate supramolecular hydrogel membrane (Ag+/SA SMH membrane), and the Ag+ ions from the membrane were transformed into Ag/Ag2O complex nanoparticles under laser irradiation. The Raman signal of uranyl was strongly enhanced under the synergistic interaction of electromagnetic enhancement derived from the Ag nanoparticles and charge transfer enhancement between uranyl and Ag2O. Utilizing the peak of SA (550 cm-1) as an internal standard, a quantitative detection with a LOD of 6.7 × 10-9 mol L-1 was achieved due to a good linear relation of uranyl concentrations from 1.0 × 10-8 mol L-1 to 2 × 10-6 mol L-1. Furthermore, foreign metal ions hardly affected the SERS detection of uranyl, and the substrate could determine trace uranyl in natural water samples. Particularly, the acidity had no obvious effect on SERS signals of uranyl ions. Therefore, in addition to the detection of uranyl ions in natural water samples, the proposed strategy could also detect uranyl ions in strong acidic solutions. SIGNIFICANCE AND NOVELTY: A simple one-step method was used to prepare an Ag+/SA SMH membrane for rapid quantitative detection of uranyl ions for the first time. The proposed substrate successfully detected uranyl ions under acidic conditions by immobilizing uranyl ion in hydrogel structure. In comparison with the previous studies, a more accurate quantitative analysis for uranyl ions was achieved by using an internal standard, and the proposed strategy could determine trace uranyl in either natural water samples or strong acidic solutions.

Highly sensitive and selective determination of uranyl ions based on Ag/Ag2O-COF composite SERS substrate.

Uranium is an essential nuclear material in civilian and military areas; however, its extensive application raises concerns about the potential safety issues in the fields of environmental protection and nuclear industry. In this study, we developed an Ag/Ag2O-COF (covalent-organic framework) composite SERS substrate to detect uranyl ions (UO22+) in environmental aqueous solutions. Herein, the strong SERS effect of uranyl adsorbed in Ag/Ag2O composite and the high adsorption efficiency of COF TpPa-1 were combined to realize the trace detection of uranyl ions. This method displayed a linear range of 10-8 mol L-1 to 10-6 mol L-1 with the detection limit of 8.9 × 10-10 mol L-1 for uranyl ions. Furthermore, common metal cations and oxo-ions hardly affected the SERS detection of uranyl, which is helpful for the trace analysis of uranyl in natural water samples. Although the proposed strategy is deployed for uranyl detection, the reusable and high-efficiency system may be expanded to trace detection of other substance with Raman activity.

A novel synthesis of graphene quantum dots via thermal treatment of crude graphite oxide in a dry and alkaline condition, and their application in uranyl detection.

In this article, a novel method to synthesize graphene quantum dots was developed via thermal treatment of crude graphite oxide (GO) in a dry and alkaline condition to cut the crude GO sheets into small graphene quantum dots (named as aGQDs). The aGQDs are nano-scale reduced graphene oxide pieces with the sizes around 5-10 nm. The aGQDs could disperse in water for their richment of oxygen-containing groups. The fluorescence properties were carefully investigated. The aGQDS aqueous solution shows a bright yellow-green fluorescence under the UV illumination. Besides, the uranyl ions show a strong fluorescence quenching effect on the a aGQD aqueous solution even at a low concentration (~10-7 M) compared with other common ions in natural water-body, which makes that these aGQDs could be applied as a chemosensor for detection of uranyl ions with good sensitivity and selectivity.

Graphene quantum dot electrochemiluminescence increase by bio-generated H2O2 and its application in direct biosensing.

In this study, a novel signal-increase electrochemiluminescence (ECL) biosensor has been developed for the detection of glucose based on graphene quantum dot/glucose oxidase (GQD/GOx) on Ti foil. The proposed GQD with excellent ECL ability is synthesized through a green one-step strategy by the electrochemical reduction of graphene oxide quantum dot. Upon the addition of glucose, GOx can catalytically oxidize glucose and the direct electron transfer between the redox centre of GOx and the modified electrode also has been realized, which results in the bio-generated H2O2 for ECL signal increase in GQD and realizes the direct ECL detection of glucose. The signal-increase ECL biosensor enables glucose detection with high sensitivity reaching 5 × 10-6 mol l-1 in a wide linear range from 5 × 10-6 to 1.5 × 10-3 mol l-1. Additionally, the fabrication process of such GQD-based ECL biosensor is also suitable to other biologically produced H2O2 system, suggesting the possible applications in the sensitive detection of other biologically important targets (e.g. small molecules, protein, DNA and so on).

The physical chemistry of uranium (VI) immobilization on manganese oxides.

Manganese oxides show strong affinity towards uranium, and have a promising application in uranium immobilization in environmental protection. We successfully synthesized a series of Mn oxide materials of different structures and investigated their U(VI) immobilization performances. The results showed that all Mn oxides share similar sorption capacities per unit surface area, implying similar physical chemistry during immobilization. Among these Mn oxides, α-MnO2 shows the most outstanding performance for uranium uptake (280 mg/g). More detailed studies on interfacial properties of U(VI) on α-MnO2 were performed to elucidate the binding mechanism. The uptake was largely influenced by acidity, but less impacted by ionic strength, indicative of an inner-sphere binding mode. The selectivity for uranium is much higher than other selected metal ions, i.e. Co2+, Ni2+, Eu3+, etc. ATR-FTIR, and EXAFS results showed that in both mild acidic and neutral conditions, U(VI) formed bidentate binuclear structure on α-MnO2, as evidenced by υas(O = U=O) at 912 cm-1 and the number of Mn in U coordination shell. UO2(OH)2 precipitate was found at the molecular level in neutral condition (pH 7-8). The results reveal the physical chemistry in uranium immobilization process on manganese oxide surfaces and helps to better understand the uranium environmental migration. Furthermore, it provides an alternative approach for radioactive water purification.

Synthesis of sandwich-like Mn3O4@reduced graphene oxide nano-composites via modified Hummers' method and its application as uranyl adsorbents.

Efficient and sustainable remediation technologies for uranium have recently been gaining more and more interest. Adsorption techniques are facile, effective and universal for kinds of heavy metal ions. In this paper, sandwich-like Mn3O4@reduced graphene oxide (Mn3O4@G) nano-composites were prepared facilely and greenly by adding NaOH solution into crude graphite oxide suspension prepared via the Hummers' method to modify the pH. The Mn3O4@G nanocomposites possess a reasonable maximum equilibrium adsorption quantity 195.6 mg [U] g-1. Moreover, the magnetism of Mn3O4@G makes it easy to remove Mn3O4@G from water by strong magnet field.

[Association between CTLA-4 gene polymorphism and Henoch-Schönlein purpura in children].

OBJECTIVE: To investigate the association between CTLA-4 gene polymorphism and Henoch-Schönlein purpura (HSP) in children. METHODS: Sixty children who were diagnosed with HSP were enrolled as the case group, consisting of 33 males and 27 females. Thirty healthy children were enrolled as the control group. The patients were further divided into HSP nephritis (HSPN) and non-HSPN groups (n=30 each) according to the presence or absence of nephritis. Polymerase chain reaction-restriction fragment length polymorphism was used to analyze the genotype and allele frequencies at +49 and -1722 loci. RESULTS: AA, AG, and GG genotypes were detected at +49; neither genotype nor allele frequencies showed significant differences between the case and control groups, between the HSPN and non-HSPN groups, and between male and female patients (P>0.05). TT, TC, and CC genotypes were detected at -1722; neither genotype nor allele frequencies showed significant differences between the case and control groups and between male and female patients (P>0.05). There were significant differences in CC genotype frequency and T and C allele frequencies between the HSPN and non-HSPN groups (P<0.05). Combinational analysis of +49 A/G and -1722 T/C showed no significant differences in the genotype frequency between the case and control groups and between male and female patients (P>0.05). GG-CC combination showed a significant difference between the HSPN and non-HSPN groups (P<0.05). CONCLUSIONS: CTLA-4 +49 A/G polymorphism is not associated with HSP. CC genotype and C allele of CTLA-4 -1722 and the combination of GG at +49 A/G and CC at -1722 T/C may be risk factors for HSPN.

(4S,5S)-2-(2-Bromo-phen-yl)-1,3-dioxolane-4,5-dicarboxamide.

The asymmetric unit of the title compound, C(11)H(11)BrN(2)O(4), contains two crystallographically independent mol-ecules in which the bromo-phenyl rings are oriented at dihedral angles of 39.28 (3)°. The dioxolane rings adopt envelope conformations. Intra-molecular N-H⋯O hydrogen bonds result in the formation of four five-membered rings, having planar and envelope conformations. In the crystal structure, inter-molecular N-H⋯O hydrogen bonds link mol-ecules into chains along the b axis, forming R(2) (2)(8) ring motifs.

(4S,5S)-2-(4-Chloro-phen-yl)-1,3-dioxolane-4,5-dicarboxamide.

The title compound, C(11)H(11)ClN(2)O(4), is an important inter-mediate for the preparation of platinum anti-cancer drugs. The dioxolane ring adopts a twist conformation with an equatorially attached chloro-phenyl substituent. In the crystal structure, mol-ecules are linked into a two-dimensional network parallel to (001) by N-H⋯O and C-H⋯O hydrogen bonds.