We report a simple and sensitive aptamer-based colorimetric detection of mercury ions (Hg(2+)) using unmodified gold nanoparticles as colorimetric probe. It is based on the fact that bare gold nanoparticles interact differently with short single-strand DNA and double-stranded DNA. The anti-Hg(2+) aptamer is rich in thymine (T) and readily forms T-Hg(2+)-T configuration in the presence of Hg(2+). By measuring color change or adsorption ratio, the bare gold nanoparticles can effectively differentiate the Hg(2+)-induced conformational change of the aptamer in the presence of a given salt with high concentration. The assay shows a linear response toward Hg(2+) concentration through a five-decade range of 1 x 10(-4) mol L(-1) to 1 x 10(-9) mol L(-1). Even with the naked eye, we could identify micromolar Hg(2+) concentrations within minutes. By using the spectrometric method, the detection limit was improved to the nanomolar range (0.6 nM). The assay shows excellent selectivity for Hg(2+) over other metal cations including K(+), Ba(2+), Ni(2+), Pb(2+), Cu(2+), Cd(2+), Mg(2+), Ca(2+), Zn(2+), Al(3+), and Fe(3+). The major advantages of this Hg(2+) assay are its water-solubility, simplicity, low cost, visual colorimetry, and high sensitivity. This method provides a potentially useful tool for the Hg(2+) detection.

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We report a highly efficient bifunctional catalyst, Pd/SO 3 H-MIL-101(Cr), consisting of Pd nanoparticles immobilized on a mesoporous sulfonic acid-functionalized metal-organic framework SO 3 H-MIL-101(Cr), which exhibits high catalytic performance in promoting biomass refining. The use of SO 3 H-MIL-101(Cr) as a support renders highly dispersed Pd nanoparticles with uniform size distribution, sufficient reactants contact in aqueous media, and rapid activation of the reactants induced by the Brønsted acid coordination sites (sulfonic acid groups from SO 3 H-MIL-101(Cr)). Thus, the 2.0 wt.% Pd/SO 3 H-MIL-101(Cr) catalyst exhibits novel synergy in the hydrodeoxygenation of vanillin (a typical model compound of lignin) at low H 2 pressure under mild conditions in aqueous media. Excellent catalytic results (100% conversion of vanillin with exclusive selectivity for the 2-methoxy-4-methylphenol product) could be achieved, and no loss of catalytic activity and selectivity were observed after seven recycles in succession.13 achieved over the 2.0 wt.% Pd/SO 3 H-MIL-101(Cr) catalyst including a 100% conversion of vanillin with a 100% selectivity for the 2-methoxy-4-methylphenol product within 120 min (entry 3 in Table 1). While in the presence of 2.0 wt.% Pd/MIL-101(Cr) catalyst, a rather low catalytic activity and selectivity were obtained when the reaction was carried out at the same conditions (entry 4). This is probably due to the lower acid strength of the MIL-101(Cr) as compared to that of the SO 3 H-MIL-101(Cr) support. Over the pure support SO 3 H-MIL-101(Cr) or MIL-101(Cr), however, no reaction took place, implying that Pd nanoparticles are inevitable for the vanillin hydrodeoxygenation (entries 1 and 2). Moreover, the 2.0 wt.% Pd/SO 3 H-MIL-101(Cr) catalyst was also compared with the commercially available Pd/C catalyst under the same conditions. The textural properties of the 2.0 wt.% Pd/C are shown in Table S1. The loading amounts of Pd within the Pd/SO 3 H-MIL-101(Cr), Pd/MIL-101(Cr) and Pd/C catalysts, determined by the ICP-AES analysis, were found to be 1.98 wt.%, 1.99 wt.% and 2.01 wt.%, respectively, very close to the nominal amount of 2.0 wt.%. The results (entry 5 in Table 1) clearly show that the 2.0 wt.% Pd/SO 3 H-MIL-101(Cr) catalyst gives significantly higher activity and 2-methoxy-4-methylphenol selectivity as compared to the Pd/C catalyst. It should be noted that the selectivity for 2-methoxy-4-methylphenol over the prepared 2.0 wt.% Pd/SO 3 H-MIL-101 catalyst is also significantly higher than that reported by Xiao et al [25] over 4.5 wt.% Pd/MSMF under the same reaction conditions with a similar conversion of vanillin (entry 6). The high selectivity over the 2.0 wt.% Pd/SO 3 H-MIL-101(Cr) catalyst is probably due to the readily accessible Brønsted acidic sites distributed throughout the framework as well as an abundance of mesoporous cages of MIL-101(Cr) thus, greatly facilitating the transfer of substrates [46,47].

The separation and removal of oil or organic pollutants from water is highly imperative. The oil phases in surfactant-free oil-in-water emulsions or in free oil/water mixtures can be smartly enriched and transported by using superhydrophobic/superoleophilic iron particles (SHIPs) under a magnetic field. For water-in-oil emulsion, SHIPs-based composite membranes selectively allow the oil to pass through. Their convenient and scalable preparation, excellent separation performance, and good reusability are of great advantages for practical applications in wastewater treatment, the cleanup of oil spills, emulsion concentration, and fuel purification.

Receptors are crucial to the analytical performance of sensor arrays. Different from the previous receptors in sensor arrays, herein, peroxidase-mimicking DNAzymes were innovatively used as receptors to develop a label-free chemiluminescence sensor array for discriminating various heavy metal ions in complex samples. The peroxidase-mimicking DNAzymes are composed of functional oligonucleotides and hemin, including G-triplex-hemin DNAzyme (G3-DNAzyme), G-quadruplex-hemin DNAzyme (G4-DNAzyme), and the dimer of G-quadruplex-hemin DNAzyme (dG4-DNAzyme). Circular dichroism (CD) spectroscopy demonstrated that different metal ions diversely affect the conformation of G-quadruplex and G-triplex, resulting in a change in the activity of peroxidase-mimicking DNAzyme. Thus, the unique fingerprints formed to easily discriminate seven kinds of heavy metal ions by principal component analysis (PCA) within 20 min. The discrimination of unknown metal ions in tap water further confirmed its ability for discriminating multiple heavy metal ions. Moreover, it will not bring water pollution due to the good biocompatibility of DNA. Therefore, it not only merely offers a label-free, rapid, environment-friendly, and cheap (1.49 $) sensor assay for discriminating metal ions but also comes up with an innovative way for developing sensor arrays.

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Abstract：Utilizing superhydrophobic porous materials in oil/water separation has attracting increasing research interest, however, most of these materials are usually complicated to fabricate or easily lose their functions in harsh circumstance. In this study, dispersion of poly [(3,3,3-trifluoropropyl)methylsiloxane] (PTFPMS) micro-nano aggregations in acetone/water was facially prepared via a simple phase separation method. The aggregations can be easily coated on the skeletons of various 2D and 3D porous substrates, endowing the porous materials superhydrophobicity. The prepared superhydrophobic materials show excellent resistance to chemical erosion, mechanical abrasion, and high temperature (up to 400 ˚C). The robust superhydrophobicity promise the application of the resultant porous materials in the harsh environment, and examples of using these superhydrophobic porous materials to separate oil/water mixtures have been demonstrated. This simple and universal method is suitable for large-scale preparation of porous materials with robust superhydrophobicity.