High CO2 and H-2 selectivity are important issues for methanol steam reforming (MSR) to provide H-2 as a clean energy carrier. The structure sensitivity and the factors governing the activity and selectivity for MSR on Cu catalysts are systematically investigated using density functional theory calculations and microkinetic simulation. Potential energy surfaces including water dissociation, methanol dehydrogenation, formaldehyde desorption and coupling with oxygen-containing intermediates, and formation of hydrogen and carbon dioxide are calculated over Cu(111), (100), (221), (211), and (110) surfaces, respectively. It is found that Cu(110) facet is the most active and selective toward carbon dioxide; Cu(22l) is also active but highly selective toward formaldehyde, whereas Cu(111) is nearly inactive. Degree of rate control analysis shows that the activity is controlled mainly by methanol dehydrogenation to formaldehyde, whereas the degree of selectivity control shows that the selectivity toward formaldehyde or carbon dioxide depends sensitively on competition between formaldehyde desorption and coupling with surface oxygen. For Cu(110), abundance of both methoxy and oxygen as well as available vacant sites key for its high activity and selectivity toward carbon dioxide, whereas lack of oxygen on Cu(221) makes the corresponding surface highly selective for formaldehyde. The present work highlights the great influence of Cu surface orientations on the activity and selectivity for MSR.

Hongkonoids A-D (1-4), the first example of ascorbylated terpenoids featuring a unique 5,5,5-fused tricyclic spiroketal butyrolactone moiety and diterpenoid-derived long chain, were isolated from Dysoxylum hongkongense. Their structures were unambiguously assigned by a combination of spectroscopic data, chemical degradation, X-ray crystallography, CD analysis, and total synthesis. The total syntheses of compounds 1-4 were effectively accomplished by a convergent strategy with the longest linear sequences of 12-14 steps and overall yields of 5.4-9.6%. Notably, we exploited a bioinspired one-pot method to construct the key intermediate 14 from an easily made compound 12 by involving the cascade reactions of an elaborate Claisen rearrangement, deprotections, and a 5-exo-trig cyclization. The desired major epimer 14a was then transformed to the main building block 21. Assembly of 21 and the long chain vinyl iodide 7 was made by an NHK coupling reaction to furnish the framework of 1-4. Some of the hongkonoids and/or synthetic analogs showed significant to moderate inhibitory activities against NF-κB, 11β-HSD1, and sterol synthesis. The most active NF-κB inhibitor 34 exhibited distinct inhibition on the LPS-induced inflammatory responses in RAW 246.7 and primary BMDM cells.

First-principle based microkinetic simulations are performed to investigate methanol synthesis from CO and CO2 on Cu(221) and CuZn(221) surfaces. It is found that regardless of surface structure, the carbon consumption rate follows the order: CO hydrogenation > CO/CO2 hydrogenation > CO2 hydrogenation. The superior CO hydrogenation activity mainly arises from the lower barriers of elementary reactions than CO2 hydrogenation. Compared to Cu(221), the introduction of Zn greatly lowers the activity of methanol synthesis, in particularly for CO hydrogenation. For a mixed CO/CO2 hydrogenation, CO acts as the carbon source on Cu(221) while both CO and CO2 contribute to carbon conversion on CuZn(221). The degree of rate control studies show that the key steps that determine the reaction activity of CO/CO2 hydrogenation are HCO and HCOO hydrogenation on Cu(221), instead of HCOOH hydrogenation on CuZn(221). The present work highlights the effect of the Zn doping and feed gas composition on methanol synthesis.

Identifying the intrinsic activity of the distinct sites which coexist in oxide-supported metal particles is vital but challenging for rational design of catalysts. We treat the challenge here by density functional theory calculations to differentiate unbiasedly the intrinsic reactivity of a variety of sites observed under reaction conditions for methanol steam reforming on Cu/ZnO catalyst. Metallic Cu and CuZn alloy are found to be less active but highly selective toward formaldehyde because water dissociation is demanding, which limits the formation of hydroxyl and subsequent coupling necessary to yield CO2. Cu/ZnO interface is highly active and selective for H-2/CO2 because of its superior activity for water and methanol activation. Distinct hydrogen affinity at Cu/ZnO interface also leads to more favorable CO2 production via H2COO, in contrast to via HCOOH at (bi)metallic sites. The distinct reactivity of various structural motifs exposed and the importance of the metal/oxide for selectivity revealed is valuable for optimal design of catalysts.

Identification of the active site is important in developing rational design strategies for solid catalysts but is seriously blocked by their structural complexity. Here, we use uniform Cu nanocrystals synthesized by a morphology-preserved reduction of corresponding uniform Cu 2 O nanocrystals in order to identify the most active Cu facet for low-temperature water gas shift (WGS) reaction. Cu cubes enclosed with {100} facets are very active in catalyzing the WGS reaction up to 548 K while Cu octahedra enclosed with {111} facets are inactive. The Cu–Cu suboxide (Cu x O, x ≥ 10) interface of Cu(100) surface is the active site on which all elementary surface reactions within the catalytic cycle proceed smoothly. However, the formate intermediate was found stable at the Cu–Cu x O interface of Cu(111) surface with consequent accumulation and poisoning of the surface at low temperatures. Thereafter, Cu cubes-supported ZnO catalysts are successfully developed with extremely high activity in low-temperature WGS reaction.

With the development and wide applications of engineered nanomaterials (ENMs), their impacts on human health have received increasing concerns. ENMs can enter human body through respiratory pathway, digestive tract, skin penetration, intravenous injection, and implantation, and then they are carried to distal organs via bloodstream and lymphatic functions to perturb physiological systems. It is very important to investigate the interactions between ENMs and biomolecules (the basic building blocks of the human body) such as phospholipid, protein, DNA, and some other small biological molecules. The chapter intends to discuss the chemical basis of interactions between ENMs and biomolecules, and the effects of the differences in surface morphology, composition, and modified groups of ENMs. The in-depth understanding of interactions between ENMs and biomolecules could lay foundations for further elucidating the effects of ENMs on human cells, organs, and physiological systems, which paves the way for human and environmental friendliness in the production and usage of ENMs.

The environmental copper pollution seriously threatens the health of organisms and the safety of ecosystem. Therefore, the development of a simple and sensitive method to detect copper ion is very important. In this study, we have developed a fluorescent biosensor based on biological recognition element pyoverdine to selectively detect copper ion. The fluorescence of pyoverdine is quenched obviously after binding with copper ion. A good linearity within the range of 0.2-10 mu M (R= 0.997) is attained and the detection limit is 50 nM. The biosensor has been successfully utilized for the detection of copper ion in drinking water, seawater and bio-samples and the results agree well with those obtained by the inductively coupled plasma mass spectrometry. Therefore, the established biosensor is a creditable method to detect copper ion with high sensitivity and selectivity, which can be utilized as a powerful tool to monitor copper pollution in the environment. (C) 2016 Elsevier B.V. All rights reserved.

A naked-eye sensitive ELISA-like assay was developed based on gold-enhanced peroxidase-like activity of gold nanoparticles (AuNPs). Using human IgG (H-IgG) as an analytical model, goat anti-human IgG antibody (anti-IgG) adsorbed on microtiter plate and AuNPs-labeled anti-IgG acted as capture antibody and detection antibody, respectively. Because the surfaces of AuNPs were blocked by protein molecules, the peroxidase-like activity of AuNPs was almost inhibited, evaluated by the catalytic oxidation of peroxidase enzyme substrate 3,3',5,5'-tetramethylbenzidine (TMB), which could produce a bright blue color in the presence of H2O2. Fortunately, the catalytic ability of AuNPs was dramatically increased by the deposition of gold due to the formation of a new gold shell on immunogold. Under optimal reaction conditions, the colorimetric immunoassay presented a good linear relationship in the range of 0.7-100 ng/mL and the limit of detection (LOD) of 0.3 ng/mL calculated by 3σ/S for UV-vis detection, and obtained LOD of 5 ng/mL for naked-eye detection. The obtained results were competitive with conventional sandwich ELISA with the LOD of 1.6 ng/mL. Furthermore, this developed colorimetric immunoassay was successfully applied to diluted human serum and fetal bovine serum samples, and predicted a broad prospect for the use of peroxidase-like activity involving nanomaterials in bioassay and diagnostics.

Here, we propose a plasmonic enzyme-linked immunosorbent assay (ELISA) based on highly sensitive colorimetric detection of alkaline phosphatase (ALP), which is achieved by iodine-mediated etching of gold nanorods (AuNRs). Once the sandwich-type immunocomplex is formed, the ALP bound on the polystyrene microwells will hydrolyze ascorbic acid 2-phosphate into ascorbic acid. Subsequently, iodate is reduced to iodine, a moderate oxidant, which etches AuNRs from rod to sphere in shape. The shape change of AuNRs leads to a blue-shift of longitudinal localized surface plasmon resonance. As a result, the solution of AuNRs changes from blue to red. Benefiting from the highly sensitive detection of ALP, the proposed plasmonic ELISA has achieved an ultralow detection limit (100 pg/mL) for human immunoglobulin G (IgG). Importantly, the visual detection limit (3.0 ng/mL) allows the rapid differential diagnosis with the naked eye. The further detection of human IgG in fetal bovine serum indicates its applicability to the determination of low abundance protein in complex biological samples.

A sensing strategy for chromogenic detection of molecular biothiols has been proposed based on fluorescein isothiocyanate (FITC) functionalized magnetic core-shell Fe3O4/Ag hybrid nanoparticles. Ag coated magnetic Fe3O4 nanoparticles were initially synthetized. FITC was subsequently conjugated on the surface of core-shell nanoparticles by Ag-SCN linkage and then the fluorescence of FITC was quenched. Upon addition of molecular biothiols, since the Ag S bond is stronger than Ag-SCN, a place-displacement between thiols and FITC would occur and thereby the fluorescence of FITC would recover. Thus, a fluorescence "off-on" probe was attained by virtue of biothiols, so after magnetic separation, the fluorescence signal change of FITC in clear solution could be employed for quantitative determination of typical molecular biothiols such as glutathione (GSH) and cysteine (Cys). High sensitivity was obtained with the detection limits of 10 nM and 20 nM for GSH and Cys, respectively. As well as, the assay strategy presented excellent selectivity toward molecular biothiols against other amino acids. Furthermore, confocal imaging was achieved in living cells, indicating that this fluorescent probe is potentially applicable for imaging molecular thiols in biological systems. (C) 2013 Elsevier B.V. All rights reserved.

We have described a simple and low-cost visual method for on-site detection of hydrogen sulfide (H2S) in air based on the antiaggregation of gold nanoparticles (AuNPs). The bubbling of H2S into a weak alkaline buffer solution leads to the formation of HS-, which can stabilize the AuNPs and ensure the AuNPs maintain their red color even in a Tris buffer solution containing 80 mM NaCl with the presence of Tween 80. The stabilization of the AuNPs is attributed to the adsorption of negatively charged S2- on the AuNPs surface. In contrast, without the bubbling of H2S, AuNPs aggregate and change color from red to blue. Under optimal conditions, the proposed method exhibits excellent visual sensitivity with a naked-eye detectable limit of 0.5 ppm (v/v), making the on-site detection of H2S possible. This method also possesses good selectivity toward H2S over other gases by using a simple SO2 removal device. The successful determination of the concentrations of H2S in local air indicates the potential application of this cost-effective method.

Although many water-related catalytic reactions on Cu-ZnO catalysts, such as methanol steam reforming and water gas shift, have been extensively investigated, little is known about water dissociation on Cu-ZnO catalysts. To reveal the active center for water dissociation on Cu-ZnO catalysts, we performed density functional theory calculations on various domains of Cu-ZnO catalysts, including Cu surfaces, supported ZnO films, and Cu-ZnO interfaces. It is found that water dissociation is hindered by a relatively large energy barrier on both the planar and the stepped Cu surfaces. On supported ZnO films, the barrier of water dissociation is significantly lowered compared with the Cu surfaces and the reaction is essentially thermo-neutral, thus the dissociation reaction will easily reach a state of dynamic equilibrium and dissociative and molecular water can coexist on the film. At the Cu-ZnO interface, water dissociation is exothermic and proceeds essentially without an energy barrier. The enhanced activity of the Cu-ZnO interface is due to the strong adsorption of both the H atom and hydroxyl group, and the step-like structure at the interface. The low energy barrier of hydroxyl diffusion and water-assisted hydrogen diffusion on ZnO films allows water dissociation to occur continuously at the interface. This work highlights the unique role of the Cu-ZnO interface in water dissociation on Cu-ZnO catalysts.

A novel label-free colorimetric strategy was reported for sensitive detection of copper ions (Cu(2+)) by using the decelerating etching of gold nanorods (GNRs). H2O2 was employed as the oxidant for corrosion of GNRs, leading to the decrease of the aspect ratio of GNRs. In the absence of Cu(2+), the redox corrosion of GNRs by H2O2 occurred rapidly, causing the distinct color change of GNRs from bluish green to purplish red. By virtue of the strong and specific catalysis by Cu(2+) of the decomposition of H2O2, the rate of redox corrosion can be decelerated. Relevant experimental parameters, including pH value, concentrations of NaSCN and H2O2, incubation temperature and time were evaluated. Under optimal conditions, our method gave a good linear range of 10-300 nM (R = 0.9985) for Cu(2+) and the detection limit with the naked eye is as low as 10 nM. Thus, the proposed colorimetric sensor is simple, sensitive (4.96 nM) and selective, and it has been successfully applied to detect Cu(2+) in shellfish samples. Moreover, the potential mechanism was also discussed.