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The effective recognition of antioxidants is considered to have far-reaching significance in medical diagnosis. Here, an efficient visual sensing strategy is developed to identify multiple antioxid...

Air pollution is a serious problem. Refractory thiophene sulfides, which cause air pollution, bring great challenges to their rapid and accurate identification. In this work, we propose a fluorescent sensor array based on two perovskite nanocrystals (CsPbBr

A series of Schiff’s base derivatives was rationally designed, synthesized, and evaluated as multi-function agents for the treatment of Alzheimer’s disease (AD). The results revealed that compound 3b was a novel multifunctional agent. It acted as a highly selective monoamine oxidase-B inhibitor (IC50 = 8.4 nM), which was explained by the docking study. Compound 3b also was an antioxidant agent (2.3 eq) and could significantly inhibit self-induced Aβ1-42 aggregation (31.8%). Meanwhile, compound 3b was a selective metal chelator and could inhibit Cu2+-induced Aβ1-42 aggregation (62.3%). Furthermore, compound 3b presented good neuroprotective effects on H2O2-induced PC12 cell injury. More importantly, compound demonstrated good blood brain barrier permeability and druglike properties. Therefore, compound 3b, a promising multi-targeted active molecule, offers an attractive starting point for further study in the drug-discovery process against AD.

In this paper, the photocatalytic activity of industrial titanium dioxide (TiO2) based nacreous pigments was researched as functional building materials for photocatalytic NO remove. Three industrial TiO2 based nacreous pigments were selected to estimate the photocatalytic activity for NO remove. This study is a good proof that pearlescent pigments can eliminate NO, and its performance is positively correlated with its titanium dioxide content. And this research will widen the application of nacreous pigments in functional building materials, and provide a new way to eliminate in door nitric oxide pollution.

A gold nanoparticle (AuNP)–based sensing strategy based on rapid reduction of Au(I→0) is proposed. As a proof-of-concept study, the proposed sensing principle is designed for simultaneous and colorimetric detection and discrimination of multiple proteins. In the presence of H2O2, the target proteins could reduce Au(I) (i.e. HAuCl2) to AuNPs with different sizes, shapes and dispersion/aggregation states, thus resulting in rapidly colorimetric identification of different proteins. The optical response (i.e. color) of AuNPs is found to be characteristic of a given protein. The color response patterns are characteristic for each protein and can be quantitatively differentiated by statistical techniques. The sensor array is capable of discriminating proteins at concentrations as low as 0.1 μg/mL with high accuracy. A linear relationship was observed between the total Euclidean distances and protein concentration, providing the potential for protein quantification using this sensor array. The limit of detection (LOD) for catalase (Cat) is 0.08 μg/mL. The good linear range (from 0 to 8 μg/mL) has been used for the quantitative assay of Cat. To show a potentially practical application, this method was used to detect and discriminate proteins in human urine and tear samples.

A simple, rapid, sensitive, selective and label-free method is presented for the colorimetric determination of lincomycin (Lin) by using HAuCl4 and NaOH. Upon the addition of Lin, the mixture of HAuCl4 and NaOH shows a color change from colorless to blue (or dark blue). The limit of colorimetric detection is as low as 1 μM, observed both in Milli-Q water and real samples. The selectivity of Lin detection is excellent compared with 9 other common antibiotics. On the basis of the “three-color” principle of Thomas Young, we extracted the red, green and blue (RGB) alterations of the sensor in the absence and presence of different concentrations of Lin. The color changes are quantitatively illustrated by the total Euclidean distances (EDs = [ΔR2 + ΔG2 + ΔB2]1/2). The good linear relationship between the EDs and Lin concentration is used for the quantitative assay of Lin. The developed method demonstrates great potential for the detection of Lin in environmental water and milk.

The phase equilibria and compositions in the magnesium (Mg) rich part of the Mg-Er-Si ternary system at 300 and 400 °C were systemically investigated through the equilibrated alloy method by using x-ray diffraction and scanning electron microscopy assisted with energy dispersive spectroscopy of x-ray. The results show that in the composition range of our study the equilibrium of Er2MgSi2 with the (Mg) solid solution, Er5Mg24, and Mg2Si exists at both temperatures. A certain amount of Mg atoms can be replaced by Er and Si element, but they cannot replace Mg atom simultaneously. The homogeneity ranges of Mg solid solution as well as the solid solubilities of the intermediate phases at different temperatures are reported.

A general approach is presented for synthesis of multicolored gold nanoparticles (GNPs) by Au(I)-mediated generation of interlocking rings in proteins and antibiotics. The Au(I) ions are shuttled from proteins to antibiotics, and this causes the formation of interlocking rings. The multicolored GNPs of different sizes were synthesized in the rings by using the rapid nucleation method. To take the unique colors of GNPs, a functional array was designed for the colorimetric determination and discrimination of antibiotics, specifically of amoxicillin, chlortetracycline, erythromycin, spiramycin, neomycin, thiamphenicol, gentamycin and lincomycin. The method is based on the "three color" (RGB) principle. The color response patterns are characteristic for each antibiotic and can be quantitatively differentiated by statistical techniques. The limits of detection (LOD, at S/N = 3) for spiramycin (Sp) have been calculated to be 0.18 μM and 0.10 μM in water and milk, respectively. The good linear range (from 0.3 to 3.5 μM) has been used for the quantitative assay of Sp in a certified reference material. Graphical abstractSchematic presentation of gold nanoparticles (GNPs) synthesis via formation of interlocking rings in protein and antibiotics. The Au(I) ions mediate protein and antibiotics to be interlocking rings, which are quickly fixed via microwave reaction. The GNPs are synthesized and assembled in the rings.

Solar-energy driven, fresh water production from seawater has been considered as a promising strategy to yield potable water. However this approach is typically expensive, energy intensive, as well as poorly yielding of clean water under natural sunlight. This has limited the practical application of solar-energy driven, fresh water production. Accordingly, we have investigated the development of new films with low cost and higher efficiency for solar desalination. We designed a hybrid film with a high desalination efficiency of over 99 % and the maximum desalination capacity of 10 kg/m2/h under simulated sunlight. The hybrid film was composed of a hydrophilic polymer framework (chitin) and a solar absorber (CuS) with an abundant porous structure for internal channel transportation. Chitin can greatly promote water evaporation in the hydrogel network, whilst the presence of CuS in the network facilitates efficient light-to-heat conversion. The internal channels of the chitin composite maintain a sufficient water supply for continuous solar vapor generation. Such hybrid films also have the advantages of excellent strength, high elasticity, as well as high cycling rates.

Mitochondria, the power generators in cell, are a primary organelle of oxygen consumption and a main source of reactive oxygen/nitrogen species (ROS/RNS). Peroxynitrite (ONOO-), known as a kind of RNS, has been considered to be a significant factor in many cell-related biological processes, and there is great desire to develop fluorescent probes that can sensitively and selectively detect peroxynitrite in living cells. Herein, we developed a fluorescent carbon-dots (C-dots) based mitochondria-targetable nanoprobe with high sensitivity and selectivity for peroxynitrite sensing in living cells. The C-dots with its surface rich in amino groups was synthesized using o-phenylenediamine as carbon precursor, and it could be covalently conjugated with a mitochondria-targeting moiety, i.e. triphenylphosphonium (TPP). In the presence of peroxynitrite, the fluorescence of the constructed nanoprobe (C-dots-TPP) was efficiently quenched via a mechanism of photoinduced electron transfer (PET). The nanoprobe exhibited relatively high sensitivity (limit of detection: 13.5nM) and selectivity towards peroxynitrite in aqueous buffer. The performance of the nanoprobe for fluorescence imaging of peroxynitrite in mitochondria was investigated. The results demonstrated that the nanoprobe showed fine mitochondria-targeting ability and imaging contrast towards peroxynitrite in living cells. We anticipate that the proposed nanoprobe will provide a facile tool to explore the role played by peroxynitrite in cytobiology.

Some europium-based dithienylethenes have been synthesized and their structures have been confirmed by IR spectroscopy and elemental analysis. The photochromic properties and luminescent behaviors of these compounds in solution have been measured upon irradiation with UV or visible light. UV/vis absorption and luminescence spectra indicated that these dithienylethenes displayed obvious photochromism and luminescent switching properties. Specially, when compared with other europium-based dithienylethenes, the triphenylamine and terpyridyl-based dithienylethene showed the photocyclization-dependent ratiometric luminescent switch behavior.

Nitrogen and boron doped carbon quantum dots (NB-CQDs) with yellow-green emission were prepared via hydrothermal method using 2-hydroxyphenylboronic acid and ethylenediamine in aqueous solution. The as-prepared NB-CQDs exhibited bright yellow-green emission, excellent stability in aqueous solution with high ionic strength and good biocompatibility. We further explored the applications of NB-CQDs for sensing metal ions in aqueous solution. We found that the NB-CQDs could be utilized to sense Cr2O72− in aqueous solution due to the Cr2O72−-induced fluorescence quenching. In the sensing system, as low as 0.5 μM Cr2O72− can be successfully detected and a good linear relationship in the range of 0–250 μM has been obtained. And the NB-CQDs can be also used as ink for writing on paper, revealing the NB-CQDs can be applied for anti-counterfeiting. Moreover, the NB-CQDs exhibit negligible cytotoxicity and good biocompatibility, which is favorable for bioimaging applications. And the NB-CQDs were successfully applied for fluorescence imaging in HeLa cells.

Tight-controlling of the aspect ratios (ARs) and fine-tailoring of the crystallographic facets of gold nanorods (GNRs) are critical for their further applications in material, biological, and medical fields. However, the high-yield synthesis of GNRs with certain facets and ARs is still challenging because it requires grasping of various components and complicated interactions in the reaction system. Herein, we first report the pH-adjusting method to synthesize uniform and monodispersed GNRs in high yield with the (200) facet and fine-tuned their ARs within an optimal pH range. Through optimizing the experimental parameters, we found that the formation of GNRs was significantly influenced by the concentrations of silver ions and cetyltrimethylammonium bromide (CTAB). Based on the precise control over the quantity of silver ions and CTAB additives, we further optimized the pH in the buffer system. Under the optimized weakly acidic conditions (pH 5.5–7.0), HAuCl4 was reduced by NH2OH to form single-crystalline GNRs with a preferential growth along the [200] facet (i.e. [100] direction), which was supported by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Interestingly, there was a linear relationship between the ARs and pH values over a narrow pH range of 5.5–6.5. The pH-dependent reducing ability of NH2OH enhanced with the increasing pH.

In this paper, transition metal phosphide (TMP) was used as cocatalyst to enhance the photocatalytic activity of Cd0.5Zn0.5S solid solution for nitrogen fixation under visible light irradiation. The Ni2P/Cd0.5Zn0.5S photocatalyst was characterized by X-ray diffraction patterns (XRD), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectra (DRS) and X-ray photoelectron spectroscopy (XPS). The photocatalytic data showed that Ni2P/Cd0.5Zn0.5S had higher activity than pure Cd0.5Zn0.5S for photocatalytic dinitrogen (N2) fixation in the absence of any scavengers. After 1 h visible light irradiation (λ > 400 nm), the concentration of NH3 reached to 101.5 μmol L−1. And the quantum efficiency at 420 nm monochromatic light reached 4.32%, which much higher than other semiconductors. Time-resolved PL spectra, photocurrent and electrochemical impedance (EIS) spectroscopy revealed that higher photo-induced carrier separation efficiency of Ni2P/Cd0.5Zn0.5S. This work introduced Cd0.5Zn0.5S solid solution photocatalyst to reduce nitrogen, and offered a greenly, economically and efficiently way for nitrogen fixation.

A simple, rapid, sensitive, selective and label-free method is presented for the colorimetric determination of lincomycin (Lin) by using HAuCl

The authors report on a colorimetric method for the determination of Cr(VI) using gold nanoparticles (AuNPs) modified with the reagent 1,5-diphenylcarbazide (DPC). The detection scheme is based on the well-known redox reaction that occurs between DPC (on the AuNPs) and Cr(VI) ion, this followed by complexation between oxidized DPC and Cr(III). This complexation then triggers aggregation of the AuNPs and a color change from red to blue. The method is highly selective for Cr(VI) and has a 0.3 μM limit of detection which is much lower than the maximal permitted level in drinking water (i.e. ~1 μM) as regulated by the Chinese Ministry of Environmental Protection. The assay was applied to the rapid determination of Cr(VI) in real environmental water and seafood samples.

In this work, a low-cost and environmentally friendly solvothermal route to the synthesis of indium oxide nanorod clusters was described in the presence of sodium chlorate and urea. The morphologies and structures of the as-prepared samples were characterized by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). The results clearly revealed that the as-prepared indium oxide was composed of nanorods with a diameter of about 15 nm. The gas sensing properties of the as-prepared indium oxide samples were tested towards various gases. The indium oxide nanorod cluster based sensor showed high response and good selectivity toward NO2 at an operating temperature of 150 °C, giving a response of about 41 to 500 ppb.

Colorimetric sensor arrays demonstrate numerous superior features in chemo- and bio-sensing, but they are generally not applicable to less-reactive analytes. Based on the findings that N-methyl carbamate pesticides could be decomposed into reactive phenols in basic media, herein, a novel strategy of strong base pre-treatment was developed and employed for the colorimetric sensor array detection and differentiation of the N-methyl carbamate pesticides in an indirect manner. With the use of five inexpensive and commercially available phenol responsive indicators, such a colorimetric sensor array can be facilely fabricated. Classification analysis (e.g. hierarchical clustering analysis (HCA) and principal component analysis (PCA)) reveals that the as-fabricated sensor array has an extremely high dimensionality and, consequently, exhibits excellence in discriminating a variety of N-methyl carbamates from other types of pesticides and potential interferants, and further identifying them exactly from each other. Moreover, semi-quantitative detection could also be achieved through combining HCA/PCA, recognition patterns, and corresponding fitting curves. Overall, the as-developed method exhibits high selectivity and sensitivity, good anti-interference, simultaneous detection and identification capability for each of the N-methyl carbamate pesticides, and potential applicability in real samples. Most importantly, this study demonstrates that pre-treatment strategies are very effective in expanding the range of applications of colorimetric sensor array methodology to less-reactive analytes.

The thickness of 2D BiOCl nanosheets along [001] direction control the internal electric fields intensity. In order to enhance the photocatalytic properties of BiOCl, decreasing the thickness is the best choice. In this paper, black ultrathin BiOCl nanosheet (BU–BiOCl) with expanded spacing of the (001) crystal plane and oxygen vacancy was synthesized in high viscosity and alcohol group concentration glycerol system. It was characterized by X-ray diffraction patterns (XRD), X-ray photoelectron spectroscopy (XPS), X-ray photoelectron scanning electron microscope (SEM), high-resolution transmission electron microscopy (HRTEM), electron spin resonance (ESR), UV–vis diffuse reflectance spectra (DRS) and photoluminescence (PL) spectra. The experimental characterization and theoretical calculation results also indicated that expanded facets spacing and oxygen vacancy of as-synthesized BU-BiOCl enhanced separation efficiency of photoinduced carriers and photon absorption efficiency. Therefore, BU-BiOCl showed higher activity than bulk BiOCl for H 2 production under visible light irradiation.

The chemical elements of proteins are similar to that of DNA (e.g., C, H, O, and N), and DNA shows different knotted architectures. So we imagine that proteins may show a wealth of highly complex structures, especially when proteins interact with each other. The imagination was proved by synthesizing gold nanoparticles (GNPs) to capture the lifelike protein structures. The optical responses (i.e., color) of as-prepared GNPs are found to be characteristic to a given protein (or heavy metal ion). Based on the “three colors” principle of Thomas Young, we extracted the red, green, and blue (RGB) alterations of as-synthesized GNPs to fabricate multichannel sensor arrays for proteins (or heavy metal ions) discrimination. The designed multichannel sensor arrays demonstrate possibilities in semiquantitative analysis of multiple analytes (e.g., proteins and heavy metal ions). This work is believed to open new opportunities for GNPs-based label-free sensing.

A highly selective method is presented for the colorimetric determination of dopamine (DA) using gold nanoparticles (AuNPs). DA caps on the surface of AuNPs (DA-AuNPs) induces the aggregation of AuNPs in alkaline solution. The DA-AuNPs are modified by the hydrolysate of thioglycolic acid (TGA 2 − ) through Au–S bonds. The aggregation of AuNPs is accelerated by TGA 2− , due to the strong hydrogen-bonds (NH⋯OC and OH⋯OC) formed between TGA 2 − and DA. Upon the addition of DA, the solution shows a color change from red to purple (or yellow), which is also monitored to detect DA in human urine and fetal bovine serum samples. Here, the limits of colorimetric detection are as low as 10 −7 M observed in Milli-Q water, urine and serum. Based on UV–vis absorption spectra, the limits of detection have been calculated to be 3.3×10 −8 M, 1.0×10 −7 M and 9.4×10 −8 M in Milli-Q water, urine, and serum, respectively. All the limits of detection are lower than the lowest abnormal concentrations of DA in urine (5.7×10 −7 M) and blood (1.6×10 −5 M). The good linear ranges from 0 to 10 −6 M are used for the quantitative assay of DA in urine and serum samples. The applicability of our detection system is also verified by analysis of DA in urine and serum samples. The developed approach is without using complex financial instruments.

We have grown a series of high-quality single crystals of K0.8Fe2−x Cu x Se2(0 ⩽ x ⩽ 2) by Bridgman method and investigated their physical properties by measurements of X-ray diffraction, electrical resistivity, and magnetic susceptibility. The elemental composition analysis shows that it is easy to incorporate Cu dopants. The electrical conductivity and dc magnetic susceptibility measurements show that these doped samples are semiconductors with spin glass behavior at low temperature. The activation energy has a similar trend to the entropy of mixing for two kinds of atoms in the lattice which suggests the semiconducting and spin glass behavior that may be caused by the the random distribution of Fe and Cu ions in the Fe/Cu plane.

The different sized and shaped Au NPs have intrigued considerable attention, because they possess different surface plasma resonance (SPR) absorption bands and thus result in many colorimetric Au NP-based detection applications. In this article, four different sized and shaped Au NPs of nanodots/rods were prepared and characterized. The as-prepared Au NPs were modified by the negatively charged anions of [SCH2CO2]2− to investigate both the size and shape effects of modified Au NPs on colorimetric detection of Co2+ and the corresponding SPR absorption properties. The different-shaped Au NPs possess different SPR absorption properties. The Au nanorods appeared to be colorimetric sensitive for Co2+ sensing.

Metal-mediated interlocking rings won the 2016 Nobel Prize in Chemistry. The metal-directed interlocking rings in macromolecular systems (e.g., proteins) may be similar to the form of Maxwell's electromagnetic waves; the metal ions may shuttle among the rings in the special environment. To verify this hypothesis, we designed a general approach to synthesize the multicolored gold nanoparticles (GNPs) mediated by Au(I)-directed interlocking rings in proteins. The Au(I) ions shuttled among these interlocking rings in the strong alkaline solution. Through the rapid nucleation method, the multicolored GNPs of different morphology and sizes were synthesized in the multiple honeycombed templates. On the basis of the "three-color" principle of Thomas Young, we extracted the red, green, and blue (RGB) alterations of GNPs to fabricate a visual sensor array for protein discrimination. The fingerprints (ΔRGB) were obtained from the target proteins and fed into computer programs. The proposed sensing platform was also applied to detect lysozyme in human tears with satisfactory results. Importantly, we forecasted that lysozyme could be the effective drug for curing dacryocystitis and nasolacrimal duct obstruction diseases.

A simple and reliable colorimetric detection system based on anti-aggregation of gold nanoparticles (AuNPs) is proposed for rapid detection of Hg2+ with high selectivity and sensitivity. O-phenylenediamine (OPD) can cause the aggregation of AuNPs due to formation of the strong covalent NH-Au bond, and then induce color change of the AuNPs solution from red to blue. However, in the presence of Hg2+, OPD prefers to combine with Hg2+ rather than AuNPs resulting in inhibition of the color change. Based on the anti-aggregation mechanism, Hg2+ can be detected by observing the color change of AuNPs solution containing OPD. After optimization, the selectivity of this Hg2+ detection system by the naked eyes and UV-vis spectra is excellent comparing with other ions. The limit of the detection CLOD) is 0.1 mu M by the naked eyes and 5.0 nM by UV-vis spectroscopy, which is lower than the mercury toxic level (10 nM) defined by US Environmental Protection Agency. It's a good linear relationship between A(520)/A(680) and Hg2+. concentration from 0.01 mu M to 2.0 mu M, which is used for the quantitative assay of Hg2+. The applicability of our detection system is also verified by analysis of Hg2+ in tap water and lake water. (C) 2014 Elsevier B.V. All rights reserved.

A facile, simple and low-cost approach for synthesizing highly fluorescent carbon quantum dots (CQDs) from thermal treatment of sustainable hair has been developed. The resultant CQDs exhibited strong blue emission with a quantum yield of 10.75%, excellent photostability and high stability in high salt conditions. As the fluorescence of CQDs can be efficiently quenched by Hg2+, the CQDs can be constructed as a nanosensor for Hg2+ with good sensitivity and selectivity. And as low as 10 nM Hg2+ can be successfully detected.

A new kind of analytical reagent, hexadecyl trimethyl ammonium bromide (CTAB), and dithizone product-modified gold nanoparticle dispersion, is developed for colorimetric response to 10 types of heavy metal ions (M(n+)), including Cr(VI), Cr(3+), Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+), and Pb(2+). The color change of the modified gold nanoparticle dispersion is instantaneous and distinct for Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+), and Pb(2+). The color change results from the multiple reasons, such as electronic transitions, cation-π interactions, formation of coordination bonds, and M(n+)-induced aggregation of gold nanoparticles (AuNPs). The different combining capacity of heavy metal ions to modifiers results in the different broadening and red-shifting of the plasmon peak of modified AuNPs. In addition, Cr(VI), Cu(2+), Co(2+), Ni(2+), and Mn(2+) cause the new UV-vis absorption peaks in the region of 360-460 nm. The interactions between the modifiers and AuNPs, and between the modifiers and M(n+), are investigated by using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The results confirm that AuNPs are modified by CTAB and dithizone products through electrostatic interactions and Au-S bonds, respectively, and the M(n+)-N bonds form between M(n+) and dithizone products. Furthermore, the experimental and density functional theory calculated IR spectra prove that dithizone reacts with NaOH to produce C6H5O(-) and [SCH2N4](2-). The validation of this method is carried out by analysis of heavy metal ions in tap water.

Multidimensional sensing offers advantages in accuracy, diversity and capability for the simultaneous detection and discrimination of multiple analytes, however, the previous reports usually require complicated synthesis/fabrication process and/or need a variety of techniques (or instruments) to acquire signals. Therefore, to take full advantages of this concept, simple designs are highly desirable. Herein, a novel concept is conceived to construct multidimensional sensing platforms based on a single indicator that has capability of showing diverse color/fluorescence responses with the addition of different analytes. Through extracting hidden information from these responses, such as red, green and blue (RGB) alterations, a triple-channel-based multidimensional sensing platform could consequently be fabricated and the RGB alterations are further applicable to standard statistical methods. As a proof-of-concept study, a triple-channel sensing platform is fabricated solely using dithizone with assistance of cetyltrimethylammonium bromide (CTAB) for hyperchromicity and sensitization, which demonstrates superior capabilities in detection and identification of ten common heavy metal ions at their standard concentrations of wastewater-discharge of China. Moreover, this sensing platform exhibits promising applications in semi-quantitative and even quantitative analysis individuals of these heavy metal ions with high sensitivity as well. Finally, density functional theory calculations are performed to reveal the foundations for this analysis.

An in-situ reduction method has been reported to prepare gold nanoparticles (GNPs) of 40–110 nm by using the green reducing agents of proteins, which are activated by H2O2 and the superoxide anion ("Equation missing"). The protein of collagen turns HAuCl4 to the aqueous Au(I) ainions, which are further reduced by other proteins to be highly monodispersed and spherical GNPs of different sizes. The GNPs reduced by different proteins are found to be with the exposed {100} facets, the distinctive UV-vis absorption spectra and various colors (See Fig. 1). By means of extracting the color responses, such as red, green and blue (RGB) alterations, an in-situ reduction method-based multidimensional sensing platform is fabricated in the process of GNPs synthesis. Without further modification of GNPs, nine common proteins are found to be well detected and discriminated at different concentrations. Moreover, this sensing platform also demonstrates great potentials in qualitative and semiquantitative analysis on the individuals of these proteins with high sensitivity. Furthermore, the validation of this multidimensional sensing platform has been carried out by analysis on the spiked proteins in human urine and the target proteins in complex matrix (e.g. lysozyme in human tear).

We previously reported a colorimetric assay method for Co(2+) based on the thioglycolic acid (TGA) functionalized hexadecyl trimethyl ammonium bromide (CTAB) modified Au NPs. However, the detection limit of 3×10(-7) M was still higher than that of the sanitary standard for drinking water (6.8×10(-8) M). In addition, the interactions between the modifier and Au NPs, and between the modifier-Au NPs and Co(2+) remain to be clarified and confirmed. Thus, in the present study, the modified Au NPs solution was dialyzed and its detection limit was optimized to be 5×10(-10) M. The interactions between the modifier and Au NPs, and between the modifier-Au NPs and Co(2+) were investigated in both experimental characterizations and theoretical calculations, consistently confirming that the Au NPs were modified by the negatively charged anions of [SCH(2)CO(2)](2-) through Au-S bonds and Co(2+) was recognized by the modifier-Au NPs through Co-O chelate bonds. The results of X-ray photoelectron spectroscopy (XPS) suggest that there were no chemical bonds formed between CTAB and Co(2+). Moreover, the colorimetric assay of Co(2+) using the modified Au NPs has been proved to be a rapid, very sensitive and highly selective method. The validation of the method was carried out by analysis of a certified reference material, GSBZ 50030-94.

Intermolecular interactions involving aromatic rings are of pivotal importance in many areas of chemistry, biology and materials science. Mimicking recent atomic force microscopy (AFM) experiments that measured the adhesion forces of single pi-pi complexes, here interactions between pyrene/coronene and graphite have been probed by force-probe molecular dynamics (FPMD) simulations. The pyrene or coronene molecule was connected to a virtual spring through a flexible poly(ethylene glycol) (PEG) linker and was pulled away from graphite in water under constant velocity. Pyrene and coronene showed similar unbinding pathways featuring four states, with a transition and an intermediate state connecting the bound and unbound states in terms of distance and interplanar angles. Transient conformations with tilted orientations (approximately 40 degrees) and with one side of the aromatic structure still in contact with the graphite surface (approximately 70 degrees) were identified as the transition and intermediate states, respectively, similar to previously observed perpendicularly stacked benzene dimers. The distance to transition state x(tr) was determined to be 0.23 +/- 0.03 nm both for pyrene/graphite and coronene/graphite. The complexes share similar unbinding pathways, but coronene binds to graphite more strongly than to pyrene.

A full structural search of the canonical, zwitterionic, protonated and deprotonated lysine conformers in gas phase is presented. A total of 17,496 canonical, 972 zwitterionic, 11,664 protonated and 1458 trial deprotonated structures were generated by allowing for all combinations of internal single-bond rotamers. All the trial structures were initially optimized at the AM1 level, and the resulting structures were determined at the B3LYP/6-311G ∗ level. A total of 927 canonical, 730 protonated and 193 deprotonated conformers were found, but there were no stable zwitterionic structures in the gas phase. The most stable conformers of the canonical, protonated and deprotonated lysine were further optimized at the B3LYP/6-311++G ∗∗ level. The energies of the most stable structures were determined at the MP2/6-311G(2df,p) level and the vibrational frequencies were calculated at the B3LYP/6-311++G ∗∗ level. The rotational constants, dipole moments, zero-point vibrational energies, harmonic frequencies, vertical ionization energies, enthalpies, Gibbs free energies and conformational distributions of gaseous lysine were presented. Numerous new structures are found and the lowest-energy lysine conformer is more stable than the existing one by 1.1 kcal/mol. Hydrogen bonds are classified and may cause significant red-shifts to the associated vibrational frequencies. The calculated proton affinity/dissociation energy and gas-phase basicity/acidity are in good agreement with the experiments. Calculations are also presented for the canonical lysine–H 2 O and zwitterionic lysine–H 2 O clusters. Interaction between lysine and H 2 O significantly affects the relative conformational stabilities. Only one water molecule is sufficient to produce the stable zwitterionic structures in gas phase. The lowest-energy structure is found to be zwitterions when applying the conductor-like polarized continuum solvent model (CPCM) to the lysine–H 2 O complexes.

A simple, rapid colorimetric detection method for Pb(2+) in aqueous solution has been developed by using sodium thiosulfate (Na2S2O3) and hexadecyl trimethyl ammonium bromide (CTAB) modified gold nanoparticles (Au NPs). Na2S2O3 was added into the Au NP solution and thiosulfate ions (S2O3(2-)) were adsorbed on the surface of the Au NPs due to electrostatic interactions. Au atoms on the surface of the Au NPs were then oxidized to Au(i) by the O2 that existed in the solution in presence of thiosulfate. The addition of Pb(2+) (the final concentration was lower than 10 μM), accelerated the leaching of the Au NPs, and Pb-Au alloys also formed on the surface of the Au NPs. There was an obvious decrease in the surface plasmon resonance (SPR) absorption of the Au NPs. The lowest concentration for Pb(2+) that could be detected by the naked eye was 0.1 μM and using UV-vis spectroscopy was 40 nM. This is lower than the lead toxic level defined by the US Environmental Protection Agency (US EPA), which is 75 nM. In this method, CTAB, as a stabilizing agent for Au NPs, can accelerate the adsorption of S2O3(2-) on the surface of the Au NPs, which shortened the detection time to within 30 min. Moreover, this detection method is simple, cheap and environmentally friendly.