Substrate For Molecules Research Articles

A semiconductor SERS sensor of corrosion-resistant PPy/GO composite film by electrochemical growth for detecting crystal violet residues in fresh fish tissue

Crystal violet (CV) residues in Marine food have produced a severe health threat in human life. In this study, we proposed a semiconductor surface-enhanced Raman scattering (SERS) sensor of corrosion-resistant Polyaniline/Graphene oxide (PPy/GO) film by electrochemical growth method to detect CV residues in fresh fish tissue. A PPy/GO dispersion solution was one-step deposited on a stainless steel sheet surface by electrochemical polymerization process to form a PPy/GO composite film acting as a semiconductor SERS substrate. Since the substrate of PPy/GO film was mainly composed of GO sheet without other metals, it had a good corrosion resistance. The SERS enhancement factor and charge transfer intensity PCT of PPy/Go SERS substrate for CV molecules were up to 1.18 × 106 and 0.903, respectively. Furthermore, the limit of detection (LOD) of PPy/GO SERS substrate could reach 1.58 nM. In addition, SERS sensor of PPy/GO film could identify CV residues in fresh fish tissues, and its recovery rate was 91.8 %–107 %. This preparing method and detecting method we proposed PPy/GO SERS substrate provide a new pathway for detecting CV residues in Marine food.

Uniaxial tensile study of calcium aluminosilicate hydrate (C-A-S-H): Structure, dynamics and mechanical properties

Calcium aluminosilicate hydrate (C-A-S-H) is the main hydration product of environmentally friendly concrete, which uses aluminum-rich industrial waste residue to partially replace cement raw materials. In order to understand the structure and properties of C-A-S-H gel at the molecular level. The structure, dynamics and mechanical properties of C-A-S-H gel at different Al/Si ratios were studied by reactive molecular dynamics simulation. The results showed that the doping of aluminates substances caused changes in the silicate-aluminate skeleton and inter-layer water molecules in C-A-S-H gels. As the Al/Si ratio increased, more water molecules dissociated and associated with Al atoms to produce Al-O(H)-Si and Al-OH. In addition, the presence of Al-O-Si chains not only imposed geometrical constraints on the inter-layer water molecules, but also increased the attraction of the substrate for water molecules. Furthermore, the mechanical behavior and deformation mechanism of C-A-S-H gels were investigated based on uniaxial tensile tests. The inter-layer bond strength and stiffness of C-A-S-H gels increased significantly with increasing tensile load and aluminate branching structure.

Flexible SERS strip based on HKUST-1(cu)/biomimetic antibodies composite multilayer for trace determination of ethephon

A surface-enhanced Raman scattering (SERS) sensor based on the folding and assembly characteristics of the three-dimensional structure of paper fibers, the skeleton controllability of metal-organic framework materials (MOFs), and the morphology designability of plasmonic noble metal materials has been established for rapid on-site determination of ethephon in food. HKUST-1(Cu) was assembled onto a carbon-treated chromatographic paper matrix by electrodeposition, and its skeleton respiration and sponge effect were used to overcome the bottleneck problem of poor affinity of SERS substrate for target molecules. Further coupled with the targeted recognition specificity of biomimetic antibodies, a paper-based interface with high specificity of molecular sensitivity was constructed. A sandwich multi-stage progressive enhancement structure was designed to couple plasma pine branch-shaped silver material in situ at the interface to realize superposition and collaborative amplification of SERS signals. When the paper-based strip sensor was used to monitor ethephon, it demonstrated a linear range of 10−3 to 10 mg kg−1 and a detection limit of around 1.39 × 10−4 mg kg−1. The construction and application of the paper-based HKUST-1(Cu)/biomimetic antibodies/pine branch-shaped silver material sensor will provide technical means and theoretical support for the rapid and efficient identification of biological ripening agent residues in food with multi-level signal enhancement.

Modifying rGO with multicarbonyl organic molecule for lithium sulfur batteries with high performance

The “shuttle effect” of polysulfide in the cycling process seriously hinders the practical application of lithium-sulfur batteries. Herein, a perylene-based organic molecule with multiple carbonyl groups (PN) was introduced to modify rGO and form a PN-rGO composite network. PN with large conjugated planar structure is potential to be highly distributed throughout the electrode. The large specific surface area of rGO provides a substrate for PN molecules and could avoid their aggregation. Moreover, PN-rGO can provide a rapid and continuous transporting path for lithium ions and electrons, thus improving conductivity and accelerating the electrochemical dynamics of the battery. At the same time, the carbonyl groups in PN can effectively adsorb polysulfide through SO interaction, and the shuttle effect of polysulfide could be alleviated. A high discharge specific capacity of 1071 mAh g−1 is retained after 200 cycles at 0.2C. In addition, the composite showed a higher rate performance of 589 mAh g−1 at 5C, compared to pristine rGO (283 mAh g−1). This work demonstrates that the rational design of organic small molecule to modify carbon materials is potential to inhibit the shuttle effect as well as to acquire stable cathode material. Our work may provide a foundation for the future design of functionalized organic molecules as energy storage materials.

Low temperature-promoted surface plasmon resonance effect and ultrasensitive surface-enhanced Raman scattering detection of creatinine

Creatinine is a key biomarker for diagnosing and monitoring kidney disease, so rapid and sensitive testing is very important. Raman spectroscopy is particularly suitable for quantitatively detecting the creatinine in the human environment because it is sensitive to subtle changes in the concentration of the analyte. In this work an effective strategy is provided to promote the activity of surface-enhanced Raman scattering spectroscopy by enhancing the photon-induced charge transfer efficiency at low temperature. The nano-gold icosahedron (Au<sub>20</sub>) is obtained by the seed-growing method, which is used as an active substrate for SERS. The ultra-low temperature (98 K) SERS detection technology is used to realize the rapid and sensitive detection of the dye molecule crystal violet (CV) and creatinine in normal saline. The experimental results show that at room temperature of 296 K, the detection limit of Au<sub>20</sub> substrate for CV molecules is as low as 10<sup>–12</sup> mol/L, and the signals are uniform; at a low temperature of 98 K, the detection limit of CV molecules can reach 10<sup>–14</sup> mol/L, which is two orders of magnitude lower than that at 296 K. As a result, the adopted cryogenic temperature can effectively weaken the lattice thermal vibration and reduce the release of phonons, then suppress phonon-assisted non-radiative recombination. So, it will increase the number of photo-induced electrons to participate in the photo-induced charge transfer efficiency. Finally, we perform the label-free detection of creatinine in saline by using an Au<sub>20</sub> substrate. The results show that the detection limit of the SERS substrate for creatinine is 10<sup>–6</sup> mol/L at 296 K, and the linear correlation coefficient of the 1619 cm<sup>–1</sup> peak is 0.9839. At a low temperature of 98 K, the detection limit of creatinine concentration is as low as 10<sup>–8</sup> mol/L, and the linear correlation coefficient of the 1619 cm<sup>–1</sup> peak becomes 0.9973. It can be seen that low temperature may further improve the detection limit of creatinine concentration and the linearity of characteristic peak. In summary, the current work provides a new idea for accurately detecting the creatinine concentration in the field of biomedicine.

First-principles studies on sensing properties of delta arsenene nanoribbons towards hexane and heptane molecules

The adsorption of hexane and heptane on delta arsenene nanoribbon (delta-AsNR) are studied with regard to the density functional theory method. Firstly, the structural stability of delta-AsNR is ascertained with formation energy. The band structure of delta-AsNR shows semiconductor behaviour. The delta-AsNR is used as a sensing substrate for hexane and heptane molecules. Based on the energy of assimilation, average band gap alteration, and Bader charge transference, the surface assimilation of hexane and heptane molecules on delta-AsNR are explored. The density of states variation of delta-AsNR upon hexane and heptane adsorption also shows the variation in electronic properties of delta-AsNR. Thus, based on the results it is evident that delta-AsNR can be deployed as a novel chemosensor for hexane and heptane molecules evolved from the sewage.

DDRE-24. TARGETING PURINE METABOLISM TO OVERCOME GLIOBLASTOMA THERAPY RESISTANCE

Intratumoral genomic heterogeneity in glioblastoma (GBM) is a barrier to overcoming radiation (RT) resistance. To discover genotype-independent mediators of RT resistance, we correlated RT resistance with the concentration of approximately 700 metabolites across 23 GBM cell lines. Purine metabolites, especially those containing the base guanine, were most correlated with RT resistance. Similarly, increased abundance of tumor purines was associated with decreased survival in GBM patients treated with RT. This relationship is causal. Purine supplementation protected RT-sensitive GBMs from RT and promoted the repair of RT-induced double strand DNA breaks (DSBs). In vitro and in vivo stable isotope tracing confirmed that GBM cell lines and orthotopic patient-derived xenografts primarily generated purines through the de novo synthetic pathway. RT treatment further increased de novo purine synthesis in GBM through signaling via the DNA damage response. Inhibition of de novo GTP synthesis with mycophenolic acid (MPA) sensitized multiple GBM cell lines and neurospheres to RT by slowing the repair of RT-induced DSBs. MPA-induced radiosensitization was GTP-dependent as it was rescued by nucleoside supplementation. Modulating pyrimidine metabolism affected neither RT resistance nor DSB repair, suggesting these GTP-specific effects are due to active signaling rather than its ability to act as a physical substrate for DNA repair and candidate signaling molecules have been identified. These results were recapitulated in vivo with mycophenolate mofetil (MMF), the orally bioavailable FDA-approved prodrug of MPA. MMF potentiated RT efficacy, reduced tumor guanylates and slowed the repair of RT-induced DSBs across multiple models. Because de novo purine synthesis is activated by many of the oncogenic alterations that drive GBM, its inhibition is a promising genotype-independent strategy to overcome GBM RT resistance. We have now begun a clinical trial to determine whether combining MMF and RT is safe and potentially efficacious in patients with GBM.

Theoretical study on the adsorption and predictive catalysis of MnN4 embedded in carbon substrate for gas molecules

Toxic gases destroy the ecological environment and endanger human health, which enlightened the researchers in development of new materials and technologies that effectively collect and capture toxic gases, and convert to harmless gases with the aid of catalyst. Density functional theory (DFT) calculations are performed to evaluate the changes in adsorption energy, charge transfer, sensitivity and Gibbs free energy for MnN4-decorated graphene (MnN4-Gra), graphene nanoribbons (MnN4-GNR), graphene nanosheets (MnN4-GNS), carbon nanotubes (MnN4-CNT) and C60 fullerenes (MnN4-C60) after adsorbing gas molecules, including NO, NO2, CO, SO2, NH3, H2S, N2O, O2, H2O and CO2. The most stable adsorption configuration of the molecule on MnN4-CS can be determined by molecular electrostatic potential and adsorption energy. The adsorption properties of MnN4-CS are mainly affected by doped atoms, curvature and size of the substrate. Among five tested materials, MnN4-C60 has good adsorption energy for toxic gases and is suitable for collecting and trapping gases. MnN4-Gra, MnN4-GNR and MnN4-GNS are evaluated as catalysts for oxygen reduction reaction (ORR), MnN4-Gra, MnN4-GNR, MnN4-CNT are suitable as catalysts for CO oxidation. Also the normal operating temperatures of gas sensors were determined by Gibbs free energy and molecular dynamics (MD). This investigation provides valuable information for designing high-performance gas sensors.

Dual boronate affinity nanoparticles-based plasmonic immunosandwich assay for specific and sensitive detection of ginsenosides.

Ginsenoside is a large family of triterpenoid saponins from Panax ginseng with various important biological functions. It is crucial to develop effective analytical approach for qualitative and quantitative analysis of ginsenosides. Herein, a dual boronate affinity nanoparticles-based plasmonic immunosandwich assay has been developed for analysis of ginsenosides. An imprinted Au NPs-coated glass slide was prepared via controllable oriented surface imprinting and used as specific extraction substrate for target molecules. In the meantime, Ag-cored Raman nanotags were used for specific labeling of target molecules. The MIP-based recognitions ensured the specificity of the assay, while enhanced Raman signal derived from the imprinted substrate-target-nanotags sandwich-like complexes provided high sensitivity. The proposed immunosandwich assay exhibited wide linear range (10ng/mL to 10μg/mL), high sensitive (LOD: 1.7ng/mL, LOQ: 5ng/mL) and good reproducibility (RSD: 8.6%). For real-world applications, successful quantitative analysis of ginsenoside Re in ginseng was performed. Therefore, this dual boronate affinity nanoparticles-based plasmonic immunosandwich assay holds great promise in many important applications such as pharmaceutical analysis.

Beta-diketones in the intensification of the luminescence of the silk fibroin films doped rare earth ions

Silk fibroin (SF) is a structural protein found in Bombyx mori cocoons and has properties that are potentially applicable in photonics. This biocompatible matrix is an interesting substrate for different ions and molecules. Furthermore, its variable refractive index allows photons to be guided in this material enabling their use as biocompatible and resorbable waveguides, which can be used to provide optical energy for various applications, e.g., therapy or imaging in living tissue. Rare earth ions (RE) play a widely known role in the field of photonics. However, there are few studies involving the production of light in doped SF with RE ions, and the literature results have shown different sensitization of Eu3+ and Tb3+ ions by the SF matrix. This study presented a consistent work on material synthesis, related studies on spectroscopy of RE ions, and the role of beta-diketonate ligand on the energy transfer mechanisms with the emission improvement in the investigated material. As a result, an intensification of emission was observed for Eu3+ doped sample in the presence of 2-thenoyltrifluoroacetone ligand, but similar results were not carried out with acetylacetone ligand insertion. A possible cause was the different access by beta-diketonate to the lanthanide ion in SF matrix due to the ligand–SF interaction. The results presented have characterized the RE–SF interactions and supported the mechanisms of energy transfer improvement for excitation of different RE ions in this matrix being important for future applications in photonics.

Towards functionalization of graphene: in situ study of the nucleation of copper-phtalocyanine on graphene

Molecular films present an elegant way for the uniform functionalization or doping of graphene. Here, we present an in situ study on the initial growth of copper phthalocyanine (CuPc) on epitaxial graphene on Ir(111). We followed the growth up to a closed monolayer with low energy electron microscopy and selected area electron diffraction (μLEED). The molecules coexist on graphene in a disordered phase without long-range order and an ordered crystalline phase. The local topography of the graphene substrate plays an important role in the nucleation process of the crystalline phase. Graphene flakes on Ir(111) feature regions that are under more tensile stress than others. We observe that the CuPc molecules form ordered domains initially on those graphene regions that are closest to the fully relaxed lattice. We attribute this effect to a stronger influence of the underlying Ir(111) substrate for molecules adsorbed on those relaxed regions.

An Electrochemical Sensor based on p-aminothiophenol/Au Nanoparticle-Decorated HxTiS2 Nanosheets for Specific Detection of Picomolar Cu (II)

ABSTRACT An ultrasensitive electrochemical sensor for Cu 2+ detection was first developed based on p-aminothiophenol (PATP) anchored on the surface of Au nanoparticle-decorated hydrogen-incorporated TiS 2 nanosheets (PATP/Au-H x TiS 2 ). In the synthesis process, the plane edges of H x TiS 2 nanosheets offered Au nanoparticles with incubation sites for the heterogeneous nucleation and growth. On the other hand, Au nanoparticles were not only served as an excellent electrical catalyst to facilitate electron transfer and as a substrate for loading PATP molecules by Au-S valent bonds, but also could effectively avoid the aggregation of H x TiS 2 nanosheets. Due to the synergetic effects from Au-H x TiS 2 for signal amplification, the as-formed electrochemical sensor exhibited highly sensitive and selective assaying of Cu 2+ with a detection limit of 90 pM (3σ) and a linear range from 0.2 nM to 5 μM, under optimal conditions. Its specificity was ascribed to the strong coordination interaction between Cu 2+ and N atoms of imine moieties in PATP after electrochemical oxidation.

Cannabinoid CB1 receptors mediate the effects of dipyrone.

Dipyrone is a non-steroidal anti-inflammatory drug used primarily as an analgesic and antipyretic. Some hypothesize that dipyrone activity can modulate other pathways, including endocannabinoid signalling. Thus, the aim of the present study was to evaluate the possible role of endocannabinoids in mediating dipyrone activity. This study is based on the tetrad effects of cannabinoids, namely an antinociceptive and cataleptic state, hypolocomotion and hypothermia. Dipyrone (500mg/kg, i.p.) treatment decreased locomotor activity, increased the latency to a thermal analgesic response and induced a cataleptic and hypothermic state. These reactions are similar to the tetrad effects caused by the cannabinoid agonist WIN55,212-2 (3mg/kg, i.p.). The cannabinoid CB1 receptor antagonist AM251 (10mg/kg, i.p.) reversed the effects of dipyrone on locomotor activity, the cataleptic response and thermal analgesia. Both AM251 (10mg/kg, i.p.) and the transient receptor potential vanilloid 1 (TRPV1) antagonist capsazepine (10mg/kg, i.p.) accentuated the reduction in body temperature caused by dipyrone. However, the CB2 receptor antagonist AM630 did not alter the hypothermic response to dipyrone. These results indicate involvement of the endocannabinoid system, especially CB1 receptors, in the analgesic and cataleptic effects of dipyrone, as well as hypolocomotion. However, cannabinoid receptors and TRPV1 were not involved in the hypothermic effects of dipyrone. We hypothesize that the mechanism of action of dipyrone may involve inhibition of cyclo-oxygenase and fatty acid amide hydrolase, which together provide additional arachidonic acid as substrate for endocannabinoid synthesis or other related molecules. This increase in endocannabinoid availability enhances CB1 receptor stimulation, contributing to the observed effects.

M‐shaped Grating by Nanoimprinting: A Replicable, Large‐Area, Highly Active Plasmonic Surface‐Enhanced Raman Scattering Substrate with Nanogaps

Plasmonic nanostructures separated by nanogaps enable strong electromagnetic-field confinement on the nanoscale for enhancing light-matter interactions, which are in great demand in many applications such as surface-enhanced Raman scattering (SERS). A simple M-shaped nanograting with narrow V-shaped grooves is proposed. Both theoretical and experimental studies reveal that the electromagnetic field on the surface of the M grating can be pronouncedly enhanced over that of a grating without such grooves, due to field localization in the nanogaps formed by the narrow V grooves. A technique based on room-temperature nanoimprinting lithography and anisotropic reactive-ion etching is developed to fabricate this device, which is cost-effective, reliable, and suitable for fabricating large-area nanostructures. As a demonstration of the potential application of this device, the M grating is used as a SERS substrate for probing Rhodamine 6G molecules. Experimentally, an average SERS enhancement factor as high as 5×10⁸ has been achieved, which verifies the greatly enhanced light-matter interaction on the surface of the M grating over that of traditional SERS surfaces.

Contrast inversion of the h-BN nanomesh investigated by nc-AFM and Kelvin probe force microscopy

Single sheets of hexagonal boron nitride (h-BN) on transition metals provide a model system for layered insulating materials as well as a functional substrate for molecules and metal clusters. The progress in the understanding of h-BN layers on transition metals was mainly driven by scanning tunnelling microscopy (STM) and photoelectron spectroscopy (PES) measurements within the last decade, while direct measurements of mechanical and electrical properties are still rare. Our investigations of the two-dimensional (2D) h-BN nanomesh on a Rh(111) substrate by high-resolution noncontact atomic force microscopy (nc-AFM) reveal a complex surface structure including a frequently observed contrast inversion. Detailed 2D force spectroscopy measurements are revealing towards a mechanical elastic deformation of the h-BN monolayer caused by the tip–sample interaction. Furthermore, Kelvin probe force microscopy (KPFM) and spectroscopy measurements show local work function variations of the nanomesh, proving the results obtained by PES but additionally providing detailed local information.

Structural properties of the active layer of discotic hexabenzocoronene/perylene diimide bulk hetero junction photovoltaic devices: The role of alkyl side chain length

We investigate thin blend films of phenyl-substituted hexa-peri-hexabenzocoronenes (HBC) with various alkyl side chain lengths ((CH 2)n, n = 6, 8, 12 and 16)/perylenediimide (PDI). These blends constitute the active layers in bulk-hetero junction organic solar cells we studied recently [1]. Their structural properties are studied by both scanning electron microscopy and X-ray diffraction measurements. The results support the evidence for the formation of HBC donor–PDI acceptor complexes in all blends regardless of the side chain length of the HBC molecule. These complexes are packed into a layered structure parallel to the substrate for short side chain HBC molecules (n = 6 and 8). The layered structure is disrupted by increasing the side chain length of the HBC molecule and eventually a disordered structure is formed for long side chains (n > 12). We attribute this behavior to the size difference between the aromatic parts of the HBC and PDI molecules. For short side chains, the size difference results in a room for the side chains of the two molecules to fill in the space around the aromatic cores. For long side chains (n > 12), the empty space will not be enough to accommodate this increase, leading to the disruption of the layered structure and a rather disordered structure is formed. Our results highlight the importance of the donor–acceptor interaction in a bulk heterojunction active layer as well as the geometry of the two molecules and their role in determining the structure of the active layer and thus their photovoltaic performance.

Chip-Based Genotyping: Translation of Pharmacogenetic Research to Clinical Practice

The observation of interindividual differences in drug tolerance is perhaps as old as pharmacotherapy itself. Since the 1950s several monogenetic traits have been described that explain differences in drug response or drug toxicity in population subsets (1). These early discoveries have evolved into our current understanding of pharmacogenetics as a complex trait. Therapy selection guided by gene test, however, has still not made the transition into clinical practice. In the current issue of Clinical Chemistry , Daly et al. (2) present a dedicated single-microarray assay, or gene chip, for comprehensive genotyping of potentially thousands of variants in genes involved in drug metabolism, excretion, and transport. These expanded capabilities are necessary because of the complexity of drug disposition. Single polymorphisms alone do not adequately predict drug disposition because multiple routes of metabolism or transport may compensate for deficiencies in a single pathway (3). For example, the anticancer drug irinotecan is not only metabolized by UGT1A1 but is also a substrate for transporter molecules coded by ABCB1 , ABCC2 , ABCG2 , and SLCO1B1 (4). Comprehensive genotyping based on gene chips allows large-scale studies on the utility of validated and exploratory biomarkers. The pharmacogenetic gene chip developed by Daly et al. (2) covers the 7 valid genomic biomarkers of drug disposition listed by the US Food and Drug …

Plasma-Induced Formation of Ag Nanodots for Ultra-High-Enhancement Surface-Enhanced Raman Scattering Substrates

We report here plasma-induced formation of Ag nanostructures for surface-enhanced Raman scattering (SERS) applications. An array of uniform Ag patterned structures of 150 nm diameter was first fabricated on a silicon substrate with imprint lithography; then the substrate was further treated with an oxygen plasma to fracture the patterned structures into clusters of smaller, interconnected, closely packed Ag nanoparticles (20-60 nm) and redeposited Ag nanodots ( approximately 10 nm) between the clusters. The substrate thus formed had a uniform ultrahigh SERS enhancement factor (1010) over the entire substrate for 4-mercaptophenol molecules. By comparison, Au patterned structures fabricated with the same method did not undergo such a morphological change after the plasma treatment and showed no enhancement of Raman scattering.

Influence of the local adsorption environment on the intramolecular contrast of organic molecules in noncontact atomic force microscopy

Thin epitaxial layers of the organic molecule 3,4,9,10-perylenetetracarboxylic dianhydrite on a Cu(111) surface were imaged using noncontact atomic force microscopy in ultrahigh vacuum. The second layer molecules show a distinct intramolecular structure, which is compared to the internal charge distribution of the molecule. The molecules in the first layer, though, exhibit no detectable intramolecular features. This effect is discussed with respect to the presence of the metallic substrate for the first layer molecules, which demonstrates the strong influence of the local adsorption environment on the internal electronic properties of organic molecules.

Structural and photoelectrochemical characteristics of nanocrystalline ZnO electrode with Eosin-Y

Structural and photoelectrochemical characteristics of nanocrystalline ZnO solar cell have been studied in relation to sintering temperature and thickness of ZnO electrode. Photoelectrochemical properties depend strongly on fabrication conditions. Short circuit current and open circuit voltage were dependent on the sintering temperature of ZnO electrodes. This suggests ZnO nanoparticles network to act not only as a large surface area substrate for the dye molecules but also as a transport medium for electrons injected from the dye molecules. The incident monochromatic photon-to-current conversion efficiency was improved by increasing the thickness of the ZnO electrode. The best conversion efficiency was 2.4% for a 1 cm 2 cell.