Electronic structures of the SrTiO(3)(110) surface in different reconstructions

The surface of SrTiO(3)(110) single crystal is prepared in monophase with different reconstructions. The increase of surface Ti concentration is responsible for the evolution of the reconstruction from (4×1) to (2×8), and to a new (1×10) structure. It also induces the enhancement of the surface metallicity, characterized by the appearance of the in-gap states and the increasing Drude weight as measured by the electron and photoelectron spectroscopies. We attribute the metallicity to the reduced Ti ions, which is consistent with the observed band structures and the shift of the phonon energy. It is indicated that a heterointerface between a reduced titanate layer and SrTiO(3) crystal with unique electronic structure can be obtained by the simple treatment.     

Ultrafast electron-phonon coupling in hollow gold nanospheres

Electronic energy relaxation in hollow gold nanospheres (HGNs) was studied using femtosecond time-resolved transient absorption spectroscopy. A range of HGNs having outer diameter-to-shell thickness aspect ratios of 3.5 to 9.5 were synthesized by a galvanic replacement method. The HGNs exhibited electron-phonon relaxation times that decreased from 1.18 ± 0.16 to 0.59 ± 0.08 ps as the aspect ratio increased over this range. The corresponding electron-phonon coupling constants, G, ranged from (1.67 ± 0.22) to (3.33 ± 0.45) × 10(16) W m(-3) K(-1). Electron-phonon coupling was also determined for solid gold nanospheres (SGNs) with diameters spanning 20 nm to 83 nm; no size dependence was observed for these structures. The HGNs with high aspect ratios exhibited larger electron-phonon coupling constants than the SGNs, whose average G value was (1.9 ± 0.2) × 10(16) W m(-3) K(-1). By comparison, low-aspect ratio HGNs exhibited values comparable to SGNs. The electron-phonon coupling of high-aspect ratio HGNs was also influenced by the surrounding fluid dielectric; slightly smaller G values were obtained when methanol was the solvent as opposed to water. This coupling enhancement observed for high-aspect ratio HGNs was attributed to the large surface to volume ratio of these structures, which results in non-negligible contributions from the environment.     

Photoactivated Fluorescence Enhancement in F,N-Doped Carbon Dots with Piezochromic Behavior

Photoactivation in CdSe/ZnS quantum dots (QDs) on UV/Vis light exposure improves photoluminescence (PL) and photostability. However, it was not observed in fluorescent carbon quantum dots (CDs). Now, photoactivated fluorescence enhancement in fluorine and nitrogen co-doped carbon dots (F,N-doped CDs) is presented. At 1.0 atm, the fluorescence intensity of F,N-doped CDs increases with UV light irradiation (5 s–30 min), accompanied with a blue-shift of the fluorescence emission from 586 nm to 550 nm. F,N-doped CDs exhibit photoactivated fluorescence enhancement when exposed to UV under high pressure (0.1 GPa). F,N-doped CDs show reversible piezochromic behavior while applying increasing pressure (1.0 atm to 9.98 GPa), showing a pressure-triggered aggregation-induced emission in the range 1.0 atm–0.65 GPa. The photoactivated CDs with piezochromic fluorescence enhancement broadens the versatility of CDs from ambient to high-pressure conditions and enhances their anti-photobleaching.     

Immunodetection of inactivated Francisella tularensis bacteria by using a quartz crystal microbalance with dissipation monitoring

Francisella tularensis are very small, gram-negative bacteria which are capable of infecting a number of mammals. As a highly pathogenic species, it is a potential bioterrorism agent. In this work we demonstrate a fast immunological detection system for whole F. tularensis bacteria. The technique is based on a quartz crystal microbalance with dissipation monitoring (QCMD), which uses sensor chips modified by a specific antibody. This antibody is useful as a capture molecule to capture the lipopolysaccharide structure on the surface of the bacterial cell wall. The QCMD technique is combined with a microfluidic system and allows the label-free online detection of the binding of whole bacteria to the sensor surface in a wide dynamic concentration range. A detection limit of about 4 × 10(3) colony-forming units per milliliter can be obtained. Furthermore, a rather short analysis time and a clear discrimination against other bacteria can be achieved. Additionally, we demonstrate two possibilities for specific and significant signal enhancement by using antibody-functionalized gold nanoparticles or an enzymatic precipitation reaction. These additional steps can be seen as further proof of the specificity and validity.     

Photoactivated Fluorescence Enhancement in F,N‐Doped Carbon Dots with Piezochromic Behavior

Photoactivation in CdSe/ZnS quantum dots (QDs) on UV/Vis light exposure improves photoluminescence (PL) and photostability. However, it was not observed in fluorescent carbon quantum dots (CDs). Now, photoactivated fluorescence enhancement in fluorine and nitrogen co‐doped carbon dots (F,N‐doped CDs) is presented. At 1.0 atm, the fluorescence intensity of F,N‐doped CDs increases with UV light irradiation (5 s–30 min), accompanied with a blue‐shift of the fluorescence emission from 586 nm to 550 nm. F,N‐doped CDs exhibit photoactivated fluorescence enhancement when exposed to UV under high pressure (0.1 GPa). F,N‐doped CDs show reversible piezochromic behavior while applying increasing pressure (1.0 atm to 9.98 GPa), showing a pressure‐triggered aggregation‐induced emission in the range 1.0 atm–0.65 GPa. The photoactivated CDs with piezochromic fluorescence enhancement broadens the versatility of CDs from ambient to high‐pressure conditions and enhances their anti‐photobleaching.     

Grating coupler integrated photodiodes for plasmon resonance based sensing

In this work, we demonstrate an integrated sensor combining a grating-coupled plasmon resonance surface with a planar photodiode. Plasmon enhanced transmission is employed as a sensitive refractive index (RI) sensing mechanism. Enhanced transmission of light is monitored via the integrated photodiode by tuning the angle of incidence of a collimated beam near the sharp plasmon resonance condition. Slight changes of the effective refractive index (RI) shift the resonance angle, resulting in a change in the photocurrent. Owing to the planar sensing mechanism, the design permits a high areal density of sensing spots. In the design, absence of holes that facilitate resonant transmission of light, allows an easy-to-implement fabrication procedure and relative insensitivity to fabrication errors. Theoretical and experimental results agree well. An equivalent long-term RI noise of 6.3 × 10(-6) RIU/√Hz is obtained by using an 8 mW He-Ne laser, compared to a shot-noise limited theoretical sensitivity of 5.61 × 10(-9) RIU/√Hz. The device features full benefits of grating-coupled plasmon resonance, such as enhancement of sensitivity for non-zero azimuthal angle of incidence. Further sensitivity enhancement using balanced detection and optimal plasmon coupling conditions are discussed.     

Photochemically Enhanced Emission by Introducing Rational Photoactive Subunits into an Aggregation-Induced Emission Luminogen

Herein, we propose a rational design strategy by introducing photoactive thienyl and pyridyl groups into an AIE-active tetraarylethene skeleton to achieve highly efficient photochemistry-activated fluorescence enhancement from dominantly photo-physical aggregation-induced emission behavior, and prove that such photoactivated fluorescence enhancement is perfectly suited for superstable photocontrollable dual-mode patterning applications in both solution and solid matrix. It is found that the photoactivated fluorescence of designed AIEgen is attributed to the irreversible cyclized-dehydrogenation reaction under UV irradiation, and the oxidation product has a brighter fluorescence in both solution and solid states owning to its rigid and planar structure. The overall transformation rate of the AIEgen from its opened form to dehydrogenated form is up to nearly 100 % in a short period of UV irradiation, and the fast transformation and the stable product of this photochemical reaction guarantees super stability of photocontrolled patterning, which can be applied in photoactivated dual-mode patterning and advanced anti-counterfeiting.     

Label-free "digital detection" of single-molecule DNA hybridization with a single electron transistor

Here we present a novel assay that eliminates fluorescent labels and enables "digital detection" of single-molecule DNA hybridization in complex matrixes with greatly simplified protocols. Electronic coupling of the binding state of a single oligonucleotide to the quantum dot (QD) of a single electron transistor (SET) affords direct observation of binding events in real-time via "molecular gating". The change of electrostatic charge associated with the molecular capture is used in lieu of a gate electrode to modulate the SET conductivity. Target oligos containing base mismatches do not elicit SET response under 0.1X SSC at room temperature nor do changes in ionic strength or pH. Furthermore, hybridization is detected even in optically inaccessible matrixes such as serum or quanidinium thiocyanate lysis buffer.     

Surface,Interface and Structure Optimization of Metal-Organic Frameworks: Towards Efficient Resourceful Conversion of Industrial Waste Gases

Industrial waste gas emissions from fossil fuel over-exploitation have aroused great attention in modern society. Recently, metal-organic frameworks (MOFs) have been developed in the capture and catalytic conversion of industrial exhaust gases such as SO₂, H₂S, NO_x, CO₂, CO, etc. Based on these resourceful conversion applications, in this review, we summarize the crucial role of the surface, interface, and structure optimization of MOFs for performance enhancement. The main points include (1) adsorption enhancement of target molecules by surface functional modification, (2) promotion of catalytic reaction kinetics through enhanced coupling in interfaces, and (3) adaptive matching of guest molecules by structural and pore size modulation. We expect that this review will provide valuable references and illumination for the design and development of MOF and related materials with excellent exhaust gas treatment performance.     

Immobilization of DNA onto poly(dimethylsiloxane) surfaces and application to a microelectrochemical enzyme-amplified DNA hybridization assay

This paper describes immobilization of DNA onto the interior walls of poly(dimethylsiloxane) (PDMS) microsystems and its application to an enzyme-amplified electrochemical DNA assay. DNA immobilization was carried out by silanization of the PDMS surface with 3-mercaptopropyltrimethoxysilane to yield a thiol-terminated surface. 5'-acrylamide-modified DNA reacts with the pendant thiol groups to yield DNA-modified PDMS. Surface-immobilized DNA oligos serve as capture probes for target DNA. Biotin-labeled target DNA hybridizes to the PDMS-immobilized capture DNA, and subsequent introduction of alkaline phosphatase (AP) conjugated to streptavidin results in attachment of the enzyme to hybridized DNA. Electrochemical detection of DNA hybridization benefits from enzyme amplification. Specifically, AP converts electroinactive p-aminophenyl phosphate to electroactive p-aminophenol, which is detected using an indium tin oxide interdigitated array (IDA) electrode. The IDA electrode eliminates the need for a reference electrode and provides a steady-state current that is related to the concentration of hybridized DNA. At present, the limit of detection of the DNA target is 1 nM in a volume of 20 nL, which corresponds to 20 attomoles of DNA.     

Adhesion promotion through controlled surface modifications

We present and discuss series of experiments conducted on systems controlled at the molecular level in order to identify the molecular mechanisms of polymer adhesion. A special emphasis is paid to 1) adhesion enhancement through block copolymers at an interface between two incompatible polymers (amorphous or semi‐crystalline); 2) adhesion promotion between an elastomer and a solid, by soft end grafted connector polymer molecules able to interdigitate into the elastomer. We show that surface modifications based on surface anchored polymer chains are efficient for adhesion enhancement because they allow the interface to sustain mechanical stresses. The coupling between surface and bulk stresses is finally what governs the adhesion energy and we examine how one can understand and optimize this coupling.     

Surface enhanced Raman scattering of p-aminothiophenol self-assembled monolayers in sandwich structure fabricated on glass

A sandwich structure consisting of Ag nanoparticles (NPs), p-aminothiophenol (p-ATP) self-assembled monolayers (SAMs), and Ag NPs was fabricated on glass and characterized by surface enhanced Raman scattering (SERS). The SERS spectrum of a p-ATP SAM in such sandwich structure shows that the electromagnetic enhancement is greater than that on Ag NPs assembled on glass. The obtained enhancement factors (EF) on solely one sandwich structure were as large as 6.0 +/- 0.62 x 10(4) and 1.2 +/- 0.62 x 10(7) for the 7a and 3b(b(2)) vibration modes, respectively. The large enhancement effect of p-ATP SAMs is likely a result of plasmon coupling between the two layers of Ag NP (localized surface plasmon) resonance, creating a large localized electromagnetic field at their interface, where p-ATP resides. Moreover, the fact that large EF values (approximately 1.9 +/- 0.7 x 10(4) and 9.4 +/- 0.7 x 10(6) for the 7a- and b(2)-type vibration modes, respectively) were also obtained on a single sandwich structure of Au NPsp-ATP SAMsAg NPs in the visible demonstrates that the electromagnetic coupling does not exist only between Ag NPs but also between Au and Ag NPs. The lower EF values on Au-to-Ag NPs compared to those on Ag-to-Ag NPs demonstrate that the Au-to-Ag coupling must be less effective than the Ag-to-Ag coupling for the induction of SERS in the visible.     

Array-enhanced Logical Stochastic Resonance in Coupled Bistable Systems

We investigate the impact of coupling on the reliability of the logic system as well as the logical stochastic resonance (LSR) phenomenon in the coupled logic gates system. It is found that compared with single logic gate, the coupled system could yield reliable logic outputs in a much wider noise region, which means coupling can obviously improve the reliability of the logic system and thus enhance the LSR effect. Moreover, we find that the enhancement is larger for larger system size, whereas for large enough size the enhancement seems to be saturated. Finally, we also examine the effect of coupling strength, it can be observed that the noise region where reliable logic outputs can be obtained evolves non-monotonically as the coupling strength increases, displaying a resonance-like effect.     

Mechanosynthesis of a Copper complex for redox initiating systems with a unique near infrared light activation

The first use of a new mechanosynthesized copper complex (Cu(acac)(2dppba)) as a initiator for the redox and redox photoactivated polymerization of methacrylates under air is proposed. This paper (i) describes the mechanosynthesis of this complex, (ii) outlines the relative efficiency of the complex for redox polymerization (mechanosynthesized product vs. solvent synthesized product), (iii) follows the polymerization enhancement under a 405 nm light, and (iv) demonstrates the high performance of this complex in near infrared photoactivated redox polymerization where a completely colorless polymer is obtained (unprecedented under NIR irradiations, 785 nm, here). The light activated polymerization exhibit higher conversions, better time controls (activation control) and higher surface conversions than redox polymerization. The mechanosynthesis is well characterized by two solvent‐free methods (visual color change and Electron Spin Resonance) and two solvent‐based methods (high resolution‐electrospray ionization‐mass spectrometry (HR‐ESI‐MS) and UV–vis spectrometry). The involved mechanisms are discussed. Mechanosynthesis of copper complexes opens new perspectives for copper (photo)redox polymerization catalysts as the environmental impact and economical costs of the complex synthesis are significantly reduced. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3646–3655     

SERS as a bioassay platform: fundamentals, design, and applications

Bioanalytical science is experiencing a period of unprecedented growth. Drivers behind this growth include the need to detect markers central to human and veterinary diagnostics at ever-lower levels and greater speeds. A set of parallel arguments applies to pathogens with respect to bioterrorism prevention and food and water safety. This tutorial review outlines our recent explorations on the use of surface enhanced Raman scattering (SERS) for detection of proteins, viruses, and microorganisms in heterogeneous immunoassays. It will detail the design and fabrication of the assay platform, including the capture substrate and nanoparticle-based labels. The latter, which is the cornerstone of our strategy, relies on the construction of gold nanoparticles modified with both an intrinsically strong Raman scatterer and an antibody. This labelling motif, referred to as extrinsic Raman labels (ERLs), takes advantage of the well-established signal enhancement of scatterers when coated on nanometre-sized gold particles, whereas the antibody imparts antigenic specificity. We will also examine the role of plasmon coupling between the ERLs and capture substrate, and challenges related to particle stability, nonspecific adsorption, and assay speed.     

基于工具酶信号放大技术电化学发光法检测凝血酶

利用巯基乙胺将合成的金纳米粒子氨基化;基于纳米粒子负载羧基化的联吡啶钌和巯基DNA制得电化学发光信号探针;采用酶循环信号放大技术,获得大量含新增DNA的溶液来捕获信号探针;以金电极为载体,将巯基DNA自组装到电极表面,依次杂交互补DNA和信号探针,构建电化学发光生物传感器.在优化的条件下,此传感器对凝血酶具有良好的响应,在3.0× 10-13～6.0×10-11 mol/L范围内,凝血酶的浓度与发光强度呈良好的线性关系,检出限为1.8× 10-13 mol/L(3a).采用酶切循环放大技术制备的生物传感器具有灵敏度高,选择性和重现性良好等特点.     

Role of Reduced Defects for Coupling Reactions of Acetaldehyde on Anatase TiO2(001)-(1×4) Surface

The chemistry of acetaldehyde (CH₃CHO) adsorbed on the anatase TiO₂(001)-(1×4) surface has been investigated by temperature-programmed desorption (TPD) method. Our experimental results provide the direct evidence that the perfect lattice sites on the anatase TiO₂(001)-(1×4) surface are quite inert for the reaction of CH₃CHO, but the reduced defect sites on the surface are active for the thermally driven reductive carbon-carbon coupling reactions of CH₃CHO to produce 2-butanone and butene. We propose that the coupling reactions of CH₃CHO on the anatase TiO₂(001)-(1×4) surface should undergo through the adsorption of paired CH3CHO molecules at the reduced defect sites, since the existing reduced Ti pairs provide the suitable adsorption sites.     

Fluorescence enhancement at hot-spots: the case of Ag nanoparticle aggregates

We report the enhancement of the fluorescence emitted from dye-labeled DNA upon co-aggregation with silver nanoparticles. The co-aggregation process is induced by the polycationic molecule spermine, which both neutralizes the charge of the DNA backbone and aggregates the nanoparticles. This simple method generates nanoparticle aggregates with very short (1-2 nm) inter-particle distance. Even though no spacer layer was used, large enhancements of the fluorescence, in the range of 15-740× (depending on the original quantum yield of the dye used), were observed. Theoretical modeling shows that this occurs as the local enhancement of the electromagnetic field near the hotspots is sufficiently large to overcome the quenching by the surface, even at short distances of 1 nm. The predicted trend of increased SEF enhancement with a decrease in initial quantum yield is observed. The average enhancements observed in this system are on-par with the best results obtained on nanostructured surfaces to date.     

Immunomagnetic diffractometry for detection of diagnostic serum markers

We describe an integrated approach for detection of diagnostic markers using in situ assembled optical diffraction gratings in combination with immunomagnetic capture. Folate receptor (FR), a serum protein indicative of various cancers, was chosen as a model system to demonstrate the potential of the method. Magnetic beads coupled to FR antibody were used to capture FR from serum. The FR-bound magnetic beads self-assembled onto microcontact-printed folate-coupled BSA (F-BSA) patterns to form diffraction gratings which served to detect FR by measuring the diffraction intensities caused by laser illumination. The FR-containing beads, upon binding to the F-BSA surface, served as intrinsic signal enhancement agents, circumventing the need for additional enzymatic signal amplification or fluorescent labeling steps. With this approach, a detection sensitivity of 700 fM (20 pg/mL) was achieved. The potential use of this approach in clinical diagnostics was demonstrated by measuring FR concentration in blood samples obtained from cancer patients.     

Synthesis of Cage-Shaped Borates Bearing Pyrenylmethyl Groups: Efficient Lewis Acid Catalyst for Photoactivated Glycosylations Driven by Intramolecular Excimer Formation

We describe the synthesis and characterization of a photoactivated boron-based Lewis acid catalyst based on a cage-shaped triphenolic ligand with three pyrenylmethyl moieties. The obtained cage-shaped borate functioned as a photoactivated Lewis acid catalyst thanks to the flexible three pyrenylmethyl moieties. The deformation of the cage-shaped scaffold driven by intramolecular excimer formations of the pyrenes is a critical factor in realizing the photoactivation. Mannich-type reactions and glycosylations significantly were accelerated under 370 nm light irradiations. It is noteworthy that various glycosyl fluorides, which are not easily activated in photocatalytic systems due to their high C−F bond stability, are activated by the photoimproved catalytic activity of the catalyst.