Search

Quartz crystal microbalance (QCM) is one of the powerful tools for the studies of molecular recognition and chiral discrimination. Its efficiency mainly relies on the design of the functional sensitive layer on the electrode surface. However, the organic sensitive layer may easily cause dissipation of oscillation or detachment and weaken the signal transfer during the molecular recognition processes. In this work, we reveal for the first time that the bare metal surface without the organic selector layer has the capability for chiral recognition in the QCM system. During the adsorption of various chiral amino acids, relatively higher selectivity of D-enantiomers on gold (Au) surface was shown by the QCM detection. Based on analyses of the surface crystalline structure and density functional theory calculations, we demonstrate that the chiral nature of Au surface plays an important role in the selective binding of specific D-amino acids. These results may open new insights on chiral detection by QCM system. It will also promote the construction of novel chiral sensing systems with both efficient detection and separation capability.

The enantiodiscrimination properties of stereomerically pure inherently chiral calix[4]arene acetic acids, as well as their esters and amides in relation to 1-phenylethylamine stereoisomers in liquid and gaseous phases were studied by means of proton magnetic resonance spectroscopy (1 H NMR) and quartz crystal microbalance (QCM) techniques. Series of QCM sensors with thin films of inherently chiral calix[4]arenes, immobilized on the quartz resonator surfaces by spin-coating and spreading drop methods have been fabricated. It was shown that sensors based on calix[4]arene acetic acids are able to recognize R- and S-forms of 1-phenylethylamine in gaseous phase under concentration level of 10-400 ppm.

In this study, surface plasmon resonance (SPR) and quartz crystal microbalance (QCM) sensors were prepared for the detection of amoxicillin from the commercial and local chicken eggs by using molecular imprinting technique. Amoxicillin imprinted poly(hydroxyethyl methacrylate-methacrylic acid) polymeric film was synthesized onto the surface of the SPR and QCM chips by ultra violet polymerization to determine lower concentrations of amoxicillin. Ellipsometry, contact angle analysis, and atomic force microscopy measurements were used for the surface morphology of the polymeric film layer. The ellipsometric thickness of AMOX imprinted and nonimprinted SPR and QCM chip surfaces were measured as 35 ± 0.9 nm, 32.89 ± 1.9 nm, 30 ± 0.6 nm, and 28 ± 0.22 nm, respectively. Contact angles of bare gold surfaces, AMOX imprinted SPR and QCM chip surfaces were measured to be as 82.3° ± 0.15, 79.2° ± 0.14, 75.01° ± 1.07, and 69.11° ± 0.89, respectively. The range of linearity was measured as 0.1 to 10 ng/mL for amoxicillin imprinted SPR and QCM sensors. The maximum residue limit of AMOX in eggs is at 10 µg/kg in accordance with the "Positive List System for Agricultural Chemical Residues in Foods." The response time for the test, including adsorption, desorption, and regeneration, was approximately 45 min. The limit of detections for SPR and QCM sensors were found to be 0.0005 and 0.0023 ng/mL, respectively. The reusabilities of amoxicillin imprinted SPR and QCM sensors were observed by the equilibration-binding-regeneration. Validation studies of the AMOX imprinted SPR and QCM sensors were performed by liquid chromatography-tandem mass spectrometry.

In this study, the different graphene derivatives, graphene oxide (GO), carboxylic acid-modified graphene (G-COOH), and amine-modified graphene (G-NH2 ), were used to prepare polyvinylidene fluoride (PVDF) composite membranes. The membrane modification performance was evaluated using the extended Derjaguin-Landau-Verwey-Overbeek theory and quartz crystal microbalance dissipation monitoring. The results show that the addition of low-dose GO and G-NH2 can improve membrane surface porosity and permeability. The hydrophilicity and electron donor monopolarity of PVDF/GO composite membranes were enhanced by adding more than 0.024 wt% GO, thus improving its antifouling ability. In addition, the enhancement of hydrophilicity, free energy of cohesion, and antifouling ability of composite membrane modified with G-COOH and G-NH2 was more significant compared with that of GO with the same dosage, which implies the important role of functional group in additives. This study provides new insights for the blending modification of PVDF membranes by systematically comparing the addition of graphene derivatives with different functional groups. PRACTITIONER POINTS: The comprehensive comparison of membrane modification with different graphene derivatives was investigated. The enhancement of hydrophilicity and antifouling ability of membranes modified with G-COOH and G-NH2 was more significant than that of GO. The free energy of cohesion of nanocomposite membrane was affected by the functional group of additives. G-NH2 composite membrane had the best comprehensive performance with great hydrophilicity, permeability, and antifouling performance.

A simple, inexpensive, rapid and label‐free detection of phenylarsine oxide (PAO) in the field is a significant and unmet need because of its fatally acute and chronic effects on human health. A chemically easy and applicable surface modification procedure can fill this deficiency. In order to determine the cheaper, simpler and rapid surface functionalization technique, gold surface of quartz crystal microbalance (QCM) sensor was modified with ethanol‐dependent (3‐mercaptopropyl)trimethoxysilane (MPS) coating at pH=4.5 first, and then seconder ethanol‐dependent linker layers, which contain (3‐mercaptopropyl)trimethoxysilane (MPS), dimercaprol (BAL) or 2‐mercaptoethanol (ME), were tested at pH=9.0, respectively. QCM measurements were performed to analyze the stability of each layer in deionized water (DIW) and drinking water for both negative control and arsenic detection performance. Among those examined procedures, the procedure with acidic MPS + basic ME resulted in the best stability in aqueous mediums with a frequency change nearly zero and sensitivity with a frequency shift of 180 (±22) Hz for a concentration of 100 ng/mL PAO in DIW. By using the optimum surface functionalization method, the minimum PAO with a concentration of 1 ng/mL in drinking water was measured as a frequency of 33 (±9) Hz. Besides, this surface modification technique can be applied to the more readily available and cheaper sensor platforms, such as impedimetric electrochemical sensors.

Thiol etching reaction of gold is still suffering from a lack of deep understandings on the reaction kinetics and mechanism. Herein, by using the sensor of quartz crystal microbalance (QCM) as the sacrificial probe, the etching reaction of gold has been studied in employing cysteamine (CS) as a typical thiol etchant. The etching reaction is verified as diffusion-controlled and shows a half-order reaction kinetics. It is demonstrated that intact thiol and amino on CS are both crucial for its etching ability to gold. Applied potentials can affect the electron transferring and hence can be used to regulate the etching of gold. Our results also reveal that only two carbon atoms of the spacer between thiol and amino on CS are very critical to the excellent etching ability. This work exhibits a new route to explore the thiol etching reaction of gold and well elucidates the reaction kinetics and mechanism.

Amorphous molybdenum sulfide is an attractive electrode material for Li/Mg batteries and an efficient Pt-free catalyst for the hydrogen evolution reaction in water. By using the electrochemical quartz crystal microbalance (EQCM) analysis, new insights were gained into the electrochemical polymerization of the [Mo3 S13 ]2- cluster, which generates amorphous molybdenum sulfide thin films. In this work, it is shown that, at the anodic potential, a two-electron oxidative elimination of the terminal disulfide ligand within the [Mo3 S13 ]2- cluster induces the polymerization. A reductive elimination of the terminal disulfide ligand also occurs at the cathodic potential, inducing the polymerization. However, in sharp contrast to the anodic polymerization, according to which the film growth is rapid, the cathodic polymerization competes with the electrochemical reductive corrosion of the readily grown film, therefore occurring at a significant lower growth rate.

The integration of enzymes with synthetic materials allows efficient electrocatalysis and production of solar fuels. Here, we couple formate dehydrogenase (FDH) from Desulfovibrio vulgaris Hildenborough (DvH) to metal oxides for catalytic CO 2 reduction and report an in-depth study of the resulting enzyme–material interface. Protein film voltammetry (PFV) demonstrates the stable binding of FDH on metal-oxide electrodes and reveals the reversible and selective reduction of CO 2 to formate. Quartz crystal microbalance (QCM) and attenuated total reflection infrared (ATR-IR) spectroscopy confirm a high binding affinity for FDH to the TiO 2 surface. Adsorption of FDH on dye-sensitized TiO 2 allows for visible-light-driven CO 2 reduction to formate in the absence of a soluble redox mediator with a turnover frequency (TOF) of 11±1 s −1 . The strong coupling of the enzyme to the semiconductor gives rise to a new benchmark in the selective photoreduction of aqueous CO 2 to formate. authorsversion published

Electrochemical quartz crystal microbalance (EQCM) with damping monitoring is applied for real-time analysis of solid-electrolyte interphase (SEI) formation in diphenyl octyl phosphate (DPOP) and vinylene carbonate (VC) modified electrolytes. Fast SEI formation is observed for the DPOP containing electrolyte, whereas slow growth is detected in VC-modified and reference electrolytes. QCM measurements in a dry state show considerable reduction of the mass quantity for DPOP and reference samples and minor mass decrease for the SEI layer formed in the presence of VC. The results indicate that VC enhances SEI stability, whereas the addition of DPOP or no additive results in incorporation of loosely attached species, leadubg to SEI instability. Resonance frequency damping, Δw, and dissipation factor, D, are used for analyzing mechanical properties of the SEI layers. The apparent increase of Δw and D during SEI formation in presence of DPOP suggests a pronounced viscoelasticity of the layer. QCM results are compared with surface morphology and chemical composition, revealing excellent agreement of the applied characterization approaches.

Polymeric antimicrobial peptide mimics are a promising alternative for the future management of the daunting problems associated with antimicrobial resistance. However, the development of successful antimicrobial polymers (APs) requires careful control of factors such as amphiphilic balance, molecular weight, dispersity, sequence, and architecture. While most of the earlier developed APs focused on random linear copolymers, the development of APs with advanced architectures proved to be more potent in the mimicry of antimicrobial peptides. We recently developed multivalent bottlebrush APs with improved antibacterial and hemocompatibility profiles, outperforming their linear counterparts. Understanding the rationale behind the outstanding biological activity of these newly developed antimicrobials is vital to further improving their performance. This work investigates the physicochemical properties governing the differences in activity between linear and bottlebrush architectures using diverse spectroscopic and microscopic techniques. Linear copolymers are more solvated, thermo-responsive and possess facial amphiphilicity resulting in random aggregations when interacting with liposomes mimicking E. coli-membranes. The bottlebrush copolymers adopt a more stable secondary conformation in aqueous solution in comparison to linear copolymers, conferring rapid and more specific binding mechanism to membranes. The advantageous physicochemical properties of the bottlebrush topology seem to be a determinant factor in the activity of these promising APs.

A simple and robust method is presented to immobilize a heparin-analog polyelectrolyte on inert hydrophobic surfaces. It is demonstrated that an amphiphilic block copolymer consisting of linear polyglycerol sulfate (lPGS) and a benzophenone modified anchor block can be bound to polystyrene surfaces in a facile dip-coating procedure. The chaotropic salt guanidinium chloride is used to overcome the aggregation of the polymer as well as the repulsion between highly hydrated sulfate groups and the polystyrene surface. Irradiation with UV light tethers the polymer chains covalently to the surface. The resulting coating exhibits an aggregate morphology that resembles the aggregation behavior in solution, with a coating thickness of 8 nm. The behavior of the surfaces is dominated by the polyelectrolyte brush coating. They swell and collapse in response to different ionic strengths of the surrounding medium, and bind proteins via electrostatic interactions. The coating is stable toward physiological conditions over the course of several weeks. Coated surfaces bind to proteins of the complement cascade when in contact with dilute blood serum, which results in a decrease of complement activity to 78 �� 4%. The coating procedure can also be applied to other nonactivated polymer surfaces, as demonstrated on a polypropylene fleece.

Background Natures and amounts of water retained at the surface of stratum corneum (SC) of human skins, affecting skin health and penetration of chemical components, remain unclear. Methods A keratin film, a main component of human SC surface, was measured by IR micro-spectroscopy combined with a quartz crystal microbalance (QCM) and a relative humidity (RH) control system. Results Water contents increased with RH up to about 19 wt% and were correlated linearly with the OH + NH band areas in IR spectra of the keratin film. The OH + NH band areas for the triple helix collagen film are about twice as large as those for the keratin film (double helix). The free water component increases with RH by keeping the bound water component minor for the keratin film. About twice of water retention capacity of the collagen film can be due to increasing adsorption of free water, interacting possibly with hydrophobic aliphatic CH surfaces. Conclusion The present results suggest relatively low water contents less than about 19 wt% of outermost SC layers of human skin composed mostly of keratin exposed to ambient RH conditions. The triple helix collagen can be used as an effective moisturizing agent.

BACKGROUND: Proton‐exchange membrane (PEM) has a significant effect on the performance and overall cost of microbial fuel cells (MFCs). In this study, a novel composite PEM is fabricated by compositing sulfonated graphene oxide (SGO) with the Poly(vinylidene fluoride)‐g‐Poly(styrene sulfonic acid) (PVDF‐g‐PSSA) copolymer. The performance of MFCs with these newly prepared composite PEMs as separators was evaluated. A Quartz crystal microbalance with dissipation (QCM‐D) combined with membrane‐coated sensor crystals was used to investigate the biofouling mechanism of PEMs in MFCs at a micro‐perspective. RESULTS: The successful sulfonation of GO was confirmed by Fourier transform infrared spectrometry and X‐ray photoelectron spectroscopy. When the SGO loading was 1.0 wt%, the SGO/PVDF‐g‐PSSA membrane had higher water uptake (32.56%), proton conductivity (0.083 S cm⁻¹) and excellent hydrophilicity (contact angle 70.78°) than that of Nafion 117. QCM‐D results further confirmed its better anti‐fouling property vs that of the PVDF‐g‐PSSA, GO/PVDF‐g‐PSSA, and Nafion 117 membranes. Moreover, the MFC working with the SGO/PVDF‐g‐PSSA membrane exhibited the highest maximum power density and best stability of power production after 3 months of operation. CONCLUSION: The SGO/PVDF‐g‐PSSA‐1.0 composite PEM can be used as an alternative material to Nafion in MFCs and is conducive to the long‐term stable operation of MFCs. © 2018 Society of Chemical Industry

In this Focus Review, nanoarchitectonic approaches for mechanical-action-based chemical and biological sensors are briefly discussed. In particular, recent examples of piezoelectric devices, such as quartz crystal microbalances (QCM and QCM-D) and a membrane-type surface stress sensor (MSS), are introduced. Sensors need well-designed nanostructured sensing materials for the sensitive and selective detection of specific targets. Nanoarchitectonic approaches for sensing materials, such as mesoporous materials, 2D materials, fullerene assemblies, supported lipid bilayers, and layer-by-layer assemblies, are highlighted. Based on these sensing approaches, examples of bioanalytical applications are presented for toxic gas detection, cell membrane interactions, label-free biomolecular assays, anticancer drug evaluation, complement activation-related multiprotein membrane attack complexes, and daily biodiagnosis, which are partially supported by data analysis, such as machine learning and principal component analysis.

A quartz crystal microbalance method with dissipation (QCM-D) and attenuated total reflection Fourier-transform infrared (ATR-FTIRS) spectroscopy were used to study the adsorption of L-cysteine (L-Cys) on Pt. Through QCM-D, it was possible to verify that the viscoelastic properties of the adsorbed species play an important role in the adsorption, rendering Sauerbrey's equation inapplicable. The modelling of QCM-D data exposed two different processes for the adsorption reaction. The first one had an activation time and is fast, whereas the second is slow. These processes were also resolved by ATR-FTIRS and identified to be water and anion adsorption preceded by L-Cys adsorption. Both techniques reveal that the degree of surface coverage is pH dependent. Spectroscopic data indicate that the conformation of L-Cys(ads) changes with pH and that the structures do not fully agree with those proposed in literature for other metallic surfaces. The assembling of the adsorbed monolayer appeared to be very fast, and it was not possible to determine or quantify this kinetics. The conformation is also controlled by applied potential, and the anion adsorption and interfacial water depends on the conformation of the adsorbed molecules.

We have investigated different surface functionalization methods to immobilize CD19 antibody on gold surface to capture B lymphoblast cells associated with the acute lymphoblastic leukemia disease. Quartz Crystal Microbalance measurements were performed to analyze the binding kinetics of each layer and determine the optimum method, which results in higher cell capture rates. The random orientation of antibody and oriented antibody through protein G was investigated and protein G presence resulted in 15,2Hz frequency shift for 10(4)cells/mL. The 3-mercaptopropyltrimethoxysilane (MPS) and 11-Mercaptoundecanoic acid (MUA) coatings of gold surface together with 4-(N-Maleimidomethyl)cyclohexane-1-carboxylic acid 3-sulfo-N-hydroxysuccinimide ester sodium salt (Sulfo-SMCC) and N-Ethyl-N'-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC)/N-hydroxysulfosuccinimide (NHS) linker layers were tested on QCM for protein G and antibody binding. The results indicate that MUA, EDC/NHS, protein G, antibody CD19 is the optimum surface modification among the tested combinations. By using the optimum surface functionalization method, minimum 10(3) cell per mL was measured as 1.9Hz frequency shift., We have investigated different surface functionalization methods to immobilize CD19 antibody on gold surface to capture B lymphoblast cells associated with the acute lymphoblastic leukemia disease. Quartz Crystal Microbalance measurements were performed to analyze the binding kinetics of each layer and determine the optimum method, which results in higher cell capture rates. The random orientation of antibody and oriented antibody through protein G was investigated and protein G presence resulted in 15,2 Hz frequency shift for 104 cells/mL. The 3-mercaptopropyltrimethoxysilane (MPS) and 11-Mercaptoundecanoic acid (MUA) coatings of gold surface together with 4-(N-Maleimidomethyl)cyclohexane-1-carboxylic acid 3-sulfo-N-hydroxysuccinimide ester sodium salt (Sulfo-SMCC) and N-Ethyl-N’-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC)/N-hydroxysulfosuccinimide (NHS) linker layers were tested on QCM for protein G and antibody binding. The results indicate that MUA, EDC/NHS, protein G, antibody CD19 is the optimum surface modification among the tested combinations. By using the optimum surface functionalization method, minimum 103cell per mL was measured as 1.9 Hz frequency shift.

Hamamoto, Ryo Ito, Hidemi Hirohara, Makoto Chang, Ryongsok Hongo-Hirasaki, Tomoko Hayashi, Tomohiro eng Biotechnol Prog. 2017 Nov 29. doi: 10.1002/btpr.2586. Membrane fouling commonly occurs in all filter types during virus filtration in protein-based biopharmaceutical manufacturing. Mechanisms of decline in virus filter performance due to membrane fouling were investigated using a cellulose-based virus filter as a model membrane. Filter performance was critically dependent on solution conditions; specifically, ionic strength. To understand the interaction between immunoglobulin G (IgG) and cellulose, sensors coated with cellulose were fabricated for surface plasmon resonance and quartz crystal microbalance with energy dissipation measurements. The primary cause of flux decline appeared to be irreversible IgG adsorption on the surface of the virus filter membrane. In particular, post-adsorption conformational changes in the IgG molecules promoted further irreversible IgG adsorption, a finding that could not be adequately explained by DLVO theory. Analyses of adsorption and desorption and conformational changes in IgG molecules on cellulose surfaces mimicking cellulose-based virus removal membranes provide an effective approach for identifying ways of optimizing solution conditions to maximize virus filter performance. (c) 2017 American Institute of Chemical Engineers Biotechnol. Prog., 000:000-000, 2017.

Herein, a strategy to control conformational changes in grafted polymer brushes via photoinduced crosslinking of photoreactive groups embedded into the lateral architecture of a polymer brush is reported. Poly(methylmethacrylate)-based polymer brushes containing UV-light (λ = 325 nm) photoreactive o-methyl benzaldehyde moieties are synthesized using surface-initiated reversible deactivation polymerization. The conformational changes in polymer brushes upon UV-light triggered crosslinking are comprehensively analyzed through a full suite of surface sensitive characterization methods including time of flight secondary ion mass spectrometry, quartz crystal microbalance with dissipation monitoring, UV/vis spectroscopy, atomic force microscopy, nanoplasmonic sensing, and neutron reflectometry. The spatiotemporal control of the induced conformational changes is demonstrated via photolithography experiments. To enable an additional level of control, a second gate, the visible light (λ = 445 nm) active styrylpyrene moiety, is incorporated into the polymer brush architecture. Critically, wavelength-selective crosslinking behavior is observed in the diblock copolymer structures allowing to crosslink specific sections of the lateral brush architecture as a function of irradiation wavelength.

Alginate and chitosan are among the most common biopolyelectrolytes. Surfactants can be included in alginate and chitosan formulations in order to improve their physical and functional properties. In the present study, the effect of the anionic surfactant sodium dodecyl sulfate (SDS) on alginate-chitosan polyelectrolyte multilayer (PEM) films is reported for the first time. Layer-by-layer deposition technique was employed to prepare the PEM samples and the samples were characterized by ellipsometry, X-ray reflectivity, atomic force microscopy, and quartz crystal microbalance with dissipation. Incorporation of SDS into PEM formulations increased the film thickness and an increased adsorption behavior between alginate and chitosan layers are observed. Since the concentration of SDS was below its critical micelle concentration, no micelle formation was expected and hydrophobic-hydrophobic interaction between alginate and SDS might be the main reason. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017

The diffusion-controlled solid−solid-state transformation of TTF to (TTF)2MoO4 and (TTF)2WO4 is reported at TTF-modified glassy carbon, indium tin oxide (ITO), Au, and Pt electrodes in contact with aqueous MoO42− or WO42− electrolytes. Electrocrystallization of (TTF)2MoO4 and (TTF)2WO4 onto the electrode surface also was achieved by oxidation of TTF to TTF+ in the presence of Na2MoO4 and Na2WO4 in the mixed CH3CN/H2O (90 : 10 v/v) solvent containing 0.1 M Bu4NPF6 as the supporting electrolyte. Mechanistic aspects of the solid−solid state interconversion reactions and electrocrystallization have been probed by using cyclic voltammetry, chronoamperometry, electrochemical quartz crystal microbalance (EQCM), and electrochemical surface plasmon resonance (ESPR), whereas the morphology of the electrocrystallized materials was established by using scanning electron microscopy (SEM). Vibrational (IR, Raman) and UV/Vis spectroscopic methods, as well as other techniques, were used to establish that the products of electrooxidation are (TTF)2MoO4 and (TTF)2WO4.

A thiolated catechol (CA) consisting of 1,6-Hexanedithiol (HDT) and CA was modified on a gold (Au) electrode to obtain an amperometric L-cysteine sensor with detection limit of 60.6 nM. The preparation of thiolated CA was conducted via a thiol addition between HDT and electro-oxidized CA (EOCA). Briefly, the thiol addition reaction was accomplished by potential cycling of HDT/Au electrode in 0.1 M phosphate buffer (PB, pH 7.2) containing CA, and an EOCA-HDT/Au electrode was produced. The obtained EOCA-HDT/Au electrode exhibits a pair of well-defined redox peaks (at 0.22/0.10 V) of o-quinone moiety, which effectively mediates the oxidation of L-cysteine in a 0.1 M PB (pH 7.2), with an over-potential decrease by ca. 0.12 V (versus bare Au electrode). Electrochemical quartz crystal microbalance, cyclic voltammetry and surface-enhanced Raman spectra were used to study relevant processes and/or film properties. The amperometric L-cysteine sensor has good anti-interferent ability and reproducibility. It also has acceptable recovery for detection of L-cysteine in urine samples.

The knowledge of VLE-data of mixtures with performance chemicals, such as ionic liquids (ILs), is very important for technical applications. This study provides new insights into the utilization of quartz crystal microbalances (QCM) for reliable absorption measurements in ILs. The validity of the Sauerbrey equation for rigid films and bulk liquids is widely discussed in literature. This work shows how to ensure the validity of the Sauerbrey equation during absorption measurements in thin liquid films. Furthermore, the advantages of the employment of rough electrodes for absorption measurements within thin liquid films in comparison to polished ones are described in detail. Important recommendations in application of the QCM systems regarding gravimetric measurements are presented.

We investigate the interaction between anionic surfactants (AS) and a self-assembled monolayer (SAM) using cyclic voltammetry (CV), electrochemical impedance spectrum (EIS) and electrochemical quartz crystal microbalance (EQCM). The AS include two common fluorosurfactants, which have been previously formulated in aqueous film-forming foam (AFFF): perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), and two common detergents: sodium dodecyl sulphate (SDS) and sodium dodecyl benzenesulfonate (SDBS). The AS can re-configure the SAM arrangement, particularly on nanoporous gold surface due to the high density of defects and pinholes of SAM, which results in changes to the electrochemical redox kinetics and interface capacitance of the SAM. Based on the experimental results, we hypothesis that AS insert and dope the pristine monolayer, which is evidenced with EQCM and EIS.

The paper overviews various methods that are used for the analysis of output signals generated by enzyme-based logic systems. The considered methods include optical techniques (optical absorbance, fluorescence spectroscopy, surface plasmon resonance), electrochemical techniques (cyclic voltammetry, potentiometry, impedance spectroscopy, conductivity measurements, use of field effect transistor devices, pH measurements), and various mechanoelectronic methods (using atomic force microscope, quartz crystal microbalance). Although each of the methods is well known for various bioanalytical applications, their use in combination with the biomolecular logic systems is rather new and sometimes not trivial. Many of the discussed methods have been combined with the use of signal-responsive materials to transduce and amplify biomolecular signals generated by the logic operations. Interfacing of biocomputing logic systems with electronics and "smart" signal-responsive materials allows logic operations be extended to actuation functions; for example, stimulating molecular release and switchable features of bioelectronic devices, such as biofuel cells. The purpose of this review article is to emphasize the broad variability of the bioanalytical systems applied for signal transduction in biocomputing processes. All bioanalytical systems discussed in the article are exemplified with specific logic gates and multi-gate networks realized with enzyme-based biocatalytic cascades.

Antibacterial coatings are rapidly developing in recent years and applying to medical treatment, water reservoir and other fields. Here we report an easy, feasible and biocompatible method that combines the adhesive property of polydopamine (PDA), loaded platforms effect, antibacterial property of graphene oxide (GO) with the antimicrobial enzyme lysozyme of chicken egg(cLY), endowing substrate like glass slides with antimicrobial actions. The PDA/rGO-cLY film is determined by Fourier transforms infrared spectroscopy (FT-IR), Raman; the micromorphology of the PDA/rGO film is observed by scanning electron microscopy (SEM). The loading quantity of cLY onto PDA/rGO film is confirmed by fluorescence microscope and Quartz crystal microbalance (QCM). More significantly, the PDA/rGO-cLY film indicated extraordinary antibacterial property for Escherichia coli (E.coli), and maintained a high bacteriostatic percentage after a period of time. This platform should be applicable also to other bactericide and the modified surface could be used in many fields.

Redox-active conducting polymers are ubiquitous in sensing devices, owing to their good conductivity, ease of synthesis, and processability. The necessity of proton transfer during their redox energy modulations projected them as universal pH sensors, owing to Nernstian dependence of electromotive force (EMF) on the pH. Here, we show that the pH-dependent Nernstian EMF of redox-active conducting polymeric interfaces becomes universal only with a cation-selective ionomer cover, without which the interface transforms depending on the chemistry of the conjugate base, owing to the dependency of the polymer's redox energy on the nature of the conjugate base. For an uncovered redox-active polymer, galvanostatic intermittent titration (GITT) and electrochemical quartz crystal microbalance (EQCM) studies demonstrate a clear distinction in the kinetics of psuedocapacitive charge injection between spherical and tetrahedral anions, leading to a multifunctional ion-sensing probe. Nonetheless, for a polymer with a cation-selective ionomer cover, GITT and EQCM measurements demonstrate a unified response, irrespective of the nature of the conjugate bases, owing to rectified cationic transport, leading to a universal pH sensor. A bifunctional ion-sensing meter is constructed by coupling the redox-active polymer probe with a non-polarizable interface and it can signal the end user the cation concentration and the type of conjugate base in a single measurement.

Oligospirobifluorenes represent promising building blocks for the generation of microporous sensor materials based on their restricted flexibility. The contact with specific solvents leads to a change of the three-dimensional spirobifluorene structure. The single fluorene moieties unfold to an open structure with an increased volume due to intermolecular interactions with the solvent, detectable by NMR spectroscopy. The induced microporosity was further investigated by affinity comparisons of aromatic analytes with high fundamental frequency quartz crystal microbalances.

A molecularly imprinted polymer (MIP)-based chemosensor for the selective determination of a chosen toxin, N-nitroso-l-proline (Pro-NO), was devised and fabricated. By means of DFT, the structure of the pre-polymerization (functional monomer)-template complex was modeled. This complex was then potentiodynamically electropolymerized in the presence of cross-linking monomer to form a MIP-Pro-NO thin film. Next, the Pro-NO template was extracted from MIP-Pro-NO with 0.1 m NaOH. Piezoelectric microgravimetry (PM) on an electrochemical quartz crystal microbalance and electrochemical (differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS)) techniques were used to transduce binding of Pro-NO to molecular cavities of the MIP-Pro-NO. With DPV and EIS chemosensing, the limits of detection (LODs) were about 80.9 and 36.9 nM Pro-NO, respectively; and the selectivity coefficients for urea, glucose, creatinine, and adrenalin interferences were 6.6, 13.2, 2.1, and 2.0, respectively, with DPV as well as 2.3, 2.0, 3.3, and 2.5, respectively, with EIS. With PM under flow injection analysis conditions, the LOD was 10 μm Pro-NO. The MIP-Pro-NO chemosensor detectability and selectivity with respect to interferences were sufficiently high to determine Pro-NO in protein-providing food products.

Using cyclic voltammetry (CV), in-situ scanning tunneling microscopy (STM) and electrochemical quartz crystal microbalance (EQCM) the initial stages of lithium deposition on Au(111) from a solution of lithium bis(trifluoromethylsulfonyl)imide in the commercially available ionic liquid 1-methyl-1-propylpiperidinium bis(trifluoromethylsulfonyl)imide (MPPipTFSI) were investigated. We could identify three distinct cathodic peaks in the potential range from 0 to -2.5 V (vs. Pt quasi-reference electrode), corresponding to different lithium deposition modes. While in the potential region of the under-potential deposition (UPD) (-1.2 to -1.8 V) the growth of monoatomic high islands (300-370 pm) takes place, Li bulk deposition occurs at potentials