Self-reporting molecularly imprinted polymer with the covalently immobilized ferrocene redox probe for selective electrochemical sensing of p-synephrine

Article simultaneously imprinting the p-synephrine 1 template and covalently immobilizing a a ferrocene redox probe in a (bis-bithiophene)-based polymer. The resulting molecularly imprinted polymer (MIP) was deposited on the Pt electrode as a thin film to form a redox self-reporting MIP film-based chemosensor

Application of the Impedance Spectroscopy as a New Tool for Studying Biodiesel Fuel Aging Processes

Fatty acid methyl esters (FAME), which are presently the main component of biodiesel fuels, undergo relatively fast oxidation processes. This behavior prevents long term storage of this fuel. From laboratory practices, it transpires that even after a very short period of storage, the oxidative stability of the biodiesel exceeds the values required by European regulations. Therefore, the goal of this work was to devise a parameter (marker) allowing for fast and convenient identification of the chemical stability of biodiesel. Moreover, we were aiming to devise a marker which can also be used for the evaluation of the chemical stability of other hydrocarbon fuels containing biocomponents. To this end, in the presented study, selected biodiesel samples were subjected to controlled aging processes in laboratory conditions at 95 °C and oxygen flow according to the norm. Then, physico-chemical parameters were selected that are critical from the point of view of the fuel practical application. Those included density, refractive index, oxidative stability and resistance to oxidation. The appropriate physico-chemical properties were measured before and after an aging process conducted for various times. Simultaneously, electrochemical impedance spectroscopy (EIS) studies were performed for all the studied samples yielding the electrical parameters of the sample, including resistance, relaxation time and capacitance. Subsequently, a correlation between the results of the EIS studies and the selected critical parameters has been established. The obtained results indicate that the resistance, relaxation time and capacitance of the studied biodiesel fuel increase with aging time. This indicates the formation of long chain compounds with increased polarity. Interestingly, the electrical parameter changes are faster at the early stages of the aging process. This suggests a change of the oxidation mechanism during prolonged aging. The devised methodology of impedimetric biodiesel testing can be proposed as a fast and inexpensive method of fuel chemical stability evaluation, allowing for estimating the useful storage time of biodiesel in real conditions

Recent advances in the electrochemistry of fullerene/transition metal co-polymers

A review, with 20 refs. on formation and properties of the thin C60/transition metal layers is presented. These films can be prepd. by electroredn. from soln. contg. the fullerene and different metal precursors. So far, films contg. Pt, Pd, Rh, Ir, and Au atoms or ions were obtained. These layers exhibit redox cond. The electrochem. switching between the doped (conducting) and undoped (nonconducting) states involves both electron and ion transport within the film. The overall control of charge percolation through the copolymer is governed by the transport of supporting electrolyte cations. The structure and compn. of the layer depend on the relative concn. of the polymer precursors present in the grown soln. In the case of C60/Pd films, layers grown in solns. contg. an excess of the Pd complex consist of (-C60-Pd-)n polymeric chains sepd. by metallic Pd clusters. These layers are relatively flat and uniform. In the polymeric chains, the electrons are transferred through the chain by hopping between neighboring C60 units. The conduction bands in the Pd clusters make an exchange of electrons between sepd. (-C60-Pd-)n chains possible. Films formed in solns. with high concn. of Pd(II) complex are less uniform, rough, and porous. Metallic clusters dispersed in the polymeric layer also influence the charge transfer in redox systems at the film/electrolyte interface. The layer formed in soln. with relatively low concn. of Pd(II) complex inhibits the process of charge transfer at the polymer/electrolyte interface. On the other hand the layer contg. dispersed metal particles acts as a semi-metallic phase and does not influence the heterogeneous electron exchange. The reduced polymeric layers also exhibit the ability to exchange counterions between the solid and liq. phase and the layers can be doped with the redox active ions

Extended-gate field-effect transistor (EG-FET) with molecularly imprinted polymer (MIP) film for selective inosine determination

A novelrecognitionunitofchemicalsensorforselectivedeterminationoftheinosine,renaldisfunction biomarker,wasdevisedandprepared.Forthatpurpose,inosine-templatedmolecularlyimprinted polymer (MIP) film wasdepositedonanextended-gate field-effect transistor(EG-FET)signaltransducing unit. TheMIP film waspreparedbyelectrochemicalpolymerizationofbis(bithiophene)derivatives bearing cytosineandboronicacidsubstituents,inthepresenceoftheinosinetemplateandathiophene cross-linker.AfterMIP film deposition,thetemplatewasremoved,andwasconfirmed byUV\u2013visible spectroscopy.Subsequently,the film compositionwascharacterizedbyspectroscopictechniques,andits morphology andthicknessweredeterminedbyAFM.The finally MIP film-coated extended-gate fieldeffect transistor(EG-FET)wasusedforsignaltransduction.Thiscombinationisnotwidelystudiedinthe literature,despitethefactthatitallowsforfacileintegrationofelectrodepositedMIP film withFET transducer. The lineardynamicconcentrationrangeofthechemosensorwas0.5\u201350 \u3bcM withinosinedetect- ability of0.62 \u3bcM. Theobtaineddetectabilitycompareswelltothelevelsoftheinosineinbody fluids which areintherange0\u20132.9 mM forpatientswithdiagnoseddiabeticnephropathy,goutorhyperur- icemia, andcanreach25 mM incertaincases.Theimprintingfactorforinosine,determinedfrompie- zomicrogravimetricexperimentswithuseoftheMIP film-coated quartzcrystalresonator,wasfoundto be 5.5.Higherselectivityforinosinewithrespecttocommoninterferentswasalsoachievedwiththe present molecularlyengineeredsensingelement.Theobtainedanalyticalparametersofthedevised chemosensor allowforitsuseforpracticalsamplemeasurements

Potentiometric chemosensor for neopterin, a cancer biomarker, using an electrochemically synthesized molecularly imprinted polymer as the recognition unit

With an established procedure of molecular imprinting, a synthetic polymer receptor for the neopterin cancer biomarker was devised and used as a recognition unit of a potentiometric chemosensor. For that, bis-bithiophene derivatized with cytosine and bithiophene derivatized with boronic acid were used as functional monomers. The open-circuit potential (OCP) based transduction under flow-injection analysis conditions (FIA) determined neopterin in the concentration range of 0.15-2.5mM with the 22\u3bcM limit of detection (LOD) and 7.01(\ub10.15)mVmM-1 sensitivity indicating its potential suitability in clinical analysis applications. The molecularly imprinted polymer (MIP) film showed an appreciable apparent imprinting factor of ~6. The chemosensor successfully discriminated the interferences including the 6-biopterin and pterin structural analogs of neopterin as well as glucose and creatinine. Moreover, it determined neopterin in synthetic serum samples

Structure and properties of C60-Pd films formed by electroreduction of C60 and palladium(II) acetate trimer: evidence for the presence of palladium nanoparticles

The compn., surface morphol., structure, and electrochem. properties of thin solid films of the polymer, C60-Pd, were studied by Raman spectroscopy, XPS, powder X-ray diffraction (XRD), and energy dispersive X-ray fluorescence (EDXRF) as well as being examd. by SEM (SEM), high resoln. transmission electron microscopy (HRTEM) with selective area diffraction (SAD) and by cyclic voltammetry (CV), resp. The C60-Pd films were deposited onto Au or Pt electrodes by electroreductive co-polymn. of C60 and the palladium(ii) acetate trimer, [Pd(ac)2]3, in a mixed acetonitrile-toluene (4:1, vol./vol.) soln. of 0.1 M tetra(n-butyl)ammonium perchlorate under multicyclic voltammetry or potentiostatic conditions. The structure and compn. of the C60-Pd films were dependent on the relative concn. of the polymer precursors, i.e., C60 and [Pd(ac)2]3, in the soln. for electropolymn. That is, in films grown in solns. with a high [Pd(ac)2]3:C60 ratio, (-C60-Pd-)n polymeric chains were sepd. by the Pd nanoclusters. These films were relatively smooth and uniform. In contrast, films electropolymd. in solns. with a low [Pd(ac)2]3:C60 ratio were rough, porous and much less uniform. The presence of the Pd nanoclusters in the C60-Pd film influenced the electrode processes of probing redox species dissolved in soln. That is, electro-oxidn. of an N,N,N',N'-tetramethyl-1,4-phenylenediamine (TMPDA) electrochem. redox probe was partially inhibited at the electrode coated by the C60-Pd film with a relatively low Pd nanocluster content. In contrast, electro-oxidn. of TMPDA was effectively mediated by the C60-Pd film contg. appreciable amts. of dispersed Pd nanoclusters

Semi-Covalent Imprinting for Selective Protein Sensing at a Femtomolar Concentration Level

Protein imprinting is challenging mainly because of their large molecular size. It is very difficult [...