Why PEDOT:PSS Should Not Be Used for Raman Sensing of Redox States (and How It Could Be)

Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) has been recently proposed for Raman sensing of redox-active species in solution. Here, we investigated the rationale of this approach through systematic experiments, in which the Raman spectrum of PEDOT:PSS was analyzed in the presence of either nonoxidizing or oxidizing electrolytes. The results demonstrated that Raman spectra precisely reflect the conformation of PEDOT units and their interactions with PSS. Two different responses were observed. In the case of oxidizing electrolytes, the effect of charge transfer is accurately transduced in Raman spectrum changes. On the other hand, reduction induces a progressive separation between the PEDOT and PSS chains, which decreases their mutual interaction. This stimulus determines characteristic variations in the intensity, shape, and position of the Raman spectra. However, we demonstrated that the same effects can be obtained either by increasing the concentration of nonoxidizing electrolytes or by deprotonating PSS chains. This poses severe limitations to the use of PEDOT:PSS for this type of Raman sensing. This study allows us to revise most of the Raman results reported in the literature with a clear model, setting a new basis for investigating the dynamics of mixed electronic/ionic charge transfer in conductive polymers

Why PEDOT:PSS Should Not Be Used for Raman Sensing of Redox States (and How It Could Be)

Here we investigated the rationale of this approach through systematic experiments, in which the Raman spectrum of PEDOT:PSS was analyzed in the presence of either non-oxidizing and oxidizing electrolytes. The results demonstrated that Raman spectra precisely reflect the conformation of PEDOT units and their interactions with PSS. Two different responses were observed. In the case of oxidizing electrolytes, the effect of charge transfer is accurately transduced in Raman spectrum changes. On the other hand, reduction induces a progressive separation between the PEDOT and PSS chains, which decreases their mutual interaction. This stimulus determines characteristic variations in intensity, shape and position of the Raman spectra. However, we demonstrated that the same effects can be obtained either by increasing the concentration of non-oxidizing electrolytes or by deprotonating PSS chains. This poses severe limitations to the use of PEDOT:PSS for this type of Raman sensing. This study allows to revise most of the Raman results reported in literature with a clear model, setting a new basis for investigating the dynamics of mixed electronic/ionic charge transfer in conductive polymers

Polychlorinated biphenyls, glycaemia and diabetes in a population living in a highly polychlorinated biphenyls-polluted area in northern Italy: a cross-sectional and cohort study

<em>Background</em>. Polychlorinated biphenyls (PCBs) have been found to be associated with diabetes in some, but not all, studies performed so far. The aim of this study was to assess the association between PCB serum levels and glycaemia and diabetes in people living in Brescia, a highly industrialised PCB-polluted town in Northern Italy. <em>Design and Methods</em>. 527 subjects were enrolled in a cross-sectional population-based study: they were interviewed face-to-face in 2003 and also provided a blood sample under fasting conditions. The concentration of 24 PCB congeners was determined using gas-chromatography (GC/MS). Subsequently, all subjects were included in a follow-up (cohort) study. According to the Local Health Authority health-care database, subjects were considered to be diabetic if they had diabetes at interview time (prevalent cases) or during a 7-year follow-up (incident cases). <em>Results</em>. A total of 53 subjects (10.0%) were diabetics: 28 had dia- betes at enrolment and other 25 developed the disease subsequently. Diabetes frequency increased according to the serum concentrations of total PCBs and single PCB congeners, but no association was found when estimates were adjusted for education, body mass index, age and gender by logistic regression analysis. Accordingly, glycaemia increased with PCB serum levels, but no association was observed when multiple regression analysis, including confounding factors, was performed. Conclusions. This study does not support the hypothesis that PCB environmental exposure is strictly associated with diabetes or glycaemia

Polychlorinated biphenyls and thyroid hormone serum concentrations among people living in highly polluted area: a cross-sectional population-based study

Background: Polychlorinatedbiphenyls(PCBs)mayinteractwithseveralthyroidfunctions.Severe environmentalpollutionbyPCBshasbeenobservedinBrescia,Italy,duetothepresenceofafactory that producedthesecompoundsuntil1984. Objectives: WeaimedtoinvestigatethecorrelationbetweenserumlevelsoftotalPCBsandPCB153and thyroidhormoneserumlevelsinadultsinacross-sectionalpopulation-basedstudy. Methods: A totalof527subjectswereenrolled;theywereface-to-faceinterviewedabouttheirhistory of thyroiddiseaseandprovidedabloodsampleunderfastingconditions.Theserumlevelsoffreeand totaltriiodothyronine(FT3andTT3),thyroxine(FT4andTT4)andthyroid-stimulatinghormone(TSH), anti-thyroperoxidase(anti-TPO)andanti-thyroglobulin(anti-TGA),andlipid-adjustedtotalPCBsand PCB 153weredetermined. Results: There wasnostatisticallysignificantdifferenceintotalPCBandPCB153concentrationsin subjectswithandwithoutthyroiddisease.Inverse,weak,statisticallysignificantcorrelationswere foundbetweentotalPCBsandFT3(Spearman’s r ¼ 0.09) andbetweentotalPCBsandPCB153andTSH (Spearman’s r ¼ 0.16and 0.12,respectively).However,multipleregressionanalysiswithFT3andTSH serum levelsasdependentvariablesandtotalPCBsandPCB153serumlevelsaspredictors,including age, genderandBMI,showedapositive,ratherthannegative,associationofPCBsandPCB153withFT3 and noassociationwithTSH. Conclusions: This studydoesnotsupportthehypothesisthatrelativelyhighPCBenvironmental exposurecandeterminesubstantialalterationsinthyroidfunctionamongadultpeople