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Sensors and Actuators B 140 (2009) 445–450

Contents lists available at ScienceDirect

Sensors and Actuators B: Chemical

journa l homepage: www.e lsev ier .com/ locate /snb

n organic field effect transistor as a selective NOx sensor operatedt room temperature

. Marinelli a, A. Dell’Aquilaa, L. Torsi a,b,∗, J. Teyd, G.P. Surannac, P. Mastrorilli c,. Romanazzi c, C.F. Nobilec, S.G. Mhaisalkard, N. Cioffia,b, F. Palmisanoa,b

Dipartimento di Chimica, Università degli Studi di Bari, via Orabona 4, 70125, Bari, ItalyCentro di Eccellenza TIRES – Università degli Studi di Bari, via Orabona 4, 70125, Bari, ItalyDipartimento di Ingegneria delle Acque e di Chimica del Politecnico di Bari, via Orabona 4, 70125, Bari, ItalySchool of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue Block N4.1, 639798 Singapore, Singapore

r t i c l e i n f o

rticle history:eceived 4 December 2008

a b s t r a c t

A solution processable decyl alkyl chain functionalised 9,10-ter-anthryleneethynylene (D3A) amorphousorganic semiconductor, endowed with good stability in air, has been investigated as NOx OTFT sensor. The

eceived in revised form 6 March 2009ccepted 9 April 2009vailable online 3 May 2009

eywords:rganic thin film transistors

D3A OTFT operated at room temperature exhibited differential sensitivity to NO and NO2. NO2 detectiondown to 250 ppb could be achieved with very low cross sensitivity to interfering species such as carbonmonoxide and hydrogen sulphide.

© 2009 Elsevier B.V. All rights reserved.

Ox sensorsrganic semiconductors

. Introduction

The research effort on chemically selective and reliable NOx sen-ors constitutes a highly interesting area of investigation as NOx

re not only pollutants but also biomarkers since they are pro-uced by specific cellular proteins [1–3]. Nitrogen oxides, in factainly arise from combustion and their presence plays a criti-

al role on several environmental issues such as the generationf photochemical smog, ozone and acid rains. NOx inhalation mayesult in pulmonary inflammations and the alarm threshold iselow 1 ppm. Conversely, NO is specifically involved in immun-defense and antiviral mechanisms of airway epithelium cells andn alteration of its concentration in exhaled breath is a marker ofpathological status. A concentration increase of exhaled NO haseen correlated to chronic inflammatory airway diseases such assthma, bronchitis and other respiratory infections including bacte-ial and viral illnesses [4–6]. Typically, NO concentration in exhaledreath of healthy subjects ranges from 5 to 10 ppb while for asth-atic patients it falls in the range of 50–100 ppb [7,8]. Conversely,

low NO concentration has been related to effects connected to

he human immunodeficiency virus (HIV-1) and to the cystic fibro-is, thus suggesting the existence of mechanisms that suppress theO-related host defense [4,9,10]. Recently, the potential therapeu-

∗ Corresponding author.E-mail address: torsi@chimica.uniba.it (L. Torsi).

925-4005/$ – see front matter © 2009 Elsevier B.V. All rights reserved.oi:10.1016/j.snb.2009.04.035

tic role of the NO gas in cancer treatment has also been investigated[11]. In principle, NO can be non-invasively detected in exhaledbreath and this opens wide perspectives in clinical diagnostics thatfuel a vivid interdisciplinary/intersectorial research activity thateventually could lead to the development of low-cost, portablesystems for early disease diagnosis but also for environmental mon-itoring.

To date, several NOx sensors have been proposed to fulfill theseneeds and, though some of them are very sensitive to NOx withdetection limit ranging from 10 to 200 ppb, they generally suf-fer from low selectivity or require high working temperatures(60–300 ◦C). Examples of such devices are: amperometric sensors[12,13], semiconducting metal oxide sensors [14–18] and resistivesensors based on Metal-phthalocyanines [19–21], conjugated sys-tems [22] as well as carbon nanotubes [23,24].

Organic thin film transistor (OTFTs) sensors have attractedmuch attention only quite recently [25], although they have beenproposed for the first time several years ago [26,27]. These sens-ing devices can offer reliable and reversible multi-parametricresponses upon exposure to the target gases [28], apart from thegreat advantage of being operated at room temperature. Moreoverthey can be easily integrated into an electronic circuit and their

selectivity can be tuned through a proper choice of the organicsensing layer [29]. As an example, chiral differential detection hasbeen recently demonstrated at unprecedented low concentration[30]. More recently, the high potential of OTFTs as multi-parametersensors was proven by NO2 detection at very low (10 ppb) con-

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46 F. Marinelli et al. / Sensors an

entrations with an amorphous poly(triarylamine) based OTFTperated at room temperature and integrated in a pulsing oscillator31]. The amorphous nature of the active layer film seems to play aey role too [32] and it has been proposed that the sensing processroceeds via adsorption, with interactions occurring preferentiallyt defect sites [31]. However, issues such as cross-sensitivity withotential interferents and operating linearity range have not beenully addressed.

We have recently described the synthesis of a 9,10-bis[(10-ecylanthracen-9-yl)ethynyl]anthracene (D3A) oligomer as wells the field effect properties of its spin coated films. In theer-anthryleneethynylene structure, three neighboring anthracenenits are chemically linked by two ethynylene bonds, hence facil-

tating the extension of the effective charge transport beyond aingle anthracene unit. With respect to 9,10-anthrylenes, the intro-uction of ethynylene moieties between the anthracene units wasonceived to build a planar �-framework potentially endowed withood intermolecular interaction capability also in a disordered film.razing incidence X-ray diffraction data indicated the lack of bulk

ong range order in annealed spin coated D3A thin-films. At the sameime the scanning tunnelling microscope (STM) images revealed thetrong tendency to form highly ordered 2D self assembled monolay-rs. A structure comprising an amorphous bulk along with a betterrdered structure at the interface with the gate dielectric can beypothesised for the D3A films. OTFTs based on the D3A exhibitedobilities as high as 0.055 cm2/V s and on/off ratios higher than 105

33]. Fully amorphous OTFTs apparently exhibit lower mobilities31,34].

In this work, the D3A organic semiconductor was tested as activeayer in a NOx OTFT sensor. The results reported show that the D3ATFT, operated at room temperature, exhibits differential sensitivi-

ies towards NO and NO2 down to 250 ppb along with very low crossensitivity towards CO and H2S. To the best of our knowledge thiss the first report on a sensitive NOx device operated at room tem-erature that also exhibit minimized cross-sensitivity to potential

nterferents.

. Experimental

Fig. 1a shows the chemical structure of the 9,10-Bis[(10-ecylanthracen-9-yl)ethynyl]anthracene molecule D3A that wasrepared following the synthetic route reported elsewhere [33].

n Fig. 1b the structure of the device is reported. It is a bottomource/drain contacts OTFT with the organic semiconductor act-ng both as transistor channel material and as sensing layer. The

3A organic semiconductor was deposited by spin coating from0.05 wt% chloroform solution. The resulting film 10 nm thickas deposited directly onto a SiO2 (100 nm)/n-doped Si substratehere Au/Ti source (S) and drain (D) pads were photolithograph-

cally patterned with channel width and length of W = 11230 and

ig. 1. (a) Molecular structure of p-channel D3A organic active and sensing layer. (b) ScheOTFT) used in the study.

ators B 140 (2009) 445–450

L = 30 �m, respectively. Before contacts definition the Si/SiO2 sub-strates were cleaned as follows: the wafers were immersed in apiranha solution for 8 min to remove traces of adsorbed organicmaterials, rinsed with de-ionized water and then dried in a nitro-gen flow. They were then washed according to the standard cleaning1 (NH4OH/H2O2/H2O) and standard cleaning 2 (HCl/H2O2/H2O)steps to remove particles and metallic contaminants [35]. Thedevices characteristics were measured with a Keithley semicon-ductor parameter analyzer while keeping the device at roomtemperature.

Carbon monoxide, hydrogen sulfide and nitrogen oxides weresupplied directly from certified cylinders (2 ppm for H2S and NO2;5 ppm for NO and CO) connected to a gas delivery system by meansof four independent valves, to avoid contaminations. Nitrogen wasused both to dilute the test gases and as carrier gas. The test gasesand N2 were mixed by means of computerized flow meters andwere delivered onto the sensing element at a constant flow rateof 200 sccm. The D3A OTFT was exposed to each gas at differentconcentrations through a nozzle of ca. 3 mm in diameter allocatedabove the device active layer. The source-drain current, Ids, vs. timecurves (transient Ids curves) were acquired at fixed source-drain andsource-gate voltage (Vg = −40 V and Vds = −40 V) while exposing theD3A OTFT to the test mixtures for 60 s. Afterwards, the device wasexposed to a pure N2 flux for 120 s. The D3A OTFT sensing propertieswere evaluated also through the measurements of the device trans-fer characteristic (Ids vs. Vg) curves in nitrogen and, subsequently, inthe analyte atmosphere. In this case Vds was kept constant at −40 V,while Vg was swept between +10 V and −40 V.

3. Results and discussion

The typical current–voltage (Ids vs. Vds) characteristics at differ-ent gate biases for a bottom contact OTFT embodying D3A as activelayer are shown in Fig. 2a while Fig. 2b shows the I1/2

ds vs. Vg plotat Vds = −30 V. The devices exhibit a p-type behavior as negativebiases are needed to observe field effect current amplification. Thekey figure of merits (mobility and threshold voltage) in saturationregimes were extracted from the equation:

√Ids =

√Ci�

W

2L(Vg − Vt) at Vds > Vg (1)

where Ci is the capacitance of the gate dielectric layer per unit areaand Vt is the threshold voltage. A threshold voltage of −8.2 V and afield effect mobility of 1.2 × 10−3 cm2/V s are extracted in this casewhile the on/off ratio is 104. These figures of merit are comparable

with those previously reported for D3A bottom contact devices [33].

The D3A OTFT was exposed to NO2, NO and CO analytes andthe transient Ids current responses are reported in Fig. 3a, alongwith the base line in N2. Concentrations as low as 250 ppb ofNO2 can be detected; moreover, the Ids current systematically

matic view of the architecture of the bottom contact-organic field effect transistor

F. Marinelli et al. / Sensors and Actuators B 140 (2009) 445–450 447

and (

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Fig. 2. (a) Typical output Ids − Vds characteristics at different gate voltage

ncreases at each NO2 exposure cycle and a very good reversibil-ty can be derived, along with quite short response times. A similarehavior was observed when exposing the OTFT to an NO con-aining atmosphere, though in this case detection was down to00 ppb. Sensing properties evaluated by means of transient cur-ent measurements usually show reproducibility and drift issues.TFT sensors in both respects are no exception as it can be seen inig. 3a. It is however true that the current variations upon expo-ure to many different analytes exhibit repeatability within fewercents [25,28]. On the other hand drift current issues are gen-rally minimized when measurements are carried out by means ofransfer characteristics as shown later on in this work. The inter-ction of strong electron-acceptor molecules, such as NO2, with a-type organic semiconductor, such as D3A, leads to a change ofhe transport properties, ascribable to a doping process, as already

eported in previous studies, such as for instance that involvinghe amorphous poly(triarylamine) based OTFT already mentioned31]. Indeed, similar current increases (resistance decreases) in

etal and metal-free thin film of phthalocyanines [20,36,37], por-hyrine [38] and tailored phenylene–thienylene conjugated system

ig. 3. (a) Typical Ids transient response curves of D3A OTFT upon exposure to different courrent in N2 is reported as well. (b) Plot of �Ids response vs. analyte concentration at Vg =

b) plot of I1/2ds

vs. Vg at constant Vds = −30 V of a bottom contact D3A OTFT.

[22] exposed to oxidant analytes have been already reported andthe occurrence of charge transfer processes has been postulated[39]. The elicited materials are sensitive to low NO2 concentra-tions, but relatively high temperatures (>60 ◦C) are required toensure response time in 3–15 min range and device full recovery[20,30,37,40]. This is more striking considering that not in all suchcases a chemisorption process can be postulated. Conversely theD3A based OTFT exhibits a fast response already at room tempera-ture and no heating is required to achieve a full baseline recovery.In this case a physisorption process is more likely to occur and thesensing mechanism most probably involves interactions at defectsites, which causes a current increase. The proposed sensing activ-ity is in accordance with a previous report on poly(triarylamine)based OTFT exposed to NOx that operates at room temperature aswell [31]. The similarities between the poly(triarylamine) and the

D3A active layers include the conjugated structure involving phenylunits as well as the amorphous nature of the thin-film. Specificadvantage of the D3A OTFTs over the elicited poly(triarylamine)ones is the two orders of magnitude higher field effectmobility.

ncentrations of NO, NO2 and CO (red, blue and black traces, respectively). Base line−40 V.

448 F. Marinelli et al. / Sensors and Actuators B 140 (2009) 445–450

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other hand, enhance the hole charge density, shifting the thresh-old voltage in positive direction [31,44]. According to the multipletrapping and release (MTR) model [49] the increase of charge carrierdensity results in more traps being filled. Hence a charge carrier can

ig. 4. (a) Ids − Vg transfer characteristics measured at Vds = −40 V in N2 atmosphe�Ids) at Vg = −40 V and Vds = −40 V relative to NO2 exposures in 0.25–2 ppm range.eplicates, is shown.

D3A OTFT exposed to different concentrations of NO gas0.6–5 ppm range) gave sensing responses similar to those observedor NO2, as shown in Fig. 3a. The average current changes per unitoncentration were significantly smaller for NO compared to NO2.his can be explained considering that NO2 has a strong electroncceptor character while NO is a weaker electron withdrawingolecule. On the other hand, a closed-electronic shell molecule,

uch as CO, and a reducing gas, such as H2S, were almost unde-ectable in the 0.6–5 ppm and the 0.2–2 ppm concentration ranges,espectively. The response of the OTFT to different concentrations ofO in the 0.6–5 ppm concentration range is also reported for com-arison in Fig. 3a. Data relevant to the exposure to H2S are similaro those obtained with CO. Such data indicate very low cross sensi-ivities to hydrogen sulfide and carbon monoxide, while providingdifferential responses towards NO and NO2.

The response–concentration regression lines for NO and NO2 areeported in Fig. 3b. The linear dependence is apparent with regres-ion coefficients higher than 0.9992. D3A OTFT showed differentialensitivity toward NOx gases as can be seen from the slope values ofhe regression curves: 0.37 �A/ppm for NO2 that is ∼4 times greaterhan that observed for NO (0.096 �A/ppm).

The responses of the D3A OTFT were evaluated also by measuringhe device transfer characteristics in the analyte atmosphere (the Idsurves measured vs. Vg while keeping Vds constant at −40 V). Suchperating configuration, already used in previous works [30,41],enerally allows an improvement of the response repeatability [30]nd a better investigation of the sensing properties. The Ids–Vg

ransfer characteristic curves were taken by exposing a D3A basedTFT sensor alternatively to a flow of pure N2 and to streams ofifferent NO2 concentrations in nitrogen. The scan rate allowed theeasurement of each curve in 25 s. The dotted line in Fig. 4a repre-

ents the transfer characteristic measured in a flux of 2 ppm of NO2hile the solid one is relevant to the same curve measured in N2.

he extent of the response was estimated as:

Ids = [Ids(NO2) − Ids(N2)] (2)

It is apparent that �Ids is a function of the gate-bias and theaximum response to NO2 exposure was 7.15 �A. For the exposure

o NO, similar responses were detected but the average responseas less pronounced and, as expected, CO and H2S responses were

lmost negligible confirming the above mentioned results involvingransient current measurements. The response of D3A OTFT exposedo different NO2 concentrations in the 0.25–2 ppm range was linear

ith a regression coefficient of 0.9993 (see Fig. 4b). Three repli-

ates for each concentration were gathered and used to performhe linear regression analysis. Response repeatability (expressed aselative standard deviation, RSD) was in the 2–12% range, in lineo what already observed for thiophene based OTFTs exposed to

lid line) and in a 2 ppm NO2 atmosphere (dotted line). (b) Gas sensing responsesalibration curve fitting of the data points (with the error bars), averaged over three

alcohols [25]. Sensitivity to NO2 was 3.21 (�A/ppm) with a lowestdetectable concentration of 250 ppb (S/N = 6) (Fig. 4).

The reported experimental evidences suggest that the responsesare related to the electrophilic interaction of NO2 and NO moleculeswith the �-orbital system of the anthrylene–ethynylene units.Molecules adsorbed on the active or defect sites of the D3A thinfilm produce a larger hole carrier density leading to a source-draincurrent increase. In this respect it is interesting to discuss the per-centage variation of the field effect mobility (�) and the thresholdvoltage (Vt) extracted from the transfer characteristics measured inN2 and in the analyte atmosphere (see Fig. 5). It was noted that thefield effect mobility increases with the NO2 concentration while thethreshold voltage remains almost constant. As far as the thresholdvoltage is concerned the shift direction is the result of the differ-ent interactions that can possibly take place between the analyteand the organic sensing layer. Negative threshold shifts are usuallyobserved for dipolar molecules such as water [42–44] alcohols [45]and phosponates [46] that interact with p-type organic semicon-ductor through Van-der-Waals interactions. Polar molecules act asacceptor-like deep trap states for the charge carriers moving at theinsulator–organic semiconductor interface. A shift in the thresh-old voltage is therefore correlated to the modulation of the workfunction at the semiconductor–insulator interface induced by theadsorption of the polar molecules. The threshold voltage change canbe estimated according to the Poisson equation [47,48]. Oxidizingmolecules such as nitrogen dioxide and 2,4-dinitrotoluene, on the

Fig. 5. Plot of relative Vt and � variation at different NO2 concentration extrapolatedfrom the I1/2

dsvs. Vg curve for D3A OTFT (with the error bars).

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ove through a longer distance without being trapped eventuallyesulting in a mobility increase and in a positive threshold voltagehift. The hole carrier concentration increases, due to the electronithdrawing nature of NO2, provides a positive shift of the thresh-

ld voltage. At the same time, the polar NO2 molecules enhances theole trap level at semiconductor–insulator. The resulting negativehreshold voltage shift supposedly offsets the effect of the chargearrier increase induced from the oxidant nature of NO2. A similarffect was already observed for the poly(triarylamine)/NOx system31]. However threshold voltage and mobility changes upon expo-ure of an organic active layer to a target analyte involve generallymuch more complex mechanism. The case of the interaction with2S, that holds a dipole moment that is almost triple with respect toO2, provides an example. As already anticipated, no current vari-tion was seen in this case, which can be explained considering theon-oxidant nature of this molecule. Apparently, the doping pro-ess dominates over the dipole induced charges. This view seemso be confirmed by the lack of response to CO, as opposed to the NO,onsidering that they both hold comparably weak associated dipoleoment but are endowed with remarkably different redox proper-

ies. However, effects connected to the interaction of H2S with theold source and drain pads cannot be ruled out at this stage. Fur-her investigations are still under way in order to further explainhe observed results.

. Conclusions

Organic thin film transistors based on a decyl functionalysed ter-nthrylene-ethynylene (D3A structure) have been investigated as aOx OTFT sensor. The D3A OTFTs exhibited differential sensibility

o NO and NO2 down to sub-ppm level at room temperature withery low cross sensitivity to potential interfering gases such as car-on monoxide and hydrogen sulphide. Moreover D3A OTFTs can be,

n principle, easily fabricated by solution process compatible withcreen printing techniques.

cknowledgement

We acknowledge partial financial support from Regioneuglia–Project DM01 related with the Apulian Technological Dis-rict on Mechatronics–MEDIS.

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iographies

. Marinelli has done his PhD at the University of Bari. He received his DiplomaMSc) in analytical chemistry and his Doctorate (PhD) in chemistry of innovative

aterials at Bari University. His main research interests are the fabrication and themployment of field effect transistors for sensor applications.

. Dell’Aquila has done his PhD at the university of Bari. He received his DiplomaMSc) in organic chemistry and his Doctorate (PhD) in chemistry of innovative mate-ials at Bari University. His main research field is the development of novel organicemiconductor for field effect transistors and sensor applications.

. Torsi received the PhD in chemistry from the University of Bari in 1993 and joinedell Laboratories in Murray Hill (NJ-USA) as a post-doc in 1994. She is full professor ofnalytical chemistry since 2005 at the University of Bari. Her main research interestsre in the fields of organic devices and sensors as well as functional materials andanostructures. She is the co-ordinator of the European ITN Marie Curie NetworkFlexSMELL”. The research activity is documented by over 120 products includingrticles in Science and Nature Materials. She has given so far almost 50 invited lecturesnd her papers have gathered 2700 citations with h-index of 24. Lately, she hashaired several international conferences including SPIE, MRS and E-MRS. She isember of the Italian Chemical Society and national coordinator of the Analytical

hemistry Division Group on “Sensor”. She is European Editor of the internationalournal “Science of Advanced Materials (SAMs).”

. Tey is currently pursuing her PhD in materials engineering from Nanyang Techno-ogical University (Singapore), and has previously graduated from the same facultyor her bachelor and master degree. Her research interest is on organic thin-film tran-istor fabrication and characterization, which includes new organic semiconductoraterials and carbon nanotube. Her current research focus is on the development

f liquid gated carbon nanotube transistor for biological sensing applications.

.P. Suranna Associate Professor of Chemistry for the first Faculty of Engineeringf the Polytechnic of Bari since January 2003. Research assistant since 1996, in998 received his PhD in “Chemistry of materials for special uses” He has published0 articles, all in peer reviewed ISI international journals. In the last five years heas concentrated his activity on the synthesis and characterization of materials forrganic electronics.

ators B 140 (2009) 445–450

P. Mastrorilli is full professor of Chemistry at the Polytechnic of Bari since 2001.He was born in 1966 and educated in Bari, Italy. He studied Chemistry at the Fac-ulty of Science (1984–1989) where he also received his Ph.D. in Chemistry in 1993.His research activity, documented by a hundred papers on peer-reviewed journals,include p-conjugated materials, coordination chemistry and catalysis.

G. Romanazzi received his “Laurea” in chemistry from the University of Bari in 2000,and his PhD in chemistry of Materials for Special Uses from the University of ReggioCalabria in March 2004. After a post-doctoral position at the Polytechnic of Bari, inMarch 2005 he started his career as researcher and assistant professor of chemistryat the same University. Currently, his research interests deal with the synthesis andcharacterization of new pi-conjugated materials as potentially active materials inOrganic Thin-Film Transistors (OTFTs).

C.F. Nobile is full professor of chemistry at the first Faculty of Engineering of thePolytechnic of Bari since 1986 and currently the deputy director of the Departmentof Water Engineering and of chemistry. His scientific interests are mainly directedtowards the: synthesis and characterization of nickel triad metal complexes with pri-mary and secondary phosphanes; study of the catalytic properties of transition metalcomplexes in homogeneous and heterogeneous phase, towards C–C bond formation,hydrogenation and selective oxidation of various organic substrates; synthesis andcharacterisation of new polyconjugated materials. He has as asset a wide scien-tific production on the principal international journals about inorganic chemistry,catalysis and materials chemistry.

S. Mhaisalkar is an associate professor in the school of Materials Science & Engi-neering at the Nanyang Technological University, Singapore. At NTU, he also holdsthe posts of Director, NTU Advanced Materials Research Centre and Head, Mate-rials Technology Division. Prior to joining NTU in 2001, Subodh has over 10 yearsof research and engineering experience in the microelectronics industry where heheld senior managerial positions in STATS Singapore, National Semiconductor, andSIMTech. Professor Subodh’s areas of expertise and research interests include PrintedElectronics, Nanobioelectronics, and Clean Energy Harnessing & Storage. professorSubodh received his Bachelors’ degree from IIT-Bombay and his MS/PhD degreesfrom The Ohio State University.

N. Cioffi graduated in chemistry – summa cum laude – in 1997 at the University ofBari, where he accomplished his PhD studies in chemistry of Innovative Materials,working on the development, characterisation and analytical application of newnanostructured materials. In 2001 he received the “Best Young Researcher” Awardfrom the Anal. Chem. Division of the Italian Chemical Society (SCI). Since April 2005,he is assistant professor at the University of Bari. Since 2003, NC is one of the fourmembers of the SCI Anal. Spectr. Board. He is also regional councilor of SCI. He servesas referee 18 international Journals and is member of the Editorial Board of thejournals: Research & Reviews in ElectroChemistry, Sensor Letters, The Open MaterialsScience Journal. He has co-edited a special issue of Sensor Letters (August 2008).The scientific production of Nicola Cioffi is documented by two invited seminars,64 papers on peer-reviewed journals and textbooks, 2 applications for Europeanpatent, seven extended abstracts and 104 communications presented at nat.l andinternat.l conferences. His research interests are in the field of nanomaterials forthe life sciences, including: sensors, bio-analysis, mass spectrometry & proteomicsresearch, antibacterial/bioactive nanomaterials, catalysis.

1986. He has authored about 160 research papers mainly devoted to electrochemicalbiosensors, food chemistry and environmental analysis. More recent research inter-ests are in the field of proteomics and lipidomics. Currently he is a member of theAdvisory Board of The Analyst (Royal Society of Chemistry) and of the Editorial Boardof International Journal of Analytical Chemistry (Indawi Publishing Corporation).