WO1990005160A1 - Thin film chemiresistive sensors - Google Patents
Thin film chemiresistive sensors Download PDFInfo
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- WO1990005160A1 WO1990005160A1 PCT/GB1989/001312 GB8901312W WO9005160A1 WO 1990005160 A1 WO1990005160 A1 WO 1990005160A1 GB 8901312 W GB8901312 W GB 8901312W WO 9005160 A1 WO9005160 A1 WO 9005160A1
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- phthalocyanine
- gas sensor
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D183/00—Coating compositions based on macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon, with or without sulfur, nitrogen, oxygen, or carbon only; Coating compositions based on derivatives of such polymers
- C09D183/04—Polysiloxanes
- C09D183/08—Polysiloxanes containing silicon bound to organic groups containing atoms other than carbon, hydrogen, and oxygen
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G79/00—Macromolecular compounds obtained by reactions forming a linkage containing atoms other than silicon, sulfur, nitrogen, oxygen, and carbon with or without the latter elements in the main chain of the macromolecule
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
Abstract
Chemiresistive gas sensors made from monomeric phthalocyanines suffer from changes in conductivity with varying humidity and are limited in their application. Polymeric films of general formula (XMO)n of a phthalocyanine or ''related structure'' as herein defined are formed by: (a) the step of depositing the compound XMY2 on a substrate; and (b) subjecting the compound XMY2 to hydrolysis followed by heat treatment, wherein X is a phthalocyanine or related structure, M is an element selected from group 4 or 5 of the periodic table or the transition elements, O is oxygen, n is an integer and Y is a halogen. These films show sensitivity towards inorganic and organic compounds and (PcSiO)n can be used at different levels of humidity. Uses include environmental monitoring and explosive detection.
Description
■min Film Che iresistive Sensors
The invention relates to thin filmmaterialswhich are sensitive to selected chemical species.
Anumber of sensorsfor reactive gasesr e.g. θ2,ci2 havebeenreportedwhich utiliseelectrical conductivitychanges inthe thin filmsofmonomericmetal (M) phthalocyanine (PC)# (MPc) complexes, e.g. CuPcr PbPc upon interaction with reactive gases of the type mentioned.
However these monomeric metal phthalocyanines suffer from the following disadvantages for use as gas sensors.
Theyareaffectedbychangesinthe relativehumidityoftheirenvironmentand undergo a significant decrease in conductivity as the relative humidity increases. Increasing the relative humidity from 0 to 64% causes a significant decrease in conductance for PbPc films. This makes it very difficult to produce accurate qualitative or quantitative resultsabout the presence of a gas as the detection of a gas and measurement of its concentration arederived frommeasuring theconductivityofmonomericmetal phthalocyanines relative to a base conductivity. It would therefore be desirable for any gas sensor which utilises changes in conductivity of the sensor to be unaffected by changes in humidity sothat there is a staticbase conductivity for the sensor.
Monomericphthalocyaninesarealsoadverselyaffectedbyproblemsassociated with phase changes and at higher temperaturesabove200oς thevolatilemetal phthalocyanine monomers1 speed of response and recovery is significantly degraded after a few daysr vastly reducing their effectiveness as sensors. Dramatic sensitivitylossesareexperiencedforCoPc CuPcandPbPcat>230oc to temperature-induced phase changes in these materials. As a result of these disadvantages it is impractical to use sensors formed fromMPcmonomers in other thana controlledenvironmentwherevariations in humidity and temperature can be carefully controlled. A further disadvantage of using metal phthalocyanine monomers is their relative inability to detect organic compoundvapours thus being limited to inorganic gases. A sensor capable of detecting organic compound vapours would be useful in such fields for air pollution and explosive detection.
Apart from some gas sensing work on phthalocyanine systems containing
trivalentmetalssuchasPcAlFwhich existsas (PcAlF)x stacks inadeposited film/ verylittle attention hasbeen given to thepossibleuses ofpolymeric phthalocyanines as gas sensing materials.
Thepresent inventionseekstoovercometheabovementioneddisadvantagesby providing a method of producing polymeric films of phthalocyanines and the like for use in gas sensing.
Accordingly there is provided a method for producing a polymer of general formula (XMO)nof aphthalocyanineor "related structure" asherein defined which comprises:
(a) the step of depositing the compound X Y2 on a substrate; and
(b) subjecting the compound XMY2 to hydrolysis followed by heat treatmentr wherein X is aphthalocyanine or related structure, M is an element selected from group 4 or 5 of the periodic table or the transition elements/ 0isoxygen/ nisanintegerandYisahalogen.
The polymeric product of the above process is of thegeneral formula (XMO)n where X and Mr 0 and n are as defined above.
The term "related structure" with regard to phthalocyanines as used herein refers to organic structures which comprise stable ring compounds such as those of the general groups known as porphryns and corrins. It is however necessary that the structures be capable of accommodating the element M.
Preferably X is a phthalocyanine which is optionally substituted.
Preferably M is selected from silicon/ germanium or tin.
Preferably Y is chlorine.
Preferably the polymer is producedas afilm. Typical filmthickness is500 run.
Preferably the substrateused for deposition is capable ofwithstanding the heat treatment. Typically the heat treatment is of the order of 400oc but thiswill dependonfactorssuchasthetypeofpolymericfilmbeingproduced and the pressure in the reaction zone of the substrate.
Preferablythesubstrateisanaluminasubstrate. Foreaseofpreparationof gas sensors by the method of the invention the substrates are preferably provided with interdigitated electrodes to facilitate electrical measurements. Preferably the electrodes are platinum or gold.
Thepolymeric film is preferablyproduced by avacuumdeposition technique.
Preferably the deposition takes place onto a heatable substrate. Other suitable techniques will be apparent to those skilled in the art.
The compounds M?2 can be hydrolysed to XM(OH)2 by various techniques.
Preferably the compounds are hydrolysed in an autoclave. Typical of conditions necessary are 130o at 2 bar for 3 hours tohydrolyse Pc Cl2' film where Pc is phthalocyanine/ to PcM(0H)2.
Becauseoptimumconversionisnotnecessarilytotal theconditionsarelikely to be chosen such that less that total hydrolysis takes place although the conditions will vary with circumstances and requirements.
The hydrolysed compounds [XM(0H)2] are subsequently condensed to the form
(XMO)nbyheattreatment. Theheattreatmentispreferablycarriedoutunder reducedpressure/ ideally invacuum. Thetemperatures involvedareusually about400OCbutwill dependmainlyuponthecompoundwhich isbeingconverted.
Accordingtoafurtherembodimentofthepresent inventionthereisprovideda gassensorwhichcomprisesapolymericfilmofformula (XMO1)nwhereinX/Mand n are as described above and 0' is selected from oxygen/ sulphur/ CN or NCN.
Compounds of formula (XM0*)n and especially (PcMO)n show changes in conductivityin thepresence of certain reactivegases and canmakegoodgas sensors when in the form of a film.
Usually thevalue of n is between 10-100 and is preferably about 50 although this value is not critical.
Preferablythe film isprovided on a substrate togivemechanical strengthto the film. Preferably the substrate is made from alumina.
Preferably the substrate is provided with a pattern of electrodes. These whenconnected tothe filmallowchanges in theconductivityofthefilmtobe measured.
Preferably the films are phthalocyanine films. Preferably the phthalocyanine films are either of formula (PcGeO)n or (PeSiO)n.
Both of these films exhibit a sensitivity towards inorganic reactive gases suchasNO2 andCl2 and candetect thesegasesatlevelsof1partperbillion. This compares favourably with the sensitivity of known monomeric phthalocyanine based detectors such as PbPc.
Whilst the invention should not be limited in this regard/ ithasbeen found that the magnitude of any change in conductivity of the film sensor is normally proportional to the electron affinity of the reactive gas in question providing that the gasmolecules areplanar. The sizeand shapeof themoleculesof reactivegascanalsobe important. It isbelievedthatthe structure of the sensors comprises cofaciallystackedunitssuch that inthe
polymer (PcSiO)n the distance between the phthalocyanine rings is 0.333nm. ThisdistancecanbevariedbysubstitutionofsiliconbyanotherMsuchasGe which gives an inter-ring distance of 0.351nm or Sn which gives 0.383- 0.395nm. Alternatively substitution of 0 by sulphur/ CN or NCN will also result in a variation in inter-ring distances. This variation can be utilised to tune polymers to be sensitive to a particular reactive gas or classes of gasses. For example the polymer (PcSiO)n responds well to nitrobenzene but not nitrotoluenes whereas (PcGeO)n responds to both and a combination ofboth sensors canbeused todistinguishbetween nitrobenzene and nitrotoluenes. Substitution of the rings of phthalocyanines etcmay also be used to increase selectivityby sterichinderance of the inter-ring spaces.
Gas sensors based on (PcSiO)n and (PcGeO)n have the advantage ofpossessing good thermal stability and the problems of phase changes associated with sensorssuchasmonomericPbPcarereducedtotheextentthatsensorstability canbeextended intothe rangeof200-250OCwithout anysignificanteffecton sensitivity. Increasing the temperature of operationhas the advantage of increasing the speed of sensor response.
The increased stability also tends to give rise to a longer life for the sensors enablingprolongedoperation at temperatures inexcessof200oςwith consequent improvements in recovery times.
Ithasalsobeen foundthatthedarkd.c. electrical resistancesofthinfilms typically (500mm) of siliconandgermaniumphthalocyaninepolymers/ (PCMO)n whereM is silicon or germanium/ decrease inthepresenceofpartpermillion by volume (ppmv) levels of certain classes of organic compounds (i.e. electron acceptors) inair. Thisprovides a useful means for detecting and measuring the concentration of various organic coπpounds for which metal phthalocyaninemonomers (MPc) showlittleornoresponse/ andpolymersofthe type (PCMC n can therefore extend the sensing capabilities of Pc-based che iresistors. It appears that the increased size of organicmolecules/ such as nitrobenzene/ over MCtø and Cl2 etc prevents detection bymonomeric (MPc) sensors but that the polymers (PcMO)n respond to certain organic vapours and nitrobenzene can be detected to a level of about lpp v under optimum conditions. Typical organic vapours which can be detected by the sensors are planar pi-acceptors and include nitroaromatics/ aliphatic nitrates/ nitrites and nitrocompounds/ halogenated hydrocarbons and other molecules possessing significant electron affinities.
Potential applications include the detection of explosives/ propellants (nitrobenzene/ mononitro- and dinitrotoluenes) and selected halogenated hydrocarbonse.g. trichoroethylene. Anotheruseenvisagedisenvironmental testing for airborne contaminants which because of the nature of the polymers, detection capability could be organic or inorganic. Devices utilising the invention*s films are able to supplement the role of "sniffer" devices based on ionisation techniques eg electron capture/ ion mobility and mass spectrometry.
One particular use is in relation toa compoundusedasa sacrificial coating for electrical application such as on circuit boards. Ideally the sacrificial coating is provided as a spraywhich canprovide a coating over the electrical apparatus and if overheating occurs the coating layer vapourises releasing reactive gas which is detected by the sensor. It is possible for the sacrificial layer to be made to decompose when a predetermined temperature is reached thereby releasing reactive gas. This may prevent fires occuring or may even be used todetect thepossibility of circuit failure when component temperatures rise above a predetermined level.
A further advantage displayed by the sensor filmand especially (PcSiO)n is that the sensor is unaffected by changes in thehumidityof its environment/ the conductivity being insensitive to variation inhumidity. Thisallowsa baseline conductivity tobe determinedwhich is the sameover awide range of humidity and means that conductivity changes can be attributed to gas detection and in proportion to the gas concentration.
Whilst it is envisaged that these sensorswouldoperatebymeasuringchanges in their conductivity it is also possible for them to be used as optical sensors which change colour when exposed to certain gases. This operates because the phthalocyanines which are typically coloured/ will undergo a changein theirPi electron structurewheninthepresenceofreactivegases, whichresultsinlightbeingabsorbedatadifferentwavelengthresultingina change in colour.
Because of their conductive nature, films made by this invention have potential aslightweightconductorsandcanbedepositedonsubstratecircuit
boards with a mask in place to leave an electrically conductive pathway.
Accordingtoafurther embodiment oftheinventionthefilmsmaybedoped, for example with iodine, to alter their electro-optical properties. Doped polymeric films of the invention may exhibit enhanced electrical conductivity as a result of their possessing a more segregated stack structure than thenon-conductingintegratedstacks inmetal phthalocyanine monomers (MPc)/ whichlackanyformalcovalentbonds. Itisbelievedthatit isthisdifferenceinstructurebetweenthepolymersoftheinventionandthe MPcmonomers which allows the polymers todetect certain classes of organic compounds and in some cases even more selectively.
The inventionwill nowbedescribedbywayof exampleonlyandwith reference to the accompanying Drawings of which:
Figure1 showsa cofaciallystackedmetallophthalocyanineaccording to the invention;
Figure 2 shows a schematic representation of integrated and segregated stacking for donor-acceptor complexes;.
Figure3a shows typical response-timeprofilesfor0-50ppbnitrogen dioxide;
Figure 3b shows typical response-time profiles for chlorine;
Figure 4 is a log-log graph of resistance (R) against NC2 concentration;
Figure5 illustrates thecomparative effectof relativehumidityon the resistance of Germanium and Silicon films;
Figure6showsagraphoftimeagainstresponseforvarioussensorsto tetracyanoethylene;
Figure 7 shows a graph of time against response for the sensors
(PcSiO)n and (PcGeO)n to the detection of tetrachloroethylene;
Figure8 shows a graph similar to that in Figure7 but for detecting ethyleneglycol dinitrate;
Figure9 shows a graph similar to that inFigure 7 but for detecting
Otto fuel;
Figure10 showsa graph similar tothat inFigure7 but for detecting n-butyl nitrate;
Figure11 shows a graph similar tothat inFigure7 but fordetecting tert-butyl nitrite;
Figure12 shows a graph similar tothat inFigure7 but for detecting nitrobenzene;
Figure13 shows a graph similar tothat inFigure7 but fordetecting
4-nitrotoluene;
Figure14 shows a graph similar tothat inFigure7 but fordetecting
1/3-dinitrobenzene;
Figure15 shows a graph similar tothat inFigure7 but for detecting
2/4-dinitrotoluene;
Figure16 shows a graph similar to that inFigure7 but for detecting
2-nitropropane;
Figure17 shows a graph similar tothat inFigure7 but fordetecting trinitrotoluene;
Figures 18 (a) and (b) show the variation of response produced by various compounds with different electron affinities to sensors of
(a) (PcSiO)n and (b) (PcGeO)n; and
Figure 19 shows a graph of log R against log[concentration] for nitrobenzene on (PσGeO)n.
Films (ca.500nmin thickness) ofpoly(phthalocyaninatosiloxane)/ (PcSiO)n, its germanium analogue, (PcGeO)n, as shown in Figure1 (n>50 in bothcases), andleadphthalocyanine (PbPc) (350 or1600n ) (thestackingarrangementsfor MPc and (PcMO)n integrated and segregated/ are shown in Figure 2) were deposited in vacuo (10-6 mbar) on heatable alumina substrates (3x3x0.3 mm) patternedwithinterdigitatedplatinumelectrodes (ModelEL1340-A-P-P-1-NR- TO5; Rosemount Ltd./ Bognor Regis, U.K.) to facilitate electrical measurements or onzincselenideplatesfor infraredspectroscopy. Further details of the Rosemount substrates (including temperature control) and vacuum deposition procedures are given in the referencebelow. ThePCMCI2 films were then autoclaved (130OC/2 bar) for 3 hr to form PcM(OH)2 derivatives. The optimum conversion to PcM(OH)2 was ca 70%, determined by visible absorption spectroscopy. Heating the PcM(OH)2 films at 400OC for lhr in vacuo (10~5 mbar) yielded the corresponding (PcMO)n polymers, ϋnreacted PC CI2 evaporated during this process. Observations of the
3510απ-l (o-H stretch) band in the infrared spectra of the films, recorded before and after polymerisation, gave estimated values of n > 50.
(a) Some of the (PcMO)n coated substrates were mounted in a specially constructedtestrigandexposedtoNO2orCl2atppbconcentrationsgenerated byaccuratelydilutingcertified standards (BOCSpecialGasesLtd/ Wembley, UK) withpurifiedair. Whenahumidenvironmentwasrequiredaproportionof the air flow was diverted through a water bubbler maintained at constant temperature. Dark d.c. resistance measurements weremade on groups of six filmsusingaModel617 Electrometer Model705Scanner (KeithleyInstruments Ltd., Reading, U.K. controlled by an IBM PC.
The resistances of thin filmsof (PcSiO)nand (PcGeO)n (N>50) weremeasured in purified air and in 50 ppb concentrations of O2 or CI2. Where appropriate/ comparisons were made with films of PbPc/ a material of well establishedNO2 sensitivity (referencebelow). Thebehaviour of thePcMCl2 and PcM(0H)2 derivatives inNQ2 was also briefly examined but nomeaningful data were obtained.
Table 1 summarises the resistance (R) ranges of films heated at 150oc, recordedbeforeandafterexposureto O2, togetherwithvaluesoftheaverage response calculated from:
Response = IR(50ppb)-R(Oppb)]/R(Oppb).ιoo%
which is a measure of the relative sensitivities. (PcSiO)n consistently gave stable resistances which (like PbPc) decreased significantly in 5 ppb
NO2. The high resistance (PcGeO)n films initially responded well but repeated exposure resulted in more conductive films (see (ii) in Table 1) whichwereless Oζ responsive. Afewdaysincleanairor5ppbNQ2, however, restored these films to their original high resistance condition. The anomalous behavious of (PcGeO)n is not readily explicable but might arise from the preference of the germanium polymer to accommodate more acceptor molecules (e.g. iodine) during doping than the silicon polymer. Typical response-time profiles for 0-50 ppb NO2 are shown in Figure 3(a). Thesensitivitiesand responsetimesof thepolymerfilmscomparefavourably with PbPc at 170OC. The polymers are also highly sensitive to chlorine (Figure 3(b)). In the case of NO2, the variation of resistance with
concentrationover the5-5000 ppb rangewas also investigated. Plots oflog Rversuslog[NO2] (Figure4) arelinear, asreportedpreviouslyformonomeric phthalocyaninesand themagnitudes of the slopes (logR log [ O2] (seeTable 1) indicate the relative sensitivities.
Theeffectof temperatureon response toNO2 was studiedoverthetemperature range 120-250OC and the results are summarised in Table 2. Losses in sensitivity were experienced for all the films but were smaller for the polymers than for PbPc. The polymers .could be operated continuously for several months at 200OC, with consequent improvements responseand recovery times/ whereas 350 nm PbPc films evaporated after 1-2 days at this temperature. As expected, the inherently low volatility of the polymers substantially reduced losses through evaporation. Furthermore, the presence of strong M-C-M bonds linking the Pc rings in (PcMO)n imposes a structural limitation on phase changes occurring at elevated temperatures. Thus, thesignificantNO2 sensitivity losses reported forCoPc,CuPcandPbPc filmsoperatedcontinuouslyat250ocwhichmaybeattributed totemperature- induced phase changes in those materials, do not occur for (PcSiO)n and (PcGeO)n.
The effects of relative humidity (0-70% RH; 150-170OC) on the resistances of thepolymer films, andPbPc, were also investigated. Both (PcGeO)nandPbPc exhibited increased resistanceswith humidity, withaverageresponsesof35% and55%, respectively, over the 0-70% RH range. In contrast, (PcSiO)n films werebarely affected. Comparative results for (PcSiO)n andPbPc (Figure5) show that the silicon polymer has a distinct advantage in environments of varying humidity.
(b) Pairsoftheaboveprepared (PcMO)nandPbPccoatedsubstrates (normally maintained at 200 C were mounted inside a blackened 2.0L glass chamber, heated to ca. 70OC to reduce adsorption of involatile samples. Test compoundswereintroducedasvapoursintothischamberbymeansofaspecially designedprobeconsisting of aplainheatablealumina substrate (3x3x0.3mm; Rosemount Ltd., Model E11340-NR-P-P-1-NR-NR platinum resistance thermometer) fixedatoneendofanextendedB19 coneequippedwithelectrical feedthroughs connected to a temperature control circuit similar to that employedtomaintain the temperature of ameasuring substrate. In atypical experiment/ 2.0 uL of a ca.1% v/vsolutionofthetestcompound inacetonewas spotted on to the substrate, with the heating circuit switched off, and the
probe was inserted into the test chamber. The substrate was then rapidly heated tovaporise the acetoneandthetestcompound, givinga concentration ofca.2ppmvof thelatter. Thetemperatureofthesubstratewasusuallyset at a value 10oc below the boiling point (b.p.) of the test compound; for compounds having b.p. less than lOOOc no heating was required. Dark d.c. resistance measurements were made using a Model 617 Electrometer/Model 705 Scanner (Keithley InstrumentsLtd., Reading/ U.K>.) controlled bt an IBM PC. Resistances were recorded at 1 minute intervals before (Ro) and after (R(sample)) introduction of the test sample. Responses were calculated using
Response = [(R(sample)-Ro))/Ro].100%
At the conclusion of each experiment the test samplewas removedbyflushing the chamber with purified air (ca.10% relative humidity) at 1 L/min for a minimum of 90 minutes. The chamber was then stoppered for a further 30 minutes to allow equilibration before starting to record the baseline resistances of thephthalocyanine films in preparation for the next sample.
Asummaryof responsesisgiveninTable3 togetherwithresponsetimes, ratio of (PcGeO)n:(PcSiO)n response and estimates of electron affinity (where applicable). Typical response-time profiles are shown in Figures 6 to17. (PcMO)n films held at 200OC or 150OC consistently exhibited decreases in resistance in the presence of ppmv concentrations of planar pi acceptor moleculesornon-planarmoleculescontainingpiacceptormoieties, similar concentrations of neutral n-pentane or weak electron donors (benzene or acetone) did not produce any response. A higher concentration of ca. 300 ppmv acetone, the solventusedtointroducecompounds intothetestchamber, caused a slight decrease in conductance.
Comparisonsweremadebetween (PcMO)nfilmsandfilmsofthemonomerPbPc, the single crystal structure of which consists of cofacially stacked rings (inter-ring distance= 0.373 nm) notlinkedbycovalentbonds. At200ocno significant decreases in resistance were observed for PbPc films to nitrobenzene/ TCNE (Fig 6)/ para-chloranil/ n-butylnitrite, or trichloroethylene. Theseobservationssuggestthatincreasesinelectrical conductance resulting from donor-acceptor interactions with suitable organicmolecules are a property not sharedbyPbPcmonomers. Nitrobenzene
gave no response with PbPc, even at room temperature.
The response-time profiles for a selection of tested compounds are shown in Figures 6 to 17. The profiles indicate that the electronic structure and stereochemistryof the tested compoundscanhaveaprofoundinfluenceonthe electrical resistances of cofacially stackedphthalocyaninepolymer films. However the magnitude of the changes in conductivity in a film is usually proportional tothe electronaffinityoftheanalytes/ providing theanalyte molecule is planar.
Figure18 demonstrates the variation of responsewith electron affinity for various compoundswith respect to the sensors (PcSiO)nand (PcGeO)n. These results however fail to take account of steric effects which would also be expected to influence the response of the sensors.
Resistance-concentration data for both nitrobenzene and NO2 interactions with the (PcMO)n polymers at 200oc as shown inFigure19 with (PcGeO)nas the sensor/ show the stability of nitrobenzene with respect to catalytic decomposition toNO2. NQ2 was the onlypossibledecompositionproductwith sufficient electron affinity to interact with the sensors (PcMO)n. The detection limit for nitrobenzene was about 1 ppm.
ΪAELE1
The responses of (PcSiO)n, (PcGeO)n and PbPc films at 150oc to NO2 in
Material Range of R in Range of R in Average log R loglNO^] dry air (ohm) 50 ppb NO2 Response (ohm) (%)
(PcSiO)n (0.8-3.5)xlθ7 (0.6-5.4)xlθ691 -0.78
(PcGeO)n(i)(1.0-5.0)xlθ9 (0.4-2.0)xlθ897 -1.30 (ii) (0.5-1.0)xl08 (2.0-5.0)xlθ764
PbPc (2.4-5.0)xlθ7 (2.0-8.0)xlθ688 -0.81
TABLE 2 The average responses of (PcSiO)n/(PcGeO)n and PbPc films at different temperatures (T) to O2 in air
T (oc) Av response (%) Av response (%) Av response (%) of (PcSiO)n of (PcGeO)n of PbPc
94
97 88 95 64 51
94 35 26
71
Table 3
Thevaluegiven forpara-Chloroanil under "responsePbPc%" isanequilibrium response after drift (not reproducible).
The term t50 is the estimated timeto50% equilibriumresponseand t90 isthe estimated time to 90% equilibrium response.
Wheretrinitrotoluenewasthetestcompoundthe2/4/6-trinitrotolueneisomer
predominated.
TheAvresponse% for (PCSiO)nwithpara-Chloroanilwasconsideredalowvalue because of difficulty in vaporising the sample.
OTTO fuel contains 76% PGDN (propylene gylcol dinitrate).
The concentration of Fluorocarbon 12 was lOOOpp v.
The concentration of Methylchloroform was lOppmv.
The concentration of Trichloroethylene was 7.5ppmv.
Scant attention has been paid to the exploitation of polymeric phthalocyanines as gas sensingmaterials. These arelessvolatileandalso lesssusceptibletophasechangesthanmonomericphthalocyanines, therefore, should prove attractive as alternative sensing materials in certain applications. Polymers of the type (PcM0)n (]¥NSi/Ge/Sn; n=10-100) which are composed of cofacially stacked Pc rings linked by metal-oxygen-metal bonds, are considered to be prime candidates for gas sensing because they possess good thermal stability andbecause their electrical conductivities are similar to those of monomeric MPcs.
Ref B Bott and TAJones, Ahighly sensitive O2 sensorbased on electrical condictivitychangesinphthalocyaninefilms. SensorsandActuators, 5(1984) 43-53.
Claims
1. A method of producing a polymer of general formula (XMO)n of a phthalocyanine or "related structure" as herein defined characterised in that it comprises:
(a) the step of depositing the compound X Y2 on a substrate; and
(b) subjecting the compound XMY2 to hydrolysis followed by heat treatment, wherein X is a phthalocyanine or related structure, M is an element selected from group4 or 5 of the periodic table or the transition elements/ 0 isoxygen/ n isan integer andYisahalogen.
2. Apolymericproductproducedbythemethodofclaim1andcharacterisedin that the polymericproduct is of the general formula (XMO)nwhere X andM, 0 and n are as defined in claim 1.
3. A method of producing a polymer as claimed in claim 1 characterised in that X is a phthalocyanine which is optionally substituted.
4. A method of producing a polymer as claimed in claim 1 characterised in that M is selected from silicon, germanium or tin.
5. A method of producing a polymer as claimed in claim 1 characterised in that Y is chlorine.
6. A method of producing a polymer as claimed in claim 1 characterised in that the polymer is produced as a film.
7. A method of producing a polymer as claimed in claim 1 characterised in that the substrate is alumina.
8. A method of producing a polymer as claimed in claim 1 characterised in that the substrates are provided with interdigitated electrodes to facilitate electrical measurements.
9. A method of producing a polymer as claimed in claim 1 characterised in that a polymeric film is produced by a vacuum deposition technique.
10. Amethodofproducingapolymerasclaimedinclaim1characterisedinthat M2 is hydrolysed to XM(OH)2 in an autoclave.
11. Amethodofproducingapolymerasclaimedinclaim1characterisedinthat theheat treatment ispreferablycarried outunder reducedpressure, ideally in vacuum.
12. A gas sensor which comprises a polymeric film of formula (XMO')n characterised in that X,M and n are as described in claim 1 above and 0' is selected from oxygen, sulphur, CN or NCN.
13. Agassensorasclaimed inclaim12 characterised inthatthevalueofnis between 10-100.
14. Agas sensor as claimed in claim13 characterised in thatn is about50.
15. A gas sensor as claimed in claim 12 characterised in that the film is provided on a substrate.
16. Agassensor asclaimed inclaim15 characterised inthatthesubstrateis made from alumina.
17. Agassensorasclaimedinclaim15 characterised inthatthesubstrateis provided with a pattern of electrodes.
18. A gas sensor as claimed in claim 12 characterised in that the films are phthalocyanine films.
19. A gas sensor as claimed in claim 18 characterised in that the phthalocyanine films are either of formula (PcGeO)n or (PcSiO)n.
20. Agas sensor as claimed in claim12 characterised in that the inter-ring distance can be varied by substitution of M for other metals or by other substitutions to tune thepolymers tobe sensitive to aparticular reactive gas or classes of gasses.
21. A gas sensor as claimed in claim 12 characterised in that it is for detecting a thermal decomposition product of a sacrificial coating.
22. A gas sensor as claimed in claim 12 characterised in that the sensor is doped to alter its electro-optical properties.
23. Apolymericfilmofformulaasdescribedinclaim1abovecharacterised in that the films are used as lightweight conductors.
24. Apolymeric filmasclaimed inclaim23 characterised inthat thefilmis deposited on a substrate circuit boards with a mask in place to leave an electrically conductive pathway.
25. Apolymeric filmas claimed inclaim23 characterised inthat thefilmis doped to alter its electro-optical properties.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9109036A GB2242685B (en) | 1988-11-02 | 1991-04-26 | Thin film chemiresistive sensors |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB888825618A GB8825618D0 (en) | 1988-11-02 | 1988-11-02 | Thin film chemiresistive sensors |
| GB8825618.5 | 1988-11-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO1990005160A1 true WO1990005160A1 (en) | 1990-05-17 |
Family
ID=10646170
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/GB1989/001312 WO1990005160A1 (en) | 1988-11-02 | 1989-11-02 | Thin film chemiresistive sensors |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0441826A1 (en) |
| JP (1) | JPH04501461A (en) |
| GB (2) | GB8825618D0 (en) |
| WO (1) | WO1990005160A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CZ303823B6 (en) * | 2011-09-01 | 2013-05-15 | Centrum organické chemie s.r.o. | Sensing element for measuring moisture, especially for measuring high values of relative humidity up to 90 percent RH even at temperature values above 80 degC and process for its production |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106153686A (en) * | 2016-07-25 | 2016-11-23 | 杨林 | Full-automatic tobacco conveying buffer storage |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3119392A1 (en) * | 1981-05-15 | 1983-01-27 | Bayer Ag, 5090 Leverkusen | Doped and substituted polymeric phthalocyaninatometalloxanes |
| JPS6213412A (en) * | 1985-07-12 | 1987-01-22 | Nok Corp | Ultra-thin high-molecular complex film and its production |
| JPS633031A (en) * | 1986-06-23 | 1988-01-08 | Canon Inc | Electrically conductive metal phthalocyanine film and method for forming same |
-
1988
- 1988-11-02 GB GB888825618A patent/GB8825618D0/en active Pending
-
1989
- 1989-11-02 EP EP19890912116 patent/EP0441826A1/en not_active Ceased
- 1989-11-02 WO PCT/GB1989/001312 patent/WO1990005160A1/en not_active Application Discontinuation
- 1989-11-02 JP JP51119189A patent/JPH04501461A/en active Pending
-
1991
- 1991-04-26 GB GB9109036A patent/GB2242685B/en not_active Expired
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3119392A1 (en) * | 1981-05-15 | 1983-01-27 | Bayer Ag, 5090 Leverkusen | Doped and substituted polymeric phthalocyaninatometalloxanes |
| JPS6213412A (en) * | 1985-07-12 | 1987-01-22 | Nok Corp | Ultra-thin high-molecular complex film and its production |
| JPS633031A (en) * | 1986-06-23 | 1988-01-08 | Canon Inc | Electrically conductive metal phthalocyanine film and method for forming same |
Non-Patent Citations (4)
| Title |
|---|
| DIRK C.W. ET AL: "Cofacial Assembly of Partially Oxidized Metallomacrocyles as an Approach to Controlling Lattice Architecture in Low-Dimensional Molecular Solids. Chemical and Architectural Properties of the "Face-to-Face" Polymers (M(Phthalocyaninato)o) n, Where M = SI, Ge, and Sn", JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, vol. 105, no. 5, 9 March 1983 (1983-03-09), pages 1539 - 1550 * |
| PATENT ABSTRACTS OF JAPAN vol. 011, no. 192 (C - 429)<2639> 19 June 1987 (1987-06-19) * |
| PATENT ABSTRACTS OF JAPAN vol. 012, no. 202 (C - 503)<3049> 10 June 1988 (1988-06-10) * |
| YUDASAKA M. ET AL: "Formation of Si(Phthalocyaninato)(OH)2 and [Si(Phthalocyaninato)0]n Films and their Optical and Electrical Properties", THIN SOLID FILMS, vol. 151, no. 3, 17 August 1987 (1987-08-17), LASANNE, CH, pages 115 - 119, XP025831186, DOI: doi:10.1016/0040-6090(87)90144-1 * |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CZ303823B6 (en) * | 2011-09-01 | 2013-05-15 | Centrum organické chemie s.r.o. | Sensing element for measuring moisture, especially for measuring high values of relative humidity up to 90 percent RH even at temperature values above 80 degC and process for its production |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8825618D0 (en) | 1988-12-07 |
| GB9109036D0 (en) | 1991-06-12 |
| EP0441826A1 (en) | 1991-08-21 |
| GB2242685B (en) | 1992-07-01 |
| GB2242685A (en) | 1991-10-09 |
| JPH04501461A (en) | 1992-03-12 |
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