US20150308956A1 - Method for the detection of analytes via luminescence quenching - Google Patents

Method for the detection of analytes via luminescence quenching Download PDF

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US20150308956A1
US20150308956A1 US14/649,780 US201314649780A US2015308956A1 US 20150308956 A1 US20150308956 A1 US 20150308956A1 US 201314649780 A US201314649780 A US 201314649780A US 2015308956 A1 US2015308956 A1 US 2015308956A1
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compound
analyte
sensing element
triaryl amine
luminescent
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Paul Leslie Burn
Paul Meredith
Paul Edward SHAW
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University of Queensland UQ
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Assigned to THE UNIVERSITY OF QUEENSLAND reassignment THE UNIVERSITY OF QUEENSLAND ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: BURN, PAUL LESLIE, MEREDITH, PAUL, SHAW, Paul Edward
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
    • G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
    • G01N21/64—Fluorescence; Phosphorescence
    • G01N21/6428—Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes"
    • G01N21/643—Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes" non-biological material
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C211/00—Compounds containing amino groups bound to a carbon skeleton
    • C07C211/43—Compounds containing amino groups bound to a carbon skeleton having amino groups bound to carbon atoms of six-membered aromatic rings of the carbon skeleton
    • C07C211/54—Compounds containing amino groups bound to a carbon skeleton having amino groups bound to carbon atoms of six-membered aromatic rings of the carbon skeleton having amino groups bound to two or three six-membered aromatic rings
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D333/00—Heterocyclic compounds containing five-membered rings having one sulfur atom as the only ring hetero atom
    • C07D333/02—Heterocyclic compounds containing five-membered rings having one sulfur atom as the only ring hetero atom not condensed with other rings
    • C07D333/04—Heterocyclic compounds containing five-membered rings having one sulfur atom as the only ring hetero atom not condensed with other rings not substituted on the ring sulphur atom
    • C07D333/06—Heterocyclic compounds containing five-membered rings having one sulfur atom as the only ring hetero atom not condensed with other rings not substituted on the ring sulphur atom with only hydrogen atoms, hydrocarbon or substituted hydrocarbon radicals, directly attached to the ring carbon atoms
    • C07D333/14—Radicals substituted by singly bound hetero atoms other than halogen
    • C07D333/20—Radicals substituted by singly bound hetero atoms other than halogen by nitrogen atoms
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
    • G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
    • G01N21/64—Fluorescence; Phosphorescence
    • G01N21/6408—Fluorescence; Phosphorescence with measurement of decay time, time resolved fluorescence
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
    • G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
    • G01N21/64—Fluorescence; Phosphorescence
    • G01N21/645—Specially adapted constructive features of fluorimeters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/0004—Gaseous mixtures, e.g. polluted air
    • G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
    • G01N33/0027—General constructional details of gas analysers, e.g. portable test equipment concerning the detector
    • G01N33/0036—General constructional details of gas analysers, e.g. portable test equipment concerning the detector specially adapted to detect a particular component
    • G01N33/0057—Warfare agents or explosives
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
    • G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
    • G01N33/52—Use of compounds or compositions for colorimetric, spectrophotometric or fluorometric investigation, e.g. use of reagent paper and including single- and multilayer analytical elements
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/01—Arrangements or apparatus for facilitating the optical investigation
    • G01N21/03—Cuvette constructions
    • G01N2021/0346—Capillary cells; Microcells
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
    • G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
    • G01N21/64—Fluorescence; Phosphorescence
    • G01N21/6428—Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes"
    • G01N2021/6432—Quenching
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
    • G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
    • G01N21/64—Fluorescence; Phosphorescence
    • G01N21/645—Specially adapted constructive features of fluorimeters
    • G01N2021/6482—Sample cells, cuvettes

Definitions

  • the present invention relates to the detection of analytes, in particular explosives and explosives-related materials.
  • An approach for direct detection of a target analyte relies on the use of luminescent compounds. When some compounds are exposed to light of a certain wavelength, they absorb the light (photoexcitation) and emit light of a different wavelength (luminescence, which can either be fluorescence or phosphorescence). This emitted light can be measured/detected. However, certain analyte molecules may also interact with the (excited) luminescent compound to cause an increase or decrease in the intensity of the emitted light. This change can also be detected and, as such, can be used to indicate the presence of the analyte molecules. Sensors embodying the luminescence quenching approach are commercially available. The sensing materials are comprised of thin films containing luminescent conjugated polymers.
  • the present invention provides a method of detecting an analyte, which method comprises:
  • step (ii) detecting a difference between the luminescent properties measured in step (i) and the luminescent properties of the compound prior to measurement of luminescent properties in step (i);
  • step (iii) determining whether the analyte is present based on the difference in luminescent properties detected in step (ii).
  • the present invention also provides a sensing element for use in the detection of an analyte based on a luminescent response, the sensing element comprising a luminescent compound comprising a triaryl amine moiety provided as a coating on a substrate.
  • the sensing element is used in sensor devices that employ the methodology of the present invention.
  • the present invention also provides a sensor device for the detection of an analyte based on a change in the measured luminescence, the sensor device comprising a sensing element in accordance with the present invention.
  • the sensor device employs the methodology of the present invention.
  • FIG. 1 is a schematic showing components of a sensing device
  • FIG. 2 is a plot of photoluminescence intensity versus time when a conventional conjugated polymer sensing device is exposed to a variety of analytes
  • FIG. 3 is a plot of photoluminescence intensity versus time when a sensing device including the triaryl amine compound shown is exposed to a variety of analytes;
  • FIG. 4 is a plot of photoluminescence intensity versus time when a sensing device including the triaryl amine compound shown is exposed to a variety of analytes;
  • FIG. 5 is a plot of photoluminescence intensity versus time when a sensing device including a dendrimer that does not contain a triaryl amine is exposed to a variety of analytes;
  • FIG. 6 is a plot of photoluminescence intensity versus time when a sensing device including the triaryl amine compound shown is exposed to a variety of analytes;
  • FIG. 7 is a plot of photoluminescence intensity versus time when a sensing device including the triaryl amine compound shown is exposed to a variety of analytes;
  • FIG. 8 is a plot of photoluminescence intensity versus time when a sensing device including the triaryl amine compound shown is exposed to a variety of analytes;
  • FIG. 9 is a plot of photoluminescence intensity versus time when a sensing device including the triaryl amine compound of Example 6 is exposed p-nitrotoluene (pNT) dissolved in a variety of everyday chemicals and chemical combinations;
  • pNT p-nitrotoluene
  • FIG. 10 a is a plot of photoluminescence intensity versus time when a sensing device including the triaryl amine compound shown in FIG. 10 b is exposed to a variety of analytes;
  • FIG. 11 is a plot of photoluminescence intensity versus time when a sensing device including the triaryl amine compound shown is exposed to a variety of analytes;
  • FIG. 12 is a plot of photoluminescence intensity versus time when a sensing device including the triaryl amine compound shown is exposed to a variety of analytes.
  • FIG. 13 is a plot of photoluminescence intensity versus time when a sensing device including the triaryl amine compound shown is exposed to different of analytes.
  • the method of the invention comprises:
  • step (ii) detecting a difference between the luminescent properties measured in step (i) and the luminescent properties of the compound prior to measurement of luminescent properties in step (i);
  • step (iii) determining whether the analyte is present based on the difference in luminescent properties detected in step (ii).
  • step (d) determining whether the analyte is present based on the difference in luminescent properties detected in step (c).
  • This embodiment relies on there being a change in measured luminescent properties as a result of exposure of the luminescent compound to an analyte.
  • the real time implementation of this embodiment would involve excitation and measurement of luminescent properties prior to sampling for an analyte. Determining the initial luminescent response of the compound (i.e. before exposure to an analyte) is important in order to give a control or base reading against which any subsequent change in luminescent response can be assessed.
  • triaryl amine compounds used in the present invention may show advantageous selectivity towards a variety of analytes.
  • the compounds can show luminescence quenching in the presence of explosive analytes and/or taggants. More specifically, the compounds show luminescence quenching in the presence of analytes and/or taggants that contain one or more nitro groups. Preferably, the compounds show luminescence quenching in the presence of a nitroaromatic analyte.
  • triaryl amine compounds used in accordance with the invention exhibit a fundamentally different photoluminescent response to certain analytes when compared with compounds, such as conjugated polymers, used in existing sensors that operate on the same principles. More particularly, triaryl amine compounds used in the present invention may exhibit a characteristic luminescence response to analytes that allows explosives and explosives-related materials to be readily detected as against every-day chemicals that would otherwise have an impact on detection. In other words, triaryl amine compounds used in accordance with the invention may provide qualitative detection selectivity with respect to explosives and explosives-related materials.
  • the triaryl amine compounds may exhibit a detectable response (decrease or increase) in the luminescence in the presence of the explosives and explosives-related materials whereas there is no response, or no significant response, in the photoluminescence in the presence of non-explosive related (everyday) materials such as perfumes, coffee etc.
  • the triaryl amine compounds may exhibit a particular response (e.g. a decrease) in the luminescence in the presence of the explosives and explosives-related materials whereas the opposite response (an increase in the context of the example given) in the photoluminescence in the presence of non-explosive related (everyday) materials.
  • triaryl amine compounds used in accordance with the present invention may be useful for selective detection of a variety of target analytes (and the scope of this may be investigated for any given compound), the compounds are believed to have particular value in relation to the selective detection of explosives and explosives-related materials as analytes.
  • these analytes are nitrogen-containing species and include explosives per se as well as related (functional) materials such as accelerants, taggants and the like.
  • the analyte may be selected from 2,4,6-trinitrotoluene (TNT high explosive), 2,3-dinitro-2,3-dimethylbutane (a taggant typically used in the explosive Semtex), 2,4,6-trinitro-m-xylene (TNX), 2,4,6-trinitrochlorobenzene (picryl chloride), 2,4,6-trinitrophenol (picric acid); ammonium picrate (Explosive D); 2,4,6-trinitro-m-cresol (TNC), 2,4,6-trinitroresorcinol (styphnic acid), 2,4,6-trinitroanisole (TNA, methyl picrate), 2,4,6-trinitrophenetole (TNP, ethyl picrate), 2,4,6-trinitroaniline (picramide, 1-monoamino-2,4,6-trinitrobenzene, MATB), 1,3-diamino-2,4,6-trinitrobenzene (DATB), 1,3,5-triamino
  • the present invention relies on the use of certain compounds that have characteristic structural features and optical properties. With respect to structure the compounds can broadly be classified as luminescent triaryl amines and the presence of the triaryl amine moiety is believed to be significant to the usefulness of the compounds in the context of the present invention.
  • the triaryl amine compound must also exhibit suitable optical properties to be useful in the present invention. That is, the compounds must be capable of interacting with an analyte molecule thereby causing a detectable change in luminescence intensity. Preferably, the compounds are, fluorescent.
  • triaryl amine compounds useful in the present invention will generally be used in sensor devices in the solid phase, usually as coatings/films on a substrate. It is obviously important that the compounds retain the desirable optical properties when provided in this form. Sensor devices useful in the context of the present invention will be discussed in more detail below.
  • the compounds can be regarded as conjugated compounds that comprise a triaryl amine moiety.
  • one or more, preferably one, conjugated molecular structure is bound to each of the three aryl groups of the triaryl amine moiety.
  • the conjugated molecular structure is bonded to the aryl group in such a way so as to preserve conjugation with the aryl group.
  • the conjugated molecular structures may be the same or different.
  • conjugated molecular structure means a structure comprising at least 5 carbon atoms with alternating single and multiple bonds that provide delocalization of electrons.
  • the conjugated molecular structure may include alkenyl, alkynyl and/or conjugated cyclic moieties.
  • the presence of conjugated molecular structures attached to the triaryl amine compounds used in the present invention is critical to their usefulness in the context of the present invention. This may be understood with reference to the underlying mechanism by which the compounds are believed to function in the present invention. Absorption by the compound of a photon produces a singlet excited state.
  • An analyte molecule may interact with the excited triaryl amine compound leading to oxidation of the excited state with the result that there is no luminescence. This effect is known as oxidative luminescence quenching.
  • the conjugated molecular structure may be at least partially conjugated provided that the intended functionality in the context of the invention is preserved.
  • triaryl amine compounds useful in the present invention have been found to exhibit selective luminescence quenching when exposed to explosives and explosives-related materials.
  • the compounds may exhibit a qualitatively different fluorescent response in the presence of everyday chemicals.
  • the analyte must have an electron affinity sufficient to separate the exciton that is formed on excitation of the triaryl amine compound. It is well known in the art how to modulate the optical and electronic properties of conjugated molecules and this can be applied to the optical and electronic properties of the triaryl amine compounds used in the current invention.
  • the triaryl amine moiety provides branching in the structure of the overall compound.
  • the triaryl amine moiety may be the only part of the molecule that provides branching or it may provide one of several branching points depending upon the architecture of the conjugated molecular structure. From this it will be understood that when the triaryl amine compound is a polymer, the triaryl amine moiety could be part of the main chain, part of a side chain group, or both. It will also be appreciated that there could be more than one triaryl amine group in a material. For example, in a polymer the triaryl amine group could be present as part of a ‘monomer unit’ repeated along the polymer backbone. Also each DENDRON of a dendrimer could contain one or more triaryl amine groups. In the case where more than one triaryl amine group is present and they are linked sequentially an individual aryl group may be attached to two or more nitrogen atoms.
  • the conjugated molecular structure may comprise one or more aryl or heteroaryl groups that can be linked directly together or via one or more alkenyl or acetylenyl groups.
  • the connection of the conjugated molecular structure to the aryl moieties of the triaryl amine group can be via an aryl, heteroaryl, alkenyl or acetylenyl carbon atom of the conjugated molecular structure.
  • connection is via an aryl or heteroaryl moiety of the conjugated molecular structure.
  • connection is via a heteroaryl group, this may be via a heteroatom.
  • the hetero-atom may be N, O or S.
  • the aryl groups are usually benzene rings, and these are typically substituted at position 2, 3, 4, 5 or 6 to provide the remainder of the conjugated molecular structure.
  • the heteroaryl group is usually a 5- or 6-membered ring structure, and may be selected from thiophene, pyridine, pyrimidine, triazine, etc.
  • the use of poly-aromatic ring structures is also possible.
  • the use of fused ring aryl and heteroaryl ring systems is also possible, including naphthalene, anthracene, carbazole, fluorene etc. It is also possible that two or more aryl groups of the triaryl amine compound are linked by a conjugated molecular structure.
  • the conjugated molecular structure may be represented by the formula (I):
  • each Ar represents an aryl moiety
  • R 1 , R 2 , R 3 are the same or different conjugated, molecular structure comprised of moieties as defined above
  • X 1 , X 2 , X 3 are independently selected from conjugated moieties and/or nitrogen atoms linking Ar with respective groups
  • R 1 , R 2 , R 3 and x, y, and z are independently 0, 1, 2, 3, or 4.
  • the respective groups X 1 , X 2 and X 3 may be the same or different.
  • the linkage between the group Ar and the group R 1 will be of formula —X 1 —X 1 — in which each X 1 may be the same or different.
  • X 1 , X 2 and X 3 When one or more of X 1 , X 2 and X 3 is a nitrogen atom, the nitrogen atom is bonded directly to a conjugated group or moiety so that the lone pair of the nitrogen atom can interact with the conjugated group or moiety. Typically, when one or more of X 1 , X 2 and X 3 is a nitrogen atom this nitrogen atom is usually part of a triaryl amine substituted moiety.
  • the aryl group may be selected from phenyl, napthyl, anthracenyl, acenapthyl, fluorenyl and azulenyl.
  • each Ar group is the same and is phenyl.
  • each group Ar is phenyl and R 1 , R 2 , R 3 are the same.
  • X 1 , X 2 , X 3 are independently selected from aryl, heteroaryl, alkenyl or acetylenyl groups.
  • one or more of X 1 , X 2 and X 3 is a conjugated repeat unit of a polymer chain or a conjugated dendrimer.
  • R 1 and R 2 may constitute the main part of a polymer chain together with two of the aryl groups and the nitrogen atom of the triaryl amine moiety of the molecule, with the remaining aryl group, X 3 if present and R 3 providing chain-branching.
  • one of the groups, say R 1 may be a polymer chain with the remainder of the molecule being present as a pendant group (side chain) of the polymer chain. In this case the group R 1 will also need to provide a point of attachment to the polymer backbone.
  • the remaining groups, R 2 and R 3 may be conjugated molecular structures as defined above, for example dendrons or simple linear-conjugated species.
  • the structure represented by formula (I) may be part of a branched compound such as a dendrimer.
  • at least one of R 1 , R 2 , and R 3 has to be a dendron.
  • R 1 , R 2 , and R 3 can simply be linear conjugate sequences, i.e. the N atom is at the centre.
  • the compound When at least one conjugated molecular structure is a dendron, the compound may be represented by formula I in which one or more of R 1 , R 2 , and R 3 may be the same or different group of formula:
  • DENDRON represents a conjugated dendritic molecular structure comprising a plurality of chain branches each of which terminates with a distal aryl or heteroaryl group
  • B represents an optional surface group attached to the distal aryl and/or heteroaryl group terminating a chain branch.
  • the individual chain branches of DENDRON may be the same or different. When present the surface groups in DENDRON may be the same or different. When a surface group is not present on a particular chain branch, that chain branch will terminate with the terminal aryl or heteroaryl group.
  • this embodiment may provide an opportunity of optimizing the electronic and processing properties independently which should give improved manufacturability of electronically optimized materials.
  • the surface groups may include halogen, C 1-10 alkyl, C 2-10 alkenyl, —C(O)R wherein R is hydrogen or C 1-10 alkyl, —CO 2 R wherein R is hydrogen or C 1-10 alkyl, hydroxy, C 1-10 alkoxy, C 2-10 alkenyloxy, C 1-10 alkylthio, C 2-10 alkenylthio, C 1-10 haloalkyl, C 2-10 haloalkenyl, C 1-10 haloalkoxy, C 2-10 haloalkenyloxy, amino, C 1-10 alkylamino, di(C 1-10 )alkylamino, C 6-14 aryloxy, —O 2 SR or —SiR 3 wherein each R is the same or different and represents hydrogen, C 1-10 alkyl or C 2-10 alkenyl.
  • substituents include hydroxy(C 1-10 )alkyl and hydroxyhalo(C 1-10 )alkyl groups, for example hydroxy(C 1-4 alkyl and hydroxyhalo(C 1-4 )alkyl groups.
  • a surface group that allows further reaction may interact to provide cross-linking.
  • the surface group may be selected from, for example, as alkene, (meth)acrylate, an oxetane containing group or silicon-containing group.
  • DENDRON may be the same or different group of the formula:
  • A is a first aryl or heteroaryl moiety of the DENDRON
  • ARM represents a group of one or more of alkenyl, alkynyl, aryl or heteroaryl moieties for a first generation dendrimer or for higher generation dendrimers a dendritic arm extending from A, d is equal or greater than 2, and B is as defined before.
  • each of X 1 , X 2 , X 3 , R 1 , R 2 , and R 3 occupy the ortho-, meta- or para-position on the phenylene ring.
  • each of X 1 , X 2 , X 3 , R 1 , R 2 , and/or R 3 are in the para-position relative to the nitrogen atom. Accordingly, in a further aspect the compounds of formula (I) may be represented by formula (Ib):
  • X 1 , X 2 and X 3 are a substituted thiophenyl group, preferably a substituted 2,5-thiophenyl group of formula:
  • R 1a , R 2a and R 3a represent the remainder of the conjugated molecular structure represented by R 1 , R 2 and R 3 .
  • R 1a , R 2a and R 3a are bonded to the thiophenyl group by the same type of substituted aryl or substituted phenyl moiety.
  • R 1b , R 2b and R 3b are independently selected from C 1 -C 20 alkyl, or C 1 -C 20 alkoxy when m is 1, and when m is 2 or more an optionally substituted ARM as defined above.
  • each R 1b , R 2b and R 3b preferably occupies the para position of the phenyl ring.
  • R 1b , R 2b and R 3b are the same or different, preferably the same, C 1 -C 20 alkoxy, such as C 2 -C 15 alkoxy or C 3 -C 10 alkoxy.
  • each R 1b , R 2b and R 3b is the same or different, preferably the same, ARM is an optionally substituted phenyl moiety.
  • the substituent B may be selected from C 1 -C 10 alkyl and C 1 -C 10 alkoxy.
  • the phenyl moiety attached to the thiophene ring is substituted at the meta-positions by the ARM groups.
  • each ARM has a group B located at the para position and is selected from C 1 -C 10 alkyl or C 1 -C 10 alkoxy.
  • R 1 , R 2 and R 3 are each bonded to the phenyl moiety by the same or different, preferably the same, substituted aryl group selected from substituted phenyl, substituted napthyl, substituted anthracenyl, substituted acenapthyl, substituted fluorenyl, or substituted azulenyl, preferably substituted fluorenyl.
  • R 1c , R 2c and R 3c represent the remainder of the conjugated molecular structure represented by R 1 , R 2 and R 3 .
  • R 1c , R 2c and R 3c may be independently selected from optionally substituted aryl, or optionally substituted heteroaryl, n at each occurrence is independently 1, 2, or 3; and R 4 and R 5 at each occurrence is independently C 1 -C 10 alkyl, C 1 -C 10 alkoxy, glycols of differing lengths, crosslinkable groups such as vinyl, methacrylate or oxetanes that can be attached via a flexible chain.
  • R 1c , R 2c and R 3c , R 4 , and R 5 are as defined above for formula (Ie).
  • R 1c , R 2c and R 3c are the same and represent optionally substituted phenyl or optionally substituted fluorenyl.
  • R 1c ′, R 2c ′ and R 3c ′ represent the remainder of the conjugated molecular structure represented by R 1 , R 2 and R 3 .
  • R 1c′ , R 2c′ and R 3c′ may be independently selected from optionally substituted aryl or optionally substituted heteroaryl; o at each occurrence is independently 1, 2, or 3; and R 4 and R 5 at each occurrence is independently C 1 -C 10 alkyl, C 1 -C 10 alkoxy, glycols of differing lengths, crosslinkable groups such as vinyl, methacrylate or oxetanes that can be attached via a flexible chain.
  • R 1c ′, R 2c ′ and R 3c ′ are the same and represent substituted phenyl. In a further embodiment R 1c ′, R 2c ′ and R 3c ′ are the same and represent phenyl substituted 1 or 2 times with C 1 -C 20 alkyl or C 1 -C 20 alkoxy.
  • substituent groups include halogen, C 1-10 alkyl, C 2-10 alkenyl, —C(O)R wherein R is hydrogen or C 1-10 alkyl, —CO 2 R wherein R is hydrogen or C 1-10 alkyl, hydroxy, C 1-10 alkoxy, C 2-10 alkenyloxy, C 1-10 alkylthio, C 2-10 alkenylthio, C 1-10 haloalkyl, C 2-10 haloalkenyl, C 1-10 haloalkoxy, C 2-10 haloalkenyloxy, amino, C 1-10 alkylamino, di(C 1-10 )alkylamino, C 6-14 aryloxy, —O 2 SR or —SiR 3 wherein each R is the same or different and represents hydrogen, C 1-10 alkyl or C 2-10 alkenyl, C 6-14 arylthio, C 6-14 aryl and 5- to 10-membered hetero
  • the sensor devices in which the triaryl amine compounds described herein may be used are of conventional design and are operated in conventional manner.
  • a typical device is shown in FIG. 1 .
  • An excitation source is used to supply the electromagnetic radiation that interacts with the compound being used to cause the compound to generate light.
  • the compound is provided on a suitable substrate, thereby forming a sensing element.
  • the excitation source may be an LED, a laser, cathode lamp, or the like.
  • the device also includes a light detector that receives light from the compound. This detector delivers an output signal that is indicative of the intensity of light emitted by the compound.
  • the device will also include componentry (microprocessors) that allows the output of the light detector to be visualized or otherwise represented for interpretation.
  • the device will also include one or more temperature control elements for regulating and detecting the temperature of parts of the device as necessary for optimum operation.
  • the triaryl amine compound will be provided as a coating/film on a substrate over or through which a gas to be analysed is passed or delivered.
  • sensing element is used to denote the coated substrate.
  • the form the substrate takes has been found to influence the efficacy of triaryl amine compounds in selectively detecting analyte molecules of interest (explosives and explosives-related materials).
  • non-planar substrates may be preferred.
  • the substrate material may need to be effectively transparent to the wavelength of light, that is to be used to excite the triaryl amine compound used.
  • the substrate material must also be non-reactive with respect to target analytes.
  • the thickness of the coating/film of triaryl amine compound has an impact on detection efficacy.
  • the thickness may be optimized by experimentation for a given combination of substrate and triaryl amine compound.
  • the coating/film thickness will be up to 100 nm, for example in the range 10-100 nm.
  • the compound may be deposited by conventional techniques.
  • the substrate may take the form of a tube with the compound provided on the internal surface of the tube.
  • the tube typically has a circular cross-section.
  • the optimum dimensions for the tube, as well as suitable materials from which the tube is made, may be determined experimentally.
  • the compound is provided on the internal surface of a capillary tube.
  • the capillary tube may be made of a glass, such as a borosilicate glass, or silica.
  • the capillary will have an internal diameter of from 100 ⁇ m to 1 mm.
  • the length of the capillary is usually no longer than 100 mm.
  • Useful capillaries with the required externally and internal diameters are commercially available and can be cut to the appropriate length.
  • the present invention also provides a sensing device including a sensing element as described herein.
  • a conventional device containing a fluorescent conjugated polymer was found to show a ⁇ 1-2% decrease in fluorescence when exposed to a standard TNT source (not shown in FIG. 2 ), which is included with the device for verifying correct operation.
  • a standard TNT source not shown in FIG. 2
  • the majority were “detected” by a decrease in the fluorescence signal.
  • the device was exposed to the various species one at a time. The conventional device cannot readily distinguish between explosives and everyday chemicals.
  • the X-axis (time) denotes the time from commencement of the experiment at which the device is exposed to a particular species.
  • the channel of a glass capillary as above was coated with a triphenylamine centred thiophene containing dendrimer ( FIG. 4 ) by blowing a solution of the material in toluene through the capillary with a flow of nitrogen gas.
  • the coated capillary was then exposed sequentially to vapours of a range of everyday chemicals and nitroaromatic compounds.
  • the results show that the dendrimer exhibits an increase in fluorescence signal when exposed to the vapours from a series of everyday chemicals and quenching when it is exposed to the nitroaromatics DNT and pNT.
  • the modification of the structure, through the addition of dendrons has not altered the basic sensing properties.
  • a bifluorene dendrimer which is known to be strongly quenched by nitroaromatic vapours, was tested inside a glass capillary (same as Example 1) (see FIG. 5 ) to determine whether or not it featured the same selectivity observed in the triphenylamine-based compounds. The same testing procedure was followed as described for the compounds in Example 1 and 2.
  • the fluorescence signal showed quenching responses with all of the everyday chemicals except naphthalene as well as the nitroaromatics.
  • Toluene showed a combination of quenching/enhancement, which could be due to changes in the optical properties of the sensing film caused by swelling. This behaviour is similar to that of the original Comparative Example 1.
  • the triphenylamine centred fluorene dendrimer shown in FIG. 6 was tested to determine whether the triphenyl amine thiophene combination was necessary for the observed selectivity. Fluorene only-based compounds, such as the one described in Example 2, do not exhibit selectivity. All tests were again performed as in Examples 1, 2, and Comparative Example 2 by coating the inside of the sensing element (glass capillary with the same dimensions as Example 1) with the sensing compound. The results show the same selectivity behaviour as observed with the other triphenylamine-based compounds: only the nitroaromatic compounds show quenching of the fluorescence with everyday chemicals resulting in an increase in the fluorescence signal. The mono-fluorene compound was also found to be more stable to photooxidation than the thiophene-containing compound.
  • the triphenylamine based compound from Example 6 was tested to determine whether a nitroaromatic compound (p-nitrotoluene) could be detected in the presence of other chemicals. All tests were again performed in a similar manner to Examples 1, 2, and Comparative Example 2 by coating the inside of the sensing element with the sensing compound. The results, displayed in FIG. 9 , show that the p-nitrotoluene is detected with the associated responses left to right corresponding to 1 to 18 with 18 being labelled as a reference point.
  • DNT is 2,4-dinitrotoluene
  • PNT is p-nitrotoluene
  • DNB 1,4-dinitrobenzene
  • (p) denotes samples that are perfumes.
  • triphenylamine-based compound shown in FIG. 10 b was tested to further confirm that compounds incorporating triphenylamine exhibit selectivity. All tests were again performed as in Examples 1, 2, and Comparative Example 2 by coating the inside of the sensing element with the sensing compound. The results shown in FIG. 10 a across two plots show the same selectivity behaviour as observed with the other triphenylamine-based compounds: only the nitroaromatic compounds show quenching of the fluorescence with everyday chemicals resulting in an increase in the fluorescence signal.
  • the sensing behaviour is similar to that of the monofluorene compound in example 10 although the response and recovery of the fluorescence signal was slower.
  • triphenylamine-based compound shown in FIG. 13 was tested to further confirm that compounds incorporating triphenylamine exhibit selectivity. All tests were again performed in a similar manner to Examples 1, 2, and Comparative Example 2 by coating the inside of the sensing element with the sensing compound. The results are consistent with the examples for the other triphenylamine-based compounds with the nitroaromatic DNT causing a decrease in the fluorescence signal and the ethanol a small increase.

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