Fluorescence quantum yield measurements
1976; The National Institute of Standards and Technology; Volume: 80A; Issue: 3 Linguagem: Inglês
10.6028/jres.080a.038
ISSN2376-5704
Autores Tópico(s)Photochemistry and Electron Transfer Studies
ResumoFour m olecnla r jlnorescence pa rameters d esc ribe th e be havi our of a flu oresce nt molec ul e in ve ry dilute ( -10-6M ) so luti on:(i) th e flu oresce nce s pectrum FII (Il); (ii ) th e flu oresce nce pola ri za ti on PM: (iii) the radia tiv e tr a nsitio n proba bilit y kr M; a nd (iv ) the radiation less tra ns iti on proba bilit y kIM.Th ese pa ra me ters a nd th eir te mpe rature a nd so lve nt de pe nd e nce are th ose of prim a ry inte res t to the photoph ys ic is t a nd ph otoc he mi s t.FII (v ) and PM ca n be de termin e d directl y, bu t krM a nd kloll ca n only be found indirec tly fro m meas ure me nts of the seco nda ry p ara mete rs, (v) the flu oresce nce li fe tim e 7 .11, and (vi) th e flu oresce nce qu a ntum e ffi cie nc y qr M, wh e re k"M= qrMi7M a nd kIM = (1q r M ) 7M.Th e real jlno rescence para meters F (iJ) , 7 a nd cpr of more co nce nt ra ted (c> 10-5 M ) solutions us uall y diffe r from th e molec ul a r pa ra me ters FM (iJ) , 7 .11and q"M d ue to co nce n tra ti on (se lf) q ue nc hin g, so th at 7 > 7 .\,a nd cp" < q" M. The conce ntration q ue nc hin g is due to exc ime r form ati o n a nd di ssociati on (ra tes kOMc a nd k.1I0, respec ti vely) a nd it is oft e n acco mp a ni ed b y th e a ppeara nce of a n e xc im e r flu orescence spec trum Fo{li) in a dditio n to F. II (v) , so th at F (v) has t wo co mp onents.Th e excimer jlno rescence p aram eters Fo( iJ ), Po, k,.,) a nd kID, toge th e r with k"", a nd k.1I0, and th e ir so lve nt a nd te mpe ra ture de pe nde nce, a re also of prim a ry sc ie ntifi c int e res t.Th e observed (tec hnica l) jlno rescence pa ra meters F T ( v)_ 77' a nd cpUn more co nce ntra ted so1!!0 Q.1ls us ually diffe r from th e real param e te rs F ( v ), 7 and cp, .... du e to th e e ffects of se lf-a bso rpti on a nd second a ry flu oresce nce.Th e tec hni cal pa ra me te rs a lso de pe nd on th e opt ica l geo me tr y a nd th e excit a ti on wave le ngth .Th e probl e ms of de te rmining th e rea l para me te rs fro m th e obse rv ed , a nd th e molec ul a r param ete rs from th e rea l, wi ll be di sc ussed .M ethod s are avail a bl e fo r th e acc urate d ete rmin ation of F T (v) a nd 7 T T h e usual me thod of de te rminin g cpT involves co mp ari so n with a refe re nce solution R , a lthough a fe w c alo rim etri c and oth e r a bso lute de te rmin ati ons have bee n made.F or t wo so lutions excit ed und e r id e nti ca l co nditions a nd o bse rved at norm a l in cid e nce whe re n is th e so lv e nt refr activ e ind ex.cpr n' J fTCv) dv cpr" n~ J FJ,CJj)dVTwo refe re nce so lution s ta ndard s have bee n proposed , quinin e s ulph ate in N H 2 S0 4 whi c h has no se lf-abso rpti on, and 9,10-diph e nyla nthrace ne in c yclohe xane whi c h has no se lf-qu e nc hing_ Th e rela tive me ri ts of th ese so luti ons will be disc usse d, a nd poss ible ca ndid ates for a n " id ea l" flu oresce nce s ta ndard with no se lf-a bsorpti on a nd no se lf-quen c hin g will be conside re d .Key word s: Flu oresce nce life tim e; fluoresce nce qu a ntum effi cie ncy; flu orescence qu a ntum yie ld s; flu oresce nce spectrum ; flu o resce nce s tand a rd s : molec ular flu orescence param ete rs; observe d (tec hnical) flu oresce nce pa ram e te rs; po larizati on; radi ative and non-radi ative tra nsiti o n proba bilities; real flu orescence pa ra me ters _ *Paper prese nt ed at the W ork shop Se min ar •S tanda rd izat ion in Spec trop hotometry and Luminesce nce \\tl ea surem enl s' hel d at th e Na tional Burea u of S tandards.Ga ithers burg.
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