Hệ Quang Phổ Phát Quang

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Phương pháp quang phổ huỳnh quang, hệ phân giải thời gian

Transcript of Hệ Quang Phổ Phát Quang

MC LC Li cm n M u Chng 1: Tng quan v quang ph hc hunh quang phn gii thi gian 1.1. Hin tng phn r hunh quang trong phn t 1.1.1. S Jablonski 1.1.2. Thi gian sng hunh quang v hiu sut lng t 1.1.3. Hin tng dp tt hunh quang 1.1.4. Hin tng truyn nng lng cng hng 1.2. Cc c ch ti hp hunh quang trong cht bn dn 1.2.1. Kch thch n cc (ti hp vng tp cht) 1.2.2. Kch thch lng cc (ti hp vng vng) 1.2.3. C ch ti hp ca cc cp donor acceptor trong cht bn dn Chng 2: Cc phng php o phn gii thi gian 2.1. Hai phng php o phn gii thi gian c bn 2.2. Xc nh thi gian sng v thi gian phn r hunh quang 2.2.1. Theo phng php hunh quang xung 2.2.2. Theo phng php hunh quang iu bin pha 2.3. K thut o hunh quang xung 2.3.1. Phng php m n photon tng quan thi gian TCSPC 2.3.2. Streak cameras 2.3.3. Phng php trn tn s tng phi tuyn 2.3.4. Phng php ghi xung 2.4. K thut o hunh quang iu bin pha Chng 3: H thu ph hunh quang phn gii thi gian kch thch bng laser nit 3.1. Cc thit b c s dng trong h thu ph hunh quang phn gii thi gian 3.1.1. Ngun kch thch hunh quang: laser Nit TE 999 3.1.2. My n sc cch t kp GDM-1000 3.1.3. Nhn quang in R928 3.1.4. Dao ng k s TDS-2014 3.2. S h thu ph hunh quang phn gii thi gian kch thch bng laser nit 3.3. Cc thao tc tin hnh o trn h o 3.4. Chng trnh x l s liu o 3.5. Chun s sng cho h o 3.6. Kim tra ph ca laser nit Chng 4: Kt qu thc nghim 4.1. Ph pht quang phn gii thi gian ca mu ZnO 4.2. Ph pht quang phn gii thi gian ca mt s mu bt ZnS pha tp 4.2.1. Ph pht quang phn gii thi gian ca ZnS 4.2.2. Ph pht quang phn gii thi gian ca ZnS:Mn 4.2.3. Ph pht quang phn gii thi gian ca ZnS:Al 4.3. Ph pht quang phn gii thi gian ca dung dch Rhodamine 6G v laser mu R6G Kt lun Ti liu tham kho 1M U Quang ph hc hunh quang l mt lnh vc c pht trin t lu ca vt l hc. Da trn c s ph hunh quang ca cc cht, ngi ta c th xc nh c cc c trng ha l cng nh cu to ca chng. V th cc phng php quang ph hc hunh quang v ang gi vai tr quan trng trong vic nghin cu cu trc vt cht, gp phn vo s pht trin ca nhiu lnh vc khoa hoc khc nhau nh vt l, ha hc, sinh hc, y hc Cc php o ph hunh quang c th c chia lm hai dng chnh, l ph hunh quang trng thi dng v ph hunh quang phn gii thi gian. Trong , ph hunh quang trng thi dng l php o cng bc x hunh quang trung bnh theo thi gian. Ph hunh quang trng thi dng biu din s ph thuc ca cng pht quang theo bc sng, t c th xc nh c cc thng s nh cng , rng ph, v tr nh ph, phn cc Thng thng, ph hunh quang trng thi dng thu c khi s dng mt ngun sng lin tc kch thch mu vt. Ph hunh quang phn gii thi gian l php o s ph thuc vo thi gian ca ph pht quang sau khi c kch thch bi xung nh sng. So vi ph hunh quang dng thng thng, ph hunh quang phn gii thi gian a ra nhiu thng tin hn v cc qu trnh ng hc xy ra trong vt liu. N c th c s dng nghin cu cc s kin xy ra cng thang thi gian vi s phn r hunh quang nh qu trnh tn x ngc, s truyn nng lng cng hng, hay s dp tt ng hc Ngoi ra, thi gian sng ca mt vt liu trng thi kch thch o c bng phng php ny thng c dng tnh ton ngng kch laser ca hot cht pht quang hoc phn tch cc qu trnh ha hc, sinh hc. Ph hunh quang phn gii thi gian cng gip ta phn tch r rng hn cc qu trnh hunh quang cng xy ra trong vt liu khi chng b chng chp ln nhau v mt nng lng nhng li c thi gian sng hunh quang khc nhau. Do mt h o ph hunh quang phn gii thi gian l rt cn thit i vi bt k phng th nghim no 2nghin cu quang ph hc ni chung. Thm vo , cng vi s pht trin ca nhiu loi laser xung ngn cng sut cao nn php o hunh quang phn gii thi gian cng c c hi c ng dng rng ri. Trong cc k thut o hunh quang phn gii thi gian th k thut trung bnh boxcar c s dng ph bin hn c. Tuy nhin ngoi nhng u im ca h boxcar v kh nng o cc tn hiu lp li vi bng ph rng v phn gii thi gian cao (~ 100 ps) th n cng bc l nhng hn ch nh: phi s dng cc modul boxcar gi thnh cao, i hi v n nh ca tn hiu cao, thi gian thc hin mt php o ko di nn thng ch o c ti mt s thi im, kh nng lu tr v x l s liu km (phi s dng thm b chuyn i A/D ghp ni vi my tnh). Vi mc tiu khc phc nhng nhc im trn ca h boxcar v cng s dng cc thit b c sn trong phng th nghim, chng ti tin hnh xy dng v hon thin mt h o ph hunh quang phn gii thi gian c kch thch bng laser nit v s dng dao ng k s. Nh kh nng ghi nhn v lu tr d liu ca dao ng k s, h o ny c th kt hp php o thi gian sng hunh quang v o ph hunh quang phn gii thi gian trong cng mt ln o. Ngoi ra, do c ghp ni vi my tnh nn cc qu trnh o din ra hon ton t ng, cc s liu d dng c lu tr v x l. S dng h o ny, chng ti tin hnh thu ph hunh quang phn gii thi gian ca mt s mu bt pht quang v cc dung dch cht mu. T xc nh c thi gian sng trng thi kch thch ca cc phn t trong mu. Ni dung chnh ca lun vn gm 4 chng nh sau: Chng 1: Tng quan v ph hunh quang phn gii thi gian: trnh by nhng khi nim l thuyt c bn lin quan n ph hunh quang phn gii thi gian ca phn t trong dung dch v ca cht bn dn. Chng 2: Cc phng php o phn gii thi gian: trnh by v phn tch mt s phng php o phn gii thi gian v cch xc nh thi gian sng hunh quang da trn nhng kt qu o c. 3 Chng 3: H thu ph hunh quang phn gii thi gian kch thch bng laser nit: m t mt s thit b c s dng, qu trnh hot ng v quy trnh vn hnh h o cng nh cch s dng cc phn mm iu khin v x l s liu. Chng 4: Kt qu thc nghim: trnh by ph hunh quang phn gii thi gian v cc ng cong hunh quang tt dn o c ca mt s mu vt. 4Chng 1: TNG QUAN V QUANG PH HC HUNH QUANG PHN GII THI GIAN Trong chng th nht ny, chng ti s trnh by nhng khi nim c bn lin quan n cc tng phn r hunh quang xy ra trong phn t hu c v trong cc cht bn dn y l nhng i tng nghin cu u tin ca h thu ph hunh quang phn gii thi gian m chng ti xy dng. 1.1. Hin tng phn r hunh quang trong phn t Khi mt mu vt c kch thch bi cc tc nhn bn ngoi, cc in t trng thi c bn s hp th nng lng chuyn ln cc trng thi in t kch thch. T trng thi in t kch thch, s hi phc ca in t v cc trng thi in t c bn s lm bc x ra nh sng. Hin tng ny c gi l s pht quang ca vt cht khi c kch thch. Da theo bn cht ca trng thi kch thch, s pht quang c th c chia thnh hai dng: ln quang v hunh quang. Ln quang l bc x nh sng t cc trng thi kch thch bi ba (spin bng 1). Thi gian sng ln quang in hnh c th rt lu t mili giy n giy. Thm ch mt s cht ln quang cn c th pht sng n vi pht khi cc in t hi phc rt chm v mc c bn. Trong khi , hunh quang l bc x nh sng t cc trng thi kch thch n (spin bng 0) hay l s hi phc bc x ca vt cht t cc trng thi kch thch in t. Khong thi gian in t hi phc t trng thi kch thch v trng thi c bn hay cn gi l thi gian sng hunh quang () thng vo c nano giy (10-9 s). Mt s cht pht quang li c thi gian sng hunh quang di nano giy. Do khong thi gian phn r hunh quang rt ngn, nn cc h o ph pht quang phn gii thi gian i hi phi s dng cc thit b quang in t rt phc tp. Mc d c nhiu kh khn, nhng ph pht quang phn gii thi gian vn c s dng rng ri do chng a ra nhiu thng tin hn so vi cc ph pht quang trng thi 5dng thng thng. Thm vo , nhng tin b v cng ngh hin nay cng gip cho cc php o phn gii thi gian tr nn d dng hn. 1.1.1. S Jablonski Qu trnh hp th v bc x nh sng trong cc phn t thng c biu din bi s Jablonski. S Jablonski c s dng trong nhiu hnh thc minh ha cc qu trnh phn t khc nhau xy ra trong trng thi kch thch. Mt s Jablonski tiu biu c trnh by trong hnh 1.1. T hnh trn ta thy: cc trng thi c bn, trng thi in t kch thch n th nht v th hai c gi l S0, S1 v S2 tng ng, T1 l trng thi in t kch thch bi ba. Trong mi trng thi, cc mc nng lng in t dao ng c i din bi cc s 0, 1, 2 Cc qu trnh hp th v bc x c m t bi cc ng mi tn thng ng. Trong dch chuyn t mc S0 ln S1, S2 lin quan ti s hp th khi mu vt c kch thch; cc ng nt t th hin s dch chuyn khng bc x ni; ng cho t S1 v T1 th hin dch chuyn khng bc x n bi ba; cn cc ng t S1 v S0 v cc ng t T1 v S0 l cc dch chuyn bc x hunh quang v ln quang. Cc dch chuyn hp th thng xy ra trong khong thi gian 10-15 s, cn cc dch chuyn ni khng bc x din ra trong thi gian 10-12 s. Do thi gian sng hunh quang thng vo khong 10 ns, nn cc dch chuyn ni s kt thc trc mt chu k pht x. Do bc x hunh quang thng c to ra t trng thi Hnh 1.1: S Jablonski Hp th Dch chuyn ni Hunh quang Ln quang 6kch thch cn bng nhit (trng thi dao ng c mc nng lng thp nht S1). 1.1.2. Thi gian sng hunh quang v hiu sut lng t Thi gian sng hunh quang v hiu sut lng t l hai c trng quan trng nht ca mt cht pht quang. Hiu sut lng t l t s gia s lng photon bc x v s lng photon c hp th. Mt s cht c hiu sut lng t rt ln, gn bng n v (nh Rhodamine), s pht quang mnh nht. Trong khi , thi gian sng hunh quang gip xc nh khong thi gian mt cht pht quang tng tc vi mi trng da trn nhng thng tin thu c t ph bc x ca chng. ngha ca hiu sut lng t v thi gian sng hunh quang c th c biu din bi mt s Jablonski n gin (hnh 1.2). Trong s ny, ta khng m t cc qu trnh tch thot ring r phc tp lin quan n cc trng thi kch thch S1. Thay vo , ta s tp trung vo cc qu trnh dch chuyn v trng thi c bn S0. Ta gi l tc bc x photon ca cht pht quang, cn knr l tc phn r khng bc x v mc c bn S0. Do c v knr u lm suy gim mt tch ly trng thi kch thch nn hiu sut lng t c th c tnh bi: nrQk= + (1.1) Hnh 1.2: S Jablonski