Lyoluminescence in Ce 3+ activated (KNa)Br phosphor for ionizing radiation dosimetry

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1 Bull. Mter. Si., Vol., No., June, pp.. Indin Ademy of Sienes. Lyoluminesene in Ce + tivted (KN)Br phosphor for ionizing rdition dosimetry P M BHUJBAL nd S J DHOBLE Deprtment of Physis, R.T.M. Ngpur University, Ngpur, Indi Nutn Adrsh Arts, Commere nd Smt. M.H.Wegd Siene College, Umrer, Indi MS reeived My ; revised August Astrt. The lyoluminesene (LL) in γ -ry irrdited (KN)Br : Ce + phosphors re reported in this pper. LL of (KN)Br : Ce + hve een reorded for different γ -ry doses. The nture of vritions of LL pek intensities is found to e liner with γ -ry irrdition dose nd LL pek intensity is found to e dependent on onentrtions ( mol%) of dded Ce + ions in the (KN)Br host lttie. Negligile fding in the prepred smple is oserved. Keywords. Lyoluminesene; γ -ry dose; rdition dosimetry; phosphor; (KN)Br.. Introdution The mesurement of rdition dose hs eome siene of ever inresing importne due to the estimtion of risk nd enefits inherent to the uses nd to the exposure of ionizing rdition. When strongly energized, rystls re dissolved in liquid solvent like wter nd light is emitted euse of reomintion of hydrted eletrons with holes on the surfe of rystllites. This phenomenon is lled lyoluminesene (Hrvey ) nd hs een investigted y mny workers for use in dosimetry pplition. Ahnstrom () nd Arnikr nd o-workers () support the formtion of hydrted eletron (eq ) s the prerequisite for emission of light. The work in this field ppers to del more with the improvement of tehniques, oth for detetion nd preprtion of mterils, imed t hieving more relile dosimetry (Ettinger nd Puite ). However, there re numer of ftors tht influene the light yield during dissolution of γ -irrdited lkli hlides in wter, nd whih hve not een investigted in detil. Vrious studies hve een undertken to understnd the mehnism of LL (Reynolds ). The prmeters tht influene the LL intensity re, for exmple, grin size, mss of the irrdited lkli hlide, ph of the solvent, temperture of the solvent, irrdition dose, type of impurity et nd requires detiled investigtion for the development of LL dosimetri mterils (Chndr et l ). Colour entres in lkli hlides hve een studied for mny yers. Mohril nd Deshmukh () hd shown tht the olourtion in mirorystlline powders otined y rushing the eletrolytilly oloured single rystl is not stle. It is known tht the eletrolytilly produed olourtion in potssium hlides is lost within dy (Mohril nd Deshmukh ). The olour entres hve mostly een Author for orrespondene (sjdhole@rediffmil.om) studied in single rystls, while pplitions suh s dosimetry of the ionizing rdition using thermoluminesene (TL) nd lyoluminesene (LL) more often involves mesurements on powders. Ettinger () initited the pplition of LL to rdition dosimetry. It is generlly elieved tht the mehnism of olour entres prodution is similr for single rystls nd mirorystlline powder. Prodution of olour entres y γ -irrdition in NCl, KCl nd KBr is reported y Deshmukh nd o-workers (,,, ), in rystl nd mirorystlline powder. For development of LL dosimetry mterils, reserhers onentrted on n enhnement in LL intensity, oserved in ertin fluoresent (Atri nd Ettinger ; Klkr ), hemiluminesent solutions (Atri ; Chzhoor nd Mishr ) nd dye lsers (Shfer ). Reently, Shu nd o-workers () studied prtile size effet of KCl : Sr nd onluded tht the lyoluminesene intensity nnot e diretly orrelted to the rdiolysis produt (olour entre onentrtion) or the dissolution rte ut it depends on oth ftors simultneously. Suh studies would e helpful in providing informtion for lyoluminesene dosimetry nd etter insight into the kinetis of retions responsile for LL emission. It would definitely dd to our knowledge of defet intertions in generl nd prtiulrly in solids. Kher et l () nd Pupplwr et l () prepred phosphors for mesurement of rdition dose sed on ML nd LL tehnique, respetively y using the rre erth mterils s dopnt. Bngru nd o-workers (Bngru nd Murlidhrn ; Bngru et l ) lso reported the enhned luminesent properties nd thermoluminesene studies in lkli hlides y doping rre erth mterils. Mny lkli hlide sed mterils like LiF exhiit importnt dosimetri properties. The study of luminesene properties in lkli hlides is hllenging tsk to find out the possile dosimetri mteril y using lyoluminesene tehnique in the development of rdition dosimetry.

2 P M Bhujl nd S J Dhole In this pper, we report the dependene of the nture of the rdiolysis produts, LL in (K N )Br : Ce phosphor (onsidered s (KN)Br : Ce for onveniene, throughout the pper) in powder form nd omprison of it with LL hrteristis of KBr : Ce nd NBr : Ce mterils.. Experimentl All phosphors ontining different onentrtions of Ce + ( mol%) were prepred y wet hemil method. For the preprtion of (K x N x )Br mteril equimolr mss of KBr nd NBr mterils were dissolved in distilled wter. The prepred mteril ws (K N )Br, ut for onveniene it is referred to s (KN)Br in this pper. For preprtion of (KN)Br : Ce, KBr : Ce nd NBr : Ce, the required onentrtions of Ce were dded in the solution of (KN)Br, KBr nd NBr, respetively. Then the solutions were evported t C in n oven for out dys in ontrolled mnner. The rerystllized residues were normlly rushed to powder, nd then heted t Cin furne for h nd quenhed. Anlytil regent grde hemils were used in the present investigtion. The smples were exposed to γ -rys dose from Co soure hving dose rte of kgy/h. Lyoluminesene ws studied with the usul set up onsisting of LL ell, photomultiplier tue (RCA ), mplifier nd reorder t room temperture (Dhole et l ; Dhikr et l ). Distilled wter ontining mol% luminol ws used s solvent. For reording the LL, mg smple ws dissolved in ml solvent, injeted y syringe into test tue hving high trnspreny pled lose to the window of PMT. All smples were stored in the drk t room temperture during experiments. All experiments were performed under identil onditions for mny times to ensure reproduiility.. Results nd disussion. Lyoluminesene studies The irrdition of lkli hlides produes oth trpped eletron olour entres nd trpped hole olour entre. Aording to the mehnism desried y Atri () when n energized lkli hlide rystl is dissolved, the entire proess of LL tkes ple in two stges: one in the solid phse of the smple when it is irrdited with γ -rys or X-rys nd the other in the liquid phse when it undergoes dissolution. When n lkli hlide rystl dissolved in wter, the two effets our simultneously. An eletron is relesed from n F entre nd hydrted eletron (eq ) is formed. The lrge quenhing effet of the hydrted eletron eptors indites tht the relesed F-entre undergoes hydrtion efore its reomintion with V entre. The rpid reomintion of the hydrted eletron with V entre t the wter solid interphse gives luminesene. The hydrtion proess tkes ple in very short time. The rte t whih light is produed depends on the diffusion onstnt of the hydrted eletron nd the vilility of its ounterprt (the V entre) t the wter solid interphse. The presene of oth F nd V entres together is essentil for exhiition of the LL phenomenon. Shemtilly the proess n e written s follows: e trpped + H O e q, () e q + X X q, () X q X q + hν, () where X = Cl,Br nd I et. It is possile tht steps () nd () n our together without the intermedite stte, i.e. the formtion of Xq. A similr mehnism ws lso suggested y Ahnstrom (). Ettinger nd Puite () investigted typil pplitions of LL mteril in dosimetry. mg of irrdited LL mteril ws dissolved in suitle solvents nd the LL yield ws mesured in terms of the investigted light intensity per mg. However, in intervity gmm rdition therpy only out mg of the smple is reommended to void degrdtion. However, to void the role of mss effet in LL yield smll mount of prepred phosphor, i.e. mg, ws tken for eh mesurement of LL intensity nd the results re shown for LL intensity per mg, in this investigtion. Consistent with the oservtions of Atri (), it ws found tht ddition of smll quntity of luminol inresed LL intensity y orders of mgnitude. It ws found tht the optimum luminol onentrtion ws mol % nd ph of the solvent ws. Lyoluminesene, using wter ontining luminol s solvent, in (KN)Br(pure) nd (KN)Br : Ce( mol%) is shown in figure. LL glow urves show isolted single pek inditing tht only one type of luminesene entre is formed during irrdition y γ -rys in eh smple. For ll (KN)Br : Ce smples the LL intensity is more thn (KN)Br(pure) smple. Speifilly for (KN)Br : Ce( mol%), LL intensity pek height is two times higher s ompred to pure (KN)Br mteril. The oserved LL is due to the dissolution of mterils in wter ontining mol% luminol s solvent trps re relesed. The enhnement of LL intensity in Ce doped (KN)Br smples indites tht more trpping entres re formed during irrdition. This hrteristi is very pplile for development of LL dosimetri mteril.. Effet of dopnt onentrtions on LL intensity Signifint enhnement of the lyoluminesene light yield in mino ids re otined if terium ions re present in the solution, i.e. ddition of rre erth ions to solvent used in lyoluminesene results in n inrese of light intensity (Ettinger nd Anunuso ). In the present investigtion, rre erth mteril (i.e. Ce ion) is present in the solutes, i.e. in the prepred mterils. The enhnement of the lyoluminesene intensity is lso oserved.

3 Lyoluminesene in Ce + tivted (KN)Br phosphor LL intensity (ritrry units) d e f g Time (s) Figure. LL glow urve of (KN)Br(pure) nd (KN)Br : Ce ( mol%), dissolved in wter ontining luminol, exposed to gmm dose of kgy. () (KN)Br(pure), () (KN)Br : Ce( mol%), () (KN)Br : Ce( mol%), (d) (KN)Br : Ce ( mol%), (e) (KN)Br : Ce( mol%), (f) (KN)Br : Ce( mol%) nd (g) (KN)Br : Ce( mol%). Pek LL intensity (ritrry units) Conentrtion of Ce doped in (KN)Br (mol%) Figure. Vrition of pek LL intensity with different onentrtions of Ce doped in (KN)Br, exposed to gmm dose of kgy. Figure shows vrition of pek LL intensity with different onentrtions of Ce doped in (KN)Br. LL intensity is found to e dependent on the onentrtion of Ce impurity ions in the host mteril. LL intensity eomes sturted t mol% of Ce doped in (KN)Br due to onentrtion quenhing nd LL intensity dereses ove mol% due to ggregtion of impurity ions. Low onentrtion of impurity ions shows mximum lyoluminesene intensity nd ost-wise is desirle hrteristi for the development of mterils for rdition dosimetry. Figure shows omprison of vrition of LL intensity with dopnt onentrtions. LL intensity for NBr : Ce mteril is more thn KBr : Ce smple nd the LL intensity of (KN)Br : Ce mteril is in etween the LL intensities of KBr : Ce nd NBr : Ce mterils. LL intensity of (KN)Br : Ce is more thn KBr : Ce smple nd nerer to it. In the (KN)Br : Ce mterils, LL intensity dereses s ompred to NBr : Ce powder. This my e due to intertion or orienttion of ioni rdius of K + ion with the ioni rdius of N + ion in the (KN)Br : Ce mterils, sine the ioni rdius of K + ion is pm nd N + ion is pm, i.e. the ioni rdius of oth the ions is different. Formtion of olour entres in this intertion s well s the relese of luminesene entres during dissolution re responsile for LL intensity of (KN)Br : Ce mterils.. Dependene of LL on rdition dose Figure shows vrition of pek LL intensity with γ -rys exposure of (KN)Br(pure) nd (KN)Br : Ce ( mol%). LL intensity linerly inreses with γ -rys exposure up to kgy high exposure. For the (KN)Br(pure) mteril, the LL intensity lso linerly inreses up to. kgy γ -rys dose. But for Ce-doped smple, the omprtive inrese in LL intensity is found to e more. When lkli hlide rystl is exposed to high energy rdition like γ -rys or X-rys, it results into exittion of eletrons of hlide toms from vlene nd to ondution nd. Some of the exited Pek LL intensity (ritrry units) Conentrtion of Ce doped (mol%) Figure. Comprison of vrition of pek LL intensity with different onentrtions of Ce doped in () KBr, () NBr nd () (KN)Br, exposed to gmm dose of kgy.

4 P M Bhujl nd S J Dhole Pek LL intensity (ritrry units) Gmm exposure (kgy) Figure. Vrition of pek LL intensity with different gmm exposures of () (KN)Br(pure) nd () (KN)Br : Ce ( mol%). Pek LL intensity (ritrry units) Gmm exposure (kgy) Figure. Comprison of vrition of pek LL intensity with different gmm exposure of () KBr : Ce( mol%), () NBr : Ce( mol%) nd () (KN)Br : Ce( mol%). eletrons return immeditely from the ondution nd to the vlene nd. However, some of the eletrons in the ondution nd get trpped in the negtive ion vnies during their movement nd onsequently, the formtion of olour entres tkes ple. Initilly the numer of olour entres inreses with the rdition doses given to the rystls nd therey, LL intensity inreses. However, if the rystls re irrdited for long durtion, the reomintion etween eletrons nd holes tkes ple nd onsequently, the density of olour entres in the rystls ttins sturtion vlue. In ft, LL intensity ttins sturtion vlue for high rdition doses given to the rystllites (Chndr et l ). In figure, omprison of vrition of LL pek intensity with different gmm exposures is shown. From our results it is seen tht the pek LL intensity of KBr : Ce( mol%) smple inresed sulinerly up to kgy nd then it eme sturted. For the NBr : Ce( mol%) mteril, LL pek intensity inresed sulinerly up to kgy.but for (KN)Br : Ce( mol%) mteril, the pek intensity inresed linerly up to kgy. Though the LL intensity for (KN)Br : Ce( mol%) smple is found to e wek in omprison to tht of NBr : Ce( mol%) smple, ut it inreses linerly with gmm exposure. This response urve my ply n importnt role for ionizing rdition dosimetry.. Fding Figure shows effet of storge of (KN)Br : Ce( mol%) smple in drk t room temperture on the pek LL intensity nd figure shows omprison of fding in LL intensities in Pek LL intensity (ritrry units) Time (dys) Figure. Effet of storge on LL glow pek in (KN)Br : Ce( mol%), exposed to gmm dose of kgy. the smples viz. KBr : Ce( mol%), NBr( mol%) nd (KN)Br : Ce( mol%). From these grphs, it is seen tht the LL pek intensity of the smples is quite stle sine there is not muh fding of intensities s the loss of olourtion is less in drk (Hersh,; Arnikr et l ; Mohril ).

5 Lyoluminesene in Ce + tivted (KN)Br phosphor Pek LL intensity (ritrry units) Time (dys) Figure. Comprison of effet of storge on LL glow pek in () KBr : Ce( mol%), () NBr : Ce( mol%) nd () (KN)Br : Ce( mol%), exposed to gmm dose of kgy. Tody the mesurement of high dose rdition is hllenging tsk nd it is required for identl dosimetry. The prepred (KN)Br : Ce( mol%) phosphor shows dose mesurements possile up to kgy gmm exposure using lyoluminesene tehnique nd therefore, the prepred (KN)Br : Ce( mol%) phosphor my e useful for identl dosimetry.. Conlusions Lyoluminesene in (KN)Br : Ce, KBr : Ce nd NBr : Ce mterils re reported. LL in these mterils shows single isolted LL pek due to the formtion of only one type of luminesene entre. LL pek intensity is dependent on onentrtion of Ce + doping in the host mteril in ll the smples. LL pek intensity inreses linerly with γ -ry exposure up to kgy high dose for (KN)Br : Ce( mol%) mteril. For KBr : Ce( mol%) nd NBr : Ce( mol%)smples the pek intensity inreses sulinerly up to kgy nd kgy, respetively. Fding in the prepred smples is lso miniml. These hrteristis show tht the prepred (KN)Br : Ce( mol%) phosphor my e pplile for LL dosimetry for high dose mesurement, i. e. for the se of identl ionizing rdition dosimetry. Aknowledgement One of the uthors (PMB) is grteful to UGC, New Delhi, for providing finnil ssistne to rry out this work under the minor reserh projet sheme. Referenes Ahnstrom G At Chem. Snd. Arnikr H J, Deo V K nd Gijre A S J. Univ. Poon Arnikr H J, Ro B S M, Gijre M A nd Srdesi S S J. Chem. Phys. Atri N A nd Ettinger K V Nture Atri N A J. Lumin. Bngru S nd Murlidhrn G J. Lumin. Bngru S, Murlidhrn G nd Brhmnndhn G M J. Lumin. Chndr B P, Tiwri R K, Reenu Mor nd Bisen D P J. Lumin. Chzhoor J S nd Mishr U C J. Lumin. Dhikr Prdeep B, Dhole S J nd Mohril S V J. Instrum. So. Indi Deshmukh B T, Omnwr S K nd Mohril S V J. Phys. C: Solid Stte Phys. Deshmukh B T, Rughwni M G nd Mohril S V Cryst. Ltt. Defets Amorph. Mter. Deshmukh B T, Rughwni M G, Belorkr R B nd Mohril S V J. Phys. C: Solid Stte Phys. Deshmukh B T, Kokode N S nd Mohril S V J. Phys. C: Solid Stte Phys. Dhole S J, Bhujl P M, Dhole N S nd Mohril S V Nul. Instrum. Meth. Phys. Res. B Ettinger K V Tehnil Report, University of Aerdeen Ettinger K V nd Puite K J Int. J. Appl. Rdit. Isotope Ettinger K V nd Anunuso C I Nt. J. Appl. Rdit. Isotope Hrvey E N A history of luminesene (Phildelphi: The Amerin Philosophil Soiety) Hersh H N J. Opt. So. Am. Hersh H N J. Chem. Phys. Klkr C D Rdiohem. Rdio. Lett. Kher R S, Dhole S J, Pndey R K, Updhyy A K nd Khokhr M S K Rdit. Eff. Def. Solids Mohril S V PhD Thesis, Ngpur University, Ngpur Mohril S V nd Deshmukh B T Cryst. Ltt. Def. Pupplwr S P, Dhole S J nd Animesh Kumr Indin J. Pure Appl. Phys. Reynolds G T J. Lumin. Shu V, Brhme N, Bisen D P nd Shrm R J. Optoeletron. Biomed. Mter. Shfer F P Dye lsers (Selwyn nd Stemfeld)