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木木Slam新蟲 (小有名氣)
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[求助]
發(fā)射光譜的中的Gaussian Profile是怎么得到的？ 已有1人參與
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做的事稀土摻雜熒光粉。 很多文獻(xiàn)做出來的PL都是非對(duì)稱的，然后就會(huì)通過Gaussian Profile來進(jìn)一步說明。比如Eu2+占據(jù)了LiSr4(BO3)3中的Sr的位置，通過高斯擬合就會(huì)出現(xiàn)子峰，通過子峰的強(qiáng)度高低來說明是偏短波還是長波。本來以為出峰位置是自己選的（用的origin里的Analysis-Fitting-Fit multi-peaks），但是同一個(gè)材料可能分出不一樣的子峰甚至子峰數(shù)目，所以肯定是我想的不對(duì)，想請(qǐng)教大家。附上圖片和文獻(xiàn)。 第一篇，F(xiàn)ig.4的（d）圖中的Inset圖 As shown in Fig. 4(a), when excited by 272 nm, all samples exhibit a broad emission band covering from 520 to 750 nm. Besides, some obvious sharp peaks (at 594, 616 and 706 nm) overlapping with the broad band also can be observed. The broad band is ascribed to the 4f65d1–4f7 transitions of Eu2t. The sharp peaks are related to the characteristic emission of Eu3t, which indicates the incomplete reduction of Eu3t-Eu2t. Under the excitation by 305, 365 and 420 nm, each sample shows a broad asymmetric emission band centered at ?620 nm, which can be seen in Fig.4(b)–(d). The emission band can be deconvoluted into two Gaussian peaks at ?613 (peak 1) and 663 nm (peak 2) (see in the inset of Fig. 4(d)), which infers the occupation of Eu2t at two different Sr2t sites. The fitting result differs from the result by Wang et al. ， which may be caused by the different synthesis processes.  第二篇，F(xiàn)ig.3的（a）（b）圖 The blue emission band centered at 423 nm can be well decomposed into four Gaussian profiles peaking at 402(i), 436(ii), 468(iii) and 515(iv) nm, respectively. In such a case, the presence of the Gaussian peaks i, ii and iii, iv arose from the emission of Ce3t-occupancy for Sr(1) and Sr(2) sites, respectively. Based on the structural analysis above, the replacement of nearest-neighbor oxygen-richer Sr(2) by Ce3t ions (CeSr(2)) resulted in the larger crystal field splitting and the lower center of gravity of the 5d levels of Ce3t (due to covalency and nephelauxetic effect), compared to the substitution of Sr(1) by Ce3t ions (CeSr(1)). As a result, the position of the lowest 5d excited level of Ce3t is lower for CeSr(2) than that for CeSr(1). Naturally, the emission from CeSr(2) shows red-shift in comparison with that from CeSr(1). Thus, it’s reasonable that the Gaussian profiles peaking at 402(i) and 436(ii) nm are both ascribed to the 5d1 -4f1 transition of CeSr(1), and the remaining two peaks (iiiand iv) at longer wavelength are attached to that of CeSr(2). In addition, the sub-bands i and iii originate from the 5d1-2F5/2 transition of Ce3t, and the remaining two are attached to the 5d1-2F7/2 ransition of Ce3t. Corresponding to Ce3t-occupation for Sr(1) and Sr(2) sites, the energy difference between 4f ground states 2 F5/2 and 2F7/2 of Ce3t is 1939 cm1 and 2070 cm1,respectively. Both differences are in good agreement with the the theoretical value of 2000 cm1 for spin–orbit splitting between the 2F7/2 and 2F5/2 levels. The PLE and PL spectrum of single Eu2t-activated LiSr4(BO3)3 phosphors is depicted in Fig. 3(b). The excitation spectra peaking at 420 nm exhibits a broad absorption band (lem¼612 nm) from 320 to 493 nm due to the typical 4f7(8S7/2)-4f6 5d transition of Eu2t ions. Upon around 420 nm excitation, the emission spectra exhibits a single broad band with the peak at around 612 nm, which is assigned to the typical 4f65d-8S7/2 transition of Eu2t. Obviously, the broad emission band appeared to be symmetric by virtue of the superposition of two Gaussian peaks 580(v) and 646(vi) nm. The peaks v and vi correspond to 4f65d-4f7 transitions of Eu2t ions located at Sr(1) and Sr(2) sites, respectively, about which the interpretation is that it is in good accordance with Ce3t-occupation for Sr(1) and Sr(2) sites. Moreover, it is known that Eu2t ions prefer more to occupy Sr(2) sites than to occupy Sr(1) sites by the comparison of the intensity of Gaussian peaks vi and v. Besides, a significant spectral overlap is observed by the comparison between the emission band of LiSr4(BO3)3:Ce3t (see Fig. 3(a)) and the excitation band of Eu2t-activated LiSr4(BO3)3 (see Fig. 3(b)). According to Dexter0 s theory [17], it is expected that the effective resonancetype energy transfer from a sensitizer Ce3t to an activator Eu2t can occur in Ce3t/Eu2t co-doped LiSr4(BO3)3 phosphors.  第一篇：The exploration and characterization of an orange emitting long persistent luminescence phosphor LiSr4(BO3)3:Eu2+ 第二篇：Potential tunable white-emitting phosphor LiSr4(BO3)3:Ce3+, Eu2+ for ultraviolet light-emitting diodes 請(qǐng)教大家了！�。∠Ｍ写笊窕蛘哂龅竭@個(gè)問題的說說�。�！ |
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bible2
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【答案】應(yīng)助回帖
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感謝參與，應(yīng)助指數(shù) +1
木木Slam: 金幣+10, ★★★很有幫助 2016-01-07 19:13:15
感謝參與，應(yīng)助指數(shù) +1
木木Slam: 金幣+10, ★★★很有幫助 2016-01-07 19:13:15
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必須明白的前提是：分峰是一個(gè)基于物理實(shí)際的數(shù)學(xué)方法。 想必你也知道，LiSr4(BO3)3中，Sr有兩個(gè)晶體學(xué)位置，Eu取代Sr。當(dāng)Eu在不同位置上發(fā)光時(shí)，由于“每個(gè)”Eu周圍的晶體學(xué)位置不同，“每個(gè)”Eu發(fā)光的位置也不同，（統(tǒng)計(jì)學(xué)上）表現(xiàn)為一個(gè)寬譜發(fā)射可以分為兩個(gè)峰（文章1） 文章二中，Ce3+有4個(gè)峰，是因?yàn)椤懊總�(gè)”Ce的發(fā)射峰都可分解為2D3/2→2F5/2 和 2D3/2→2F7/2這兩個(gè)躍遷，2（晶體學(xué)位置）×2（躍遷），所以4個(gè)峰。 當(dāng)然文章1和文章2中，Eu的分峰數(shù)據(jù)有差別，這個(gè)有幾種原因，比如分峰數(shù)學(xué)處理的技巧有差異（選擇的峰形不同等），測量儀器的結(jié)構(gòu)有區(qū)別（光譜儀探測器的類型不同，這個(gè)可以理解為不同照相機(jī)拍出來的照片顏色肯定不是完全相同），或者是得到的數(shù)據(jù)經(jīng)過的校正不同，等等。 |
2樓2016-01-07 10:30:31
木木Slam
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3樓2016-01-07 19:12:52
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4樓2016-01-07 19:48:58
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5樓2016-01-07 19:50:38
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6樓2016-01-07 20:14:14
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這篇文章說發(fā)射峰出現(xiàn)短波偏移，然后說well fitted，請(qǐng)問怎么看出來是well fitted了？  Figure 4b shows excitation and emission spectra of the Ba5Si8O21:Eu2+ and Ba5Si8O21:Eu2+,Dy3+ phosphors at room temperature. Under the excitation at 344 nm, both samples exhibit a broad emission from 380 to 680 nm, with an emission peak at 473 nm. The broadband emission corresponds to the spin-allowed transition from the 4f to the 5d state of Eu2+ ions, and the excitation spectra monitored at 473 nm covers a broad spectral region from 250 to 455 nm. It should be noticed that the characteristic sharp peaks of Dy3+ were not detected, which can be attributed to the electrical transitions of Dy3+, 4F9/2 → 6H13/2 for 580 nm and 4F9/2 → 6H15/2 for 486 nm, respectively.(26) It is indicated that the phosphors have only one kind of emitter that is a Eu2+ cation. As mentioned in the crystal structure of Ba5Si8O21, there are three crystallographically nonequivalent Ba2+ sites which can be substituted by the Eu2+ cation to produce three nonequivalent emission centers of Eu2+ in Ba5Si8O21. Although the 4f electrons of Eu2+ are not sensitive to their surroundings, the 5d electrons are split by the crystal field. When crystal field is weak, the emission band of Eu2+ trends to the short wavelength.(27, 28) Therefore, the asymmetric emission of Ba5Si8O21:Eu2+,Dy3+ was well fitted by three Gaussian profiles (i.e., the green profile in Figure 4b). 文獻(xiàn)：http://pubs.acs.org/doi/full/10.1021/ic5026312 title：Sunlight Activated Long-Lasting Luminescence from Ba5Si8O21: Eu2+,Dy3+ Phosphor |
7樓2016-01-07 20:18:28
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8樓2016-01-07 20:28:24
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9樓2016-01-07 20:30:47
木木Slam
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10樓2016-01-07 20:43:02
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