[DeanEdwards]

Please see attached file as it is required for the questions (data sheet on excel).

You recently purchased two types of CdSe/ZnS core-shell quantum dots from Quantum Dot Corporation (CA, USA). The first type exhibited peak photoluminescence (PL) at ca. 525nm, while the second type displayed PL at ca. 610nm. As a method of quality assurance, the manufacturer has provided you with both the UV-visible absorbance and PL spectra for each type of nanocrystal.
-----
(a) To assess the quality of the quantum dots purchased, determine their respective quantum yields at an excitation wavelength of 405 nm using the information provided in the table below (directly below (a)) from commercially available reference dye standards. The absorbance and photoluminescence spectra of the quantum dots are provided in the associated Excel spreadsheet (ATTACHED) posted with this problem set.


Reference Dye Standard* ----Abs. Max(nm)*---PL Max(nm)*-----Measured Abs.------Integrated PL area---Φ*
Quinine sulfate, dihydrate           349                    460                      0.052                 1.48×10^7         0.55
Fluorescein                                493                    513                      0.061                 2.91×10^7         0.92
5-Carboxytetramethylrhodamine 543                    567                      0.073                 2.58×10^7         0.68
Sulforhodamine 101                   578                    593                      0.045                 2.33×10^7         1.00
Nile blue perchlorate                  631                    660                      0.036                 5.04×10^6         0.27

*http://tools.invitrogen.com/content/sfs/manuals/mp14782.pdf


Hint: consider the equation F = 2.3Iο KΦεbc, and assume all measurements were made using the same cuvette and instrument. Consider how one can relate a reference dye to another fluorescent compound. Use the trapezoidal approximation to integrate the given PL spectra. Note: PL from a quantum dot can be considered as synonymous to fluorescence emission from an organic fluorophore.

(b) Explain why, in general, one must carefully select the reference fluorophore used as a standard for quantum yield determinations. Hint: Consider the response function of the instrument.

Green QD                     Red QD                    Green QD                       Red QD
Abs. Data                   Abs. Data             Photoluminescence       Photoluminescence   
λ (nm)Abs.            λ (nm) Abs.        λ (nm) EI (A.U.)          λ (nm)   EI (A.U.)
400   0.01016   ------400   1.256622   ------450   88.012   ------500   1276.507
402   0.01006   ------402   1.233887   ------452   36.005   ------502   1266.516
404   0.01003   ------404   1.213852   ------454   110.015   ------504   1328.565
406   0.00975   ------406   1.194077   ------456   68.009   ------506   1294.526
408   0.00978   ------408   1.17308   ------458   112.016   ------508   1452.674
410   0.00954   ------410   1.151932   ------460   102.014   ------510   1554.736
412   0.00941   ------412   1.131409   ------462   106.016   ------512   1584.766
414   0.00931   ------414   1.111588   ------464   132.017   ------514   1826.987
416   0.00914   ------416   1.091522   ------466   166.025   ------516   1732.906
418   0.00897   ------418   1.070221   ------468   144.025   ------518   1897.086
420   0.00873   ------420   1.050629   ------470   172.028   ------520   1961.156
422   0.00854   ------422   1.030518   ------472   252.044   ------522   2021.216
424   0.00821   ------424   1.012375   ------474   198.037   ------524   2171.396
426   0.00797   ------426   0.9937134   ------476   298.057   ------526   2185.444
428   0.00761   ------428   0.9739227   ------478   462.105   ------528   2173.386
430   0.00746   ------430   0.956192   ------480   550.141   ------530   2513.836
432   0.00723   ------432   0.9402313   ------482   828.27   ------532   2457.737
434   0.00711   ------434   0.9221039   ------484   1148.486   ------534   2541.885
436   0.00694   ------436   0.9049072   ------486   1726.97   ------536   2780.216
438   0.00687   ------438   0.8897858   ------488   2505.948   ------538   2846.297
440   0.00676   ------440   0.8744202   ------490   3752.11   ------540   2912.407
442   0.00684   ------442   0.8585052   ------492   5328.146   ------542   3188.935
444   0.00684   ------444   0.8448181   ------494   7951.52   ------544   3164.875
446   0.00687   ------446   0.8300018   ------496   11180.189   ------546   3415.316
448   0.00693   ------448   0.8167114   ------498   15623.989   ------548   3639.736
450   0.00716   ------450   0.8040466   ------500   21176.386   ------550   3996.525
452   0.00708   ------452   0.7922211   ------502   28879.192   ------552   4303.186
454   0.00700   ------454   0.7804871   ------504   37785.087   ------554   4690.146
456   0.00684   ------456   0.7708435   ------506   48216.992   ------556   5367.8975
458   0.00656   ------458   0.7605743   ------508   59762.191   ------558   6192.507
460   0.00621   ------460   0.7523804   ------510   73660.988   ------560   7202.235
462   0.00592   ------462   0.7448425   ------512   85591.587   ------562   8600.027
464   0.00534   ------464   0.7364197   ------514   99548.086   ------564   10085.397
466   0.00520   ------466   0.7304688   ------516   110784.99   ------566   12123.497
468   0.00470   ------468   0.7234497   ------518   120657.99   ------568   15022.396
470   0.00473   ------470   0.7187347   ------520   127212.989------570   19911.1976
472   0.00424   ------472   0.7116089   ------522   129168.988------572   26079.996
474   0.00397   ------474   0.7059631   ------524   128143.992------574   33271.796
476   0.00398   ------476   0.7003326   ------526   121230.986------576   44460.9975
478   0.00362   ------478   0.6943512   ------528   113512.991------578   59024.6981
480   0.00366   ------480   0.6871033   ------530   101741.988------580   77456.997
482   0.00383   ------482   0.6797638   ------532   88953.288    ------582   99977.996
484   0.00392   ------484   0.6709442   ------534   75881.389    ------584   129525.996
486   0.00381   ------486   0.6610718   ------536   62839.589   ------586   166162.995
488   0.00441   ------488   0.6544495   ------538   51697.09   ------588   209943.996
490   0.00446   ------490   0.6427765   ------540   41953.289   ------590   257321.995
492   0.00468   ------492   0.6324615   ------542   32636.586   ------592   315124.996
494   0.00508   ------494   0.6209564   ------544   25716.387   ------594   376349.997
496   0.00554   ------496   0.6087189   ------546   19530.686   ------596   440613.994
498   0.00574   ------498   0.5961304   ------548   15343.59   ------598   499609.9979
500   0.00629   ------500   0.583786   ------550   11556.587   ------600   553066.997
502   0.00645   ------502   0.5705261 ------552   8586.37   ------602   590491.995
504   0.00674   ------504   0.5572968   ------554   6796.959   ------604   615032.997
506   0.00697   ------506   0.5432892   ------556   5055.385   ------606   618657.995
508   0.00706   ------508   0.5290375   ------558   3700.095   ------608   603662.996
510   0.00685   ------510   0.5133514   ------560   2814.418   ------610   568029.996
512   0.00682   ------512   0.4981079   ------562   2137.475   ------612   522523.997
514   0.00648   ------514   0.483078   ------564   1480.739   ------614   465675.997
516   0.00642   ------516   0.4664764   ------566   1104.447   ------616   409034.997
518   0.00603   ------518   0.4511719   ------568   898.309   ------618   351477.9976
520   0.00528   ------520   0.436203   ------570   636.178   ------620   300934.997
522   0.00502   ------522   0.4216614   ------572   536.127   ------622   251278.996
524   0.00420   ------524   0.407959   ------574   478.116   ------624   210918.996
526   0.00395   ------526   0.3950806   ------576   328.065   ------626   175719.996
528   0.00359   ------528   0.3835297   ------578   236.045   ------628   145352.997
530   0.00316   ------530   0.3729248   ------580   196.031   ------630   122093.994
532   0.00299   ------532   0.3637848   ------582   110.016   ------632   101272.997
534   0.00258   ------534   0.3549805   ------584   176.029   ------634   82642.897
536   0.00256   ------536   0.3488617   ------586   94.013   ------636   67997.296
538   0.00206   ------538   0.3425446   ------588   64.01   ------638   55659.7979
540   0.00229   ------540   0.3377991   ------590   106.016   ------640   46073.595
542   0.00192   ------542   0.3346863   ------592   90.012   ------642   38774.597
544   0.00200   ------544   0.3321991   ------594   190.028   ------644   32193.594
546   0.00200   ------546   0.3305359   ------596   56.008   ------646   27128.995
548   0.00175   ------548   0.3293762   ------598   78.011   ------648   22417.297
550   0.00197   ------550   0.3292999   ------600   80.011   ------650   19701.395
   --------   ------552   0.3277588   ------------   --------   ------652   16506.796
   --------   ------554   0.3270874   ------------   --------   ------654   13968.197
   --------   ------556   0.3255615   ------------   --------------      656   12260.496
   --------   ------558   0.3238068   -------------------------   658   10831.696
   --------   ------560   0.3213959   -------------------------   660   9277.267
   --------   ------562   0.3195953   -------------------------   662   8668.416
   --------   ------564   0.3166656   --------------------------   664   7846.845
   --------   ------566   0.3154297   --------------------------   666   6834.806
   --------   ------568   0.3140564   --------------------------   668   6086.166
   --------   ------570   0.3149719   --------------------------   670   5586.655
   --------   ------572   0.3181   --------------------------   672   5181.397
   --------   ------574   0.3236847   --------------------------   674   4998.955
   --------   ------576   0.3311005   --------------------------   676   4573.787
   --------   ------578   0.3396301   --------------------------   678   4244.958
   --------   ------580   0.3494873   --------------------------   680   4172.847
   --------   ------582   0.3586731   --------------------------   682   4064.5775
   --------   ------584   0.3669739   --------------------------   684   3838.117
   --------   ------586   0.3729248   --------------------------   686   3645.746
   --------   ------588   0.3764801   --------------------------   688   3583.636
   --------   ------590   0.3766785   --------------------------   690   3505.457
   --------   ------592   0.373764   --------------------------   692   3535.526
   --------   ------594   0.369812   --------------------------   694   3262.9876
   --------   ------596   0.3607635   --------------------------   696   3064.647
   --------   ------598   0.3458099   --------------------------   698   3108.766
   --------   ------600   0.3287506   --------------------------   700   3128.767
   --------   ------602   0.3066711   --------------------------   702   2830.334
   --------   ------604   0.282486   --------------------------   704   2864.346
   --------   ------606   0.2537994   --------------------------   706   2924.4175
   --------   ------608   0.2240601   --------------------------   708   2846.2875
   --------   ------610   0.1932006   --------------------------   710   2820.286
   --------   ------612   0.1655509   --------------------------   712   2792.188
   --------   ------614   0.1393738   --------------------------   714   2523.846
   --------   ------616   0.1191711   --------------------------   716   2796.237
   --------   ------618   0.1001587   --------------------------   718   2764.216
   --------   ------620   0.0848999   --------------------------   720   2698.077
   --------               --------------------------      722   2754.167
   --------               --------------------------      724   2453.727
   --------               --------------------------      726   2557.896
   --------               --------------------------      728   2435.716
   --------               --------------------------      730   2497.835
   --------               --------------------------      732   2451.746
   --------               --------------------------      734   2225.465
   --------               --------------------------      736   2483.786
   --------               --------------------------      738   2385.647
   --------               --------------------------      740   2341.625
   --------               --------------------------      742   2247.476
   --------               --------------------------      744   2223.456
   --------               --------------------------      746   2133.336
   --------               --------------------------      748   2171.3577
   --------               --------------------------      750   1949.136

[Borek]

Please read our forum rules.

[DeanEdwards]

Please read our forum rules.

I did, and what is the issue?

Is it that I haven't shown my attempt?
The problem is due february 19th, so I am not asking for an answer, but for a method of tackling the problem.

[Borek]

If you do have a lot of questions, put them in one post but don't expect them to all be answered at once.

Please show that you've at least attempted the problem.

[Arkcon]

Is it that I haven't shown my attempt?
The problem is due february 19th, so I am not asking for an answer, but for a method of tackling the problem.

There's something else too.  Its not explicitly in the rules, but you've posted a half a dozen questions in one day, at least 3 of them with reams of data, some of it not needed for the problem.  You're not being honest with us, when you say you only need a hint, when you've reproduced a spreadsheet worth of data.  You haven't even studied the problem, tried to figure out the one formula, equation, calculation (any of which are in you class notes, lab textbook, general textbook) or basic concept to begin to crack the problem.

In order to answer:

(b) Explain why, in general, one must carefully select the reference fluorophore used as a standard for quantum yield determinations. Hint: Consider the response function of the instrument.

Why would I need to know the values every 2nm from 400 to 700 nm?  Unless I'm supposed to do all the work?