Absorption and Fluorescence Emission Attributes of a Fluorescent Dye

Absorption and fluorescence emission attributes of a fluorescent dye: 2,3,5,6-tetracyano-p-hydroquinone.

Muhammad Zahida,b*, Günter Gramppb, AsimManshab,c, IjazAhamadBhattia, SadiaAsimb,c

aDepartment of Chemistry & Biochemistry, University of Agriculture Faisalabad, Pakistan.

bInstitute of Physical and Theoretical Chemistry, Graz University of Technology, Graz/Austria

c Department of Chemistry, GC University Faisalabad, Pakistan

Supporting information (Supplementary data)

Absorption spectra of TCHQ in various solvents
TCHQ in Ether

In low polarity solvents like ethers, the absorption spectra showed only one peak at 398 nm for different concentration as shown in the inset of Fig.S1.

Fig.S1: Absorption Spectra of TCHQ in diethylether for different concentrations.

1.2.TCHQ in acetone and acetonitrile

Two peaks were observed in the range of 300 to 600 nm formoderately polar solvents like acetone (Fig. S-2) and acetonitrile (Fig.S-3). Thefirst peak is in the range of 390-400 nm and the second peak is around 505 nm.

Fig. S-2: Absorption spectra of TCHQ in acetone for different concentrations.

Two peaks were observed at 392 nm and 502 nm for various concentrations of TCHQ in acetonitrile as shown in Fig. S-3. This non-linear decrease in the absorption intensity at two different wavelengths (392 nm and 502 nm) has been shown clearly in the Fig. S-4 (a) and Fig.S-4 (b).

Fig.S-3: Absorption spectra of TCHQ in acetonitrile at different concentrations.

Fig. S-4: (a) Absorbance and (b) normalized absorbance of TCHQ in acetonitrile (MeCN) for different concentrations at 392 nm and 502 nm.

1.3.TCHQ in water and ethanol

Two peaks of TCHQ were observed in water for most of the concentrations except very dilute ones (conc. < 1x10-5 M) as shown in Fig. S-5.Signal intensity at 460 nm has been decreasedrapidly as compared to the peak at 520 nm, with the decrease in concentration of the TCHQ in H2O as shown in Fig.S6.

Fig.S5: Absorption Spectra of TCHQ in H2O at different concentrations.

Fig. S6: (a) Absorbance and (b) normalizedabsorbance of TCHQ in H2O for different concentrations at 440 nm and 540 nm.

Absorption spectra of TCHQ after adding a small amount of water (less than2%) into the dilute solution of TCHQ (3 x 10-5 M) in absolute ethanol is shown in Fig.S-7.

Fig. S7: Absorption spectra of TCHQ in absolute ethanol and ethanol containing water (< 2%).

2.Fluorescence emission spectra of TCHQ in different solvents excited at various wavelengths

Fig.S-8.(a) Absorption,(b) fluorescence and (c) normalized fluorescence spectra of TCHQ in diethylether. The excitation wavelengths are 390 nm, 430 nm and 460 nm.

Fig.S-9.(a) Absorption, (b) fluorescence and (c) normalized fluorescence spectra of TCHQ in n- butylether. The excitation wavelengths are390 nm and 460 nm.

Fig.S-10.(a) Absorption, (b) fluorescence spectra of TCHQ in acetone excited at 515 nm.

Fig.S-11.(a) Absorption, (b) fluorescence and (c) normalized fluorescence spectra of TCHQ in acetonitrile. The excitation wavelengths are 390 nm and 515 nm.

Fig.S-12.(a) Absorption, (b) fluorescence and (c) normalized fluorescence spectra of TCHQ in ethanol + water (< 2 %). The excitation wavelengths are 460 nm, 515 nm and 550 nm.

Fig.S-13.(a) Absorpti*on, (b)fluorescence and (c) normalized fluorescence spectra of TCHQ in DMSO. The excitation wavelengths are515 nm, 570 nm and 670 nm.