## 3 Results and Discussion  
The main absorption bands of materials of biological origin, such as living bacteria, spores, and fungi, occur around 280 and 340 nm. They cover a wide range of excitation and emission, including protein and NADH bands. The pollens additionally display a strong band allowing excitation in visible blue light ranging from 400 nm to 470 nm. Examples of emission characteristics of plant pollens excited with 280, 340, and 460 nm, respectively, are shown in Figure 3.  
Therefore, the use of 460 nm excitation can improve the discrimination of pollens from other species. The excitation and emission peaks at 460 nm and 520 nm, respectively, are attributed to the carotenoids that are present in pollens. Emission spectra of aqueous solutions/suspensions of biological agents differ from those of dehydrated ones, as shown in the example of pure tryptophan (Figure 4). \begin{table}
\begin{tabular}{l l l} \hline \hline
**Biological Sample** & \multicolumn{1}{c}{**Source**} & **Abbrev.** \\ \hline _Bacillus cereus_ & ATCC 14579 & BC \\ _Bacillus cereus spores_ & ATCC 14579 & BCs \\ _Bacillus atrophaeus_ var. _globibi spores_ & ATCC 9372 & BGs \\ _Bacillus atrophaeus spores technical_ & MIHE (Warsaw, Poland) & BGst \\ _Bacillus megaterium_ & PCM (Wroclaw, Poland) 2006 & BM \\ _Bacillus megaterium spores_ & PCM (Wroclaw, Poland) 2006 & BMs \\ _Bacillus subtilis_ & ATCC 6633 & BS \\ _Bacillus subtilis spores_ & ATCC 6633 & BSs \\ _Bacillus thuringiensis_ & ATCC 10792 & BT \\ _Bacillus thuringiensis spores_ & ATCC 10792 & BTs \\ _Bacillus thuringiensis spores technical_ & MIHE (Warsaw, Poland) & BTst \\ _Testing spores_ & MIHE (Warsaw, Poland) & Sporal S \\ _Micrococcus luteus_ & ATCC 4698 & ML \\ _Escherichia coli_ & ATCC 25922 & EC \\ _Alternaria alternata_ & ATCC 6663 & AA \\ _Candida albicans_ & ATCC 18804 & CA \\ _Cladosporum herbarum_ & ATCC 28987 & CLH \\ _Penicillium chrysggeum_ & ATCC 9197 & PCH \\ _Penicillium breicompactum_ & ATCC 9056 & PBC \\ _Bernuda grass pollen_ & Duke Scientific Corp. (Palo Alto, CA, USA) & BER \\ _Corn pollen_ & Duke Scientific Corp. (Palo Alto, CA, USA) & COR \\ _Ragweed pollen_ & Duke Scientific Corp. (Palo Alto, CA, USA) & RAG \\ _Secale cereale pollen_ & Sigma-Aldrich (St. Louis, MO, USA) & SEC \\ _Paper mulberry pollen_ & Duke Scientific Corp. (Palo Alto, CA, USA) & PAP \\ _Artemisia tridentata pollen_ & Sigma-Aldrich (St. Louis, MO, USA) & ARTT \\ _Artemisia absinthtium pollen_ & Sigma-Aldrich (St. Louis, MO, USA) & ARTA \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Biological samples and list of their abbreviations. Additional emission modes are generated in the solid phase, and therefore, decay measurements are also possible for fluorescence excitation at 460 nm. The fluorescence lifetime data of the samples analyzed are presented in Table S1 in Supplementary Materials. Each group exhibited its best fit when using a three-component equation at an excitation of 280 nm. The three-exponential fit was observed for pollens at each examined excitation wavelength, which was also reported by [PERSON] et al. [50]. Several vegetative bacteria (EC--excited at 280 nm; BC, BS, ML, PA--excited at 340 nm; and BG, BS, BT--excited at 460 nm) showed two- or three-component fluorescence lifetimes reaching the same or similar Chi\({}^{2}\) values. Due to the complex composition of biological samples, at least two-component fitting produces satisfactory results. [PERSON] et al. [51] also obtained a three-exponential decay for pathogenic bacteria, although they calculated lifetimes about two times shorter for fast and intermediate components. Figure 5 shows fluorescence decays obtained at 280 nm excitation. The bacterial endospores presented more rapid decay than the vegetative bacteria and fungi. Figure 4: Fluorescence spectrum of tryptophan in solid (1) and in solution (2). Figure 3: Emission spectra of pollens: paper mulberry (**a**) and _Artemisia absinthtium_ (**b**). Excitation wavelengths 280, 340, and 460 nm.