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The thermal inactivation of BoNT/A, BoNT/A complex, BoNT/B, and BoNT/B complex in cow's milk in a pasteurization process similar to the industry standard is described. The high-temperature short-time (HTST) pasteurization process in the dairy industry is found to remarkably reduce the risk of consumer harm even if larger amounts of BoNT were deliberately released into the milk supply chain.

Due to the primogenic effect, the valence shells of divalent iron Fe(II) ([Ar]3d 6 ) and trivalent lanthanides Ln(III) ([Xe]4f n ) are compact enough to induce spin-state equilibrium for the 3d-block metal and atom-like luminescence for the 4f-block partner in Fe(II)-Ln(III) dyads. In the specific case of homoleptic pseudo-octahedral [Fe(II)N 6 ] units, programming spin crossover (SCO) around room temperature at normal pressure requires the design of unsymmetrical didentate five-membered ring chelating N ∩ N' ligands, in which a five-membered (benz)imidazole heterocycle (N) is connected to a six-membered pyrimidine heterocycle (N'). Benefiting from the trans influence, the facial isomer fac -[Fe(II)(N ∩ N') 3 ] 2+ is suitable for inducing SCO properties at room temperature in solution. Its connection to luminescent [LnN 6 O 3 ] chromophores working as non-covalent podates in the triple-stranded [Fe(II)Ln(L10) 3 ] 5+ helicates (Ln = Nd, Eu) controls the facial arrangement around Fe(II). The iron-based SCO behaviour of the 3d-4f complex mirrors that programmed in the mononuclear scaffold. Because of the different electronic structures of high-spin and low-spin [Fe(II)N 6 ] units, their associated absorption spectra are different and modulate the luminescence of the appended lanthanide luminophore via intramolecular intermetallic energy transfers. It thus becomes possible to detect the spin state of the Fe(II) center, encoded by an external perturbation ( i.e. writing), by lanthanide light emission ( i.e. reading) in a single molecule and without disturbance. Shifting from visible emission (Ln = Eu) to the near-infrared domain (Ln = Nd) further transforms a wavy emitted signal intensity into a linear one, a protocol highly desirable for future applications in data storage and thermometry.

Compared with the ripple of visible Eu III -based emission intensity induced by appended [Fe II N 6 ] spin crossover (SCO) units, as detected in the triple-stranded [EuFe( L1 ) 3 ] 5+ helicate, the lanthanide-based luminescent detection of Fe II spin-state equilibria could be improved significantly if the luminophore emission is shifted toward the near-infrared (NIR) domain. Replacing Eu III with Nd III in [NdFe( L1 ) 3 ] 5+ (i) maintains the favorable SCO properties in acetonitrile [critical temperature T 1/2 = 322(2) K], (ii) saturates nonradiative vibrational relaxation processes in the 233-333 K range, and (iii) boosts the crucial intramolecular Nd III → Fe II energy transfer rate processes, which are sensitive to the spin state of the Fe II metallic center. Consequently, the steady-state NIR Nd( 4 F 3/2 → 4 I J ) emission of the luminophore is amplified and linearly correlated with the low-spin-[Fe II N 6 ] and high-spin-[Fe II N 6 ] mole fractions controlled by the SCO equilibrium. This paves the way for a straightforward and direct NIR luminescent reading/sensing of the Fe II spin state in single molecules.