SUN CARE 57 1/τ= K0 f + Kq (quencher) Kq (109 M-1 S-1 ) 1.4


5.2±0.2 4.5±0.2


N C O 1.2 1.0


3.7±0.4 0.65±0.05


N 0.8 S 0 4 8 (quencher) (nm) 12 C O O O


9.2 8.8 8.4 8.0


0 5 10 15 20 (quencher) (nm)


Figure 8: Determination of the bimolecular quenching rate constants kq of quenching of PPIX fluorescence (singlet states) by the Micah compounds using PPIX fluorescence decay traces at different Micah concentrations. Inverse fluorescence lifetime vs. quencher (stabiliser) concentration.


commercial TiO2 product and prevent ROS


generation. Based on this observation, we developed our series of Hallstar EZ–FLO mineral dispersions.


Protecting skin chromophores against ROS generation: the ultimate solution to photoageing— Micah technology


O N C O


Current available technologies for combating solar energy-inflicted ageing processes can be classified into two families: Blocking or shading: This family is exemplified by present-day sunscreen products, where absorbing compounds (filters) are applied onto skin to block some of the harmful energy. This essentially


O N C O Kq


=(1.4±0.1)x108 O


N O O Kq


7 6 5 4 3 2 1 0


0 1 2 3 4 (quencher) (nm)


=(3.2±0.1)x109 M-1 s-1


7 6 5 4 3 2 1 0


0 1 2 3 4 (quencher) (nm)


Kq O =(2.5±0.1)x108 M-1 s-1 C O C N M-1 s-1 O


creates a shade to shield the skin from solar radiation. But this approach has two fundamental defects. First, the quality of the shading is highly dependent on the quality of the blocking layer established on the top of the skin, which can be influenced by many variables, making this technology far from foolproof. Second, shading from visible light is not cosmetically feasible. Any material that is capable of blocking energy in the visible spectrum will itself be coloured. To block all wavelengths of visible light, a product’s colour would essentially have to be black. Neutralising or fire-fighting: Antioxidants work by this mechanism. In this approach, the aftermath of solar energy assault is addressed. Antioxidants are employed to neutralise the harmful reactive species produced after skin is irradiated by the sun. To perform this neutralisation, antioxidants must be fairly reactive and sensitive, making their application challenging and their long- term performance unpredictable. Hallstar’s technology takes a completely


Figure 9: Determination of the bimolecular quenching rate constants kq of quenching of PPIX triplet states by Micah compounds using PPIX triplet absorption decay traces monitored at 440 nm and different Micah concentrations. Inverse triplet state lifetime vs. quencher concentration. PPIX triplet states in deoxygenated acetonitrile solutions were generated by pulsed laser excitation (532 nm).


November 2018


different approach. Micah compounds were designed to quickly and effectively resolve energy-rich components in the skin immediately after solar irradiation; they return these components to their stable ground states and preventing all harmful consequences such as ROS generation. Micah compounds are extremely stable at both ground states and excited states. In


PERSONAL CARE EUROPE O O O O CN O N C O O N C O


1/τ (106 T


S-1


) 1/τT (106 S-1 )


1/τ (106 T


S-1


)


1/τT (107


S-1


)


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