麻豆淫院

A research team has developed upconversion nanoparticles to assist in powering molecular motors. The nanoparticles can convert near-infrared radiation, which is capable of penetrating bulk material, into blue or UV light that can efficiently power the motors. As a result, these motors can now be effectively used to make bulk materials responsive or act as molecular switches in biological applications. The results were last month in the Journal of the American Chemical Society.

The collaboration included Prof. Ben Feringa at Groningen University, Prof. Hong Zhang and his Ph.D. graduate Dr. Kefan Wu at the University of Amsterdam's Van 't Hoff Institute for Molecular Sciences.

The upconversion nanoparticles solve a pressing problem of the real-life application of molecular motors: they are most effectively powered by blue or UV light. When integrated into bulk materials or when applied to devices used in biological tissues, the short penetration depth of blue or UV light hinders effective activation of the motors. Moreover, UV radiation can be quite harmful.

A solution would be to make the motors susceptible to near infrared radiation, which provides superior penetration depth and is relatively benign. However, this would require the motors to be adorned with additional molecular groups, complicating their synthesis. Furthermore, it is quite a challenge to realize adequate photo-efficiencies in molecular motors that are directly driven by infrared radiation.

An effective transfer mechanism of radiative energy

In their paper, the Groningen/Amsterdam research team now reports a novel strategy to power molecular motors with high efficiency using near infrared radiation. It builds upon the expertise of Prof. Hong Zhang in spectrally tunable upconversion nanoparticles (UCNPs) that effectively provide a radiative energy transfer mechanism.

In detail, UCNPs consisting of sodium yttrium fluoride doped with various lanthanide ions act as nanometer-scale transducers, converting NIR light into UV/visible photons. Upon absorption by molecular motors, these photons trigger unidirectional rotational motion in a way that is comparable to direct excitation by UV/visible light.

A series of experimental results on molecular motors demonstrate the efficacy of this strategy in substituting direct UV/visible irradiation. It is especially useful in biological settings that demand deep light penetration and reduced phototoxicity, and in UV/visible-light-sensitive systems like bulk solids. In addition, no complicated pre-functionalization of molecules is needed.

According to the team, the approach exhibits high generality and scope in activating molecular motors with NIR light. This holds significant potential for real applications using molecular machines in dynamic and smart materials, in particular in the biological domain.