In a examine revealed in Proceedings of the Nationwide Academy of Sciences, a analysis workforce led by Prof. Dongguo Zhang of the College of Science and Know-how of China (USTC) of the Chinese language Academy of Sciences (CAS) developed an optical module consisting of cascaded momentum-space polarization filters primarily based on vector mild area modulation.
This optical module successfully suppresses background noise whereas capturing excessive signal-to-noise ratio (SNR) microscopy photographs of particular person nano-objects.
Exact imaging of the evolution and movement conduct of particular person nano-objects, equivalent to ultrafine atmospheric particles, is essential in relation to understanding their functionalities and properties. Label-free optical microscopy has been broadly utilized in imaging and sensing of nanoparticles as a result of its distinctive non-destructive, non-invasive and quick detection traits.
Nevertheless, the energy of sunshine scattering by particular person nanoparticles in air drops considerably with particle dimension to the sixth energy. In consequence, the scattered mild depth is considerably decrease than the background noise, making it troublesome for conventional label-free optical microscopes to perform excessive SNR imaging of particular person nanoparticles.
To deal with this challenge, Prof. Zhang’s workforce developed a momentum-space polarization filter that can be utilized to switch vector area polarization.
Solely scattering mild from single nano-objects can move via the filter and be caught by the detector, whereas assorted background noise is considerably filtered and suppressed, subsequently reaching excessive distinction and excessive SNR imaging of nano-objects.
The filter was positioned on the exit finish of a complete inner reflection microscopy (TIRM) to point out how it’s used. Compared to conventional label-free black-field microscopy, black-field microscopy, which has decreased (blacker) background noise and larger detection sensitivity, was achieved by changing TIRM into black-field microscopy as soon as the filter was put in.
As such, it was made clear that black-field microscopy can be utilized to acquire real-time excessive SNR and high-contrast optical microscopy photographs of particular person protein molecules, gold nanoparticles, and perovskite nanocrystals.
Moreover, single perovskite nanocrystals endure anion-exchange reactions upon the sequential introduction of HCl and HI vapor. These processes alter the nanocrystals’ form and refractive index, therefore inflicting variations within the scattered mild indicators of the person nanocrystals.
Black-field microscopy can seize this course of in real-time, providing a novel photonic method for the detection of bodily and chemical reactions happening as a nanoobject’s properties evolve.
The momentum-space polarization filter system is exclusive in that it may be used to supply black-field imaging functionality to standard label-free optical microscopy, together with floor plasmon resonance microscopy (SPRM), TIRM, and different near-field optical microscopy, with out altering the interior construction of the microscopes. This significantly will increase the sensitivity of the microscopes in detecting particular person nano-objects.
In abstract, the workforce created a novel platform for analyzing particular person nanoparticles utilizing black-field microscopy, which holds vital promise to be used within the fields of supplies science, biology, physics, and environmental science.
Journal Reference:
Liu, Y., et. al. (2024) Cascaded momentum-space polarization filters enabled label-free black-field microscopy for single nanoparticles evaluation. Proceedings of the Nationwide Academy of Sciences. doi:10.1073/pnas.232182512