Gradient Type-II CdSe/CdSeTe/CdTe Core/Crown/Crown Heteronanoplatelets with Asymmetric Shape and Disproportional Excitonic Properties

Characterized by their strong 1D confinement and long-lifetime red-shifted emission spectra, colloidal nanoplatelets (NPLs) with type-II electronic structure provide an exciting ground to design complex heterostructures with remarkable properties. This work demonstrates the synthesis and optical characterization of CdSe/CdSeTe/CdTe core/crown/crown NPLs having a step-wise gradient electronic structure and disproportional wavefunction distribution, in which the excitonic properties of the electron and hole can be finely tuned through adjusting the geometry of the intermediate crown. The first crown with staggered configuration gives rise to a series of direct and indirect transition channels that activation/deactivation of each channel is possible through wavefunction engineering. Moreover, these NPLs allow for switching between active channels with temperature, where lattice contraction directly affects the electron–hole (e–h) overlap. Dominated by the indirect transition channels over direct transitions, the lifetime of the NPLs starts to increase at 9 K, indicative of low dark-bright exciton splitting energy. The charge transfer states from the two type-II interfaces promote a large number of indirect transitions, which effectively increase the absorption of low-energy photons critical for nonlinear properties. As a result, these NPLs demonstrate exceptionally high two-photon absorption cross-sections with the highest value of 12.9 × 10⁶ GM and superlinear behavior.     

A Real-Time Automatic Translation of Text to Sign Language

Communication is a basic need of every human being; by this, they can learn, express their feelings and exchange their ideas, but deaf people cannot listen and speak. For communication, they use various hands gestures, also known as Sign Language (SL), which they learn from special schools. As normal people have not taken SL classes; therefore, they are unable to perform signs of daily routine sentences (e.g., what are the specifications of this mobile phone?). A technological solution can facilitate in overcoming this communication gap by which normal people can communicate with deaf people. This paper presents an architecture for an application named Sign4PSL that translates the sentences to Pakistan Sign Language (PSL) for deaf people with visual representation using virtual signing character. This research aims to develop a generic independent application that is lightweight and reusable on any platform, including web and mobile, with an ability to perform offline text translation. The Sign4PSL relies on a knowledge base that stores both corpus of PSL Words and their coded form in the notation system. Sign4PSL takes English language text as an input, performs the translation to PSL through sign language notation and displays gestures to the user using virtual character. The system is tested on deaf students at a special school. The results have shown that the students were able to understand the story presented to them appropriately.