Femtosecond laser-induced size reduction and emission quantum yield enhancement of colloidal silicon nanocrystals: effect of laser ablation time

Silicon-containing nanomedicine and biomaterials: materials chemistry, multi-dimensional design, and biomedical application

The invention of silica-based bioactive glass in the late 1960s has sparked significant interest in exploring a wide range of silicon-containing biomaterials from the macroscale to the nanoscale. Over the past few decades, these biomaterials have been extensively explored for their potential in diverse biomedical applications, considering their remarkable bioactivity, excellent biocompatibility, facile surface functionalization, controllable synthesis, etc. However, to expedite the clinical translation and the unexpected utilization of silicon-composed nanomedicine and biomaterials, it is highly desirable to achieve a thorough comprehension of their characteristics and biological effects from an overall perspective. In this review, we provide a comprehensive discussion on the state-of-the-art progress of silicon-composed biomaterials, including their classification, characteristics, fabrication methods, and versatile biomedical applications. Additionally, we highlight the multi-dimensional design of both pure and hybrid silicon-composed nanomedicine and biomaterials and their intrinsic biological effects and interactions with biological systems. Their extensive biomedical applications span from drug delivery and bioimaging to therapeutic interventions and regenerative medicine, showcasing the significance of their rational design and fabrication to meet specific requirements and optimize their theranostic performance. Additionally, we offer insights into the future prospects and potential challenges regarding silicon-composed nanomedicine and biomaterials. By shedding light on these exciting research advances, we aspire to foster further progress in the biomedical field and drive the development of innovative silicon-composed nanomedicine and biomaterials with transformative applications in biomedicine.

Luminescent Amorphous Silicon Oxynitride Systems: High Quantum Efficiencies in the Visible Range

In recent years, researchers have placed great importance on the use of silicon (Si)-related materials as efficient light sources for the purpose of realizing Si-based monolithic optoelectronic integration. Previous works were mostly focused on Si nanostructured materials, and, so far, exciting results from Si-based compounds are still lacking. In this paper, we have systematically demonstrated the high photoluminescence external quantum efficiency (PL EQE) and internal quantum efficiency (PL IQE) of amorphous silicon oxynitride (a-SiN_xO_y) systems. Within an integration sphere, we directly measured the PL EQE values of a-SiN_xO_y, which ranged from approximately 2% to 10% in the visible range at room temperature. Then, we calculated the related PL IQE through temperature-dependent PL measurements. The obtained PL IQE values (~84% at 480 nm emission peak wavelength) were very high compared with those of reported Si-based luminescent thin films. We also calculated the temperature-dependent PL EQE values of a-SiN_xO_y systems, and discussed the related PL mechanisms.

Enhancement in external quantum efficiency of light-emitting diode based on colloidal silicon nanocrystals

Herein, we report an enhanced red emission from colloidal silicon nanocrystals (c-Si NCs) solution-processed light-emitting diode. c-Si NCs were synthesized by facile femtosecond laser ablation. Based on the structural characterization and opto-electrics properties analysis, both photoluminescence and electroluminescence arise from the radiative recombination of carriers due to quantum confined effect. The optical power density and highest external quantum efficiency have been obtained to be 0.79 mW cm^-2and ∼6.6%, respectively. These results indicate that Si NCs are very attractive as a potential optical source for future integrated chips.

Silicon Quantum Dots: Synthesis, Encapsulation, and Application in Light-Emitting Diodes

Silicon quantum dots (SiQDs) are semiconductor Si nanoparticles ranging from 1 to 10 nm that hold great applicative potential as optoelectronic devices and fluorescent bio-marking agents due to their ability to fluoresce blue and red light. Their biocompatibility compared to conventional toxic Group II-VI and III-V metal-based quantum dots makes their practical utilization even more attractive to prevent environmental pollution and harm to living organisms. This work focuses on their possible use for light-emitting diode (LED) manufacturing. Summarizing the main achievements over the past few years concerning different Si quantum dot synthetic methods, LED formation and characteristics, and strategies for their stabilization by microencapsulation and modification of their surface by specific ligands, this work aims to provide guidance en route to the development of the first stable Si-based light-emitting diodes.

High photoluminescence quantum yields generated from N-Si-O bonding states in amorphous silicon oxynitride films

We investigated the high absolute photoluminescence quantum yields (PL QYs) from tunable luminescent amorphous silicon oxynitride (a-SiN_xO_y) films. The PL QY of 8.38 percent has been achieved at PL peak energy of 2.55 eV in a-SiN_xO_y systems, which is higher than those of reported nanocrystal-Si embedded silicon nitride films. The existence of N-Si-O bonding states was confirmed by performing FTIR, XPS and EPR measurements. The PL QY is proportional to the concentration of N_x defects, indicating the dominant contribution of luminescent N-Si-O bonding states in radiative recombination processes. Particularly, we precisely monitored the ns-PL lifetimes evolution profile versus detected emission wavelengths, and further verified that the N-Si-O bonding states are responsible for highly efficient PL.