Silicon Microspheres Research Articles

Synergistic structural integrity and remarkable structural stability of NC@Si anodes for lithium-ion batteries

The silicon-based anode has attracted wide attention because of its high theoretical specific capacity, which is expected to greatly improve the batteries’ energy density. However, during the charge-discharge cycles, the great volume expansion of the anode active silicon seriously restricts its electrochemical stability. Herein, N-doping carbon-coated silicon microsphere was prepared for lithium-ion batteries. Benefit from the core-shell structure formed from silicon carbon, the volume change of silicon anode during the cycle is well coordinated. What's more, N-doping carbon reduces the reaction energy barrier between silicon and lithium and accelerates the electrochemical reaction, which improves the cycling performance of the battery. The specific capacity of the prepared button battery is as high as 2913.13 mAh g−1 at the current density of 0.21 mA g−1, and the average coulomb efficiency is higher than 99.84 % during the cycling. And the capacity of NC@SiO2 anode gradually stabilizes after 500 cycles.

Tuning Multipolar Mie Scattering of Particles on a Dielectric-Covered Mirror.

Optically resonant particles are key building blocks of many nanophotonic devices such as optical antennas and metasurfaces. Because the functionalities of such devices are largely determined by the optical properties of individual resonators, extending the attainable responses from a given particle is highly desirable. Practically, this is usually achieved by introducing an asymmetric dielectric environment. However, commonly used simple substrates have limited influences on the optical properties of the particles atop. Here, we show that the multipolar scattering of silicon microspheres can be effectively modified by placing the particles on a dielectric-covered mirror, which tunes the coupling between the Mie resonances of microspheres and the standing waves and waveguide modes in the dielectric spacer. This tunability allows selective excitation, enhancement, suppression, and even elimination of the multipolar resonances and enables scattering at extended wavelengths, providing transformative opportunities in controlling light-matter interactions for various applications. We further demonstrate with experiments the detection of molecular fingerprints by single-particle mid-infrared spectroscopy and with simulations strong optical repulsive forces that could elevate the particles from a substrate.

An electron beam irradiation-assisted coating method for the regulation of hydrophilicity and hydrophobicity

Multi-level electron beam irradiation enabled bifunctional gradient grafting on silicon microspheres and rapid curing of silicone rubber coatings, allowing linear control of hydrophilicity and hydrophobicity.

Carbon‐Coated Porous Hollow Silicon Microspheres for High‐Capacity and Durable Lithium Storage

AbstractSilicon‐based materials are promising lithium‐ion battery (LIB) anodes owing to their natural abundance and high capacity. However, their practical application is restricted by the poor electrical conductivity and large volume expansion. Herein, we successfully construct carbon coated porous hollow silicon microspheres (Si‐40@C) as LIB anode materials, which are derived from the acid etching of commercial AlSi alloy with subsequent chemical vapor deposition carbon coating. The porous hollow structure of Si‐40@C buffers the volume variation and promotes the transportation of Li+; the carbon coating enhances the overall conductivity as well as structural stability. The as‐prepared Si‐40@C porous hollow microspheres deliver a high reversible capacity (2029 mAh g−1 at 0.2 A g−1), good cyclability (1668 mAh g−1 after 100 cycles at 0.2 A g−1), and an ideal rate capability (1200 mAh g−1 at 10 A g−1).

Silicon Microspheres for Super‐Planckian Light Sources in the Mid Infrared

AbstractSilicon microspheres with a diameter in the range of 2–3 micrometers constitute photonic nanocavities that emit light through their Mie resonances when heated at high temperatures. At 500–600 °C these microresonators show a particular mid‐infrared (MIR) emission dominated by the lowest order modes. Such resonances feature a large free spectral range, about 600 cm−1, and a high proximity to the critical coupling condition. In fact, resonances with high‐quality factor, around 160 are found. It corresponds to the limit of detection of their measuring setup, being 600 the theoretical value. Most importantly, several modes emit light above the calculated black body limit because they feature an optical absorption cross‐section larger than their geometric one. All these characteristics set silicon microspheres as very promising zero‐dimensional materials for developing micrometric and sub‐wavelength light sources in the MIR.

Photo-Initiated in situ synthesis of polypyrrole Fe-Coated porous silicon microspheres for High-performance Lithium-ion battery anodes

A simple and environmentally friendly photoinitiated fabrication approach based on the photoelectric effect of semiconductor silicon is designed to synthesize yolk-shell like polypyrrole-iron coated porous silicon microspheres (PSi@PPy-Fe) as anode materials for LIBs. The polymerization of pyrrole monomers only occurs on the interface of silicon matrix where the vacancies are available, which effectively avoids the production of free PPy-Fe particles. XPS and first-principles calculations reveal that both the hydrogen-bond interaction and the covalent linkage are formed between Si and PPy-Fe layer, which is of great significance for maintaining good contact and strengthening the structure stability. It is demonstrated that the PPy-Fe coating may accelerate charge transfer and ion diffusion as well as prevent the Si-based materials peeling off from Cu collector. More importantly, the PPy-Fe coating could alleviate the violent structural expansion of Si anode, thus ameliorating the mechanical strength of the electrode. Consequently, the as-prepared yolk-shell like polypyrrole-iron coated porous silicon microspheres present outstanding cycling ability (1853.7 mAh/g after 200 cycles at 1 A/g) and superior rate capability (1558.4 mAh/g at 4 A/g). This work indicates that the photochemical modification strategy for Si may have a bright prospect in a wide range of fields.

Aluminum as a bi-functional reducing agent for the fabrication of graphene encapsulated silicon microspheres as anodes for high-performance lithium-ion batteries

The composites of reduced graphene oxide (rGO) encapsulated porous silicon (P-Si) microspheres are constructed using metallic aluminum as a bi-functional reducing agent at low temperatures. The preparation process of P-Si is carried out in a special reactor at 300 °C. For the reaction, SiO2 is used as the silicon source and AlCl3 is added to maintain the smooth progress of the thermite reduction reaction. Subsequently, graphene oxide is reduced by aluminum powder in an acidic liquid phase system and then the P-Si/rGO composite material is constructed by freeze-drying technique. As a kind of promising anode for lithium-ion batteries (LIBs), the porous structure of silicon microspheres can relieve the internal stress caused by volume expansion and shorten the diffusion path of lithium ions during charge/discharge processses. The flexible graphene layers can adapt the volume effect of the P-Si microspheres and therefore maintain the structural stability of the composites and enhance the electrical conductivity. The obtained P-Si/rGO composite material exhibits excellent electrochemical performance, which can maintain a superior capacity of 837 mAh g−1 upon 500 cycles under a current density of 0.5 A g−1 and exhibit satisfied cycling stability with a capacity of 704 mAh g−1 after 1000 cycles at a 1 A g−1 current density.

High reversible capacity silicon anode by segregated graphene-carbon nanotube networks for lithium ion half/full batteries

Micron-sized Si-based materials have gained much attention recently in the pursuit of high-performance and low-cost lithium-ion battery (LIBs). However, huge volume variation and poor conductivity induce a rapid performance decline of Si microparticles. Herein, porous silicon microsphere segregated in graphene and carbon nanotube network (pSi/HCNT/rGO) is constructed by one-step hybrid and reduction self-assembly strategy. Carbon nanotubes provide the “safety belt” for the entire structure to block aggregation between rGO layers. The hierarchical porous structure composed by intrinsic pore structure of pSi and flexible carbon network effectively buffers the volume expansion and ensures the structural and interface stability in the lithium storage process, which also delivers multiple conductive pathways to boost Li+/e− migration efficiency. Proper configuration design leads to high charging capacity of 2319 mAh g−1 at 0.1 A g−1, exceptional initial Coulombic efficiency of 87.5 % (vs pSi of 55.8 %) and stable long cycle performance of 583 mAh g−1 after 400 cycles at 5 A g−1 when pSi/HCNT/rGO applying in half battery. The pSi/HCNT/rGO||LiFePO4 (LFP) full battery also shows the capacity maintenance of 96 % after 150 cycles at 1 C.

Multilayer porous silicon spherical Mie resonator photodiodes with comb-like spectral response in the near infrared region

Silicon microsphere photodiodes constitute optoelectronic devices able to provide resonance-enhanced photocurrent not only in the visible but also in the near infrared range by virtue of their associated Mie resonances. They are synthesized by means of a bottom-up process that allows obtaining thousand of devices in a single batch. The microspheres have revealed an internal structural configuration that strongly influences the photocurrent response, thus providing an additional degree of freedom for tuning the properties of the photodiodes. Here, devices with a particular internal configuration consisting of a high porous core, a much less porous surrounding layer and a thin non-porous shell, have been studied. They yield comb like peaked photocurrent spectra that have been fitted to a Mie type model. In addition, net energy conversion at 1500 nm has been demonstrated.

Determination of free fatty acids in Antarctic krill meals based on matrix solid phase dispersion

Amino-modified mesoporous silicawas prepared by modifying mesoporous silica with 3-aminopropyltriethoxysilane and used as adsorbents in matrix solid-phase dispersion (MSPD) to analyze free fatty acids (FFAs) in krill meals for the first time. The adsorption–desorption experiments and Fourier-transform infrared spectroscopy showed amino-modified mesoporous silica with ordered mesoporous structure was successfully synthesized. The adsorption experiments including static and dynamic adsorption showed thatabsorption capacity of amino-modified mesoporous silica towards FFAs was better than that of aminated silicon microspheres at all concentrations. Under optimal extraction conditions, outstanding linearity (0.1–12000 nmol g−1), low LODs (0.05–1.25 nmol g−1), satisfactory recoveries (82.17–96.43%) and precisions (0.19–5.26%) were obtained. Moreover, the application of MSPD for FFAs analysis avoided complicated lipid extraction procedures and accomplished the homogenization, crushing, extraction and cleaning of the samples in one step. Consequently, this approach provides an alternative choice to the existing approach for analyzing FFAs in solid and semi-solid samples.

Metallic Tin Nanoparticle-Reinforced Tin-Doped Porous Silicon Microspheres with Superior Electrochemical Lithium Storage Properties

Improving the electronic conductivity and drastic volume expansion is attractive and challenging for constructing high-performance Si-based anode materials for lithium-ion batteries. Herein, tin-doped porous silicon microspheres embedded with tin nanoparticles (Sn–PSi@Sn) are fabricated from easily available low-cost silicon–aluminum alloy precursors through a simple and scalable strategy with a chemical replacement/etching and a low-temperature annealing process. The 3D porous framework structure of Sn–PSi@Sn microspheres may buffer severe volume expansion during the electrochemical cycling and shorten the transport paths of Li+ ions. The doping of Sn atoms in the Si crystal lattice can lead to a lattice expansion in silicon, reinforce the electronic and ionic conductivities, and minimize the effect of Li trapping, which is advantageous for enhancing the rate performance and improving the initial Coulombic efficiency. The Sn nanoparticles anchoring in porous silicon microspheres may further improve the conductivity and structure stability of Sn–PSi@Sn composites. Based on the density functional theory calculation results, the effects of partial substitution of Sn into the Si lattice mentioned above have been successfully confirmed. As a consequence, the as-prepared tin-doped porous silicon microspheres embedded with tin nanoparticles show a high reversible capacity (1165.6 mA h g–1 at the 400th cycle at 1 A g–1), excellent rate properties (1433.4 mA h g–1 at a high rate of 2.5 A g–1), and superior cycling performance at an ultrahigh rate (910.9 mA h g–1 at the 500th cycle even at a high current density of 4 A g–1). This work provides a promising strategy to design high-performance anode composites.

Utilizing DNase I and graphene oxide modified magnetic nanoparticles for sensing PD-L1 in human plasma

PurposeBased on DNase I and reduced graphene oxide (rGO)-magnetic silicon microspheres (MNPS), a highly sensitive and selective fluorescent probe for the detection of PD-L1 was developed.Design/methodology/approachHere °C we present a feasibility of biosensor to detection of PD-L1 in lung tumors plasma. In the absence of PD-L1°C the PD-L1 aptamer is absorbed on the surface of graphene oxide modified magnetic nanoparticles °8rGO-MNPS°9 and leading to effective fluorescence quenching. Upon adding PD-L1°C the aptamer sequences could be specifically recognized by PD-L1 and the aptamer/PD-L1 complex is formed°C resulting in the recovery of quenched fluorescence.FindingsThis sensor can detect PD-L1 with a linear range from 100 pg mL−1 to 100 ng mL−1, and a detection limit of 10 pg•m−1 was achieved.Originality/valueThis method provides an easy and sensitive method for the detection of PD-L1 and will be beneficial to the early diagnosis and prognosis of tumors.

Light-assisted synthesis of copper/cuprous oxide reinforced nanoporous silicon microspheres with boosted anode performance for lithium-ion batteries

Silicon is generally accepted as an outstanding anode material to promote the use of high-capacity lithium-ion batteries (LIBs). Herein, novel Cu/Cu2O reinforced nanoporous silicon microspheres are successfully constructed by a simple photodeposition-galvanic replacement method. The reduction reactions driven by photogenerated electrons and galvanic replacement jointly promote the in-situ deposition of Cu/Cu2O on porous silicon microspheres. Compared with the as-constructed anode materials in the absence of illumination, the composites obtained with the light irradiation display better electrochemical performance. The ratio of Si and Cu in the final products can be effectively adjusted by modulating the concentration of Cu2+ in the reaction solutions. Benefiting from the enhanced structure stability and excellent electronic conductivity, the final optimized product exhibits superior Li-storage performance, delivering a reversible capacity of 1240.1 mAh g−1 after 200 cycles at a high current of 1 A g−1. It is worth mentioning that the as-constructed light-assisted method provides an efficient and universal pathway to tailor and synthesize other superior Si based anode materials.

Porous Si-Cu3 Si-Cu Microsphere@C Core-Shell Composites with Enhanced Electrochemical Lithium Storage.

Low-cost Si-based anode materials with excellent electrochemical lithium storage present attractive prospects for lithium-ion batteries (LIBs). Herein, porous Si-Cu3 Si-Cu microsphere@C composites are designed and prepared by means of an etching/electroless deposition and subsequent carbon coating. The composites show a core-shell structure, with a porous Si/Cu microsphere core surrounded by the N-doped carbon shell. The Cu and Cu3 Si nanoparticles are embedded inside porous silicon microspheres, forming the porous Si/Cu microsphere core. The microstructure and lithium storage performance of porous Si-Cu3 Si-Cu microsphere@C composites can be effectively tuned by changing electroless deposition time. The Si-Cu3 Si-Cu microsphere@C composite prepared with 12 min electroless deposition delivers a reversible capacity of 627 mAh g-1 after 200 cycles at 2 A g-1 , showing an enhanced lithium storage ability. The superior lithium storage performance of the Si-Cu3 Si-Cu microsphere@C composite can be ascribed to the improved electronic conductivity, enhanced mechanical stability, and better buffering against the large volume change in the repeated lithiation/delithiation processes.

Controlled synthesis of copper reinforced nanoporous silicon microsphere with boosted electrochemical performance

As the most promising anode material for lithium-ion batteries, silicon attracts great attention. In this work, copper reinforced nanoporous silicon microsphere is synthesized by chemical dealloying method. By adjusting the content and morphology, we systematically study the relationship between morphology, components with the electrochemical performance. Results show that copper incorporation can significantly improve the electronic conductivity, buffer the volume expansion and enhance the Coulombic efficiency. The optimized Si10Cu4 can deliver a capacity of 914.1 mAh g−1 even after 500 cycles at rate of 1 C. These results may provide a new pathway to improve the electrochemical performance of silicon-based anode materials.

Thermal Emission of Silicon at Near-Infrared Frequencies Mediated by Mie Resonances

Planck’s law constitutes one of the cornerstones in physics. It explains the well-known spectrum of an ideal blackbody consisting of a smooth curve, whose peak wavelength and intensity depend on the temperature of the body. This scenario changes drastically, however, when the size of the emitting object is comparable to the wavelength of the emitted radiation. Here we show that a silicon microsphere (2–3 μm in diameter) heated to around 800 °C yields a thermal emission spectrum consisting of pronounced peaks that are associated with Mie resonances. We experimentally demonstrate in the near-infrared the existence of modes with an ultrahigh quality factor, Q, of 400, which is substantially higher than values reported so far, and set a new benchmark in the field of thermal emission. Simulations predict that the thermal response of the microspheres is very fast, about 15 μs. Additionally, the possibility of achieving light emission above the Planck limit at some frequency ranges is envisaged.

3D Super-Resolution Reconstruction Using Microsphere-Assisted Structured Illumination Microscopy

In this letter, we present a wide-field three-dimensional (3D) profiling technique with enhanced lateral resolution by combining structured illumination microscopy (SIM) with super-resolution microsphere-assisted 2D imaging method. In the measurement, a silicon microsphere is placed on the nanoscale sample to improve the spatial resolution. After that, a sinusoidal pattern produced by digital micro-mirror devices (DMD) is projected through the microsphere onto the sample. The modulation evaluation of the reflected patterns is utilized to reshape the 3D profile precisely. The experiment is conducted on the grating sample with 220 nm line-width which beyond the diffraction limit of the ordinary SIM system. The results show that the 3D map of the sample with enhanced lateral resolution can be achieved using a silica microsphere with 20 μm diameter. The measurement system is relatively simple and can achieve a very high effective numerical aperture easily. The advantages are significant with the potential to be applied in many domains from nanotechnology to biology.

Design of VO2-coated silicon microspheres for thermally-regulating paint.

Recent work has proposed an approach to design materials that regulate their own temperature. The concept is based on a temperature-dependent thermal emitter that has minimal emissivity below a target temperature, and maximal emissivity above it. Here we propose a microparticle approach suitable for scaling to large areas. We use electromagnetic and thermal simulations to show that the designed particles provide a 13x reduction in temperature variation relative to an uncoated aluminum substrate.

Ordered mesoporous Si microspheres with nitrogen-doped carbon coating for advanced lithium-ion battery anodes

Silicon is considered as a promising anode candidate for the new generation of lithium-ion batteries by virtue of its extensive sources and ultrahigh theoretical specific capacity (4200 mA h g−1). The inevitable volume change during the lithiation process will lead to a series of troubles, which has become a major obstacle to the large-scale application of silicon-based electrodes. Herein, silicon microspheres with the ordered mesoporous structure are synthesized through magnesiothermic reduction, which allows void for volume expansion to prevent electrode material from pulverizing. Subsequently, the silicon microspheres are packaged with a polydopamine driven nitrogen-doped carbon layer, which is helpful to maintain the structural stability of electrode materials and enhance the electronic conductivity. The resulting OM-Si@C composite material exhibits remarkable lithium storage properties, which behaves a superior reversible specific capacity of 1751.7 mA h g−1 at 0.1 A g−1 after 100 cycles. Furthermore, it also shows excellent rate performance (1183.9 mA h g−1 at 2 A g−1) and long cycle stability.

Femtosecond laser written diamond waveguide excitation of the whispering gallery modes in a silicon microsphere

We demonstrate light coupling from femtosecond laser written diamond waveguide operating at the telecommunication wavelengths to a silicon microsphere resonator. Type II waveguides are written on a diamond platform and Fabry-Pérot resonances are excited in the diamond waveguides by bare fiber coupling in and out of the waveguide. The Fabry-Pérot resonances have a free spectral range of 87 pm, and a maximum Q-factor of 3.9 × 104. The diamond waveguide is used to excite TM-polarized whispering gallery modes of the 1 mm silicon microsphere, since the type II waveguides support TM modes better as compared to TE modes. The whispering gallery mode spacing is measured as 0.257 nm and the highest Q-factor is 6.2 × 104. This evanescent coupling method to high Q-factor silicon microsphere resonances by femtosecond laser written diamond waveguides can be further used for filtering and sensing applications in various photonic lightwave circuits.