Silicon Nanosheets Research Articles

Förster Resonance Energy Transfer and Enhanced Emission in Cs4PbBr6 Nanocrystals Encapsulated in Silicon Nano-Sheets for Perovskite Light Emitting Diode Applications.

Encapsulating Cs4PbBr6 quantum dots in silicon nano-sheets not only stabilizes the halide perovskite, but also takes advantage of the nano-sheet for a compatible integration with the traditional silicon semiconductor. Here, we report the preparation of un-passivated Cs4PbBr6 ellipsoidal nanocrystals and pseudo-spherical quantum dots in silicon nano-sheets and their enhanced photoluminescence (PL). For a sample with low concentrations of quantum dots in silicon nano-sheets, the emission from Cs4PbBr6 pseudo-spherical quantum dots is quenched and is dominated with Pb2+ ion/silicene emission, which is very stable during the whole measurement period. For a high concentration of Cs4PbBr6 ellipsoidal nanocrystals in silicon nano-sheets, we have observed Förster resonance energy transfer with up to 87% efficiency through the oscillation of two PL peaks when UV excitation switches between on and off, using recorded video and PL lifetime measurements. In an area of a non-uniform sample containing both ellipsoidal nanocrystals and pseudo-spherical quantum dots, where Pb2+ ion/silicene emissions, broadband emissions from quantum dots, and bandgap edge emissions (515 nm) appear, the 515 nm peak intensity increases five times over 30 min of UV excitation, probably due to a photon recycling effect. This irradiated sample has been stable for one year of ambient storage. Cs4PbBr6 quantum dots encapsulated in silicon nano-sheets can lead to applications of halide perovskite light emitting diodes (PeLEDs) and integration with traditional semiconductor materials.

One-pot synthesis of interconnected carbon-coated silicon nanosheets from clay minerals for high-performance lithium-ion battery anodes

The silicon nanosheet/carbon composite emerges as a promising anode material for the next-generation commercial lithium-ion batteries. However, complex, costly, and energy-intensive synthesis procedures impede its practical application. Herein, the carbon-coated silicon nanosheets (Si/C) have been successfully synthesized via a one-pot strategy, involving a modified magnesiothermic reduction of talc followed by a reaction with CO2. The distinct chemical composition and layered nanostructure of talc enable the retention of Si nanosheets during exothermic reactions without additional templates or heat absorbents. The method shows significant potential for the scalable production of Si/C owing to the abundant silicon source, sustainable carbon source, and straightforward protocol. The resulting Si/C displays a hierarchical porous structure, with both macropores and mesopores, and an interconnected network of carbon-coated Si nanosheets. These structural characteristics facilitate rapid Li+ diffusion and enable the material to accommodate the lithiation-induced mechanical strains. As a result, the Si/C electrode exhibits outstanding electrochemical performance, including a remarkable rate capability (with a specific capacity of 1220 mAh g−1 at 10.0 A g−1) and a high initial Coulombic efficiency of 88%. The work opens a new avenue for the development of Si/C composites from natural clay minerals through an economical and scalable strategy, which would contribute to the practical application of advanced Si-based anodes in lithium-ion batteries.

Designing Compatible Ceramic/Polymer Composite Solid-State Electrolyte for Stable Silicon Nanosheet Anodes.

The commercialization of silicon anode for lithium-ion batteries has been hindered by severe structure fracture and continuous interfacial reaction against liquid electrolytes, which can be mitigated by solid-state electrolytes. However, rigid ceramic electrolyte suffers from large electrolyte/electrode interfacial resistance, and polymer electrolyte undergoes poor ionic conductivity, both of which are worsened by volume expansion of silicon. Herein, by dispersing Li1.3Al0.3Ti1.7(PO4)3 (LATP) into poly(vinylidene fluoride)-hexafluoropropylene (PVDF-HFP) and poly(ethylene oxide) (PEO) matrix, the PVDF-HFP/PEO/LATP (PHP-L) solid-state electrolyte with high ionic conductivity (1.40 × 10-3Scm-1), high tensile strength and flexibility is designed, achieving brilliant compatibility with silicon nanosheets. The chemical interactions between PVDF-HFP and PEO, LATP increase amorphous degree of polymer, accelerating Li+ transfer. Good flexibility of the PHP-L contributes to adaptive structure variation of electrolyte with silicon expansion/shrinkage, ensuring swift interfacial ions transfer. Moreover, the solid membrane with high tensile limits electrode structural degradation and eliminates continuous interfacial growth to form stable 2D solid electrolyte interface (SEI) film, achieving superior cyclic performance to liquid electrolytes. The Si//PHP-L15//LiFePO4 solid-state full-cell exhibits stable lithium storage with 81% capacity retention after 100 cycles. This work demonstrates the effectiveness of composite solid electrolyte in addressing fundamental interfacial and performance challenges of silicon anodes.

Optimization of effective electron mass in strained silicon nanosheets

This work investigated the effective mass of electrons in silicon nanosheets confined in the [001] and [1̄10] directions and having thicknesses of several nanometers with uniaxial tensile stress in the [110] direction, using density functional theory. The results show that the confinement along [1̄10] substantially reduces the effective mass in the [110] direction even in the absence of stress—a phenomenon not observed under [100] confinement. Our theoretical analysis reveals that confinement in the [110] direction acts as an effective shear strain. Furthermore, our study identifies an optimal stress that minimizes the effective mass in the transport direction, m110, thereby improving the nanosheet’s transport properties.

The well-defined three-dimensional matrix of a micro-sized silicon/carbon composite promoting lithium-ion transportation.

Micro-sized silicon is a promising anode material due to its high theoretical capacity and low cost. However, its bulk particle size poses a challenge during electrochemical cycling, and the long ion/electron transport paths within it limit the rate capability. Herein, we propose a structural engineering approach for establishing a well-defined three-dimensional (3D) micro-sized silicon/carbon matrix to achieve efficient omnidirectional ionic and electronic conductivity within micro-sized silicon and effectively mitigate the volume changes. The prepared materials, comprising ordered two-dimensional porous silicon nanosheets, offer direct two-dimensional electrolyte transport channels aligned parallel to the layer plane and porous channels oriented perpendicular to the layer plane. These well-defined omnidirectional pathways enable more efficient electrolyte mass transport than the disordered paths within the traditional 3D porous silicon anodes. A robust carbon shell, securely bonded to silicon through dual covalent bonding, effectively shields these pathways, buffering the volume changes and offering an electronically conductive 3D carbon network.

Simple construction of multistage stable silicon-graphite nanosheets composites for lithium-ion batteries

Silicon/carbon composites are considered as the preferred anode materials for high energy density lithium-ion batteries due to their high capacity. However, the high cost of raw materials and the complex preparation process have resulted in expensive cost and poor batch stability of silicon-carbon materials, which have impeded their widespread adoption on a large scale. In this study, a multistage stable silicon-graphite nanosheets composite (Si-NSs/G-NSs@C) with intercalated and core-shell structure was produced from low-cost precursors of silicon nanosheets (Si-NSs) and graphite nanosheets (G-NSs) by simple modification-grafting-coating and heat treatment processes. Benefiting from the effective bonding, citric acid carbon coating, intercalation and core-shell structure, the Si-NSs/G-NSs@C composite exhibits excellent performance for lithium storage. The Si-NSs/G-NSs@C electrode, using the sodium alginate binder system, displays the reversible specific capacity of 821.4 mAh g−1 at 400 mA g−1, with the capacity retention rate of 80% after 200 cycles. When employing lithium polyacrylate as the binder, the composite electrode demonstrates the reversible specific capacities of 1048.9 mAh g−1 at 400 mA g−1 and 723.6 mAh g−1 at 1000 mA g−1. After 200 cycles, the capacity retention rates were 81% and 85%, respectively. In summary, the low-cost precursors, simple and controllable preparation process and excellent electrochemical performance will further promote the market application of silicon/carbon anode materials.

Nontypical Wulff-Shape Silicon Nanosheets with High Catalytic Activity.

Nanostructured silicon with an equilibrium shape has exhibited hydrogen evolution reaction activity mainly owing to its high surface area, which is distinct from that of bulk silicon. Such a Wulff shape of silicon favors low-surface-energy planes, resulting in silicon being an anisotropic and predictably faceted solid in which certain planes are favored, but this limits further improvement of the catalytic activity. Here, we introduce nanoporous silicon nanosheets that possess high-surface-energy crystal planes, leading to an unconventional Wulff shape that bolsters the catalytic activity. The high-index plane, uncommonly seen in the Wulff shape of bulk Si, has a band structure optimally aligned with the redox potential necessary for hydrogen generation, resulting in an apparent quantum yield (AQY) of 12.1% at a 400 nm wavelength. The enhanced light absorption in nanoporous silicon nanosheets also contributes to the high photocatalytic activity. Collectively, the strategy of making crystals with nontypical Wulff shapes can provide a route toward various classes of photocatalysts for hydrogen production.

Accelerated hydrogen production on atomically thin silicon nanosheets photocatalyst with unique surface adsorption chemistry

Compared with widely explored layered materials, the atomically thin layer based on nonlayered materials and their thickness dependent properties are less reported. Recently, silicon nanosheet as a novel non-layered 2D material is getting burgeoning attentions. Herein, based on density functional theory calculations, we reveal that freestanding atomically thin silicon nanosheets display favorable hydrogen evolution kinetics including small hydrogen adsorption energy and low hydrogen evolution barrier, which is distinct from multilayer silicon nanosheets and bulk silicon surface. This unique surface adsorption chemistry greatly contributes to the photocatalytic hydrogen production process. Atomically thin silicon nanosheets were further prepared by a liquid phase exfoliation approach and its cocatalyst-free photocatalytic hydrogen production performance is evaluated. The results confirmed that the photocatalytic activity of atomically thin silicon nanosheets vigorously outperforms that of bulk silicon and multilayer silicon flakes. The average hydrogen production rates of A-SiNS can reach158.8 μmol h−1 g−1, which is about 3.2 times higher than that of M-SiNS (49.5 μmol h−1 g−1). This work not only supports atomically thin silicon nanosheets as a potential candidate for photocatalytic reactions but also brings new insights into its unique physiochemical properties and applications.

Exfoliability of two-dimensional silicon nanosheets from calcium disilicide and its enhanced performance as lithium-ion battery anode material

Two-dimensional silicon nanosheets are a promising pathway for achieving stable silicon anode materials due to their large specific surface area, lower diffusion energy barrier, and controlled volume change. The soft chemical topochemical reaction of calcium disilicide is a top-down approach for synthesizing silicon nanosheets of interest due to its potential for large-scale applications. However, the as-reacted material is composed of multilayer silicon nanosheets still held together by interlayer Van der Waal forces which limit its performance and cycling stability as LIB anode material. The current work investigates the exfoliation of soft topochemical-synthesized 2D silicon nanosheets, and a strategy for controlling nanosheet morphology, exfoliability, yields, and LIB performance is outlined herein. The soft topochemical reaction for the top-down synthesis of silicon nanosheets in anhydrous ethanol demonstrates improved exfoliability and initial specific capacities of up to 2390 mAh/g and retentions up to 96.6 % (200 cycles). The exfoliation mechanism and yields were discussed concerning the underlying solute-solvent interactions and sonication hydrodynamic cavitation. Exfoliation yields of up to 10 % are achieved, which is higher than any other reported in the literature for soft chemical synthesis, thus demonstrating the process' potential for large-scale applications.

Luminescent Silicon Nanosheet Paracrystals from Elemental- and Hydride-Based Syntheses of CaSi2 Precursors: Implications for Photonic and Optoelectronic Applications

Layered silicon nanosheets (SiNSs) have attracted considerable attention owing to their unique combination of chemical and physical properties, which makes them an exciting candidate for next-generation on-chip light sources and lasers. Despite over 150 years of research on SiNSs, the effects of the CaSi2 precursor quality on SiNSs have not been studied. Here, we report a comparison of CaSi2 (and SiNSs derived therefrom) synthesized from two reaction pathways: (1) melting Ca and Si (elemental melting, or EM-CaSi2) and (2) the less-explored reaction between CaH2 and Si (hydride synthesis, or HS-CaSi2). We demonstrate that both reaction pathways lead to CaSi2, but the HS-CaSi2 pathway requires only a single step without the need to melt the CaSi2 product and at a temperature below the peritectic decomposition of CaSi2. We find that the EM-CaSi2 exhibits grains that lay flat against the substrate, whereas the HS-CaSi2 has little preferred orientation. We deintercalated both EM- and HS-CaSi2 with HCl at −35 °C to yield hydrogen-terminated SiNSs. We characterized the SiNSs and found that the HS-SiNSs and EM-SiNSs exhibit properties that are nearly identical, with the exception that the morphology of the precursor is imparted to the SiNSs. These results provide the community with a one-step method to synthesize CaSi2 and demonstrate that the morphology of CaSi2 and SiNSs can be controlled with different synthetic techniques.

Highly sensitive plasmonic biosensor enhanced by perovskite-graphene hybrid configuration

This study theoretically proposes a highly sensitive plasmonic biosensor comprising a silver film, perovskite nanosheets, bi-layer silicon nanosheets, and a graphene overlayer. The introduction of perovskite-graphene hybrid structure can reduce the optical reflectivity of the proposed biosensor configuration so that photons are converted into energy to support surface plasmon resonance (SPR) enhancement. Unlike conventional angular modulation, our proposed biosensor configuration is designed using phase modulation, offering sensitivity enhancements as high as 3 orders of magnitude. Excellent biosensing performances have been examined by optimizing the silver film thickness and the number of perovskite nanosheets. Considering a tiny refractive index change of 0.0012 refractive index unit (RIU) caused by biomolecules adsorption behavior, the optimal plasmonic biosensor configuration of 46-nm silver film–5.7-nm silicon interlayer-1-layer CH3NH3PbI3 perovskite film–0.7-nm silicon interlayer-1-layer graphene can produce the highest detection sensitivity of 1.2314 × 105 degree/RIU. In addition, an excellent linear response in the differential phase can be obtained, as the refractive index variation of the sensing interface can be as low as 10−6 RIU, showing great potential in performing ultrasensitive biosensing.

Controlled Isotropic Canalization of Microsized Silicon Enabling Stable High-Rate and High-Loading Lithium Storage.

Silicon is attractive for lithium-ion batteries and beyond but suffers large volume change upon cycling. Hierarchical tactics show promise yet lack control over the unit construction and arrangement, limiting stability improvement at the practical level. Here, a protocol is developed as controlled isotropic canalization of microsized silicon. Distinct from the existing strategies, it involves isotropic canalization by honeycomb-like radial arrangement of silicon nanosheets, and canal consolidation by controlled dual bonding of silicon with carbon. The proof-of-concept nitrogen-doped carbon dual-bonded silicon honeycomb-like microparticles, specifically with a medium density of CNSi and COSi bonds, exhibit stable cycling impressively at high rates and industrial-scale loadings. Two key issues involve isotropic canalization facilitating ion transport in all directions of individual granules and controlled consolidation conferring selective ion permeation and securing charge transport. The study highlights the configurational isotropy and interfacial bonding density, and provides insight into rational design and manufacture of silicon and others with industry-viable features.

Solid Silicon Nanosheet Sandwiched by Self-Assembled Honeycomb Silicon Nanosheets Enabling Long Life at High Current Density for a Lithium-Ion Battery Anode.

A two-dimensional silicon nanosheet (2D Si NS) is promising as a lithium-ion battery anode. However, insufficient cycling life at high current density hampers its practical applications due to its easy fragileness. Rationally engineering the Si micro/nanostructure is promising to address this issue. Unfortunately, the precise construction of a dedicated micro/nanostructure into 2D Si NS meets serious challenges. Herein, a facile strategy is developed to synthesize a sandwich-like honeycomb Si NS/solid Si NS/honeycomb Si NS (h/s/h-Si NS) anode through self-assembled preparation of a sandwich-like honeycomb SiO2 NS/solid SiO2 NS/honeycomb SiO2 NS template, followed by magnesiothermic reduction. This unique structure effectively enhances the mechanical strength, enlarges the specific surface area, and reserves sufficient space to accommodate the anode volume change. A conductive carbon layer is further coated on the h/s/h-Si NS (h/s/h-Si@C NS) to construct a stable electrode/electrolyte interface. The optimal h/s/h-Si@C NS displays outstanding performance with high initial Coulombic efficiency (86%), high reversible capacity (1624 mAh g-1 after 100 cycles at 1000 mA g-1), good rate capability (over 1000 mAh g-1 at 4000 mA g-1), and long cycling life even at 4000 mA g-1 (93% retained capacity after 1000 cycles). This work provides a new strategy for constructing high-performance Si electrodes for lithium-ion battery applications.

In situ synthesis of stable silicon carbide-reinforced silicon nanosheets from organoclay for high-performance lithium-ion battery anodes

The extreme volume change of silicon anode causes fast capacity decay and short cycle life of lithium-ion batteries (LIBs). Thus, the development of stable Si-based anodes to avoid fractures of electrode materials is critical to their commercial applications. Herein, we designed a mechanically stable silicon carbide-reinforced silicon (Si/SiC) material via a facile molten salt-assisted magnesiothermic reduction of the carbonized organoclay. The as-prepared Si/SiC sample inherited the intrinsic layered structure of clay minerals. Benefiting from the atomic-scale direct contact of silicon oxide and carbon in organoclay precursor, β-SiC nanoparticles grew in situ in the Si nanosheets to form a heterostructure with strong bonding, thanks to their similar cubic crystal structure. The Si/SiC anodes exhibited enhanced cycling performance as anodes in LIBs, as compared with pure nanosilicon, which was attributed to the incorporation of SiC nanoparticles, the robust interface structure, and the hierarchical pore structure. Specifically, the Si/SiC nanocomposites containing 11 wt% SiC exhibited a high gravimetric capacity of 1507 mAh g−1, with 72% capacity being retained after 100 cycles at 1 A g−1. Coupled with the LiCoO2 cathode, the full cell showed a high capacity of 148 mAh g−1 after 100 cycles at 0.5C, demonstrating its potential for application in LIBs.

Enhanced Optical and Electronic Properties of Silicon Nanosheets by Phosphorus Doping Passivation.

In this paper, we use the spin-on-dopant technique for phosphorus doping to improve the photoelectric properties of soft-chemical-prepared silicon nanosheets. It was found that the luminescence intensity and luminescence lifetime of the doped samples was approximately 4 fold that of the undoped samples, due to passivation of the surface defects by phosphorus doping. Meanwhile, phosphorus doping combined with high-temperature heat treatment can reduce the resistivity of multilayer silicon nanosheets by 6 fold compared with that of as-prepared samples. In conclusion, our work brings soft-chemical-prepared silicon nanosheets one step closer to practical application in the field of optoelectronics.

Effect of different exfoliation solvents on the saturable absorption properties of germanene and silicene nanosheets prepared by the liquid-phase exfoliation

Germanene and silicene, as graphene analogs of germanium and silicon, have similar structures and properties to graphene, exhibiting exciting nonlinear optical absorption properties. Herein, 2D germanium nanosheets and 2D silicon nanosheets were successfully prepared by liquid-phase exfoliation method using ethanol, isopropanol, and N-methylpyrrolidone as exfoliation solvents, respectively. The dual-arm detection technique was used to systematically research the saturable absorption properties of the nanosheets prepared with different exfoliation solvents from the same material under the excitation of a picosecond pulsed laser. The nonlinear experiment results show that the saturable absorption properties of 2D germanium nanosheets and 2D silicon nanosheets are affected by different exfoliation solvents, and these influences from different exfoliation solvents have their advantages and disadvantages. In addition, the difference in saturable absorption properties of germanium nanosheets and silicon nanosheets under the same experimental conditions is compared. The saturable absorption behavior of germanium nanosheets in the near-infrared band is better than that in the visible band, while the silicon nanosheets have stronger saturable absorption behavior in the visible band. Both germanium nanosheets and silicon nanosheets exhibit superior SA properties, which have a wide range of application prospects in generating ultrashort pulses in ultrafast lasers as saturable absorbers. Our work provides a new idea for the study of nonlinear absorption properties of 2D materials and provides a reference and basis for further optimization and improvement of the properties parameters of saturable absorbers. Additionally, it inspires further research on the nonlinear absorption properties of semiconductor materials.

Chlorination of Hydrogenated Silicon Nanosheets Revealed by Solid-State Nuclear Magnetic Resonance Spectroscopy

Chlorination of Hydrogenated Silicon Nanosheets Revealed by Solid-State Nuclear Magnetic Resonance Spectroscopy

In-depth static and low frequency noise assessment of p-channel gate-all-around vertically stacked silicon nanosheets

In this work are investigated the DC and low frequency noise room-temperature operation of p-channel gate-all-around (GAA) vertically stacked silicon nanosheets (NS). The key DC parameters are estimated using methodologies which are not affected by the impact of the access resistance. Low frequency noise studies shown that the carrier number fluctuations correlated to the mobility fluctuations mechanism explain the 1/f behavior from weak to moderate inversion. It is also discussed how access resistance can have an affect on the Coulomb scattering coefficient estimation. In strong inversion, the access resistance noise contribution is seen to dominates the total 1/f noise.

Exceptional ultrafast nonlinear optical response of functionalized silicon nanosheets.

The present work reports on the ultrafast saturable absorption (SA), optical limiting (OL), and the nonlinear refractive response of hydride-terminated silicon nanosheets (SiNS-H) differently functionalized with styrene and tert-butyl methacrylate (tBuMA), namely, SiNS-styrene and SiNS-tBuMA, using 50 fs, 400 nm and 70 fs, 800 nm laser pulses. SiNS-styrene and SiNS-tBuMA exhibit dramatically enhanced nonlinear optical (NLO) responses compared to SiNS-H, with their absorptive nonlinearity strongly dependent on the laser excitation wavelength. More specifically, the studied functionalized SiNSs reveal strong SA behavior under 400 nm laser excitation, with NLO absorption coefficients, saturable intensities, and modulation depths comparable to various two-dimensional (2D) materials, known to exhibit strong SA, such as graphene, black phosphorous (BP), some transition metal dichalcogenides (TMDs), and some MXenes. On the other hand, under 800 nm laser excitation, SiNS-styrene and SiNS-tBuMA show highly efficient OL performance with OL onset values of about 0.0045 and 0.0065 J cm-2, respectively, which are significantly lower than those of other 2D nanostructures. In addition, it is shown that both SiNS samples have great potential in already existing Si-based optoelectronic devices for optical-switching applications since they exhibit very strong NLO refraction comparable to that of bulk Si. The results of the present work demonstrate that the chemical functionalization of SiNSs provides a highly efficient strategy for the preparation of 2D Si-based nanostructures with enhanced NLO response in view of several optoelectronic and photonic applications, such as OL, SA, and all-optical switching.

Silicon Cutting Waste Derived Silicon Nanosheets with Adjustable Native SiO2 Shell for Highly‐Stable Lithiation/Delithiation

Silicon is an excellent candidate for the next generation of ultra-high performance anode materials, with the rapid iteration of the lithium-ion battery industry. High-quality silicon sources are the cornerstone of the development of silicon anodes, and silicon cutting waste (SCW) is one of them while still faces the problems of poor performance and unclear structure-activity relationship. Herein, a simple, efficient, and inexpensive purification method is implemented to reduce impurities in SCW and expose the morphology of nanosheets therein. Furthermore, HF is used to modulate the abundant native O in SCW after thermodynamic and kinetic considerations, realizing the mechanical support for the internal Si in the form of an amorphous SiO2 shell. Afterward, SCNS@SiO2 -2.5 with a 1.0nm thick SiO2 shell exhibits a reversible capacity of 1583.3 mAhg-1 after 200 cycles at 0.8 Ag-1 . Ultimately, the molecular dynamics simulations profoundly reveal that the amorphous SiO2 shell is transformed into the extremely ductile Lix SiOy shell to ditch stress and relieve strain during the lithiation/delithiation process.