A highly sensitive ratiometric near-infrared nanosensor based on erbium-hyperdoped silicon quantum dots for iron(Ⅲ) detection

Ratiometric fluorescent detection of iron(Ⅲ)(Fe^(3+))offers inherent self-calibration and contactless analytic capabilities.However,realizing a dual-emission near-infrared(NIR)nanosensor with a low limit of detection(LOD)is rather challenging.In this work,we report the synthesis of water-dispersible erbium-hyperdoped silicon quantum dots(Si QDs:Er),which emit NIR light at the wavelengths of 810 and 1540 nm.A dual-emission NIR nanosensor based on water-dispersible Si QDs:Er enables ratiometric Fe^(3+)detection with a very low LOD(0.06μM).The effects of pH,recyclability,and the interplay between static and dynamic quenching mechanisms for Fe^(3+)detection have been systematically studied.In addition,we demonstrate that the nanosensor may be used to construct a sequential logic circuit with memory functions.

Activation of silicon quantum dots for emission

The emission of silicon quantum dots is weak when their surface is passivated well. Oxygen or nitrogen on the surface of silicon quantum dots can break the passivation to form localized electronic states in the band gap to generate active centers where stronger emission occurs. From this point of view, we can build up radiative matter for emission. Emissions of various wavelengths can be obtained by controlling the surface bonds of silicon quantum dots. Our experimental results demonstrate that annealing is important in the treatment of the activation, and stimulated emissions at about 600 and 700 nm take place on active silicon quantum dots.

Fabrication of Silicon Carbide Quantum Dots via Chemical-Etching Approach and Fluorescent Imaging for Living Cells

A simple chemical-etching approach is used to prepare the silicon carbide quantum dots (QDs). The raw materials of silicon carbide (SiC) with homogeneous nanoparticles fabricated via self-propagating combustion synthesis are corroded in mixture etchants of nitric and hydrofluoric acid. After sonication and chromatography in the ultra-gravity field for the etched products, aqueous solution with QDs can be obtained. The microstructure evolution of raw particles and optical properties of QDs were measured. Different organophilic groups on the surface like carboxyl, oxygroup, and hyfroxy were produced in the process of etching. Fluorescent labeling and imaging for living cells of Aureobasidium pulluans were investigated. The results indicated that SiC QDs were not cytotoxic and could stably label due to the conjugation between organophilic groups of QDs and specific protein of cells, it can be utilized for fluorescent imaging and tracking cells with in vivo and long-term-distance. Moreover, mechanism and specificity of mark were also analyzed.

The Role of Silion Oxide Layers in Luminescence of Ensembles of Silicon Quantum Dots

Based on the quantum confinement-luminescence center model, to ensembles of spherical silicon nanocrystals (nc-Si) containing two kinds of luminescence centers (LCs) in the layers surrounding the nc-Si, the relationship between the photoluminescence (PL) and the thickness of the layer is studied with the excitation energy flux density as a parameter. When there is no layer surrounding the nc-Si, the electron-heavy hole pair can only recombine inside the nc-Si, then the PL blueshift with reducing particle sizes roughly accords with the rule predicted by the quantum confinement model of Canham. When there presences a layer, some of the carriers may tunnel into it and recombine outside the nc-Si at the LCs to emit visible light. The thicker the layer is, the higher the radiative recombination rate occurred outside the nc-Si will be. When the central scale of the nc-Si is much smaller than the critical scale, the radiative recombination rate outside the nc-Si dominates, and visible PL will be possible for some nc-Si samples with big average radius, greater than 4 nm, for example. When there is only one kind of LC in the layer, the PL peak position does not shift with reducing particle sizes. All these conclusions are in accord with the experimental results. When there are two or more kinds of LCs in the layer, the PL peak position energy and intensity swing with reducing particle sizes.

Controlling spins in silicon quantum dots

Spins in silicon(Si)quantum dots(QDs),as a new type of solid state qubits,is expected to be a competitive contender in the long run of scalable quantum computation[1].Quantum computation is believed to be the next-generation computing technology to solve the problems that no classical computer can feasibly tackle.In the last decade.

Nonlinear Doping, Chemical Passivation and Photoluminescence Mechanism in Water-Soluble Silicon Quantum Dots by Mechanochemical Synthesis

A series of boron- and phosphorus-doped silicon wafers are used to prepare a series of doped silicon nanocrystals （nc-Si） by high-energy ball milling with carboxylic acid-terminated surface. The sizes of the nc-Si samples are demonstrated to be 〈 S nm. The doping levels of the nc-Si are found to be nonlinearly dependent on the original doping level of the wafers by x-ray photoelectron spectroscopy measurement. It is found that the nonlinear doping process will lead to the nonlinear chemical passivation and photoluminescence （I3L） intensity evolution. The doping, chemical passivation and PL mechanisms of the doped nc-Si samples prepared by mechanochemical synthesis are analyzed in detail.

Silicon quantum dots delivered phthalocyanine for fluorescence guided photodynamic therapy of tumor

Imaging-guided cancer therapy provides a simultaneous tumor imaging and treatment, which helps to eliminate the excessive toxicity to the healthy tissues. For this purpose, multifunctional probes capable of both imaging and curing are needed. In this work, we synthesize water-soluble silicon quantum dots（Si QDs） smaller than 5 nm. Such Si QDs are used for delivering the hydrophobic drug phthalocyanine（Pc）. The as-prepared Si/Pc nanocomposite particles show efficient transmembrane delivery into cells and feasible biocompatibility. Moreover, these composite particles emit dualchannel fluorescence signals even after cellular internalization and demonstrate robust photostability in the Si channel.More interestingly, the Si/Pc composite particles show efficient photodynamic therapy effects against tumors both in vitro and in vivo.

Recent progress in epitaxial growth of Ⅲ–Ⅴ quantum-dot lasers on silicon substrate

In the past few decades,numerous high-performance silicon(Si)photonic devices have been demonstrated.Si,as a photonic platform,has received renewed interest in recent years.Efficient Si-basedⅢ–Ⅴquantum-dot(QDs)lasers have long been a goal for semiconductor scientists because of the incomparable optical properties of Ⅲ–Ⅴcompounds.Although the material dissimilarity betweenⅢ–Ⅴmaterial and Si hindered the development of monolithic integrations for over 30 years,considerable breakthroughs happened in the 2000s.In this paper,we review recent progress in the epitaxial growth of various Ⅲ–ⅤQD lasers on both offcut Si substrate and on-axis Si(001)substrate.In addition,the fundamental challenges in monolithic growth will be explained together with the superior characteristics of QDs.

1.3-μm InAs/GaAs quantum dots grown on Si substrates

We compare the effect of InGaAs/GaAs strained-layer superlattice(SLS) with that of GaAs thick buffer layer(TBL)serving as a dislocation filter layer. The InGaAs/GaAs SLS is found to be more effective than GaAs TBL in blocking the propagation of threading dislocations, which are generated at the interface between the GaAs buffer layer and the Si substrate. Through testing and analysis, we conclude that the weaker photoluminescence for quantum dots(QDs) on Si substrate is caused by the quality of capping In_(0.15)Ga_(0.85)As and upper GaAs. We also find that the periodic misfits at the interface are related to the initial stress release of GaAs islands, which guarantees that the upper layers are stress-free.

Investigation into the InAs/GaAs quantum dot material epitaxially grown on silicon for O band lasers

InAs/GaAs quantum dot(QD)lasers were grown on silicon substrates using a thin Ge buffer and three-step growth method in the molecular beam epitaxy(MBE)system.In addition,strained superlattices were used to prevent threading disloca-tions from propagating to the active region of the laser.The as-grown material quality was characterized by the transmission electron microscope,scanning electron microscope,X-ray diffraction,atomic force microscope,and photoluminescence spectro-scopy.The results show that a high-quality GaAs buffer with few dislocations was obtained by the growth scheme we de-veloped.A broad-area edge-emitting laser was also fabricated.The O-band laser exhibited a threshold current density of 540 A/cm^(2) at room temperature under continuous wave conditions.This work demonstrates the potential of large-scale and low-cost manufacturing of the O-band InAs/GaAs quantum dot lasers on silicon substrates.

Silicon quantum dots-based fluorescent sensor for the detection of cobalt with high sensitivity and selectivity

Fluorescent silicon quantum dots(Si QDs)were hydrothermally synthesized from a mixture of 3(2-aminoethylamino)propyl(dimethoxymethylsilane)(AEAPDMMS)and poly(vinylpyrrolidine)(PVP).The resulting Si QDs exhibited good water solubility and high stability.Under the optimized conditions,the probe revealed an excellent linear fluorescence quenching effect on Co2+ranging from 1μmol/L to 120μmol/L with a limit of detection of 0.37μmol/L(based on 3 s/k).The quenching mechanism was studied,showing that static quenching(SQE)causes the main effect.Furthermore,the test paper based on Si QDs was prepared,which is cost-effective,high sensitivity,good selectivity,easy to use and show excellent anti-interference capability.This method was applied to analyze the content of Co2+in environmental water samples with satisfying results.

Bifunctional Silicon Quantum Dots for Antibacterial Application and Highly Sensitive Detection of Tetracycline

Silicon quantum dots(SiQDs)with high water-soluble and favorable photostability were prepared by a one-step hydrothermal method.The average diameter of SiQDs was 2.02 nm characterized by transmission electron microscope.It was to be noted that the as-prepared SiQDs showed eff ective antibacterial activity,which was attributed to electrostatic interaction and the generation of reactive oxygen species.The minimum inhibitory concentration of SiQDs against Escherichia coli and Staphylococcus aureus was 0.45 mg/mL and 0.38 mg/mL,respectively.Besides,based on the static quenching eff ect-induced fluorescence quenching mechanism,the SiQDs exhibited high sensitivity and selectivity for detecting tetracyclines(TC).A good linear relationship was obtained between the fluorescence intensity of SiQDs and the concentration of tetracycline(TC)in the range of 0–0.08μmol/L(R^(2)=0.9993)with a detection limit of 0.0176μmol/L.Furthermore,the TC content in the honey samples was determined using the SiQDs.All the results suggest that the as-prepared SiQDs can be a potential fluorescent probe for application in antibacterial and analysis.

Perspective:optically-pumped Ⅲ–Ⅴ quantum dot microcavity lasers via CMOS compatible patterned Si (001) substrates

Direct epitaxial growthⅢ–Ⅴquantum dot(QD)structures on CMOS-compatible silicon substrates is considered as one of the most promising approaches to achieve low-cost and high-yield Si-based lasers for silicon photonic integration.However,epitaxial growth ofⅢ–Ⅴmaterials on Si encounters the following three major challenges:high density of threading dislocations,antiphase boundaries and thermal cracks,which significantly degrade the crystal quality and potential device performance.In this review,we will focus on some recent results related to InAs/GaAs quantum dot lasers on Si(001)substrates byⅢ–Ⅴ/Ⅳhybrid epitaxial growth via(111)-faceted Si hollow structures.Moreover,by using the step-graded epitaxial growth process the emission wavelength of InAs QDs can be extended from O-band to C/L-band.High-performance InAs/GaAs QD microdisk lasers with sub-milliwatts threshold on Si(001)substrates are fabricated and characterized.The above results pave a promising path towards the on-chip lasers for optical interconnect applications.

Synthesis of temperature and salt resistance silicon dots for effective enhanced oil recovery in tight reservoir

The intensive development of tight reservoirs has positioned them as a strategic alternative to conventional oil and gas resources. Existing enhanced oil recovery(EOR) methods struggle to effectively exploring reservoir oil, resulting in low recovery rates. Novel and effective means of developing tight reservoirs are urgently needed. Nanomaterials have shown promising applications in improving water flooding efficiency, with in-depth research into mechanisms that lower injection pressure and increase water injection volumes. However, the extent of improvement remains limited. In this study, a silicon quantum dots(Si-QDs) material was synthesized via a hydrothermal synthesis method and used to prepare a nanofluid for the efficient recovery of tight reservoir. The Si-QDs, with an approximate diameter of 3 nm and a spherical structure, were surface functionalized with benzenesulfonic acid groups to enhance the performance. The developed nanofluid demonstrated stability without aggregation at 120℃ and a salinity of 60000 mg/L. Core flooding experiments have demonstrated the attractive EOR capabilities of Si-QDs, shedding light of the EOR mechanisms. Si-QDs effectively improve the wettability of rocks, enhancing the sweeping coefficient of injected fluids and expanding sweeping area.Within this sweeping region, Si-QDs efficiently stripping adsorbed oil from the matrix, thus increasing sweeping efficiency. Furthermore, Si-QDs could modify the state of pore-confined crude oil, breaking it down into smaller particles that are easier to displacement in subsequent stages. Si-QDs exhibit compelling EOR potential, positioning them as a promising approach for effectively developing tight oil reservoirs.

Single-electron transport through single and coupling dopant atoms in silicon junctionless nanowire transistor

We investigated single-electron tunneling through single and coupling dopant-induced quantum dots(QDs) in silicon junctionless nanowire transistor(JNT) by varying temperatures and bias voltages. We observed that two possible charge states of the isolated QD confined in the axis of the initial narrowest channel are successively occupied as the temperature increases above 30 K. The resonance states of the double single-electron peaks emerge below the Hubbard band, at which several subpeaks are clearly observed respectively in the double oscillated current peaks due to the coupling of the QDs in the atomic scale channel. The electric field of bias voltage between the source and the drain could remarkably enhance the tunneling possibility of the single-electron current and the coupling strength of several dopant atoms. This finding demonstrates that silicon JNTs are the promising potential candidates to realize the single dopant atom transistors operating at room temperature.

Silicon with Clusters of Impurity Atoms as a Novel Material for Optoelectronics and Photovoltaic Energetics

The paper presents unique functional capabilities of silicon with nanoclusters of impurity atoms with various characters. It is shown that, depending on the nature of the clusters, it is possible to expand the spectral diapason of sensitivity towards the IR region and obtain silicon with anomalously high negative mag-netoresistance (Δρ/ρ > 100%) at room temperature. The formation of clusters of impurity atoms with different nature and concentration in the lattice of semiconductor materials is a new approach for obtaining bulk-nanostructured silicon with unique physical properties.

Molecular Dynamics Study on Mechanical Properties in the Structure of Self-Assembled Quantum Dot

Stress and strain in the structure of self-assembled quantum dots constructed in the Ge/Si(001) system is calculated by using molecular dynamics simulation. Pyramidal hut cluster composed of Ge crystal with {105} facets surfaces observed in the early growth stage are computationally modeled. We calculate atomic stress and strain in relaxed pyramidal structure. Atomic stress for triplet of atoms is approximately defined as an average value of pairwise (virial) quantity inside triplet, which is the product of vectors between each two atoms. Atomic strain by means of atomic strain measure (ASM) which is formulated on the Green’s definition of continuum strain. We find the stress (strain) relaxation in pyramidal structure and stress (strain) concentration in the edge of pyramidal structure. We discuss size dependency of stress and strain distribution in pyramidal structure. The relationship between hydrostatic stress and atomic volumetric strain is basically linear for all models, but for the surface of pyramidal structure and Ge-Si interface. This means that there is a reasonable correlation between atomic stress proposed in the present study and atomic strain measure, ASM.

双硅源硅量子点荧光探针的合成及检测Cr(Ⅵ)应用

Cr(Ⅵ)在水中溶解性很强,超过0.1 mg/L的Cr(Ⅵ)会对环境和生命健康产生毒害作用,因此开发灵敏度高的六价铬离子的检测方法就显得尤为重要。采用N-[3-(三甲氧基硅基)丙基]乙二胺,三甲基硅基咪唑作为双硅源前驱体,柠檬酸钠为还原剂,通过水热法可制备水分散性良好的球形双硅源硅量子点(D-Si QDs)。研究结果表明,D-Si QDs为球结构且表面含有大量氨基与咪唑基团。在最优条件下制备的D-Si QDs最佳激发波长为359 nm,最大发射波长为451 nm,有着较好的光稳定性。D-Si QDs的荧光可被Cr(Ⅵ)选择性猝灭,且荧光猝灭程度与Cr(Ⅵ)浓度在0.5~100μmol/L的范围内呈良好的线性关系,检测限为0.056μmol/L;对自来水样中检测Cr(Ⅵ)回收率在100.37%~105.83%,相对标准偏差均小于2.36%。研究为开发高灵敏度Cr(Ⅵ)检测的D-Si QDs荧光探针提供了思路。

锌掺杂荧光硅量子点作为叶面光肥对生菜生长的影响

以N-氨乙基-γ-氨丙基二甲氧基硅烷分子(DAMO)作为硅源,采用水热法合成一种高分散性、光学性能稳定的锌掺杂荧光硅量子点(Si@Zn QDs)。以Si@Zn QDs作为叶面光肥,吸收太阳光中不被植物利用的紫外光,发出能使生菜吸收进行光合作用的蓝光,提高了光能利用率。通过14 d的水培试验评估Si@Zn QDs作为叶面光肥对生菜生长的影响。结果表明,Si@Zn QDs与生菜的叶绿体(CLP)复合后,提高了希尔反应活性,当锌掺杂量达0.1%时,对生菜生长的促进效果最明显。与对照组相比,干质量和鲜质量分别增加41.64%和52.20%。Si@Zn 0.1%QDs(100 mg·L^(-1))使生菜叶片中叶绿素a、叶绿素b、总叶绿素、类胡萝卜素和蛋白质含量分别提高60.56%、56.37%、61.20%、49.75%和29.90%。这项工作为锌掺杂荧光硅量子点在植物光合作用中的应用提供了科学依据。

Ultrafast optical spectroscopy of surface-modified silicon quantum dots: unraveling the underlying mechanism of the ultrabright and color-tunable photoluminescence

In this work,the fundamental mechanism of ultrabright fluorescence from surface-modified colloidal silicon quantum dots is investigated in depth using ultrafast spectroscopy.The underlying energy band structure corresponding to such highly efficient direct bandgap-like emissions in our surface-modified silicon quantum dots is unraveled by analyzing the transient optical spectrum,which demonstrates the significant effect of surface molecular engineering.It is observed that special surface modification,which creates novel surface states,is responsible for the different emission wavelengths and the significant improvement in the photoluminescence quantum yields.Following this essential understanding,surface-modified silicon quantum dots with deep blue to orange emission are successfully prepared without changing their sizes.