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.

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.

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.

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.

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.

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.

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.

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。

SiC量子点敏化g-C_(3)N_(4)光阳极在光催化燃料电池中的应用

光催化燃料电池(PFC)是一种将光催化过程中产生的化学能有效转化为电能的新型电池装置。制备了SiC量子点敏化石墨相C_(3)N_(4)(g-C_(3)N_(4))复合材料,将其作为PFC系统光阳极材料,设计并优化了一种新型复合功能双室光催化燃料电池。当阴极室引入芬顿反应作为辅助后,复合材料光阳极显示出优异的光催化和光电转化性能,两个电极室中的反应速率均得到明显增加,进而显著提高了电池体系的光电转换效率。

Preparation and Evaluation of Silicon Quantum Dots-Bonded Silica Stationary Phase for Reversed-Phase Chromatography

In this paper,silicon quantum dots(SiQDs)with green fluorescence are synthesized by solvothermal reaction of 3-(2,3-epoxypropoxy)propyltrimethoxysilane(GPTMS)and ethylenediaminetetraacetic acid(EDTA),and then SiQDs are bonded to the surface of silica to obtain a new nano-on-micro stationary phase(SiO_(2)-SiQDs)for reversed-phase chromatography.The successful preparation of SiO_(2)-SiQDs stationary phase is demonstrated by a variety of characterizations,such as transmission electron microscopy,laser confocal microscopy,elemental analysis and Fourier infrared spectroscopy.In addition,the chromatographic performance of the prepared stationary phase is evaluated and it shows good separation performance for non-polar substances such as alkylbenzene,aniline and polycyclic aromatic hydrocarbons in reversed-phase liquid chromatography.It is also verified that the stationary phase has good methyl selectivity and shape selectivity.More interestingly,the separation of prednisolone and hydrocortisone isomers can also be achieved at a low ratio of organic solvents,indicating that this new stationary phase has a good application prospect in isomer separation.

硅量子点的合成及在Cr_(2)O_(7)^(2-)检测中的应用

六价铬离子是一种能对人体产生多种危害的金属离子,它具有高水溶性和流动性,更易于对环境和生命健康产生毒害作用。所以灵敏且不受其他金属离子干扰的测量六价铬离子就显得尤为重要。本文提出了一种简单的一步合成法制备硅量子点(SiQDs),所制备出来的SiQDs在365 nm激发波长下在446 nm处呈现出较强的荧光发射峰,这使得它具有荧光探针的潜力。在加入Cr_(2)O_(7)^(2-)后,SiQDs在446 nm处的发射峰被有效猝灭,基于这一猝灭行为可以建立测定Cr_(2)O_(7)^(2-)的方法。试验表明,Cr_(2)O_(7)^(2-)浓度在10~100μmol/L范围内呈良好的线性关系(R^(2)=0.9955),检出下限为0.1964μmol/L。所制备的SiQDs具有快速、高选择性和良好的抗干扰能力,并且成功的用于Cr_(2)O_(7)^(2-)的检测。

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.

硅量子点荧光探针检测8-羟基喹啉的研究

量子点荧光探针已广泛用于酚类化合物的检测,但用于具有特殊结构的酚类化合物8-羟基喹啉(8-HQ)检测的相关研究报道很少。本文以硅烷偶联剂KH550和抗坏血酸为原料,通过一步水热法制备了蓝光硅量子点(B-SiQDs)。研究发现,8-HQ对B-SiQDs有显著荧光猝灭效应;在最佳实验条件下,8-HQ浓度在0.01~0.4 mmol·L^(-1)范围内与B-SiQDs荧光猝灭率呈良好线性关系,检测限0.12μmol·L^(-1)。将该方法用于护发素样品中8-HQ的检测,加标回收率在96%~107%范围内,相对标准偏差(RSD)低于1%,结果令人满意。

Design and mechanism insight on SiC quantum dots sensitized inverse opal TiO_(2) with superior photocatalytic activities under sunlight

The combination of SiC quantum dots sensitized inverse opal TiO_(2) photocatalyst is designed in this work and then applied in wastewater purification under simulated sunlight.From various spectroscopic techniques,it is found that electrons transfer directionally from SiC quantum dots to inverse opal TiO_(2),and the energy difference between their conduction/valence bands can reduce the recombination rate of photogenerated carriers and provide a pathway with low interfacial resistance for charge transfer inside the composite.As a result,a typical type-II mechanism is proved to dominate the photoinduced charge transfer process.Meanwhile,the composite achieves excellent photocatalytic performances(the highest apparent kinetic constant of 0.037 min^(-1)),which is 6.2 times(0.006 min^(-1))and 2.1 times(0.018 min^(-1))of the bare inverse opal TiO_(2) and commercial P25 photocatalysts.Therefore,the stability and non-toxicity of SiC quantum dots sensitized inverse opal TiO_(2) composite enables it with great potential in practical photocatalytic applications.