Aggregation/assembly induced emission (AIE) has been observed for metal nanoclusters (NCs), but the origin of the enhanced emission is not fully understood, yet. In this work, the significant contribution of metal defects on AIE is revealed by engineering the self-assembly process of Cu NCs using ethanol. The presence of ethanol leads to a rapid assembly of NCs into ultrathin nanosheets, promoting the formation of metal defects-rich surface. Detailed studies and computer simulation confirm that the metal defects-rich nanosheets possess increased Cu(I)-to-Cu(0) ratio, which greatly influences ligand-to-metal–metal charge transfer and therewith facilitates the radiative relaxation of excitons. Consequently, the Cu NCs self-assembly nanosheets exhibit obvious emission enhancement.

Aggregation-induced emission (AIE) and self-assembly induced emission (SAIE) effects have been employed to tune the emission properties of metal nanoclusters (NCs). However, it is still not possible to further enhance the photoluminescence quantum yields (PLQYs) and control the emission colors of the NCs using AIE and SAIE. On the basis of our recent work studying the contribution of Cu(I) defects in the SAIE of Cu NCs, in this article, Au(I) was doped into Cu NC self-assembled nanosheets (NSASs) to construct a more stable Au(I)-centered state. As a result, the PLQYs, emission stability, and tunability of emission colors of the Cu NSASs were significantly improved. Detailed studies reveal that the doped Au(I) induces a Au(I)–Cu(I) metallophilic interaction, which leads to a ligand-to-Cu–Au charge transfer, which facilitates the relaxation of excited electrons via a radiative pathway, thereby enhancing the emission intensity. The charge transfer from Cu to Au lowers the energy, thus leading to the red-shift of PL emission. Au(I) is likely doped into the Cu NSASs rather than in individual NCs, because 0.3% Au doping is enough to alter the emission properties. By mixing Au(I)-doped Cu NSASs with different emission colors (due to different Au doping percentages) as color conversion materials on commercially available 365 nm GaN chips, a white light-emitting diode prototype is fabricated.Keywords: Au doping; Cu nanocluster; light-emitting diode; self-assembly induced emission; two-dimensional material;

Carbon nanoparticles (C-NPs) are novel and competitive luminescent materials both in academic research and practical applications owing to their environment-friendly behavior and high abundance on Earth. Despite the successes in preparing strongly luminescent C-NPs, preserving the luminescence in solid materials is still challenging. With the aim to produce C-NP-based white-light-emitting diodes (WLEDs), in this work, solvent-dispersible C-NPs are embedded into commercial silica gel via a dual solvent evaporation route. The basic idea is to lower the evaporation rate of the solvents, thus leading to a good dispersion of the C-NPs in the silica gel. This method avoids the aggregation-induced emission quenching of C-NPs in solid materials, and therefore preserves the strong luminescence in the C-NPs/silica gel composites. The composites are further blended with polydimethylsiloxane and act as the color conversion layer on InGaN UV-blue emitting chips, which produces LEDs with a bright white emission.

CsPbX3 (X = Cl, Br, I) perovskite quantum dots (QDs) are potential emitting materials for illumination and display applications, but toxic Pb is not environment- and user-friendly. In this work, we demonstrate the partial replacement of Pb with Mn through phosphine-free hot-injection preparation of CsPbxMn1–xCl3 QDs in colloidal solution. The Mn substitution ratio is up to 46%, and the as-prepared QDs maintain the tetragonal crystalline structure of the CsPbCl3 host. Meaningfully, Mn substitution greatly enhances the photoluminescence quantum yields of CsPbCl3 from 5 to 54%. The enhanced emission is attributed to the energy transfer of photoinduced excitons from the CsPbCl3 host to the doped Mn, which facilitates exciton recombination via a radiative pathway. The intensity and position of this Mn-related emission are also tunable by altering the experimental parameters, such as reaction temperature and the Pb-to-Mn feed ratio. A light-emitting diode (LED) prototype is further fabricated by employing the as-prepared CsPbxMn1–xCl3 QDs as color conversion materials on a commercially available 365 nm GaN LED chip.Keywords: CsPbxMn1−xCl3; light-emitting diode; low lead; perovskite quantum dots; phosphine-free preparation;

Nanomaterials and nanocarriers have shown great potential in tumor theranostics, but low tumor uptake rate casts doubt on their practical applications due to competitive uptake by normal tissues and the immune system. In this work, we demonstrate the influence of electrostatic attraction and shuttle-like morphology on tumor uptake by designing positively charged Cu(II) and Fe(III) doped polyaniline (CuPani) nanoshuttles (NSs). The experimental results indicate that such nanomaterials promote cellular adhesion/internalization in vitro, and therefore enhance retention in tumor tissues. The CuPani NSs show electrostatic attraction driven nonspecific tumor recognition between oral epithelial carcinoma (KB) and Henrietta Lacks cancer (Hela) tumors. The uptake rate of CuPani NSs by negatively charged Hela tumors is up to 7.9% ID per g without any surface modification, while the uptake rate by KB tumors with a weaker charge is only 2.8% ID per g. The high tumor uptake rate is attributed to the strong electrostatic attraction of CuPani NSs with tumor tissues, which is efficient when competing against clearance by the immune system. In addition, compared with stealth effect-matched nanoparticles, the NSs show an improved tumor uptake rate due to the one-dimension-like morphology for effective cellular internalization. The synergetic enhancement of tumor uptake by electrostatic attraction and shuttle-like morphology may be helpful in the design of novel nanodevices for performing tumor theranostics.

Luminescent Cu nanoclusters (NCs) are potential phosphors for illumination and display, but the difficulty in achieving full-color emission greatly limits practical applications. On the basis of our previous success in preparing Cu NC self-assembly architectures with blue-green and yellow emission, in this work, Cu NC self-assembly architectures with strong red emission are prepared by replacing alkylthiol ligands with aromatic thiols. The introduction of aromatic ligands is able to influence the ligand-to-metal charge transfer and/or ligand-to-metal–metal charge transfer, thus permitting the tuning of the emission color and enhancing of the emission intensity. The emission color can be tuned from yellow to dark red by choosing the aromatic ligands with different conjugation capabilities, and the photoluminescence quantum yield is up to 15.6%. Achieving full-color emission Cu NC self-assembly architectures allows the fabrication of Cu NC-based white light-emitting diodes.

Ultrathin two-dimensional (2D) nanomaterials composed of abundant and inexpensive 3d metal chalcogenides are competitive candidates for practical electrocatalysts for the oxygen evolution reaction (OER). However, the bottom-up synthesis of atomically thick nanosheets is difficult for materials with inherent non-layered host crystals. Here, we demonstrate the preparation of single-unit-cell thick Co9S8 nanosheets from preassembled Co14 nanoclusters (NCs) by virtue of the flexibility of NC self-assembly in colloidal solution. Due to their free-standing properties, the NC self-assembled architectures are capable of bearing sulfurization at elevated temperatures, thus producing ultrathin Co9S8 nanosheets. The nanosheets exhibit an OER overpotential as low as 0.27 V at 10 mA cm−2 in 0.1 M KOH, which is comparable to the performance of the best Co-based OER electrocatalysts.

Self-assembly and crystallization are two common methods to control the morphologies of nanomaterials, which have many similarities. In this work, chloride is used to direct the self-assembly process of Cu nanoclusters and the subsequent growth of Cu2−xS nanocrystals. Meaningfully, chloride both promotes the transformation of Cu nanocluster self-assembled architectures from one-dimensional (1D) to 2D, and facilitates the transformation of Cu2−xS nanocrystals from nanorods to nanosheets. Such an influence is attributed to the selective adsorption of chloride ions on the specific facets of nanoclusters and nanocrystals, which alters the inter-nanocluster weak interactions during self-assembly and suppresses the activity of Cu2−xS facets during nanocrystal growth. The current results indicate that the method used to direct the morphologies of nanocrystals is extendable to control the tendency of nanocluster self-assembly.

Metal nanoclusters (NCs) have attracted broad attention for their molecular-like electronic structures and unique emission properties, but the difficulty in controlling emission color greatly limits their application in illumination and display. In this work, we demonstrate the capability to control the self-assembly induced emission (SAIE) of Cu NCs by modulating the inter-NC distance in the self-assembly materials, which is capable of tuning the emission color from green to red. The inter-NC distance is mainly modulated by controlling the experimental variables during the NC self-assembly, such as the species of the solvents and ligands, duration of assembly, temperature, and so forth. These experimental variables influence the balance of inter-NC weak interactions, thus altering the distance of as-assembled NCs. The variation of the inter-NC distance greatly influences the photo-physical behavior of Cu NCs, and in particular the ligand-to-Cu–Cu charge transfer, permitting the tuning of the emission color. As the Cu NCs self-assembly materials exhibit strong, stable, and color-tunable SAIE, they are employed as the color conversion materials for fabricating white light-emitting diodes.

Nanocomposites based on hollow Au nanostructures have gained considerable attention in theranostics applications because of their unique plasmonic structures and attractive physicochemical properties. The exploration of feasible and facile methods for constructing multifunctional nanocomposites combined with bioactive molecules is greatly needed for the development of multifunctional theranostics platforms. In this work, resveratrol, a natural polyphenol with antioxidant activity and cancer-chemopreventive propertyies is employed as the reducing agent cum coating agent for the surfactant-free preparation of Au@resveratrol hollow NPs (Au@Res HNPs). The as-prepared Au@Res HNPs were found to present good photothermal performance and chemical inhibition for cancer therapy. In vitro experiments indicated that the Au@Res HNPs can block cell cycles to inhibit cell division and lead to cell apoptosis after 808-nm laser irradiation. Because no toxic surfactants are introduced, the current protocol avoids the tedious surfactant separation and surface modification processes that are necessary for most theranostics materials.Keywords: antioxidant activity; hollow Au nanoparticles; nanocomposites; photothermal therapy; resveratrol;

FeS2 nanomaterials with two-dimensional features hold great promise for electrochemical and photovoltaic applications. However, the preparation of ultrathin FeS2 nanosheets is still challenging because of the lack of a tailor-made approach. In this work, FeS2 nanosheets with a thickness of 2.1 nm are prepared through a Fe3O4-seeded approach. Uniform Fe3O4 nanoparticles are foremost synthesized via the standard method in organic media. The injection of a S solution leads to the replacement of O in Fe3O4 through anion-exchange, which generates (110) facet-enriched FeS2 nuclei. The subsequent (110) facet-mediated oriented attachment and fusion of FeS2 nuclei produce ultrathin FeS2 nanosheets. As catalysts in the hydrogen evolution reaction, FeS2 nanosheets exhibit good electrochemical activity.

Electrophoretic deposition (EPD) is a conventional method for fabricating film materials from nanometer-sized building blocks, and exhibits the advantages of low-cost, high-efficiency, wide-range thickness adjustment, and uniform deposition. Inspired by the interest in the application of two-dimensional (2D) nanomaterials, the EPD technique has been recently extended to building blocks with 2D features. However, the studies are mainly focused on simplex building blocks. The utilization of multiplex building blocks is rarely reported. In this work, we demonstrate a controlled EPD of Cu and Au sheets, which are 2D assemblies of luminescent Cu and Au nanoclusters. Systematic investigations reveal that both the deposition efficiency and the thickness are determined by the lateral size of the sheets. For Cu sheets with a large lateral size, a high ζ-potential and strong face-to-face van der Waals interactions facilitate the deposition with high efficiency. However, for Au sheets, the small lateral size and ζ-potential limit the formation of a thick film. To solve this problem, the deposition dynamics are controlled by increasing the concentration of the Au sheets and adding acetone. This understanding permits the fabrication of a binary EPD film by the stepwise deposition of Cu and Au sheets, thus producing a luminescent film with both Cu green emission and Au red emission. A white light-emitting diode prototype with color coordinates (x, y) = (0.31, 0.36) is fabricated by employing the EPD film as a color conversion layer on a 365 nm GaN clip and further tuning the amount of deposited Cu and Au sheets.

Iron oxide (Fe3O4), polydopamine (PDA), and in particular their composites are examples of the safest nanomaterials for developing multifunctional nanodevices to perform noninvasive tumor diagnosis and therapy. However, the structures and performances of Fe3O4–PDA nanocomposites should be further perfected to enhance the theranostic efficiency. In this work, we demonstrate the fabrication of PDA-capped Fe3O4 (Fe3O4@PDA) superparticles (SPs) employing preassembled Fe3O4 nanoparticles (NPs) as the cores. Owing to the collective effect of preassembled Fe3O4 NPs, the superparamagnetism and photothermal performance of Fe3O4@PDA SPs are greatly enhanced, thus producing nanodevices with improved magnetic resonance imaging (MRI)-guided photothermal efficiency. Systematical studies reveal that the molar extinction coefficient of the as-assembled Fe3O4 SPs is 3 orders of magnitude higher than that of individual Fe3O4 NPs. Also due to the high aggregation degree of Fe3O4 NPs, the T2-weighted MRI contrast is greatly enhanced for the SPs with r2 relaxivity of 230.5 mM–1 s–1, which is ∼2.5 times larger than that of individual Fe3O4 NPs. The photothermal stability, physiological stability, and biocompatibility, as well as the photothermal performance of Fe3O4 SPs, are further improved by enveloping with PDA shell.Keywords: Fe3O4 nanoparticle; polydopamine; self-assembly; superparticle; theranostics

Two-dimensional (2D) nanomaterials have attracted much attention because of the unique layered structures and charming properties in many applications. However, with respect to stimulus-responsive 2D nanomaterials, the rigidity of most 2D nanostructures sheds doubt on achieving morphology response. In this paper, a photoresponsive 2D nanostructure is fabricated on the basis of the self-assembly of ultrasmall Cu nanoclusters (NCs) in colloidal solution. The Cu NCs are foremost decorated by the capping ligands with photoresponsive azobenzene (Azo) groups and by virtue of the flexibility of self-assembly techniques to produce nanoribbons. Because the ribbons are composed of individual NCs rather than a rigid whole, the ultraviolet (UV)-induced Cu NCs disassembly permits achieving morphology transformation. The disassembly of Cu ribbons is controlled by the Cu NCs rather than the surface ligands. However, the disassembled Cu NCs will reassemble into spheres if they are coated with Azo groups. The electrocatalytic performance of Cu self-assembly ribbons and spheres in oxygen reduction reaction is further compared. The ribbons show better catalytic activity than the spheres.

Metal nanoclusters (NCs) as a new class of phosphors have attracted a great deal of interest owing to their unique electronic structure and subsequently molecule-like optical properties. However, limited successes have been achieved in producing the NCs with excellent luminescent performance. In this paper, we demonstrate the significant luminescence intensity enhancement of 1-dodecanethiol (DT)-capped Cu NCs via self-assembly strategy. By forming compact and ordered assemblies, the original nonluminescent Cu NCs exhibit strong emission. The flexibility of self-assembly allows to further control the polymorphism of Cu NCs assemblies, and hence the emission properties. Comparative structural and optical analysis of the polymorphic NCs assemblies permits to establish a relationship between the compactness of assemblies and the emission. First, high compactness reinforces the cuprophilic Cu(I)···Cu(I) interaction of inter- and intra-NCs, and meanwhile, suppresses intramolecular vibration and rotation of the capping ligand of DT, thus enhancing the emission intensity of Cu NCs. Second, as to the emission energy that depends on the distance of Cu(I)···Cu(I), the improved compactness increases average Cu(I)···Cu(I) distance by inducing additional inter-NCs cuprophilic interaction, and therewith leads to the blue shift of NCs emission. Attributing to the assembly mediated structural polymorphism, the NCs assemblies exhibit distinct mechanochromic and thermochromic luminescent properties. Metal NCs-based white light-emitting diodes are further fabricated by employing the NCs assemblies with blue-green, yellow, and red emissions as phosphors.

As promising heavy metal-free emitting materials, Ag–In–Se nanocrystals (NCs) are conventionally synthesized using organic phosphine agents and exhibit near-infrared emissions. In this work, we demonstrate a rapid phosphine-free approach for synthesizing Ag–In–Se alloy NCs with the emissions tunable to the visible region on the basis of the phosphine-free dissolution of Se powder. At room temperature, Se powder is reduced by dodecanethiol and dissolved in oleylamine to produce a Se precursor. The resultant Se precursor is highly active, which permits rapid synthesis at a relatively low temperature, such as at 90 °C for 150 s. By optimizing the size, structure, and composition, the photoluminescence quantum yield of the as-synthesized Ag–In–Se NCs is enhanced to up to 10%. The growth of the Ag–In–Se NCs involves composition and phase transition, which strongly depend on the reaction temperature. The Ag2Se nuclei form first, and the Ag–In–Se NCs are produced by doping In3+ into the preformed Ag2Se nuclei. Tetragonal phase Ag–In–Se is obtained below 170 °C, while the orthorhombic phase appears over 190 °C. The potential of Ag–In–Se NCs as red emitting phosphors for lighting-emitting diodes is further demonstrated.

Electron transition materials on the basis of transition metal ions usually possess higher photothermal transduction efficiency but lower extinction ability, which have not been considered as efficient photothermal agents for therapeutic applications. In this work, we demonstrate a facile and feasible approach for enhancing 808 nm photothermal conversion effect of d orbits transition Cu(II) ions by forming Cu-carboxylate complexes. The coordination with carboxylate groups greatly enlarges the splitting energy gap of Cu(II) and the capability of electron transition, thus enhancing the extinction ability in near-infrared region. The cupreous complexes are further loaded in biocompatible and biodegradable polymer nanoparticles (NPs) of chitosan to temporarily lower the toxicity, which allows the photothermal therapy of human oral epithelial carcinoma (KB) cells in vitro and KB tumors in vivo. Animal experiments indicate the photothermal tumor inhibition rate of 100%. In addition, the gradual degradation of chitosan NPs leads to the release of cupreous complexes, thus exhibiting additional chemotherapeutic behavior in KB tumor treatment. Onefold chemotherapy experiments indicate the tumor inhibition rate of 93.1%. The combination of photothermal therapy and chemotherapy of cupreous complex-loaded chitosan NPs indicates the possibility of inhibiting tumor recurrence.Keywords: chemotherapy; chitosan; cupreous complexes; nanocomposites; photothermal therapy

Despite the success of galvanic replacement in preparing hollow nanostructures with diversified morphologies via the replacement reaction between sacrificial metal nanoparticles (NPs) seeds and less active metal ions, limited advances are made for producing branched alloy nanostructures. In this paper, we report an extended galvanic replacement for preparing branched Au–Ag NPs with Au-rich core and Ag branches using hydroquinone (HQ) as the reductant. In the presence of HQ, the preformed Ag seeds are replaceable by Au and, in turn, supply the growth of Ag branches. By altering the feed ratio of Ag seeds, HAuCl4, and HQ, the size and morphology of the NPs are tunable. Accordingly, the surface plasmon resonance absorption is tuned to near-infrared (NIR) region, making the branched NPs as potential materials in photothermal therapy. The branched NPs are further coated with polydopamine (PDA) shell via dopamine polymerization at room temperature. In comparison with bare NPs, PDA-coated branched Au–Ag (Au–Ag@PDA) NPs exhibit improved stability, biocompatibility, and photothermal performance. In vitro experiments indicate that the branched Au–Ag@PDA NPs are competitive agents for photothermal ablation of cancer cells.Keywords: hydroquinone; metal nanostructures; nanocomposites; photothermal therapy; polydopamine;

Surface ligand dynamics of colloidal quantum dots (QDs) has been revealed as an important issue for determining QDs performance in their synthesis and postsynthesis treatment, such as ligand-related photoluminescence, colloidal stability, and so forth. However, this issue is less associated with the preparation of highly luminescent nanocomposites, which usually leads to poor performance and repeatability. In this work, on the basis of the studies about surface ligand dynamics of aqueous QDs, highly luminescent QDs–cellulose composites are prepared and employed to fabricate high color purity light-emitting diodes (LEDs). Detailed investigations indicate that the species of QD capping ligands and in particular the temperature are the key for controlling the ligand dynamics. The preparation of nanocomposites using less dynamic ligand-modified QDs at low temperature overcomes the conventional problems of QD aggregation, low QD content, luminescence quenching and shift, thus producing highly luminescent QDs–cellulose composites. This protocol is available for a variety of aqueous QDs, such as CdS, CdSe, CdTe, and CdSexTe1–x, which permits the design and fabrication of QD-based LEDs using the nanocomposites as color conversion layer on a blue emitting InGaN chip.Keywords: aqueous quantum dot; cellulose; ligand dynamics; nanocomposites; white light-emitting diode;

Multiplex luminescent probes with good water-dispersibility are basic materials in current biological research as labels and sensors. In this work, we demonstrate a facile approach to fabricate water-dispersible dual-mode luminescent probes by co-assembling down-conversion CdTe nanoparticles (NPs) and up-conversion NaYF4:Yb,Tm(Er) NPs. 3-Mercaptopropionic acid (MPA)-capped CdTe NPs are water soluble, while oleic acid (OA)-capped NaYF4:Yb,Tm(Er) NPs are dispersed in chloroform. There also exists an excess of Cd–MPA complex in the CdTe aqueous solution. After mixing CdTe and NaYF4:Yb,Tm(Er), the MPA on CdTe NPs and Cd–MPA complexes is capable of partially replacing the OA on NaYF4:Yb,Tm(Er) NPs, thus transferring NaYF4:Yb,Tm(Er) NPs to water and forming CdTe–NaYF4:Yb,Tm(Er) hybrid NPs. The hybrid NPs combine the down-conversion emission of CdTe and the up-conversion emission of NaYF4:Yb,Tm(Er), which can be excited both by 400 and 980 nm irradiation and exhibit dual-mode emission. Both Förster resonance energy transfer from NaYF4:Yb,Tm(Er) to CdTe and photon re-absorption are observed as the hybrid NPs are excited by 980 nm irradiation.

Marcasite FeS2 nanoparticles were synthesized for the first time in colloidal solution via a hot-injection protocol. In comparison with the previous iron sulfides, marcasite FeS2 presents better lithium ion storage and charge–discharge performance as the anode materials in lithium ion battery application.

Two-dimensional (2D) nanomaterials possessing regular layered structures and versatile chemical composition are highly expected in many applications. Despite the importance of van der Waals (vdW) attraction in constructing and maintaining layered structures, the origin of 2D anisotropy is not fully understood, yet. Here, we report the 2D self-assembly of ligand-capped Au15 nanoclusters into mono-, few-, and multilayered sheets in colloidal solution. Both the experimental results and computer simulation reveal that the 2D self-assembly is initiated by 1D dipolar attraction common in nanometer-sized objects. The dense 1D attachment of Au15 leads to a redistribution of the surface ligands, thus generating asymmetric vdW attraction. The deliberate control of the coordination of dipolar and vdW attraction further allows to manipulate the thickness and morphologies of 2D self-assembly architectures.Keywords: anisotropic vdW attraction; nanocluster; nanosheet; self-assembly; two-dimensional material;

Photothermal nanoplatforms with small size, low cost, multifunctionality, good biocompatibility and in particular biodegradability are greatly desired in the exploration of novel diagnostic and therapeutic methodologies. Despite Fe3O4 nanoparticles (NPs) have been approved as safe clinical agents, the low molar extinction coefficient and subsequent poor photothermal performance shed the doubt as effective photothermal materials. In this paper, we demonstrate the fabrication of polypyrrole (PPy)-enveloped Fe3O4 NP superstructures with a spherical morphology, which leads to a 300-fold increase in the molar extinction coefficient. The basic idea is the optimization of Fe3O4 electronic structures. By controlling the self-assembly of Fe3O4 NPs, the diameters of the superstructures are tuned from 32 to 64 nm. This significantly enhances the indirect transition and magnetic coupling of Fe ions, thus increasing the molar extinction coefficient of Fe3O4 NPs from 3.65 × 106 to 1.31 × 108 M–1 cm–1 at 808 nm. The envelopment of Fe3O4 superstructures with conductive PPy shell introduces additional electrons in the Fe3O4 oscillation system, and therewith further enhances the molar extinction coefficient to 1.12 × 109 M–1 cm–1. As a result, the photothermal performance is greatly improved. Primary cell experiments indicate that PPy-enveloped Fe3O4 NP superstructures are low toxic, and capable to kill Hela cells under near-infrared laser irradiation. Owing to the low cost, good biocompatibility and biodegradability, the PPy-enveloped Fe3O4 NP superstructures are promising photothermal platform for establishing novel diagnostic and therapeutic methods.Keywords: Fe3O4; nanocomposites; photothermal platform; polypyrrole; self-assembly

Aqueous Au nanoparticles (NPs) are employed as the building blocks to construct chainlike self-assembly architectures, which greatly enhance the photothermal performance at 808 nm. Biocompatible polypyrrole (PPy) is further adopted as the package material to coat Au NP chains, producing stable photothermal agents. As a result of contributions from chainlike Au, the PPy shell, as well as the Au–PPy composite structures, the capability of photothermal transduction at 808 nm is greatly enhanced, represented by the high photothermal transduction efficiency up to 70%. Primary animal experiment proves that the current composite photothermal agents are efficient in inhibiting tumor growth under an 808 nm irradiation, showing the potentials for in vivo photothermal therapy.Keywords: nanocomposite; nanoparticle; photothermal effect; polypyrrole; self-assembly;

Metal and metal-oxide nanoparticles (NPs) are promising catalysts for dye degradation in wastewater treatment despite the challenges of NP recovery and recycling. In this study, water-dispersible NP superstructures with spherical morphology were constructed from hydrophobic Pd and Fe3O4 NPs by virtue of the oil droplets in an oil-in-water microemulsion as templates. Control of the evaporation rate of organic solvents in the oil droplets produces solid, hollow, and bowl-like superstructures. The component Fe3O4 and in particular Pd NPs can catalyze H2O2 degradation to create hydroxyl radicals and therewith degrade various dyes, and the magnetic Fe3O4 NPs also permit recycling of the superstructures with a magnet. Because the hollow and bowl-like superstructures increase the contact area of the NPs with their surroundings in comparison to solid superstructures, the catalytic activity is greatly enhanced. To improve the structural stability, the superstructures were further enveloped with a thin polypyrrole (PPy) shell, which does not weaken the catalytic activity. Because the current method is facile and feasible to create recyclable catalysts, it will promote the practicability of NP catalysts in treating industrial polluted water.Keywords: Fe3O4 nanoparticles; Pd nanoparticles; polypyrrole; superstructure; wastewater treatment;

The discrimination of Cr(III) and Cr(VI) is considered as one of the important analytical issues for environmental protection and disease prevention, because Cr(III) and Cr(VI) have different physiological effects and toxicities. Low cost, highly sensitive fluorescent sensors are highly demanded. Herein we report a facile and feasible method for discriminating Cr(III) and Cr(VI) by employing the aqueous CdTe quantum dots (QDs) with different surface ligands by virtue of their difference in quenching QD fluorescence. The QD fluorescence quenching by Cr(III)/Cr(VI) is mainly affected by electrostatic interaction, which is greatly determined by the surface functionalities of QDs. Thus, by combining the different fluorescence quenching behavior of carboxyl-, hydroxyl-, and/or amino-functionalized QDs, Cr(III) and Cr(VI) are discriminated. In comparison to the discrimination using the QDs with single surface functionality, the current method indicates improved reliability and accuracy.

Self-assembly is the basic feature of supramolecular chemistry, which permits to integrate and enhance the functionalities of nano-objects. However, the conversion of self-assembled structures to practical materials is still laborious. In this work, on the basis of studying one-pot synthesis, spontaneous assembly, and in situ polymerization of aqueous semiconductor nanocrystals (NCs), NC self-assembly materials are produced and applied to design high performance white light-emitting diode (WLED). In producing self-assembly materials, the additive hydrazine (N2H4) is curial, which acts as the promoter to achieve room-temperature synthesis of aqueous NCs by favoring a reaction-controlled growth, as the polyelectrolyte to weaken inter-NC electrostatic repulsion and therewith facilitate the one-dimensional self-assembly, and in particular as the bifunctional monomers to polymerize with mercapto carboxylic acid-modified NCs via in situ amidation reaction. This strategy is versatile for mercapto carboxylic acid-modified aqueous NCs, for example CdS, CdSe, CdTe, CdSexTe1–x, and CdyHg1–yTe. Because of the multisite modification with carboxyl, the NCs act as macromonomers, thus producing cross-linked self-assembly materials with excellent thermal, solvent, and photostability. The assembled NCs preserve strong luminescence and avoid unpredictable fluorescent resonance energy transfer, the main problem in design WLED from multiple NC components. These advantages allow the fabrication of NC-based WLED with high color rendering index (86), high luminous efficacy (41 lm/W), and controllable color temperature.Keywords: aqueous synthesis; nanocomposites; quantum dots; self-assembly materials; white light-emitting diode;

Copper chalcogenide nanomaterials are promising photothermal materials for establishing novel diagnostic and therapeutic methods owing to the low cost but high photothermal transduction efficiency. Further progresses of the correlated technologies greatly depend on the efforts on design and construction of novel nanostructures. In this paper, we demonstrate a facile one-pot route for constructing CuS nanostructures in aqueous media via a spontaneous assembly process. In the presence of polyvinylpyrrolidone (PVP) as the capping agents, a decomposition of Cu(CH3COSH)x precursors is induced by ammonia, which produces hexagonal CuS nanoparticles (NPs) with the diameter around 22 nm. The primary CuS NPs greatly tend to self-assembly into one-dimensional structures, which are triggered by short-range anisotropic dipolar attraction and enforced by long-range isotropic electrostatic repulsion. The further fusion of the assembled NPs generates 480 × 50 nm2 CuS nanorods. Because the formation of nanorods enhances the internanorod van der Waals attraction, the nanorods finally self-assembly into shuttle-like bundles in micrometer size. In comparison to isolated NPs, the regular CuS assembly structures exhibit improved molar extinction coefficient up to 9.7 × 1016 cm–1 M–1 by shortening the distance of neighboring CuS NPs and therewith generating new electronic structures of the CuS indirect transition. Consequently, better photothermal performance is achieved.

Despite the developments in the wet chemical synthesis of high-quality semiconductor nanocrystals (NCs) with diverse elemental compositions, telluride NCs are still irreplaceable materials owing to their excellent photovoltaic and thermoelectric performances. Herein we demonstrate the dissolution of elemental tellurium (Te) in a series of alkylamides by sodium borohydride (NaBH4) reduction at relatively low temperature to produce highly reactive precursors for hot-injection synthesis of telluride NCs. The capability to tune the reactivity of Te precursors by selecting injection temperature permits control of NC size over a broad range. The current preparation of Te precursors is simple, economical, and totally phosphine-free, which will promote the commercial synthesis and applications of telluride NCs.

We demonstrate a phosphine-free method to synthesize heavy Co2+- and Fe2+-doped Cu2SnSe3 nanocrystals (NCs) by virtue of alkylthiol-assistant Se powder dissolution in organic solvents. The as-synthesized NCs exhibit a promising increase in photocurrent under AM1.5 illumination. Since the current method is simple and convenient it holds promise for facilitating the progress in photovoltaic devices from Cu-based NCs.

The discrimination of ferrous and ferric states in the human body is one of the basic issues for disease control and prevention because Fe(II) and Fe(III) are a crucial redox pair during the process of material and energy metabolism. Herein, aqueous CdTe quantum dots (QDs) with diversified surface functionalities are applied to discriminate between heme (Fe(II)) and hemin (Fe(III)) by virtue of their difference in quenching QD fluorescence. In aqueous media, the interaction between QDs and heme/hemin mainly involves electrostatic interaction, which is greatly determined by the surface functionalities of the QDs. Thus, by combining the different fluorescence quenching behavior of carboxyl- and/or hydroxyl-functionalized QDs, heme and hemin are discriminated between. In comparison to the discrimination using QDs with single surface functionality, the current method has improved reliability and accuracy.

Gold (Au) nanomaterials are promising photothermal therapeutic agents for the selective treatment of tumor cells. Further development of correlated techniques greatly depends on the current efforts to enhance the photothermal performance by fabricating novel Au architectures. In this work, water-dispersible spherical superstructures are constructed from original hydrophobic Au nanoparticles (NPs) in place of oil droplets in microemulsion as the templates. Different from the previous reports, Pluronic F127, a nonionic triblock copolymers of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide), is employed as the capping agent to directly make the superstructures biocompatible. However, due to the nonionic nature, it is difficult to control the size and morphology of Au superstructures using F127 alone. Additional positive surfactants, such as octadecyl-p-vinylbenzyldimethylammonium chloride, are necessary to assist Au superstructure formation in a controlled manner. The as-prepared Au superstructures, which possess enhanced absorption the in red and near-infrared region, exhibit more efficient photothermal behavior in comparison to individual Au NPs.

Photothermal therapy using inorganic nanoparticles (NPs) is a promising technique for the selective treatment of tumor cells because of their capability to convert the absorbed radiation into heat energy. Although anisotropic gold (Au) NPs present an excellent photothermal effect, the poor structural stability during storage and/or upon laser irradiation still limits their practical application as efficient photothermal agents. With the aim of improving the stability, in this work we adopted biocompatible polypyrrole (PPy) as the shell material for coating urchinlike Au NPs. The experimental results indicate that a several nanometer PPy shell is enough to maintain the structural stability of NPs. In comparison to the bare NPs, PPy-coated NPs exhibit improved structural stability toward storage, heat, pH, and laser irradiation. In addition, the thin shell of PPy also enhances the photothermal transduction efficiency (η) of PPy-coated Au NPs, resulting from the absorption of PPy in the red and near-infrared (NIR) regions. For example, the PPy-coated Au NPs with an Au core diameter of 120 nm and a PPy shell of 6.0 nm exhibit an η of 24.0% at 808 nm, which is much higher than that of bare Au NPs (η = 11.0%). As a primary attempt at photothermal therapy, the PPy-coated Au NPs with a 6.0 nm PPy shell exhibit an 80% death rate of Hela cells under 808 nm NIR laser irradiation.

We report a ligand decoration strategy to enlarge the lattice dilation of quantum dots (QDs), which greatly enhances the characteristic sensitivity of a QD-based thermometer. Upon a multiple covalent linkage of macrocyclic compounds with QDs, for example, thiolated cyclodextrin (CD) and CdTe, the conformation-related torsional force of CD is conducted to the inner lattice of CdTe under altered temperature. The combination of the lattice expansion/contraction of CdTe and the stress from CD conformation change greatly enhances the shifts of both UV–vis absorption and photoluminescence (PL) spectra, thus improving the temperature sensitivity. As an example, β-CD-decorated CdTe QDs exhibit the 0.28 nm shift of the spectra per degree centigrade (0.28 nm/°C), 2.4-fold higher than those of monothiol-ligand-decorated QDs.Keywords: conformation change; cyclodextrins; lattice dilation; quantum dots; thermometer

Enhancement of Se solubility in organic solvents without the use of alkylphosphine ligands is the key for phosphine-free synthesis of selenide semiconductor nanocrystals (NCs). In this communication, we demonstrate the dissolution of elemental Se in oleylamine by alkylthiol reduction at room temperature, which generates soluble alkylammonium selenide. This Se precursor is highly reactive for hot-injection synthesis of selenide semiconductor NCs, such as Cu2ZnSnSe4, Cu(InGa)Se2, and CdSe. In the case of Cu2ZnSnSe4, for example, the as-synthesized NCs possessed small size, high size monodispersity, strong absorbance in the visible region, and in particular a promising increase in photocurrent under AM1.5 illumination. The current preparation of the Se precursor is simple and convenient, which will promote the synthesis and practical applications of selenide NCs.

Up-conversion nanoparticles (UCNPs) have exhibited great potential in biological imaging and labeling. The further development of the correlated techniques strongly depends on the stability of UCNPs in buffers and biological growth media. In this paper, Pluronic F127, a nonionic triblock copolymer of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-b-PPO-b-PEO), is applied to coat the originally hydrophobic NaYF4:Yb,Er(Tm) UCNPs, leading to an oil-to-water phase transfer. After the phase transfer, F127-coated UCNPs are well dispersed in water with more than 43% UC luminescence preserved. Because of the nonionic nature of F127, the F127-coated UCNPs are quite stable in culture media, and exhibit excellent biocompatibility and low toxicity. The biocompatible decoration using F127 is facile and repeatable, thus facilitating the biological applications of UCNPs. As an example, the bioimaging of caenorhabditis elegans is demonstrated.

Detection of highly toxic and bioaccumulative heavy metal ions using fluorescent semiconductor nanoparticles (NPs) has stimulated recent research interests, but the separation of NPs after detection has failed to be achieved. In this paper, fluorescent CdTe NPs-based superparticles (SPs) were fabricated using oil droplets in microemulsion as templates. By controlling the experimental variables, SPs with different fluorescence and composition were obtained. In particular, CdTe/Fe3O4 binary SPs simultaneously exhibited strong fluorescence and magnetism, thus achieving the separation of SPs. These CdTe-based SPs showed an improved detection of Cu2+ and Ag+.

Creation of nanoparticle (NP) architectures via a self-assembly strategy is the current means to integrate and/or modulate the functionalities of NPs. In this paper, we demonstrate the capability for constructing NP spherical superstructures through the specific interaction between host and guest molecules, for instance the model system of α-cyclodextrin (α-CD) and oleic acid (OA), which are decorated on two different NPs beforehand. Subsequently, the OA-decorated hydrophobic NPs are dispersed in hexane, whereas the α-CD-decorated NPs are dispersed in water. The blending of these two immiscible solutions produces NP binary superstructures because of the multiple linkages between the α-CD- and OA-decorated NPs. Control experiments indicate that the self-assembly of NPs occurs either at the hexane/water interface to form hybrid films or in the aqueous phase to generate spherical architectures, which strongly depends on the amount and the size of α-CD-decorated NPs. The high ratio and small size of the α-CD-decorated NPs facilitate the formation of spherical architectures. Competitive experiments with the addition of host α-CD and guest sodium oleate clearly confirm that the main driving force for the NP co-assembly is the specific interaction between α-CD and OA. In addition, the flexible decoration of α-CD and OA on the NPs makes the current strategy generally applicable for a variety of NPs, such as the superstructures of Au/Fe3O4, Pt/Fe3O4, and Au/NaYF4:Yb,Tm, which is expected to promote the further application of NPs in environmental and biological sciences.

Up-conversion rare-earth nanoparticles (UCNPs) are potential alternatives to down-conversion fluorescent quantum dots for biolabeling, and the prerequisite for biological applications is the enhancement of surface hydrophilicity and physiological stability of UCNPs. In this work, we demonstrated a facile method to modulate the surface functionality of original hydrophobic UCNPs by forming a surfactant bilayer, which made UCNPs dispersible in water. After oil-to-water phase transfer, more than 30% up-conversion luminescence was preserved. It was found that the key to avoiding the aggregation of bilayer-modified UCNPs was the concentration of surfactant. High concentration of surfactant led to bilayer-modified individual UCNPs, whereas insufficient surfactant generated the water-dispersible aggregates of UCNPs, namely UCNP superstructures. Various commercially available surfactants, such as cationic cetyltrimethylammonium bromide, anionic sodium dodecyl sulfate, and nonionic polyethylene glycol tert-octylphenyl ether, were practical, making the current method versatile for anchoring functional groups on UCNPs. Moreover, bilayer-modified UCNPs could act as a platform to perform surface silication, thus further improving the biocompatibility and stability of UCNPs.

Testing the facet-dependent electrocatalytic activity of noble metal alloy nanocrystals has attracted increasing interest towards improving the performance of direct methanol fuel cells. Herein, CoPt3 nanocrystals with high shape- and facet-selectivity are synthesized via a non-injection strategy. The (111)-facet-dominant nanoflowers are more active for catalytic oxidation of methanol than the (100)-facet-dominant nanocubes and nanoparticles with irregular facets.

Bimetallic nanoparticles (NPs) comprised of gold (Au) and palladium (Pd) are promising catalysts in accelerating a variety of chemical reactions. The further performance enhancement greatly depends on the current efforts to create the synthetic methodology for optimizing NP morphology and structure. Here we report a one-pot and seedless synthesis of Au–Pd bimetallic NPs via citrate coreduction of Au and Pd ions. Due to the higher capacity of citrate in reducing Au ions, the nucleation of Au NPs is more favored than that of Pd. Consequently, the current system permits the production of bimetallic NPs with core-shell-like structure, namely an Au-rich core and Pd-rich shell. Moreover, the morphology of the as-synthesized NPs is also determined by the experimental variables, such as the Au-to-Pd feed ratio, dosage of sodium citrate, and charging sequence. With a good control of the nucleation and growth process, flowerlike Au–Pd bimetallic NPs with core-shell-like structures are synthesized. These flowerlike bimetallic NPs are the best in catalyzing formic acid oxidation and Suzuki coupling reaction in comparison to the Au–Pd bimetallic NPs with other morphologies.

Highly luminescent quantum dots (QDs) could be synthesized in “conical flask” now. Through a room-temperature N2H4-promoted strategy, water-soluble CdTe QDs were facilely synthesized by a stepwise addition of raw materials in one pot. No prepreparation of precursors, pH adjustment, heating, and even N2 protection were required. Just by adjusting the feed ratio of the reagents, different-sized QDs were easily obtained within a shortened time. More importantly, besides conventional thiol-ligands, such as thioglycolic acid (TGA), 3-mercaptopropionic acid (MPA), 1-thioglycerol (TG), 2-mercaptoethylamine (MA), glutathione (GSH), and l-cysteine (LCS), some special mercapto-compounds, for instance, 4-mercaptobenzoic acid (MBA), per-6-thio-α-cyclodextrin (α-CD-SH), and per-7-thio-β-cyclodextrin (β-CD-SH), were also practicable, which were impossible in the conventional reflux method because of the poor water-solubility of them. Furthermore, a spontaneous aggregation of MA-stabilized QDs was observed after synthesis, which facilitated the separation of QDs and recycle of N2H4-containing growth solution.Keywords: aqueous synthesis; CdTe; green chemistry; quantum dot;

1-Thioglycerol (TG)-stabilized quantum dots (QDs) are good candidate for performing a stepwise polymerization reaction with polyurethane (PU) prepolymers, but their use is limited by their worse photoluminescence (PL) in comparison to QDs stabilized by other mercapto-ligands. To overcome this problem, TG-stabilized CdTe QDs with enhanced PL were synthesized in water through a N2H4-promoted growth approach. The current synthesis significantly shortened the duration of the size evolution of QDs, particularly for obtaining samples with orange and red emissions. It also permitted QD growth at low temperatures, such as room temperature, which avoided the decomposition of TG and subsequent embedment of sulfur into the QDs as occurs in the conventional synthesis. Most importantly, the TG ligand endowed the QDs with hydroxyl coverage, making the QDs miscible with PU prepolymers in dimethyl sulfoxide, and therefore overcoming the main problem in fabricating PU-based nanocomposites of eliminating water. The hydroxyl coverage further allowed for the linkage of PU on the surface of the QDs through the reaction between –OH and –NCO, producing CdTe QD–PU bulk nanocomposites. Systematic characterization indicated that the QDs were well dispersed in the PU medium, and the size-dependent PL of QDs was also maintained.

Binary superparticles (SPs) from various functional nanoparticles are fabricated using oil droplets in microemulsion as templates. The structural stability of SPs is further improved by polymer decoration. This protocol provides a facile and flexible approach to integrate multifunctionalities in nanometre-sized spheres with long term stability.

We reported an aqueous synthesis of urchin-like gold nanoparticles (NPs) in the presence of hydroquinone through a seed-mediated growth approach. By altering the feed ratio of hydroquinone, seeds, and additional HAuCl4, the diameters of urchin-like NPs were tunable from 55 to 200 nm. Accordingly, the centers of surface plasmon resonance absorption shifted from 555 to 702 nm. Systematical analysis revealed that the generation of urchin-like particles as well as their size evolution strongly depended on the reactivity of gold ions, mainly controlled by the concentration of hydroquinone. At low hydroquinone concentration, only spherical particles were achieved. The increase of the hydroquinone concentration promoted a kinetics-favored deposition of gold atoms on the (111) lattice planes and thereby the growth of branches. Moreover, the as-prepared urchin-like particles possessed good structural stability, which could be kept in the growth solution for more than 10 days without morphology variation.

In this paper, we demonstrated a modified hot-injection method to synthesize high-quality Cu2–xSe nanocrystals (NCs) in liquid paraffin without using the hazardous and unstable alkylphosphines as the ligand of Se. The key of this method is the capability for tuning the reactivity of Se at the stage of formation of Cu2–xSe nuclei. The low reactivity of Se facilitated the decomposition of copper(II) acetylacetonate into Cu2O, whereas the increase of Se reactivity promoted the reaction between Cu and Se. By control of the experimental variables, such as reaction time, Se concentration, reaction temperature, and, particularly, the addition of the noncoordinating solvent of Se, high-quality Cu2–xSe NCs were prepared. The resultant Cu2–xSe NCs possessed an indirect band-gap absorption around 1050 nm, potentially applicable in photovoltaic investigations. As an example, the optoelectronic properties of Cu2–xSe NCs were investigated, which showed a promising increase in photocurrent under AM 1.5 illumination. Because the current method was convenient and environmentally friendly, it was believed that this work would facilitate the development of a preparation technique and industrial application of copper-based photovoltaic devices.

In this paper, we demonstrated a “one-pot” strategy for synthesizing ZnSe nanocrystals (NCs) in liquid paraffin. All materials, including Zn source, Se source, and ligand, were mixed in liquid paraffin beforehand, which avoided the injection of Se source at high temperature. The resultant ZnSe NCs possessed high photoluminescence quantum yields and narrow size distribution. Moreover, the size, shape, and crystal phase of NCs were controllable by altering the experimental variables, such as precursor concentration, Zn:Se molar ratio, and heating rate. Because the raw materials used here were low-cost and environmentally friendly, this “one-pot” synthetic protocol would facilitate the commercial scale synthesis of high-quality ZnSe NCs.

In the conventional procedure of the preparation of aqueous semiconductor nanocrystals (NCs), the growth of NCs was mainly through the thermodynamics-favored Ostwald ripening process. It required additional energy to promote NC growth, such as reflux, hydrothermal method, microwave irradiation, and sonochemical synthesis. Energy-promoted growth usually led to the decomposition of mercapto-ligands and therewith decreased the quality of NCs. Consequently, in this study, the growth of aqueous semiconductor NCs was designed through an amine-promoted kinetic process, which efficiently shortened the growth duration and avoided the decomposition of ligands, thus providing a universal method for preparing various aqueous binary and ternary NCs.

The colloidal gold superparticle (SP)/polypyrrole (PPy) core/shell composites were successfully prepared by oxidative polymerization of pyrrole monomer on the surface of poly(N-vinylpyrrolidone) (PVP)-grafted colloidal gold SPs. These core/shell composites showed strong catalytic activity and excellent stability. Control experiments indicated that the morphology and the thickness of PPy shell were controllable by adjusting the dosage of pyrrole monomer. Meaningfully, the resulting SP/PPy core/shell composites were quite stable in water, which could be stored for more than half a year without damaging their structures. As an example, we demonstrated the use of these composites as catalyst for the reduction of methylene blue (MB) dye with a reducing agent of sodium borohydride. The composites exhibited highly catalytic activity and long-term stability, implying promising applications of SP/PPy composites in catalysis.

The nucleation of aqueous semiconductor nanocrystals (NCs) was identified by investigating the evolution of precursor solution and the subsequent N2H4-promoted growth at room temperature. Current synthesis of NCs at room temperature allowed for distinguishing the nucleation and growth processes, which were inseparable in the previous aqueous synthetic methods. Experimental results indicated that the highly crystalline nucleus contributed greatly to the fluorescence of the as-prepared NCs, which was particularly important for synthesizing highly luminescent NCs with small size and alloyed structure. Thus, our finding helped to repeatably synthesize aqueous NCs, and at the same time offered an opportunity to perfect the synthetic route and further structural design of aqueous NCs.

In this paper, simple amines, such as ammonia (NH3) and hydrazine (N2H4), were deliberately added to the growing system of aqueous CdTe nanocrystals (NCs) to promote their growth at room temperature. Systematical investigations revealed that NC growth was the combination of kinetics-favored agglomeration growth and thermodynamics-favored diffusion equilibrium (or decomposition). On one hand, the rapid growth of NCs in the presence of amines was mainly an agglomeration growth. Simple amines were weak electrolytes, the presence of which greatly weakened the interparticle electrostatic repulsion. Accordingly, the adsorption and fusion of NC monomers and/or clusters were facilitated, leading to a rapid agglomeration growth of NCs. On the other hand, the growth rate and process of NCs also depended on pH, species of mercapto-ligands, and especially species and concentrations of amines. These indicated that the evolution of NCs also related to the activity of Cd and/or Te monomers in solution, which was thermodynamics-controlled. In this context, higher coordinative ability between Cd and amine (such as NH3 and alkylamines), and Cd and mercapto-ligand (such as TGA) increased the solubility of Cd monomers, facilitating the decomposition of NCs at the last stage through thermodynamics-favored diffusion. As a result, it was difficult to obtain large NCs. In contrast, moderate coordinative ability between Cd and amine (such as N2H4), and Cd and mercapto-ligand (such as TG and MPA) led to proper solubility of Cd, thus avoiding the decomposition of NCs at the last stage. Besides, pH effect indicated that high pH enhanced the antioxidation of free Te2− in a growing NC system, thus improving the reactive activity of Te monomer and thereby promoting NC growth.

In this article, the experimental variable-dependent photoluminescence (PL) evolution of transition-metal-doped ZnSe nanocrystals (NCs) is analyzed by combining the redox reaction and the electrostatics of aqueous NCs. Bulk doping of NCs involves two steps − surface adsorption of the metal impurities and the followed internal doping. The former relates to the electrostatics of aqueous NCs, whereas the latter relates to a redox reaction between the impurities and mercapto-ligands. Both of them occur on the NC surface. In this context, aqueous NCs are essentially charge-stabilized particles. The electrostatic factors that weaken the electrostatic repulsion will facilitate the adsorption of metal impurities on NC surfaces, thus benefiting the surface redox reaction. It furthermore promotes the internal doping of the metal impurities. Consequently, the trap emission and the PL evolution of NCs are facilitated. Besides, the internal doping is favored for the metal impurities with high reduction potential because they are easily reduced by mercapto-ligands. Furthermore, because the presence of metal impurities in NC solution both promotes the oxidation of mercapto-ligands and weakens the interparticle electrostatic repulsion, the colloidal solution of doped aqueous NCs is theoretically proved unstable.

Nanodevices for multimodal tumor theranostics have shown great potentials for noninvasive tumor diagnosis and therapy, but the libraries of multimodal theranostic building blocks should be further stretched. In this work, Cu(II) ions are doped into polyaniline (Pani) nanoshuttles (NSs) to produce Cu-doped Pani (CuPani) NSs, which are demonstrated as new multimodal building blocks to perform tumor theranostics. The CuPani NSs are capable of shortening the longitudinal relaxation (T1) of protons under magnetic fields and can help light up tumors in T1-weighted magnetic resonance imaging. In addition, the released Cu(II) ions from CuPani NSs lead to cytotoxicity, showing the behavior of chemotherapeutic agent. The good photothermal performance of CuPani NSs also makes them as photothermal agents to perform thermochemotherapy. By combining near-infrared laser irradiation, a complete tumor ablation is achieved and no tumor recurrence is observed.CuPani NSs perform noninvasive tumor diagnosis and therapy with enhanced properties including electrostatic attraction to Hela cells, contrast agents for MRI, and photothermal combined chemotherapy.

In the conventional procedure of the preparation of aqueous semiconductor nanocrystals (NCs), the growth of NCs was mainly through the thermodynamics-favored Ostwald ripening process. It required additional energy to promote NC growth, such as reflux, hydrothermal method, microwave irradiation, and sonochemical synthesis. Energy-promoted growth usually led to the decomposition of mercapto-ligands and therewith decreased the quality of NCs. Consequently, in this study, the growth of aqueous semiconductor NCs was designed through an amine-promoted kinetic process, which efficiently shortened the growth duration and avoided the decomposition of ligands, thus providing a universal method for preparing various aqueous binary and ternary NCs.

Creation of nanoparticle (NP) architectures via a self-assembly strategy is the current means to integrate and/or modulate the functionalities of NPs. In this paper, we demonstrate the capability for constructing NP spherical superstructures through the specific interaction between host and guest molecules, for instance the model system of α-cyclodextrin (α-CD) and oleic acid (OA), which are decorated on two different NPs beforehand. Subsequently, the OA-decorated hydrophobic NPs are dispersed in hexane, whereas the α-CD-decorated NPs are dispersed in water. The blending of these two immiscible solutions produces NP binary superstructures because of the multiple linkages between the α-CD- and OA-decorated NPs. Control experiments indicate that the self-assembly of NPs occurs either at the hexane/water interface to form hybrid films or in the aqueous phase to generate spherical architectures, which strongly depends on the amount and the size of α-CD-decorated NPs. The high ratio and small size of the α-CD-decorated NPs facilitate the formation of spherical architectures. Competitive experiments with the addition of host α-CD and guest sodium oleate clearly confirm that the main driving force for the NP co-assembly is the specific interaction between α-CD and OA. In addition, the flexible decoration of α-CD and OA on the NPs makes the current strategy generally applicable for a variety of NPs, such as the superstructures of Au/Fe3O4, Pt/Fe3O4, and Au/NaYF4:Yb,Tm, which is expected to promote the further application of NPs in environmental and biological sciences.

In this paper, we demonstrated a “one-pot” strategy for synthesizing ZnSe nanocrystals (NCs) in liquid paraffin. All materials, including Zn source, Se source, and ligand, were mixed in liquid paraffin beforehand, which avoided the injection of Se source at high temperature. The resultant ZnSe NCs possessed high photoluminescence quantum yields and narrow size distribution. Moreover, the size, shape, and crystal phase of NCs were controllable by altering the experimental variables, such as precursor concentration, Zn:Se molar ratio, and heating rate. Because the raw materials used here were low-cost and environmentally friendly, this “one-pot” synthetic protocol would facilitate the commercial scale synthesis of high-quality ZnSe NCs.

1-Thioglycerol (TG)-stabilized quantum dots (QDs) are good candidate for performing a stepwise polymerization reaction with polyurethane (PU) prepolymers, but their use is limited by their worse photoluminescence (PL) in comparison to QDs stabilized by other mercapto-ligands. To overcome this problem, TG-stabilized CdTe QDs with enhanced PL were synthesized in water through a N2H4-promoted growth approach. The current synthesis significantly shortened the duration of the size evolution of QDs, particularly for obtaining samples with orange and red emissions. It also permitted QD growth at low temperatures, such as room temperature, which avoided the decomposition of TG and subsequent embedment of sulfur into the QDs as occurs in the conventional synthesis. Most importantly, the TG ligand endowed the QDs with hydroxyl coverage, making the QDs miscible with PU prepolymers in dimethyl sulfoxide, and therefore overcoming the main problem in fabricating PU-based nanocomposites of eliminating water. The hydroxyl coverage further allowed for the linkage of PU on the surface of the QDs through the reaction between –OH and –NCO, producing CdTe QD–PU bulk nanocomposites. Systematic characterization indicated that the QDs were well dispersed in the PU medium, and the size-dependent PL of QDs was also maintained.

Detection of highly toxic and bioaccumulative heavy metal ions using fluorescent semiconductor nanoparticles (NPs) has stimulated recent research interests, but the separation of NPs after detection has failed to be achieved. In this paper, fluorescent CdTe NPs-based superparticles (SPs) were fabricated using oil droplets in microemulsion as templates. By controlling the experimental variables, SPs with different fluorescence and composition were obtained. In particular, CdTe/Fe3O4 binary SPs simultaneously exhibited strong fluorescence and magnetism, thus achieving the separation of SPs. These CdTe-based SPs showed an improved detection of Cu2+ and Ag+.

We demonstrate a phosphine-free method to synthesize heavy Co2+- and Fe2+-doped Cu2SnSe3 nanocrystals (NCs) by virtue of alkylthiol-assistant Se powder dissolution in organic solvents. The as-synthesized NCs exhibit a promising increase in photocurrent under AM1.5 illumination. Since the current method is simple and convenient it holds promise for facilitating the progress in photovoltaic devices from Cu-based NCs.

Carbon nanoparticles (C-NPs) are novel and competitive luminescent materials both in academic research and practical applications owing to their environment-friendly behavior and high abundance on Earth. Despite the successes in preparing strongly luminescent C-NPs, preserving the luminescence in solid materials is still challenging. With the aim to produce C-NP-based white-light-emitting diodes (WLEDs), in this work, solvent-dispersible C-NPs are embedded into commercial silica gel via a dual solvent evaporation route. The basic idea is to lower the evaporation rate of the solvents, thus leading to a good dispersion of the C-NPs in the silica gel. This method avoids the aggregation-induced emission quenching of C-NPs in solid materials, and therefore preserves the strong luminescence in the C-NPs/silica gel composites. The composites are further blended with polydimethylsiloxane and act as the color conversion layer on InGaN UV-blue emitting chips, which produces LEDs with a bright white emission.

Ultrathin two-dimensional (2D) nanomaterials composed of abundant and inexpensive 3d metal chalcogenides are competitive candidates for practical electrocatalysts for the oxygen evolution reaction (OER). However, the bottom-up synthesis of atomically thick nanosheets is difficult for materials with inherent non-layered host crystals. Here, we demonstrate the preparation of single-unit-cell thick Co9S8 nanosheets from preassembled Co14 nanoclusters (NCs) by virtue of the flexibility of NC self-assembly in colloidal solution. Due to their free-standing properties, the NC self-assembled architectures are capable of bearing sulfurization at elevated temperatures, thus producing ultrathin Co9S8 nanosheets. The nanosheets exhibit an OER overpotential as low as 0.27 V at 10 mA cm−2 in 0.1 M KOH, which is comparable to the performance of the best Co-based OER electrocatalysts.