Copper sulfide (Cu7S4) nanoparticles coated with an ultra-high payload (~5.0 × 107 fluorine atoms per particle) of fluorinated ligands (oleylamine functionalized 3,5-bis(trifluoromethyl)benzaldehyde, 19FOAm) exhibited a single intense 19F magnetic resonance (MR) signal and efficient near infrared photothermal performance in water medium. In vivo assessment revealed strong 19F MR signals at cancerous lesions and effective inhibition of tumor growth after photothermal treatment, indicating the great potential of these fabricated nanoprobes for simultaneous 19F MR imaging and photothermal therapy.
The construction of metal sulfides-carbon nanocomposites with a hollow structure is highly attractive for various energy storage and conversion technologies. Herein, we report a facile two-step method for preparing a nanocomposite with CoS2 nanoparticles in N-doped carbon nanotube hollow frameworks (NCNTFs). Starting from zeolitic imidazolate framework-67 (ZIF-67) particles, in situ reduced metallic cobalt nanocrystals expedite the formation of the hierarchical hollow frameworks from staggered carbon nanotubes via a carbonization process. After a follow-up sulfidation reaction with sulfur powder, the embedded cobalt crystals are transformed into CoS2 nanoparticles. Benefitting from the robust hollow frameworks made of N-doped carbon nanotubes and highly active CoS2 ultrafine nanoparticles, this advanced nanocomposite shows greatly enhanced lithium storage properties when evaluated as an electrode for lithium-ion batteries. Impressively, the resultant CoS2/NCNTF material delivers a high specific capacity of ～937 mAh·g–1 at a current density of 1.0 A·g–1 with a cycle life longer than 160 cycles.
The oxygen reduction reaction (ORR) is essential in research pertaining to life science and energy. In applications, platinum-based catalysts give ideal reactivity, but, in practice, are often subject to high costs and poor stability. Some cost-efficient transition metal oxides have exhibited excellent ORR reactivity, but the stability and durability of such alternative catalyst materials pose serious challenges. Here, we present a facile method to fabricate uniform CoxOy nanoparticles and embed them into N-doped carbon, which results in a composite of extraordinary stability and durability, while maintaining its high reactivity. The half-wave potential shows a negative shift of only 21 mV after 10,000 cycles, only one third of that observed for Pt/C (63 mV). Furthermore, after 100,000 s testing at a constant potential, the current decreases by only 17%, significantly less than for Pt/C (35%). The exceptional stability and durability results from the system architecture, which comprises a thin carbon shell that prevents agglomeration of the CoxOy nanoparticles and their detaching from the substrate.
This is the first report on the thermoelectric properties of a catalyst-free polyol method used to prepare stoichiometric Bi2?xCuxS3 samples, x = 0.1, 0.2, 0.3, 0.4, via hot pressing. Various systematic approaches to arrive at in their stoichiometric compositions are explored precisely with introduction of excess precursor of S. X-ray diffraction data analysis using Rietveld refinement confirms a polyhedral orthorhombic crystal structure with a space group Pnma, in contrast to Pbnm reported earlier. Raman data further substantiates this. X-ray photoelectron spectroscopy confirms the valence states of the constituent elements (Bi3+, Cu2+, and S2?) and energy dispersive X-ray analysis corroborates their compositions. The particle sizes of the pure Bi2S3 nanoparticles were 20, 35, and 82 nm as determined from the Scherrer formula, atomic force microscopy, and dynamic light scattering, respectively. Their transmission electron microscopy image shows rod-like nanostructures elongated in the 〈010〉 direction with an average diameter of 23 nm and a length of several hundreds of nanometers. A 34% improvement in the thermoelectric figure of merit is observed for Bi1.6Cu0.4S3 as compared to pure Bi2S3 at 300 K.
By combining ab initio calculations and experiments, we demonstrate how the band gap of the transition metal trichalcogenide TiS3 can be modified by inducing tensile or compressive strain. In addition, using our calculations, we predicted that the material would exhibit a transition from a direct to an indirect band gap upon application of a compressive strain in the direction of easy electrical transport. The ability to control the band gap and its nature could have a significant impact on the use of TiS3 for optical applications. We go on to verify our prediction via optical absorption experiments that demonstrate a band gap increase of up to 9% (from 0.99 to 1.08 eV) upon application of tensile stress along the easy transport direction.
We have demonstrated the improved performance of oxygen evolution reactions (OER) using Au/nickel phosphide (Ni12P5) core/shell nanoparticles (NPs) under basic conditions. NPs with a Ni12P5 shell and a Au core, both of which have well-defined crystal structures, have been prepared using solution-based synthetic routes. Compared with pure Ni12P5 NPs and Au-Ni12P5 oligomer-like NPs, the core/shell crystalline structure with Au shows an improved OER activity. It affords a current density of 10 mA/cm2 at a small overpotential of 0.34 V, in 1 M KOH aqueous solution at room temperature. This enhanced OER activity may relate to the strong structural and effective electronic coupling between the single-crystal core and the shell.
The size and density of Ag nanoparticles on n-layer MoS2 exhibit thicknessdependent behavior. The size and density of these particles increased and decreased, respectively, with increasing layer number (n) of n-layer MoS2. Furthermore, the surface-enhanced Raman scattering (SERS) of Ag on this substrate was observed. The enhancement factor of this scattering varied with the thickness of MoS2. The mechanisms governing the aforementioned thickness dependences are proposed and discussed.
One-dimensional hollow nanostructures have potential applications in many fields and can be fabricated using various methods. Herein, a selective-oxidation route for the synthesis of unique TexSey nanotubes (STNTs) with a controlled morphology using TexSey@Se core–shell nanowires (TSSNWs) as a template is reported. Because of the lower redox potential of TeO2/Te compared to that of H2SeO3/Se, the Te in TSSNWs can be preferentially oxidized by an appropriate oxidant of HNO2 to form STNTs. The inner diameters and wall thicknesses of the STNTs can be tuned by modulating the core diameters and shell thicknesses of the TSSNWs, respectively. The STNTs can be assembled into a monolayer composed of well-arranged nanotubes using the Langmuir–Blodgett technique. A device based on films stacked with 10 STNT monolayers was fabricated to investigate the photocoductivity of the STNTs. The STNTs exhibited a good photoresponse over the whole ultraviolet–visible spectrum, revealing their potential for application in optoelectronic devices.
Semiconductor quantum dots (QDs) are considered as ideal fluorescent probes owing to their intrinsic optical properties. It has been demonstrated that the size and shape of nanoparticles significantly influence their behaviors in biological systems. In particular, one-dimensional (1D) nanoparticles with larger aspect ratios are desirable for cellular uptake. Here, we explore a facile and green method to prepare novel 1D wormlike QDs@SiO2 nanoparticles with controlled aspect ratios, wherein multiple QDs are arranged in the centerline of the nanoparticles. Then, an excellent cationic gene carrier, ethanolamine-functionalized poly(glycidyl methacrylate) (denoted by BUCT-PGEA), was in-situ produced via atom transfer radical polymerization on the surface of the QDs@SiO2 nanoparticles to achieve stable surfaces (QDs@SiO2-PGEA) for effective bioapplications. We found that the wormlike QDs@SiO2-PGEA nanoparticles demonstrated much higher gene transfection performance than ordinary spherical counterparts. In addition, the wormlike nanoparticles with larger aspect ratio performed better than those with smaller ratio. Furthermore, the gene delivery processes including cell entry and plasmid DNA (pDNA) escape and transport were also tracked in real time by the QDs@SiO2-PGEA/pDNA complexes. This work realized the integration of efficient gene delivery and real-time imaging within one controlled 1D nanostructure. These constructs will likely provide useful information regarding the interaction of nanoparticles with biological systems.
Because of the coupling between semiconducting and piezoelectric properties in wurtzite materials, strain-induced piezo-charges can tune the charge transport across the interface or junction, which is referred to as the piezotronic effect. For devices whose dimension is much smaller than the mean free path of carriers (such as a single atomic layer of MoS2), ballistic transport occurs. In this study, transport in the monolayer MoS2 piezotronic transistor is studied by presenting analytical solutions for two-dimensional (2D) MoS2. Furthermore, a numerical simulation for guiding future 2D piezotronic nanodevice design is presented.
A facile strategy was designed for the fabrication of Fe3O4-nanoparticle-decorated TiO2 nanofiber hierarchical heterostructures (FTHs) by combining the versatility of the electrospinning technique and the hydrothermal growth method. The hierarchical architecture of Fe3O4 nanoparticles decorated on TiO2 nanofibers enables the successful integration of the binary composite into batteries to address structural stability and low capacity. In the resulting unique architecture of FTHs, the 1D heterostructures relieve the strain caused by severe volume changes of Fe3O4 during numerous charge-discharge cycles, and thus suppress the degradation of the electrode material. As a result, FTHs show excellent performance including higher reversible capacity, excellent cycle life, and good rate performance over a wide temperature range owing to the synergistic effect of the binary composition of TiO2 and Fe3O4 and the unique features of the hierarchical nanofibers.
Identification of atomic disorders and their subsequent control has proven to be a key issue in predicting, understanding, and enhancing the properties of newly emerging topological insulator materials. Here, we demonstrate direct evidence of the cation antisites in single-crystal SnBi2Te4 nanoplates grown by chemical vapor deposition, through a combination of sub-ångström-resolution imaging, quantitative image simulations, and density functional theory calculations. The results of these combined techniques revealed a recognizable amount of cation antisites between Bi and Sn, and energetic calculations revealed that such cation antisites have a low formation energy. The impact of the cation antisites was also investigated by electronic structure calculations together with transport measurement. The topological surface properties of the nanoplates were further probed by angle-dependent magnetotransport, and from the results, we observed a two-dimensional weak antilocalization effect associated with surface carriers. Our approach provides a pathway to identify the antisite defects in ternary chalcogenides and the application potential of SnBi2Te4 nanostructures in next-generation electronic and spintronic devices.
An inverted planar heterojunction perovskite solar cell (PSC) is one of the most competitive photovoltaic devices exhibiting a high power conversion efficiency (PCE) and nearly free hysteresis in the voltage–current output. However, the band alignment between the transport materials and the perovskite absorber has not been optimized, resulting in a lower open-circuit voltage (Voc) than that of regular PSCs. To address this issue, we tune the band alignment in perovskite photovoltaic architecture by introducing bilayer structured transport materials, e.g., the hole transport material poly(ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)/V2O5. In this study, solution processed inorganic V2Ox interlayer is incorporated into PEDOT:PSS for achieving improved film surface properties as well as optical and electrical properties. For example, the work function (WF) was changed from 5.1 to 5.4 eV. A remarkably high PCE of 17.5% with nearly free hysteresis and a stabilized efficiency of 17.1% have been achieved. Electronic impedance spectra (EIS) demonstrate a significant increase in the recombination resistance after introducing the interlayer, associated with the high Voc output value of 1.05 V. Transient photocurrent and photovoltage measurements indicate that a comparable charge transport process and an inhibited recombination process occur in the PSC with the introduction of the V2Ox interlayer.
Identification of metal cluster catalysis is a topic that is being investigated since a long time. Here, we report a Pd3 metal cluster catalytic reaction investigated by means of operando studies. We discovered that atomically defined tri-nuclear palladium (Pd3) is a surprisingly active catalyst for the cycloisomerization of 2-phenylethynylaniline. Operando 1H NMR spectroscopy and X-ray extended absorption fine structure (EXAFS) measurements have indicated that the structural integrity of such a catalyst remains intact throughout the reaction, which has also been confirmed by an ex situ X-ray photoelectron spectroscopy (XPS) study and catalyst recycling experiments. Kinetic data derived from operando IR spectroscopy measurements have shown that Pd3 is the active catalytic species. Density functional theory calculations have revealed a reaction pathway consistent with the kinetic data, further supported by NMR titration and X-ray crystal structure studies. Overall, the present study presents a clear example of metal cluster catalysis.
We developed a strategy based on coordination polymer to synthesize singleatom site Fe/N and S-codoped hierarchical porous carbon (Fe1/N,S-PC). The as-obtained Fe1/N,S-PC exhibited superior oxygen reduction reaction (ORR) performance with a half-wave potential (E1/2, 0.904 V vs. RHE) that was better than that of commercial Pt/C (E1/2, 0.86 V vs. RHE), single-atom site Fe/N-doped hierarchical porous carbon (Fe1/N-PC) without S-doped (E1/2, 0.85 V vs. RHE), and many other nonprecious metal catalysts in alkaline medium. Moreover, the Fe1/N,S-PC revealed high methanol tolerance and firm stability. The excellent electrocatalytic activity of Fe1/N,S-PC is attributed to the synergistic effects from the atomically dispersed porphyrin-like Fe-N4 active sites, the heteroatom codoping (N and S), and the hierarchical porous structure in the carbon materials. The calculation based on density functional theory further indicates that the catalytic performance of Fe1/N,S-PC is better than that of Fe1/N-PC owing to the sulfur doping that yielded different rate-determining steps.
Manipulating the alignment of liquid crystals (LCs) is a hot and fundamental issue for their applications in block copolymers, photonics, actuators, biosensors, and liquid-crystal displays. Here, the surface characteristic of Cu2O nanocrystals was well controlled to manipulate the orientation of the LCs. The mechanism of the orientation of the LCs induced by Cu2O nanocrystals was elucidated based on the interaction between the LCs and Cu2O nanocrystals. To comprehensively prove our assumption, different types of LCs (nematic, cholesteric, and smectic) as well as the same type of LCs with different polarities were selected in our system. Moreover, the photomechanical behaviors of the LC polymer composites demonstrated that the alignment of LCs can be effectively manipulated using Cu2O nanocrystals.
The dynamic behavior of octahedral gold nanoparticles (NPs) and nanoparticle clusters (NPCs) in aqueous solution is studied by in-situ liquid-cell transmission electron microscopy (TEM). The octahedral Au NPs/NPCs show preferential orientations in the liquid cell, due to the interaction with the SiNx window. The Au NPs show long-range reversible hopping and three-dimensional (3D) rotational motions in the liquid environment. At the same time, the Au NPCs and NPs perform slow stick-slip and stick-roll motions, respectively, with a centripetal trend. The centripetal motions were explained by a liquid evaporation-induced radial flow model, in which the NPCs/NPs trajectories are controlled by Stokes forces and surface friction by the silicon nitride window. The calculated radius-dependent force (Fc) on the NPCs/NPs shows a semi-linear correlation with the distance r between the NPCs/NPs and the center of mass, accompanied with stochastic fluctuations, in agreement with the model predictions. This work thus demonstrates the effectiveness of in situ liquid-cell TEM for the in-depth understanding of complicated liquid flow and force interactions in nanomaterials.
Metal oxide/graphene nanocomposites are emerging as promising materials for developing room-temperature gas sensors. However, the unsatisfactory performances owing to the relatively low sensitivity, slow response, and recovery kinetics limit their applications. Herein, a highly sensitive and rapidly responding room-temperature NO2 gas sensor based on WO3 nanorods/sulfonated reduced graphene oxide (S-rGO) was prepared via a simple and cost-effective hydrothermal method. The optimal sensor response of the WO3/S-rGO sensor toward 20 ppm NO2 is 149% in 6 s, which is 4.7 times higher and 100 times faster than that of the corresponding WO3/rGO sensors. In addition, the sensor exhibits excellent reproducibility, selectivity, and extremely fast recovery kinetics. The mechanism of the WO3/S-rGO nanocomposite gas sensor is investigated in detail. In addition to the high transport capability of S-rGO as well as its excellent NO2 adsorption ability, the superior sensing performance of the S-rGO/WO3 sensor can be attributed to the favorable charge transfer occurring at the S-rGO/WO3 interfaces. We believe that the strategy of compositing a metal oxide with functionalized graphene provides a new insight for the future development of room-temperature gas sensors.
Regulating the selectivity of CO2 photoreduction is particularly challenging. Herein, we propose ideal models of atomic layers with/without element doping to investigate the effect of doping engineering to tune the selectivity of CO2 photoreduction. Prototypical ZnCo2O4 atomic layers with/without Ni-doping were first synthesized. Density functional theory calculations reveal that introducing Ni atoms creates several new energy levels and increases the density-of-states at the conduction band minimum. Synchrotron radiation photoemission spectroscopy demonstrates that the band structures are suitable for CO2 photoreduction, while the surface photovoltage spectra demonstrate that Ni doping increases the carrier separation efficiency. In situ diffuse reflectance Fourier transform infrared spectra disclose that the CO2·? radical is the main intermediate, while temperature-programed desorption curves reveal that the ZnCo2O4 atomic layers with/without Ni doping favor the respective CO and CH4 desorption. The Ni-doped ZnCo2O4 atomic layers exhibit a 3.5-time higher CO selectivity than the ZnCo2O4 atomic layers. This work establishes a clear correlation between elemental doping and selectivity regulation for CO2 photoreduction, opening new possibilities for tailoring solar-driven photocatalytic behaviors.
A facile method of synthesizing Fe3O4-Au hybrid nanoparticles is reported utilizing the multifunctional nature of polyethyleneimine (PEI). An abundance of 5 nm
gold nanoparticles were attached to 50 nm Fe3O4 nanoparticles via the covalent binding between the -NH2 groups of the PEI and Au nanoparticles, as well as the electrostatic interaction between the negatively charged citrate-coated
Au nanoparticles and the positively charged PEI-coated Fe3O4 nanoparticles. The as-prepared Fe3O4-Au hybrid nanoparticles, which combine the merits of magnetic materials and gold, were successfully employed for the first
time in the dual-mode detection of carcinoembryonic antigen (CEA) via electrochemical and surface-enhanced Raman scattering
(SERS) methods. Both methods make clever use of Fe3O4-Au nanoparticles and can accurately verify the presence of antigens. In particular, the electrochemical immunosensor detection
displays a wide linear range (0.01–10 ng/mL) of response with a low detection limit (10 pg/mL), while the SERS method responds
to even lower antigen concentrations with a wider detection range. The Fe3O4-Au hybrid nanoparticles therefore exhibit great potential for biomedical applications.
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