Typical Core-shell Structure Research Articles

Epitaxial Growth of Multicolor Lanthanide MOFs by Ultrasound for Photonic Barcodes.

Epitaxially grown lanthanide metal-organic frameworks (Ln MOFs) exhibit multicolor and characteristic Ln emission with sharp emission bands, which are of great value in the field of information security and anti-counterfeiting. Epitaxial growth of Ln MOFs is generally achieved by solvothermal or hydrothermal methods, which suffer from challenges such as high reaction temperature and long growth time. Here, we report the fast epitaxial growth of multicolor lanthanide MOFs by an ultrasonic method at room temperature. The TbSmSQ shows a core-shell type structure with the Tb ion in the core and Sm in the shell within one crystal and exhibits the characteristic emission lines of Tb and Sm, respectively. The nonporous structure and large distance between lanthanide ions effectively avoid the influence of solvent vapor on the intensity and color of luminescence emission. Its application as photonic barcodes has been studied. This work demonstrates the feasibility of epitaxial growth of multicolor Ln MOFs by the ultrasonic method and its value for anti-counterfeiting and information security applications.

An intriguing way to synthesize a TiO2–ZnO hybrid nanostructure for the pragmatic application as a photocatalyst

In an attempt to counter the problem of treating wastewater more efficiently, we report the study on photocatalytic properties of metal oxide nanostructures under different light sources. A novel sonication-assisted refluxing method was employed to synthesize a binary heterostructure consisting of TiO2 and ZnO. XRD and EDS analysis of synthesized materials confirm the presence of both TiO2 and ZnO. Also, the change in the intensity of XRD peaks and elemental composition are well observed with a change in molar concentration of Ti and Zn. HR-TEM micrographs show nanostructures having hybrid Janus and Core-shell type structures. The XPS spectra were probed to identify the surface chemical species associated with the prepared heterostructures. Raman spectra confirm the smaller ZnO particles attached over agglomerated TiO2 as a shell layer as depicted in TEM results. Optical studies exhibit the modification in the band structure of the materials due to the formation of the heterostructure. The synthesized hybrid catalyst shows impressive results in photocatalytic performance. The catalytic potency of the prepared heterostructures under UV light is reminiscent of Anatase while it gets convalescent with an increment of Zn content under visible light. The photocatalytic performance of synthesized materials under sunlight shows their potential to be utilized as commercial catalysts for direct application in wastewater treatment. The kinetic study of the degradation data reveals interesting facets of the catalysis. It suggests that the photo-corrosion of the catalyst inordinately changes the rate of photocatalytic reaction which ultimately affects the photocatalytic efficiency of the catalyst. The study also discusses the role of kinetic and validation parameters in the selection of the best-fitted kinetic model with realistic arguments.

Synthesis, morphological characterization, and evaluation of nano zero-valent iron (nZVI) in the degradation of water contaminated with POPs

Nanostructured zero valence iron (nZVI) has been applied in advanced oxidative processes aimed at the treatment of water contaminated with Persistent Organic Pollutant (POP). Considering that such compounds cannot be eliminated by traditional treatment methods, this study proposes the synthesis of nZVI by the reduction of Iron Chloride III by sodium borohydride in the absence of O2, in ultrasound bath. The material obtained has only a wide diffraction halo at 45.13º of 2θ, with an average diameter of the crystallite calculated at 8.3 nm. The method of Brunauer, Emmett and Teller (BET method) analysis infer that the synthesized material is classified as mesoporous and showing a large surface area of 91.48 m2.g-1. According to transmission electron microscopy (TEM) the compound exhibits a core-shell type structure being the average size smaller than 50 nm. Thermogravimetric analysis demonstrates that the compound is thermally stable, exhibiting only a thermal event close to 70º C in which there is a loss of approximately 25% of mass related to water loss. The synthesis was efficient because there is no formation of metal oxides and no residue from the synthesis process according to FT-IR analyzes. To evaluate the effectiveness and present the parameters that most positively contributed to the degradation of water contaminated with 24 of the most common POPs, a chemometric study was applied considering the following variables: reaction time, concentration of applied iron nanoparticles and pH values. The approach reduces costs, time, and waste generation. Among the variables, reaction time is crucial, mainly due to solubility differences between compounds. Kinetic tests show increased efficiency after one hour, emphasizing a direct correlation between degradation rate and water solubility for the studied POPs.

Biscrolled hierarchical hybrid structure of PEDOT:PSS/CNTs-NMP yarn based solid state linear supercapacitor for wearable e-textile

The environmental friendly flexible solid state linear supercapacitor (FSLSc) based on the hierarchical hybrid yarn with core-shell type structure of poly(3,4-ethylenedioxythiophene): polystyrenesulfonate (PEDOT:PSS) and hydrophilic carbon nanotubes (CNTs) sheet, fabricated using novel biscrolling technique is proposed. The hierarchical hybrid yarn structure of the electrode establishes the improved electrochemical interface of PEDOT:PSS with the both the hydrophilic CNTs and an aqueous PVA/H3PO4 gel electrolyte. The exterior surface of the yarn electrode rich in PEDOT:PSS which interact with ions from electrolyte and stores charges faradaically while the core region with dense CNTs yarn contributes with its multifunctional capabilities such as EDLC type capacitor, current collector and mechanical support. The observed two-fold decrease in ESR value (∼49Ω) and two-fold increase in capacitance (∼112.76 F/g) for hybrid yarn electrode with N-methyl-2-pyrrolidone (NMP) treated hydrophilic CNTs compared to the one with pristine CNTs, confirms the improved interface of PEDOT:PSS formed with hydrophilic CNTs and aqueous electrolyte. The FSLSc devices with NMP treated CNTs hybrid yarn electrodes exhibited excellent electrochemical performance in terms of the maximum power and energy density of 980 W/kg and 3.799 Wh/kg, respectively. The FSLSc displayed remarkable cycling performance upto 5000 cycles of charge-discharge and a robust bending stability after 1000 bending cycles, making it promising for practical application of the next-generation flexible solid state electrochemical energy storage in e-textiles.

Preparation and thermal properties of latent functional thermal fluid based on size-controllable phase change nanocapsules

Size-controllable 1-octadecanol@polystyrene phase change nanocapsules (NEPCMs) were prepared using the miniemulsion polymerization and dispersed in deionized water containing multi-walled carbon nanotubes to prepare a latent functional thermal fluid (LFTF). The results demonstrate that the NEPCMs exhibit a typical core-shell structure. The average particle size (55.28–143.8 nm) of the NEPCMs can be regulated by controlling the content of compound emulsifiers. The optimal phase change enthalpy has an excellent heat storage capacity of about 222.7 J/g, the encapsulation efficiency is up to 80.63 %, and the average particle size is about 88.3 nm. The heating/cooling cycles results show that NEPCMs have excellent cycle stability. LFTF containing 10 wt% NEPCMs was considered the optimal choice for its excellent photothermal conversion efficiency (up to 64.91 %), excellent dispersion stability (zeta potential 39.17 mV) and thermal storage capacity (peak specific heat capacity 5.72 J g−1 K−1). Under the influence of solar radiation, the temperature rise curve of LFTF exhibited a rapid initial warming rate followed by a plateau period of approximately 76 min upon reaching the melting point of the NEPCMs, whose photothermal conversion efficiency is roughly 2.18 times that of water. The experimental findings demonstrate the potential application of LFTF based on NEPCMs in the solar thermal industry.

Novel mechanism of the grain boundary diffusion process with Tb based on the discovery of TbFe2 phase

The grain boundary diffusion process (GBDP) has proven to be an effective method for enhancing the coercivity of sintered Nd-Fe-B magnets. However, the limited diffusion depth and thicker shell structure have impeded the further development of magnetic properties. Currently, the primary debates regarding the mechanism of GBDP with Tb revolve around the dissolution-solidification mechanism and the atomic substitution mechanism. To clarify this mechanism, the microstructure evolution of sintered Nd-Fe-B magnets during the heating process of GBDP has been systematically studied by quenching at different temperatures. In this study, it was found that the formation of TbFe2 phase is related to the dissolution of Nd2Fe14B grains during GBDP with Tb. The theory of mixing heat and phase separation further confirms that the Nd2Fe14B phase dissolves to form a mixed phase of Nd and TbFe2, which then solidifies into the (Nd, Tb)2Fe14B phase. Based on the discovery of the TbFe2 phase, the dissolution-solidification mechanism is considered the primary mechanism for GBDP. This is supported by the elemental content of the two typical core-shell structures observed.

Reaction characteristics of Al–Mg alloy fuels with heterogeneous oxidation shell structures

Al–Mg alloy fuels are the most widely used Al-based alloy fuel in energetic material systems owing to their low ignition temperature and fast reaction. However, their surface oxide layer structure and oxidation, ignition, and combustion mechanisms differ from those of single-metal fuels. Furthermore, insufficient information has been reported on Al–Mg alloy fuels. In this study, Al–Mg alloy fuels were formed by introducing Mg into Al via centrifugal atomization. The microstructure and thermal reaction characteristics of the Al–Mg alloy fuel were evaluated. The ignition and combustion characteristics of the Al–Mg alloy fuels were monitored via single-particle ignition. When the Mg content was increased from 5 % to 40 %, a typical core–shell structure formed, the oxide shell thickness increased from 4.50 to 6.41 nm, and the content of the internal alloy compounds gradually increased. The surfaces of the Al–Mg alloy fuel particles with different Mg contents exhibited heterogeneous oxidation shells. Compared to Al powder, the Al–Mg alloy fuel exhibited better melting and oxidation peak temperatures and higher oxidation weight gain. As the Mg content was increased, the combustion of the Al–Mg alloy fuel intensified with more severe microexplosions and a shorter combustion time. The microexplosion of the Al–Mg alloy fuel was elucidated by theoretical calculations, and its combustion mechanism was proposed. The detailed description of the oxide layer structure, oxidation, and combustion of the Al–Mg alloy fuel provides a reliable explanation of its energy release mechanism in energetic material systems.

Intensely bonded high filling bismuth oxide with chloroprene rubber to achieve lead-free flexible materials for γ-rays shielding

Achieving lead-free flexible materials with excellent γ-ray shielding as well as good mechanical properties are of significance to radiation protection safety and wear comfort of wearable articles. In this paper, polydopamine (PDA) is coated on Bi2O3 particles to form a typical core–shell structure Bi2O3@PDA, which is used to intensely bond bismuth oxide (Bi2O3) with chloroprene rubber (CR). It promotes the interface interaction between Bi2O3 and CR matrix, leading to the uniform dispersion of the filler and rich interfacial compatibility in CR/Bi2O3@PDA composite with as high as 50 wt% filling. Furthermore, 50 wt% CR/Bi2O3@PDA composite displays 53.6% shielding rate for 105 keV γ-rays. Meanwhile, its tensile strength and elongation at break are 9.6 MPa and 1424.8%, respectively, which are without sacrificing too much in comparison with the neat rubber. We propose a versatile route to prepare superior integrated properties of flexible materials, which can be used as wearable articles for radiation shielding.

Macrophage membrane-camouflaged pH-sensitive nanoparticles for targeted therapy of oral squamous cell carcinoma

BackgroundOral cancer is the most common malignant tumor of the head and neck, and 90% of cases are oral squamous cell carcinoma (OSCC). Chemotherapy is an important component of comprehensive treatment for OSCC. However, the clinical treatment effect of chemotherapy drugs, such as doxorubicin (DOX), is limited due to the lack of tumor targeting and rapid clearance by the immune system. Thus, based on the tumor-targeting and immune evasion abilities of macrophages, macrophage membrane-encapsulated poly(methyl vinyl ether alt maleic anhydride)-phenylboronic acid-doxorubicin nanoparticles (MM@PMVEMA-PBA-DOX NPs), briefly as MM@DOX NPs, were designed to target OSCC. The boronate ester bonds between PBA and DOX responded to the low pH value in the tumor microenvironment, selectively releasing the loaded DOX.ResultsThe results showed that MM@DOX NPs exhibited uniform particle size and typical core-shell structure. As the pH decreased from 7.4 to 5.5, drug release increased from 14 to 21%. The in vitro targeting ability, immune evasion ability, and cytotoxicity of MM@DOX NPs were verified in HN6 and SCC15 cell lines. Compared to free DOX, flow cytometry and fluorescence images demonstrated higher uptake of MM@DOX NPs by tumor cells and lower uptake by macrophages. Cell toxicity and live/dead staining experiments showed that MM@DOX NPs exhibited stronger in vitro antitumor effects than free DOX. The targeting and therapeutic effects were further confirmed in vivo. Based on in vivo biodistribution of the nanoparticles, the accumulation of MM@DOX NPs at the tumor site was increased. The pharmacokinetic results demonstrated a longer half-life of 9.26 h for MM@DOX NPs compared to 1.94 h for free DOX. Moreover, MM@DOX NPs exhibited stronger tumor suppression effects in HN6 tumor-bearing mice and good biocompatibility.ConclusionsTherefore, MM@DOX NPs is a safe and efficient therapeutic platform for OSCC.

Effects on the magnetic properties and microstructure of Nd-Fe-B diffusion-processed using Tb oxyfluoride

Diffusion process has been proved to be an effective way to enhance the performance of Nd-Fe-B permanent magnets. In present work, the mixture of TbF3 and Tb4O7 has been used as diffusion sources and their influences on the microstructure and magnetic properties have been investigated. The results reveal that the binary mixture diffusion system outperforms the individual diffusion using either TbF3 or Tb4O7 as diffusion source. Diffusion-processed at 900 ℃ for 7 h followed by subsequently aged at 500 ℃ for 1 h, the coercivity of the magnet is increased substantially from 0.95 T to 2.33 T. The (Nd, Tb)2Fe14B/Nd2Fe14B core–shell-type structure has been formed with continuous Tb-rich grain shell.

Effect of welding state on the re-precipitation behavior of Cu-rich and NiAl nanoparticles in HAZ of 1100 MPa grade low carbon ultra-high strength steel

The influence of multi-layer multi-pass welding and post-weld heat treatment (PWHT) on the co-precipitation behavior of Cu-rich and B2–NiAl, microstructural characteristics, grain size and mechanical properties of the coarse grain heat affected zone (CGHAZ) were systematically investigated for low-carbon ultra-high-strength steel with different Ni/Cu ratio. The results show that the CGHAZ microstructure of both high (1.5Cu) and low (2.0Cu) Ni/Cu ratio steel are composed of LB and GB, the grain size increases from 10.1 ± 1.1 μm and 9.5 ± 0.7 μm to 32.1 ± 1.0 μm and 32.2 ± 2.7 μm, and the nanoparticles are dissolved and subsequently re-precipitated during the welding process, with an average radius 1.56 nm and 1.71 nm, respectively. The hardness profile of the joint shows softening at CGHAZ and the tensile strength reaches 1218 MPa and 1056 MPa respectively. After PWHT, the re-precipitated behavior of the nanoparticles was enhanced, with average radius of 1.53 nm and 1.55 nm, and the number density increases from 1.55 × 1023 m−3 and 1.06 × 1023 m−3 to 4.01 × 1023 m−3 and 3.33 × 1023 m−3, respectively. The co-precipitation evolution mechanism shows that the typical core-shell structure is transformed into individual 9 R–Cu and B2–NiAl particles, and a large number of small-sized B2–NiAl particles were re-precipitated during the aging process. The strengthening mechanism shows that martensite strengthening and grain size strengthening are weakened in the as-welded CGHAZ, and only part of the nanoparticles was re-precipitated leading to the softening of CGHAZ during welding. After PWHT, a large number of small-sized nanoparticles were re-precipitated to restore the contribution of precipitation strengthening, while small-sized nanoparticles interacted with dislocations and entangled near the M-A constituents to promote the formation of microvoids and microcracks, thus seriously deteriorating the ductility.

A smartphone sensing platform for the sensitive and selective detection of clothianidin based on MIP-functionalized lanthanide MOF.

Anovel molecularly imprinted nanomaterial (Eu (BTC)-MPS@MIP) was synthesized on the surface of silanized europium-based metal-organic frameworks (Eu (BTC)-MPS) using 1, 3, 5-benzotrioic acid (H3BTC) as a ligand. The resulting Eu (BTC)-MPS@MIP was applied to constructing a smartphone sensing platform for the sensitive and selective detection of clothianidin (CLT) in vegetables. The synthesized Eu (BTC)-MPS@MIP demonstrated the successful formation of a typical core-shell structure featuring a shell thickness of approximately 70 - 80nm. The developed sensing platform based on Eu (BTC)-MPS@MIP exhibited sensitivity in CLT detection with a detection limit of 4µg/L and a linear response in the range 0.01 - 10mg/L at excitation and emission wavelengths of 365nm and 617nm, respectively. The fluorescence sensing platform displayed excellent specificity for CLT detection, as evidenced by a high imprinting factor of 3.1. This specificity is primarily attributed to the recognition sites in the molecularly imprinted polymer (MIP) layer. When applied to spiked vegetable samples, the recovery of CLT ranged from 78.9 to 102.0%, with relative standard deviation (RSD) values falling between 2.2 and 6.2%. The quenching mechanism of Eu (BTC)-MPS@MIP toward CLT can be attributed to the inner filter effect (IFE), resulting from the optimal spectral overlap between the absorption spectrum of CLT and the excitation spectra of Eu (BTC)-MPS@MIP. The proposed method has the potential for extension to the detection of other pesticides by replacing the MIP recognition probes.

Chitosan-covered spherical natural graphite: A perfect carbon source for efficient non-PGM catalysts for electrocatalysis

Developing non-precious metal catalysts to replace Pt-based catalysts for oxygen reduction reaction (ORR) is a hotspot presently, and transition metal-nitrogen co-doped carbon (TMNC) materials have been deemed as the most promising candidates. In this work, chitosan-derived-curved-carbon covered natural spherical graphite (SG) with a well-defined core-shell structure were prepared via hydrothermal carbonization (HTC) process followed by activation under NH3 atmosphere. A series of active transition metals (M=Fe, Co, Mn) and nitrogen atom were embedded into the curved carbon to form various MNC moieties on SG surface as active sites for ORR. Among the atomic precise MNC@NSG hybrid catalysts, the FeNC@NSG shows the best ORR performance and the half-wave potential is 0.95 V (vs. RHE), which are 108 % as high as that obtained by commercial Pt/C in alkaline environment. Besides, the electrochemical stability and methanol tolerance of the catalyst is also superior to commercial Pt/C. DFT calculations reveals that the high-performance stems from the curved FeNC units in the shell and high electrical conductivity of natural SG in the core for the typical core-shell structures. Moreover, the sluggish ORR kinetics can be efficiently accelerated by the increased FeN bond length, more positive-shifted d-band center and more positive surface charge of active Fe atoms in the curved FeNC units on spherical SG. This provides an enlightenment for developing efficient non-platinum group metal (PGM) catalysts using cheap and volume natural spherical graphite as building brick for energy storage and conversion devices.

Thermal enhancement of the oxidation layer of micron-sized aluminum powder and its anti-oxidation performance

Micron-sized aluminum powder, with its typical core-shell structure, exhibits oxidation behavior upon slow heating in an oxidative atmosphere that is related to the particle size of the aluminum powder. A particle size-dependent thermal response mechanism for micron-sized aluminum powder is established: a "shell-breaking eruption" thermal response mechanism. The oxide layer is thermally enhanced, and the anti-oxidation reaction behavior mechanism of the enhanced samples is studied. Aluminum powder samples, heated slowly to specific temperatures to obtain changes in the oxide layer structure, are analyzed using a thermal analyzer to compare the slow heating response behavior of aluminum powder before and after the oxidation layer changes. It was found that after thermal enhancement of the aluminum powder oxidation layer, which changed from amorphous to γ-phase and whose thickness increased to twice the original thickness, the slow oxidation process of micron-sized aluminum powder was inhibited, and the aluminum powder was completely deactivated in the slow heating response.

Quantitative Analysis of the Impacts of Ash from Lubricating Oil on the Nanostructure of Diesel Particulate Matter

Microscopic analyses of the effects of ash on particulate matter oxidation are rather scarce. In this study, three different lubricating oils with varying ash contents were used to investigate their effects on the nanostructure of diesel particulate matter. The nanostructure and nanostructure parameters, including fringe length, fringe separation distance, and fringe tortuosity, were studied using high-resolution transmission electron microscopy. The results show that all samples obtained from blending with different lubricant oil present typical core–shell structures. The inner cores remain relatively unchanged, whereas the thickness of the outer shells increases with the increasing ash content in the lubricant oil under the same working conditions. The fringe length increases and the fringe separation distance decreases with the rising ash content in the lubricant oil operating in the same working conditions. The fringe tortuosity decreases when the ash content in the lubricant oil increases from 0.92% to 1.21%, but shows little change when the ash content in the lubricant oil increases from 1.21% to 1.92%. Based on the effects of ash on the nanostructure parameters, it can be inferred that the oxidation activity of particles decreases with increasing ash content in the lubricant oil.

Microencapsule delivery systems of functional substances for precision nutrition.

Microencapsulation, a typical core-shell structure technology, encapsulates functional active ingredients for protection, controlled release, and targeted delivery. In precise nutrition, the focus is on utilizing microcapsule delivery systems for personalized dietary supplements and disease intervention. This chapter outlines the morphological structure of microcapsules, common wall materials, and preparation techniques. It discusses the characteristics of different hydrophilic and lipophilic functional factors and their function as dietary supplements. The role of microencapsulation on the controlled release, odor masking, and enhanced bioavailability of functional factors is explored. Additionally, the application of microcapsule delivery systems in nutritional interventions for diseases like inflammatory bowel disease, alcoholic/fatty liver disease, diabetes, and cancer is introduced in detail. Lastly, the chapter proposes the future developments of anticipation in responsive wall materials for precise nutrition interventions, including both challenges and opportunities.

Evolution of physicochemical characteristics of soot in a single coal combustion flame

This study experimentally investigated the evolution of the nanomorphology, graphite crystals, oxidation reactivity, and functional groups of soot in a single coal combustion flame. Nascent (sample #1), young (sample #2), and mature (sample #3) soot were collected from a Shenhua single coal combustion flame. The soot samples were then tested and analyzed using high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy to determine their physicochemical characteristics. The results showed that the nascent soot was an individual particle, the mature soot was a highly agglomerated soot aggregate, and the young soot was a transitional particle. The primary particles of sample #1 comprised several randomly orientated individual polycyclic aromatic hydrocarbon (PAH) crystal sheets, whereas the primary particles of samples #2 and #3 were typical core-shell graphite structures. The sp2/sp3 content, volatile organic fraction, and oxidation rate constant of samples #1, #2, and #3 decreased, resulting in successively weakened reactivity. The infrared spectrum absorption of 2800–3000 and 1700–900 cm−1 indicated that the hydrogen in the three coal-derived soot samples was mainly aromatic rather than aliphatic. Furthermore, the proportion of solo and duo aromatic out-of-plane (OPLA) CH bending in samples #1, #2, and #3 increased, whereas the proportion of trio-quatro OPLA CH bending decreased.

Improved rate capability and long cycle life of metal-organic framework derived TiO2@V2O5 composite as an efficient cathode for sodium-ion batteries

Vanadium oxide on carbon nanoporous structure (V2O5/C) as a potential cathode material for sodium-ion batteries (SIBs) offers significant specific capacities in energy storage systems but suffers from slow ionic diffusivity upon long cycling at higher current rates, thereby generally resulting in substandard electrochemical performance. This study suggests a facile strategy to enhance the electrochemical performance of V2O5/C as a cathode in sodium-ion batteries via titanium (Ti) doping using the pre-synthesized Ti-doped vanadium-based metal-organic framework template (V-MIL-101) as the precursor, which can be converted into a sophisticated core-shell type structure in which titania nanoparticle-based shell surrounds the vanadium oxide with a porous carbon-based octahedral core. Structural characterization reveals that Ti-doping forms a protective layer around vanadium based MIL-101 octahedrons that, upon pyrolysis, preserves the octahedral geometry and transforms into a nanoporous core-shell structure. It also greatly enhances the electrochemical performance as a cathode for SIBs. The titania-doped vanadium oxide structures represent higher specific capacities than the undoped vanadium oxide cathode, whereas among all the titania-doped samples, the 3 wt% TiO2@V2O5/C exhibited a much higher reversible capacity of 276.2 mAh/g as compared to the other cathode samples at 0.1C current rate and was able to retain a capacity of 250.1 mAh/g with a high coulombic efficiency after 200 cycles. Titanium species induce the formation of oxygen vacancies and V+5 species, which enhance the electrode's electric conductivity and ion diffusion—the stable octahedrons with a porous structure and carbon hybridisation in 3 wt% TiO2@V2O5/C could facilitate ion/electron transfer through shortened diffusion pathways.

Development of fluorescence sensor and paper chips based on EDTA etched-CdTe@CdS QDs for the selective and sensitive detection of Cd(II) in rice samples

EDTA-etched CdTe@CdS QDs were used as the specific recognition element and signal probe of a fluorescence sensor or paper chip for the highly sensitive detection of Cd(II) with an electronic eye device as readout. The results showed that the CdTe@CdS QDs were successfully synthesized with a typical core–shell structure. Under the optimum conditions, the EDTA-etched CdTe@CdS QDs sensor achieved the sensitive detection of Cd(II) with a detection limit of 0.092 μM and a concentration range of 0.44–6.67 μM. The paper chips based on the EDTA-etched CdTe@CdS QDs sensor had a visual cut-off value of 0.44 μM with a short detection time (<15 min). The proposed method also exhibited excellent stability, high specificity, and good recovery for Cd(II) in real rice samples. These results suggested that the EDTA-etched CdTe@CdS QDs provide a promising platform for on-site and visual detection of Cd(II) in rice samples.

Hierarchical polyaniline/copper cobalt ferrite nanocomposites for high performance supercapacitor electrode

Increasing energy demand needs efficient energy storage devices, especially for mobile applications and wearable electronics. Conducting polymer based nanocomposite offers excellent charge transfer mechanism with high energy storage ability. Herein, we report preparation of polyaniline/copper cobalt ferrite (PANI/CCF) based nanocomposites to fabricate supercapacitor electrodes. In-situ polymerization of PANI ensures the formation of a well-mixed nanocomposite of PANI and CCF. Detailed structural and morphological analysis reveal the formation of a core-shell type structure with CCF as the core and PANI as the shell. The core-shell structure was formed due to the presence of a synergistic interaction between PANI and CCF. Particle size distribution shows a well distribution with an average size ~100–120 nm, contributing significantly towards high energy density at high power density. The supercapacitor electrode based on 8:1 material shows significantly high capacitance of 408.8 F g−1 at a scan rate of 5 mV s−1 and 460.1 F g−1 at 0.5 A g−1 current density. The energy storage capacity enhanced significantly for 8:1 weight ratio of PANI and CCF. The PANI/CCF 8:1 nanocomposite shows energy density of 23 and 18.2 W h kg−1 at power density of 150 and 1500 W kg−1, respectively with a good cyclic life (~91 % retention after the 1500 cycle). Consequently, PANI/CCF 8:1 nanocomposite has excellent potential for supercapacitor electrodes for energy storage applications.