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Herein, we demonstrate that a new multicolor silver nanoclusters/graphene oxide (Ag NCs/GO) hybrid material, upon target response, undergoes a configuration transformation, based on entropy-driven enzyme-free toehold-mediated strand displacement reaction, achieving emission shift and enhancement. To realize the aim above, two different synthesis routes (route I and II) of synthesizing fluorescent Ag NCs for constructing toehold displacement Ag NCs/GO biosensor is designed and performed. Influenza A virus subtype genes (H1N1 and H5N1) as a model can efficiently initiate the operation of entropy-driven displacement reaction, resulting in activatable fluorescence. Red-emitting and green-emitting Ag NCs tethering the complementary sequence of H1N1 (pDNA1) and H5N1 (pDNA2) are indirectly immobilized on GO surface through binding with capture DNA (cDNA1 and cDNA2), respectively, forming multicolor pDNA-Ag NCs/GO nanohybrid materials. However, they do not exhibit nearly fluorescence signals attributed to energy transfer from donor Ag NCs to acceptor GO. Upon adding targets H1N1 and H5N1 (tDNA1 and tDNA2), pDNA1-Ag NCs and pDNA2-Ag NCs detach from GO, based on toehold-mediated strand displacement reaction, which interferes the energy transfer and leads to significant fluorescence enhancement. More interestingly, the activatable process is accompanied by remarkable hypsochromic shift (19 nm) or bathochromic shift (21 nm) emission with quite high fluorescence recovery rates (823.35% and 693.62%). Therefore, based on these phenomena, a novel multiple approach has been developed with the assistance of toehold displacement and Ag NCs/GO nanohybrid materials. As for the remarkable emission recovery and multichannel signal, the proposed approach displays the promising application prospect in accurate diagnosis and treatment.

Summary Tin-lead perovskite solar cells (Sn-Pb PSCs) with low band gap (1.2–1.4 eV) are expected to achieve the maximum-power conversion efficiency (PCE) of single-junction devices given by the Shockley-Queisser limit. However, over 40 mol % Pb2+ is necessary to suppress the oxidation of Sn2+, which causes serious p-type self-doping. Here, we propose a new galvanic displacement reaction (GDR) method, through using lead powder as lead source and reductant simultaneously to resolve the above-mentioned issue. Lead powder could fully reduce Sn4+, but not Sn2+, in precursor, meanwhile suppressing the formation of iodide in film. Finally, Sn-Pb PSCs with low lead content and highest efficiency for MA-free-based devices (PCE: 18.34% for 8.5 mol % Pb2+, 20.01% for 18.7 mol % Pb2+) were realized. The unencapsulated devices retained unchanged or 81% of the original efficiency after storing for 2,352 h or tracking at maximum-power point (MPP) for 700 h in N2 atmosphere (O2 ≤ 50 ppm).

Transition metal carbides have sparked unprecedented enthusiasm as high-performance catalysts in recent years. Still, the catalytic properties of copper (Cu) carbide remain unexplored. By introducing subsurface carbon (C) to Cu(111), displacement reaction of proton in carboxyl acid group with single Cu atom is demonstrated at the atomic scale and room temperature. Its occurrence is attributed to the C-doping induced local charge of surface Cu atoms (up to +0.30 e/atom), which accelerates the rate of on-surface deprotonation via reduction of the corresponding energy barrier, thus enabling the instant displacement of a proton with a Cu atom when the molecules land on the surface. Such well-defined and robust Cu$^{\delta +}$ surface based on the subsurface C doping offers a novel catalytic platform for on-surface synthesis., Comment: Angewandte Chemie International Edition, Wiley-VCH Verlag, 2021

Exploring high-performance cathode materials for aqueous zinc ion batteries (ZIBs) is still one of the critical issues. Copper vanadate compound has become a potential cathode material for ZIBs with a novel displacement reaction mechanism of reversible reduction/oxidation of Cu2+/Cu0. Herein, we reported Cu0.95V2O5 nanoflowers prepared using a hydrothermal synthesis method as a capable cathode material for ZIBs. The Cu0.95V2O5 nanoflowers exhibit high specific capacity of 405 mAh·g−1 at the current density of 100 mA·g−1, benefiting from the displacement reaction mechanism and phase transformation mechanism from Cu0.95V2O5 to the open and stable architecture Cu0.4V2O5 and Zn3(OH)2V2O7·2H2O phase. The cathode exhibits excellent rate performance with a high capacity of ~ 200 mAh·g−1 at 5 A·g−1 and outstanding cycle stability with a capacity retention of 92% after 1000 cycles. It is anticipated that the novel Cu0.95V2O5 nanoflowers are promising cathode material in the application for zinc ion batteries.

In this contribution, we fabricated a composite consisting of two polymorphs of FeS2, pyrite (P-FeS2) and marcasite (M-FeS2), for high-performance Li-FeS2 battery. A series of electrochemical, microscopic, and spectroscopic characterizations indicate that the introduction of metastable M-FeS2 into P-FeS2 enables the four-electron reduction between FeS2 and lithium to generate Fe and Li2S, providing a high specific capacity of 894 mAh/g with specific energy over 1300 Wh/kg. Moreover, it is verified that the electrochemical irreversibility of this composite toward lithium storage is mainly rooted in the shuttle effect, caused by the elemental sulfur which is inevitably produced during the oxidation process of Li2S and Fe. To tackle this issue, copper (Cu) current collector is adopted to chemically immobilize the soluble lithium polysulfides and fundamentally alter the reaction pathway. It is shown that compared with Fe, Li2S prefers to react with Cu current collector to generate Cu2S through the thermodynamically facile displacement reaction mechanism benefiting from the similar lattice framework between Cu2S and Li2S. Such displacement reaction without lattice reconstruction renders the composite superior rate capability (∼730 mAh/g@2 A/g) and long lifespan (89.7% capacity retention after 3200 cycles). Present work allows for the fabrication of high-performance electrodes based on metal chalcogenides.

A simple and reproducible surface enhanced Raman scattering (SERS) substrate of bimetallic gold-silver (Au-Ag) based on discarded a Blu-ray disc read only memory (BD-ROM) was developed by simply incorporating electrochemical (EC) treatment and chemical reaction. The resurfaced AgBD-ROM substrate (r-AgBD-ROM) was fabricated by EC treatment on a Ag film layer in BD-ROM (AgBD-ROM) to generate silver nanoparticles (AgNPs) on the indented pattern surface. Then, galvanic displacement reaction of Au and Ag was carried out to prepare the bimetallic Au-Ag structure (Au-r-AgBD-ROM). The suitable size and density as well as location of NPs on the surface can be tuned via EC treatment conditions to obtain highly active SERS performance. The SERS enhancement phenomenon on our developed substrate was studied by observing the location of the SERS hot spot obtained by Raman mapping. The developed SERS substrate offers excellent stability (90 days), good uniformity [6.14% relative standard deviation (RSD)], and reproducibility (3.79% of RSD). Moreover, this substrate can be used as a promising sensor for detecting acetaminophen, ibuprofen, and mefenamic acid. This finding suggests a simple and low-priced process, which potentially facilitates fabrication of highly sensitive SERS substrates for practical applications.

We point out a novel opportunity for catalyst monolayer and core–shell structures synthesis via the surface limited redox replacement (SLRR) reaction. It is enabled by discovery of an electroless P...

Developing platinum-based nanoparticles on carbon catalysts with high activity and stability for oxygen reduction reaction (ORR) is of great significance for the practical application of fuel cells. Herein, a synchronous strategy of preparing nano-sized PtCo supported on atomic Co and N co-doped carbon nanorods (PtCo/Co–N–C NR) was developed to replace the conventional method of impregnating Pt sources into ready-made carbon materials, in which metal-organic frameworks (MOFs) with Co and Zn ions of rhombic dodecahedron were first prepared using 2-methylimidazole as building block and then their morphology was transformed into porous nanorods via the reduction of Co ions to Co–B–O complex in the MOFs by NaBH4; subsequently, Pt was deposited on the Co–Zn MOF nanorods through the displacement reaction of PtCl62- and metallic Co and coordination between MOF and PtCl62-; after pyrolysis and acid-leaching process, highly dispersed PtCo/Co–N–C NR was obtained. Attributed to its unique characteristics of hierarchical pore structure, uniform PtCo alloy nanoparticles with the average size of 7.0 nm and strong supporting interaction effect, the catalyst exhibits high ORR activity and stability with the mass activity of 577.0 mA mg−1Pt and specific activity of 1.4 mA cm−2 at 0.9 V vs RHE in 0.1 M HClO4, which is about 3.6 times and 3.5 times high than that of commercial Pt/C catalyst respectively. This strategy would provide a flexible route to develop highly active and stable ORR electrocatalysts with various morphologies for optimizing the exposure of active sites.

ZrC was produced by the combustion synthesis technology using Cu, Zr, and graphite as the starting element powders. The synthesis mechanism of ZrC was investigated by the combustion wave quenching experiment. Furthermore, the effects of sizes of C and Cu on the combustion synthesis behavior and products were also explored. Results revealed that ZrC was fabricated through the displacement reaction between C and Cu–Zr liquid. The Cu size hardly affected the combustion temperature and resultant products, indicating that the preparation cost of ZrC could be decreased by employing coarse Cu powders. With increasing C size, the burning temperature and ceramic particle size reduced. Graphite with size of 2.6 μm was used as the C source, and only ZrC nanoparticles and Cu were obtained. The products could be employed to prepare nano-sized ZrC/Cu composites without the elimination of by-products.

In this work, we have studied the displacement reaction of Al and SiO2 powder blends by mechanical alloying (MA) for 20 h and low-temperature sintering. The microstructural evolution of powder and ...

Design and synthesis of platinum catalysts within atomic level are of great significance for the practical application of fuel cells. We found that the ultrathin Co(OH)2 nanoparticles can be converted into Co3O4–Co core-shell nanostructures through a thermal annealing process in reducing atmosphere, which are uniformly distributed on the surface of 3D graphene (3DG). The Co3O4–Co core-shell nanoparticles have been successfully transformed into Co3O4–Pt core-shell nanoparticles via a controlled replacement reaction. The Co3O4–Pt @3DG contains only a few atomic layers of Pt shell, and presents a high Pt utilization nanostructure. Besides, the 3D graphene serves as a catalysts carrier with open structure, and offers a three-dimensional molecular accessibility and conducive to mass transfer. Significantly, the optimized mass activity and specific activity of 1.018 A/mgPt and 2.17 mA/cm2 have been achieved on Co3O4–Pt @3DG at 0.9 V vs RHE, which are 7.6- and 8.1- times higher than those of Pt/C (0.134 A/mgPt and 0.266 mA/cm2), respectively. The high activity is mainly attributed to the ultrathin core-shell structure with an ultrahigh Pt utilization, and the interaction between the near-surface Co3O4 and the surface Pt shell with a tensile strain to surface Pt shell, and the electrons transfer from Co to Pt.

Understanding the stability evolution of the silver nanoparticles (Ag NPs) in colloid has great benefits for its controllable preparation, storage and application. Herein, uncapped Ag NPs with diameter of 1.66 ± 0.37 nm are obtained by laser ablation of Ag target in deionized water, corresponding surface plasma resonance (SPR) bands, ζ potential and particle size distribution are monitored to investigate uncapped Ag NPs’ stability evolution. Due to negatively charged surface, uncapped Ag NPs show an excellent dispersion stability in 70 days without any external disturbance. But its dispersion stability and structure stability are destroyed easily by an oscillation treatment, resulting in a tardy growth and the formation of one-dimensional Ag nanochain. In addition, the chemical stability of uncapped Ag NPs is dramatically varied by a displacement reaction with an inserted copper wire. As comparison, two typical cationic and anionic surfactant molecules, N-hexadecyl trimethyl ammonium chloride (CTAC) and sodium dodecyl benzene sulfonate (SDBS) are severally used to prepare surface capped Ag NPs. With same treatment of Ag colloid, both two kinds of capped Ag NPs display better dispersion stability and structure stability than uncapped Ag NPs. Moreover, CTAC capped Ag NPs keep a better chemical stability than SDBS capped Ag NPs.

Rechargeable aqueous zinc-ion batteries (ZIBs) are attractive candidates for next-generation batteries. However, the challenge of uneven zinc electroplating/electrostripping on bare Zn anodes has severely restrained the practical application of ZIBs. To address this problem, a straightforward strategy of sliver particle-coated zinc plate (designated as Zn@Ag) via the metallic replacement reaction as the zinc metal anode has been employed to facilitate uniform and stable Zn-plating/stripping. The newly formed AgZn3 alloy from silver particles at the first zinc-plating cycle with good zinc affinity can effectively lower the energy barrier of zinc nucleation and promote uniform electric field distribution for the flow of Zn ions, resulting in stable zinc deposition. Benefiting from the in situ formed alloy phase, the Zn@Ag anode achieves stable cycling for over 1700 h with a very low polarization voltage of about 21 mV at 0.25 mA cm−2 and 0.25 mA h cm−2, while the bare Zn anode just exhibits less than 150 cycles with large voltage fluctuation and polarization under same conditions. As a consequence, greatly improved performance of the Zn@Ag//CNT/MnO2 full-cell with twice the capacity (177 mA h g−1) than that of bare Zn//CNT/MnO2 full-cell (71 mA h g−1) after 400 cycles at 0.6 A g−1 can be realized. This work provides a facile and effective approach to regulate Zn deposition for the achievement of long-life rechargeable ZIBs.

Epoxy resin conductive adhesives with high electrical conductivity have been prepared by adding micron-scale silver-coated copper (Cu@Ag) particles. The silver-coated copper particles have been prepared with 1 μm Cu particles as the substrates, which utilizes Cu autocatalytic properties and does not require any reducing agent. The reaction time and temperature on the properties of Cu@Ag particles have been studied. The sample has a high loading of 32.5% at 60 °C, and the activation energy of the displacement reaction is 3.2 × 103 J mol−1. The Cu@Ag particles have been immersed in a 20% HNO3 solution. We found that the conductive particles prepared under high-temperature conditions (≥50 °C) had high corrosion resistance. Through thermogravimetric analysis, it could be seen that the silver could improve the oxidation resistance of the material, and the oxidation resistance also increased with the increase of the temperature of preparing conductive particles. The Cu@Ag particles prepared under the conditions of 10, 30, 40, 60 °C and epoxy resin were prepared into conductive adhesives containing 75% conductive particles. The stability of the samples has been tested, and the results have shown that the resistivity of the conductive adhesives prepared under the condition of 60 °C and 80 hours baking was stable within 2.0 × 10−4 Ω m, and then the resistivity fluctuates in a small range, but it is consistent with the pure silver conductive adhesives.

Calcium-ion batteries (CIBs) are getting increasing attention as post-lithium-ion batteries owing to their theoretical and potential advantages in terms of energy density and cost-effectiveness. However, most of the reported cathode materials suffer from low capacity or cyclability in dried nonaqueous electrolytes. So far, all of the materials with high capacity (>100 mA h g−1) contain crystal water, which was considered to be crucial to the structural stability, enabling facile Ca diffusion. Here, we report β-Ag0.33V2O5 as a high-capacity cathode material for CIBs without crystal water. After the initial activation process, the material exhibited a capacity of 179 mA h g−1 at approximately 2.8 V (vs. Ca2+/Ca) in the ninth cycle and showed a modest cycling performance. The capacity is the highest among the Ca cathode materials without crystal water reported to date. We revealed that the activation process was caused by a replacement reaction between the silver and calcium ions. This material demonstrates that crystal water is not an essential component of CIB electrode materials for a high capacity, stimulating the ongoing research for developing higher-performance materials.

A mathematical model of the replacement of methane with carbon dioxide in hydrate at high rates of carbon dioxide injection into a reservoir is proposed. The replacement-reaction zone is modeled by the front of the methane hydrate conversion to carbon dioxide hydrate. A comparison is made with a regime that takes into account the formation of two surfaces of phase transitions, i.e., the front of dissociation of CH4 hydrate and the front of formation of CO2 hydrate. It is shown that a high injection pressure suppresses the dissociation of methane hydrate, and no replacement reaction is implemented. With significant volumes of hydrate in the reservoir, only a partial formation of carbon dioxide hydrate occurs. The critical diagram of the replacement-reaction modes is constructed.

A pine forest-inspired superior Li host with high lithiophilicity and bi-continuous electronic/ionic pathways was successfully fabricated by in situ growth of needle-branch-like Ag hierarchical porous arrays on the skeleton surface of commercial Cu foam via a simple displacement reaction of pure Cu in an AgNO3 aqueous solution. It is demonstrated that the super-lithiophilic properties of the Ag array coating and the capillary effect of its hierarchical porous structures synergistically contribute to the excellent Li-wettability of the Ag@Cu foam hosts for the fast impregnation and uniform deposition of molten Li. Moreover, the pine needle-branch-like Ag hierarchical porous array structures of the coating layers on the Cu skeleton surfaces could provide large surface areas and bi-continuous electronic/ionic pathways for uniform Li plating and stripping with fast electrochemical reaction kinetics. Consequently, the obtained Li/Ag@Cu composite anodes could effectively buffer the volume fluctuation and prohibit the Li dendrite growth, demonstrating an ultra-long-term lifetime of Li plating/stripping over 500 cycles with a low overpotential of 3 mV at 1 mA cm−2, and over 1500 cycles with an overpotential of 6 mV even at a high rate of 5 mA cm−2 in symmetric cells. Furthermore, full cell configurations with the Li/Ag@Cu composite anodes and LiFePO4, LiNi0.8Co0.1Mn0.1O2 or S cathodes also exhibit significantly enhanced cycling capacity and rate performance. These encouraging results indicate that the natural forest-inspired, pine needle-branch-like Ag hierarchical porous array coated Cu foam should be an attractive Li host for fabricating dendrite-free lithium metal anodes for advanced high-energy-density lithium metal batteries.

The expression level of nucleic acids is closely related to a variety of diseases. Herein, a highly sensitive detection of a nucleic acid based on a CoOOH-luminol chemiluminescence (CL) system without the addition of oxidants was proposed by the toehold-mediated strand displacement reaction (TSDR) and the liposome dual signal amplification strategy with the hybrid probe formed by linking soft nanoballs (SNBs) to magnetic beads (MBs) through DNA hybridization. Inspired by the free radical scavenging effect of the as-prepared carbon dots (CDs), CDs were successfully employed to quench the CL intensity of the CoOOH-luminol system. And the CDs were further encapsulated into liposomes to construct SNBs, which avoided the complex modification of CDs to maintain their original properties, as well as loaded a large number of CDs to scavenge free radicals to achieve signal amplification. Based on this, target DNA (tDNA) could be sensitively detected based on the reduced CL intensity, which achieved a dynamic detection range from 0.1 nM to 20 nM with a limit of detection as low as 59 pM (3σ/k), showing amazing promise in the biosensing of nucleic acid biomarkers.

A promising electrode for hydrogen evolution reaction (HER) has been prepared via a reduction process to form NiF2 nanorod arrays directly grown on a 3D nickel foam. We reveal NiF2@Ni nanorod arrays for a stable hydrogen evolution reaction (HER) application. The computational analysis for H2O, OH and H and experimentally in aqueous KOH endow considerable shift in Fermi levels for Ni (111) unlike for NiF2 (110) on account of an effective coalition of p-orbitals of fluorine and d-orbitals of Ni in NiF2, NiF2 under pinning the reduced overpotential of 172 mV at 10 mA cm−2 compared to Ni (242 mV) in same electrolyte. The electrocatalytic mechanism has been proposed using density functional theory (DFT) and is found in well accordance with the experimental findings of the present study. The preparation of self-grown porous nanostructured electrodes on the 3D nickel foam via a displacement reaction is possibly valuable for other metal halides for energy storage and conversion applications as these materials have inherently smaller overpotentials.

In this work, a novel colorimetric method for the detection of telomerase activity is proposed based on the cyclic strand displacement reaction. Target telomerase firstly generates an extension product, which displaces a single-stranded DNA from a partial DNA duplex. The released DNA probe further hybridizes with another DNA probe and initiates the cyclic strand displacement reaction coupling two hairpin DNA probes. The consumption of these DNA probes destroys the protection of gold nanoparticles (AuNPs) from salt-induced aggregation. By observing the color or measuring the UV-vis adsorption spectra, the level of telomerase activity can be evaluated. This method exhibits good sensitivity and provides a new method for telomerase assay for early diagnosis of cancers.

An electrochemical aptasensor with high sensitivity, specificity, and good intra-day reproducibility is reported to meet the detection needs of vascular endothelial growth factor (VEGF). The toehold-mediated strand displacement recycling amplification and VEGF aptamer are integrated in the biosensor. The probe A is hybridized with the VEGF aptamer to form the probe A–aptamer complex. When VEGF is introduced, the aptamer specifically binds with VEGF, and probe A can be liberated. Then, the free probe A captures the toehold region of the Hp1, leading the exposure of the toehold region on the other end of Hp1. Similarly, Hp2 and Hp3 are also immobilized on the surface of the electrode; thus, the methylene blue labelled on Hp2 and Hp3 causes the current response. With the signal transduction mechanism, the expression level of VEGF can be detected quantitatively. With a series of optimizations of sensor parameters, high sensitivity and specificity of the VEGF detection sensor can be achieved with a detection limit as low as 10 pg mL−1. This significant performance has good intra-day reproducibility, and it can be applied to human biological samples such as serum, urine, and saliva to detect the VEGF content.

The detection of Salmonella Typhimurium (S.typhimurium) is of great importance in food safety field. Colorimetric strategy is particularly appealing for S. typhimurium identification because of its user-friendliness and instrument-free. However, the existing colorimetric strategies still meet the challenges of low sensitivity, tedious nucleic acid extraction and expensive labeling processes. Herein, a high sensitivity and label-free colorimetric sensing strategy for S. typhimurium detection without nucleic acid extraction is constructed. Specifically, the proposed strategy is based on three-way junction (3WJ) DNA branched structure combined with nicking enzyme signal amplification (NESA). In the presence of target, cascaded signal amplification is initiated through a series of toehold-mediated strand displacement reactions (TSDRs) to recycle the trigger DNA causing formation of the numerous 3WJ DNA branched structures (3WJ-TSDRs). Then, the branches of 3WJ-TSDRs are fully utilized to hybridize with the DNAzyme signal probes to initiate NESA in the presence of Nt. BbvCI, which making every branch has a function of signal amplification. Finally, DNAzyme signal probes (green) were completely split into two fragments (colorless). The application of NESA in the branches of 3WJ-TSDRs offers a highly sensitive detection of S. typhimurium with a low limit of detection of 42 CFU mL−1. Besides, the colorimetric sensing strategy also shows strong anti-interference. The capability of the colorimetric sensing strategy in spiked samples was also investigated, showing a more intuitive results and fast detection in compare with the traditional plate counting method. With these characteristics, the proposed sensing strategy based on 3WJ-TSDRs and NESA is a promising tool for new point-of-care (POC) applications in food safety.

Rational manipulation of supramolecular structures on surfaces is of great importance and challenging. We show that imidazole-based hydrogen-bonded networks on a metal surface can transform into an isostructural coordination network for facile tuning of the pore size and guest recognition behaviours. Deposition of triangular-shaped benzotrisimidazole (H3btim) molecules on Au(111)/Ag(111) surfaces gives honeycomb networks linked by double N–H⋯N hydrogen bonds. While the H3btim hydrogen-bonded networks on Au(111) evaporate above 453 K, those on Ag(111) transform into isostructural [Ag3(btim)] coordination networks based on double N–Ag–N bonds at 423 K, by virtue of the unconventional metal–acid replacement reaction (Ag reduces H+). The transformation expands the pore diameter of the honeycomb networks from 3.8 Å to 6.9 Å, giving remarkably different host–guest recognition behaviours for fullerene and ferrocene molecules based on the size compatibility mechanism., A hydrogen-bonded network on a Ag(111) surface can transform into an isostructural Ag(i) coordination network, giving drastically different host–guest recognition behaviours.

This research is co-financed by Greece and the European Union (European Social Fund- ESF) through the Operational Programme «Human Resources Development, Education and Lifelong Learning» in the context of the project “Strengthening Human Resources Research Potential via Doctorate Research” (MIS-5000432), implemented by the State Scholarships Foundation (IKY). Η έρευνα συγχρηματοδοτείται από την Ελλάδα και την Ευρωπαϊκή Ένωση (Ευρωπαϊκό Κοινωνικό Ταμείο - ΕΚΤ) στα πλαίσια του Επιχειρησιακού Προγράμματος «Ανάπτυξη Ανθρώπινου Δυναμικού, Εκπαίδευση και Δια βίου Μάθηση» Πράξη «Ενίσχυση του ανθρώπινου ερευνητικού δυναμικού μέσω της υλοποίησης διδακτορικής έρευνας» (MIS 5000432), που υλοποιήθηκε από το Ίδρυμα Κρατικών Υποτροφιών (IKY). Summarization: This paper studies the morphological characteristics of calcium hydroxide nanoparticles in water based dispersions, produced following the main bottom-up (CaCl2/NaOH replacement reaction) and top-down methodologies. The work focuses on the effect of three different surfactants (TritonX-100, n-octylamine and amylamine) on the morphological characteristics of the resulting Ca(OH)2 nanoparticles and compares them with the ones produced in a mixture of water and 2-propanol. Moreover, in an attempt to approach the compatibility enhancement with siliceous stones, a calcium hydroxide—TEOS composite was also studied. The morphological, chemical and the mineralogical characterization of the nanoparticles produced were carried out by electron microscopy (SEM), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). It is shown that the modifications induced by the production methodologies limited the agglomeration phenomena and altered the morphological characteristics of nanoparticles, when compared to the results obtained by the original bottom-up method, resulting in the synthesis of hexagonal, plate-like, rounded and angular portlandite nanoparticles. The size range of the nanoparticles extended from 60 to 350 nm. Presented on: Journal of Cultural Heritage

The synthesis of Ti3Al(Sn)C2 usually uses elemental powder as the raw material, and the synthesis temperature is up to 1500 °C. Low-temperature ceramic sintering is the key to inhibit the formation of competitive phases and reduce the ceramic sintering cost. In this paper, a new method of low-temperature synthesis of Ti3Al(Sn)C2 was proposed, and high-purity Ti3Al(Sn)C2 sample was successfully prepared at low temperature by using the replacement reaction method. Research shows that the temperature of 600 °C for 5 h is the optimal process conditions for Ti3Al(Sn)C2 synthesis. Furthermore, the introduction of Sn changed the high-temperature oxidation resistance of Ti3AlC2. Compared to pristine Ti3AlC2, the oxidation resistance of Ti3Al(Sn)C2 at 900 °C increases by 33%. The comparative analysis of the formation energy of replacement Ti sites and Al sites shows that the formation energy of Sn-replaced Al sites is lower. These results have broad reference implications for low-temperature synthesis of other MAX phases.

MicroRNA existing in exosomes (exo-miRNA) is a crucial and reliable biomarker for cancer screening and diagnosis. However, accurate detection of ultralow exo-miRNA amounts in real samples remains a challenge. Herein, a robust and ultrasensitive electrochemical biosensor was developed based on localized DNA cascade displacement reaction (L-DCDR) and versatile DNA nanosheets (DNSs) for enzyme-free analysis of exo-miRNA. The target activated L-DCDR repeatedly by consecutive toehold-mediated strand displacement, which released plentiful P strands to hybridize with capture probes immobilized on the electrode surface and DNS tags, generating an amplified electrochemical signal for the detection of exo-miRNA. The DNS could label-free load various electroactive molecules. The electrochemical biosensor revealed high sensitivity ranging from 0.1 fM to 1 nM with a limit of detection of 65 aM and good specificity. The constructed biosensor was demonstrated to be able to detect exo-miRNA derived from gastric cancer cell line (SGC-7901) and gastric cancer patients. In addition, the developed biosensor possessed several considerable advantages including simple substrate assembly, improved reaction rate, and high signal-to-noise ratio. Therefore, this strategy has great potential in bioanalysis and clinical diagnostics.

Although atomically precise polyhydrido copper nanoclusters are of prime interest for a variety of applications, they have so far remained scarce. Herein, this work describes the synthesis of a dithiophosphate-protected copper(I) hydride-rich nanocluster (NC), [Cu30 H18 {S2 P(OnPr)2 }12 ] (1H ), fully characterized by various spectroscopic methods and single-crystal X-ray diffraction. The X-ray structure of 1H reveals an unprecedented central Cu12 hollow icosahedron. Six faces of this icosahedron are capped by Cu3 triangles, the whole Cu30 core being wrapped by twelve dithiophosphate ligands and the whole cluster has ideal S6 symmetry. The locations of the 18 hydrides in 1H were ascertained by a single-crystal neutron diffraction study. They are composed of three types: capping μ3 -H, interstitial μ4 -H (seesaw) and μ5 -H ligands (square pyramidal), in good agreement with the DFT simulations. The numbers of hydrides and ligand resonances in the 1 H NMR spectrum of 1H are in line with their coordination environment in the solid state, retaining the S6 symmetry in solution. Furthermore, two new Se-protected polyhydrido copper nanoclusters, [Cu30 H18 {Se2 P(OR)2 }12 ] (2H : R=iPr 3H : R=iBu) were synthesized from their sulfur relative 1H via ligand displacement reaction and their X-ray structures feature the exceptional case where both the NC shape and size are fully conserved during the course of ligand exchange. DFT and TD-DFT calculations allow understanding the bonding and optical properties of clusters 1H -3H . In addition, the reaction of 1H with [Pd(PPh3 )2 Cl2 ] in the presence of terminal alkynes led to the formation of new bimetallic Cu-Pd alloy clusters [PdCu14 H2 {S2 P(OnPr)2 }6 (C≡CR)6 ] (4: R=Ph; 5: R=C6 H4 F).

Li metal is considered as an ideal anode material for next-generation high energy density batteries. However, the huge volume change during cycling and uncontrollable Li dendrites growth represent the main issues of a Li metal anode, resulting in a short lifespan, low Coulombic efficiency, and serious safety risks. Herein, a modified 3D conductive skeleton is obtained via a facial replacement reaction to introduce a Sb layer on the surface of a commercial Cu foam. In this way, a lithiophilic Li–Sb layer can be in situ formed during the cell activation. This modified Cu foam can accommodate the volume changes accompanying the cycling and reduce the local current density. The lithiophilic Li–Sb layer can guide smooth Li plating/stripping without forming Li dendrites. Consequently, such a Sb-modified Cu foam substrate displays a stable and high Coulombic efficiency over 600 cycles in half cells and a super long lifespan over 1800 h in asymmetrical cells. Moreover, the lithium full cells constructed by coupling it with a LiFePO4 cathode also demonstrate excellent cycling performance over 300 cycles at 5 C.

Nb2O5 and Zr powders at a molar ratio of 1:2.5 were milled using a high-energy ball mill. The mixture powders produced Nb and ZrO2 nanopowders through a solid replacement reaction (Nb2O5+ 2.5Zr 2Nb + 2.5ZrO2). The synthesized nanopowders were consolidated via high-frequency induction heated sintering (HFIHS) within two min. The mechanical properties (hardness and fracture toughness) of nanostructured 2Nb–2.5ZrO2 composite were then evaluated. Both the hardness and fracture toughness of the 2Nb–2.5ZrO2 composite were higher than those of monolithic ZrO2.

Hollow gold (Au)-based nanostructures have recently been developed for various applications. However, current nanosynthesis approaches have not yet successfully been implemented for precisely engineering hollow Au-based nanostructures with uniform and well-defined mesoporous shell frameworks. Here, we develop an easy one-pot seedless strategy for fabricating hollow mesoporous AuAg (h-mesoAuAg) nanospheres by combining the galvanic replacement reaction with the surfactant-templated growth. Thiol-terminated multifunctional C22H45N+(CH3)2-C3H6-SH (Cl-) (C22N-SH) as the functional surfactant is the key that facilitates the formation of covalently stable C22N-S-Au(I) and C22N-S-Ag(I) intermediates. Such intermediates template in situ growth of mesoAuAg shell on initially nucleated Ag-rich seeds through the galvanic replacement reaction. Hierarchically hollow/mesoporous nanostructures and corresponding optical responses of h-mesoAuAg are also precisely engineered by tailoring synthetic parameters. With structural and compositional advantages, h-mesoAuAg nanospheres exhibit promising electrochemical performances toward methanol oxidation reaction and nonenzymatic glucose sensor.

Well-tailored metal nanostructure arrays possessing a large number of small nanogaps have been highlighted because of their ability to enhance optical and electrical properties. In addition, it has...

Present study deals with hematite/M (M = Au, Pd) catalysts converted from a double-hollow Prussian blue microstructure (DHPM). The unique Prussian blue (PB) microstructure (MS) is prepared by a template-free solvothermal synthetic route in a single-step reaction. An amine-functionalized silicate sol-gel matrix (SSG) has served as the structure-directing agent cum stabilizer for making DHPM. Synthesized DHPM is having a unique structure: a hollow core and an in situ etched porous surface. Growth mechanism is explored and revealed by analyzing several experimental parameters such as HCl concentration, Fe source, effect of the added EtOH, silane concentration, and role of silanes' amine groups. It is identified that the superstructure consisted of well-aligned PB cubes growing radially from the core of the superstructure. Metal (Au and Pd) nanoparticles (NPs) are deposited on both interior and exterior of the PB MS through galvanic displacement reaction, and thus metal NP-loaded hematite phase iron oxide (α-Fe2O3) nanomaterials were derived by annealing them in air. Catalytic activities of the hematite/M(M = Au, Pd) MS are investigated toward simultaneous catalytic reduction of o-nitrophenol and p-nitrophenol. The resultant hematite/Pd MS showed high structural stability and catalytic active sites than the hematite/Au MS, which enhances the catalytic properties for the simultaneous catalytic reduction of both nitrophenols.

Recent emerged metal-organic frameworks (MOFs), as superior drug carriers, provide novel strategies to combat pathogenic bacterial infections. Although various antibacterial metal ions can be easily introduced in MOFs for chemical bacterial ablation, such a single-model bactericidal method suffers from high-dose use, limited antibacterial efficiency, and slow sterilization rate. Hence, developing a dual bactericidal system is urgently required. Herein, we report an MOF/Ag-derived nanocomposite with efficient metal-ion-releasing capability and robust photo-to-thermal conversion effect for synergistic sterilization. The MOF-derived nanocarbon consisting of metallic zinc and a graphitic-like carbon framework is first synthesized, and then Ag nanoparticles (AgNPs) are evenly introduced via the displacement reaction between Zn and Ag+. Upon near-infrared irradiation, the fabricated nanoagents can generate massive heat to destroy bacterial membranes. Meanwhile, abundant Zn2+ and Ag+ ions are released to make chemical damage to bacterial intracellular substances. Systematic antibacterial experiments reveal that such dual-antibacterial effort can endow the nanoagents with nearly 100% bactericidal ratio for highly concentrated bacteria at a very low dosage (0.16 mg/mL). Furthermore, the nanoagents exhibit less cytotoxicity, which provides potential possibilities for the applications in the biological field. In vivo assessment indicates that the nanocomposites can realize rapid and safe wound sterilization and are expected to be an alternative to antibiotics. Overall, we present an easily fabricated structure-engineered nanocomposite with chemical and photothermal effects for broad-spectrum bacterial sterilization.

The joining of sapphire at a low temperature is necessary for the packaging of temperature-sensitive components. In current processes, the sapphire was bonded to Sn-based Ti-activated solders by mechanical scraping and stirring. To improve the efficiency and the bonding strength, the joining of sapphire by ultrasonic-assisted hot dipping and soldering at 250 °C in air was investigated. The relationship between the interfacial structure and shear strength of the soldered joints was revealed. The joints dipped for different durations and soldered for 0.5 s had similar interface morphologies, while the shear strength of the joints was controlled by the dipping duration. The shear strength of the joints dipped for 100 s reached 33 MPa. An uneven reaction layer of Ti oxides was found at the interface by TEM and EDS. A physical model was established to explain the formation of the reaction layer and the evolution of the interface microstructure. The mechanism of the interfacial reaction was discussed based on thermodynamics. The results of the thermodynamic calculations show that the replacement reaction between Ti and sapphire could not occur at the joining temperature of 250 °C. The increasing temperature induced by ultrasound at the liquid/solid interface was calculated by bubble dynamics and thermal conduction methods. It could be inferred that the reaction may be dominated by a local high temperature at the interface. Our finding demonstrates that the ultrasonic effects promote and facilitate the interfacial reaction of sapphire and Sn-3.5Ag-4Ti.

Bi-based electrode is believed to be one of the promising cathodes for the electroreduction of CO2 to formate. However, it suffers from energy- and/or time-consuming preparation process and mass transfer limitation of the reactants. Here, we fabricated a novel networked Bi-based electrode by formed in situ from Bi dendrites integrated into a Cu mesh substrate via a facile replacement reaction with energy and time savings. The as-prepared electrode was directly used as a cathode for electroreduction of CO2 to formate without further treatment. It exhibits a formate Faraday efficiency of ≈ 100 %. Additionally, partial current density for formate is as high as 68.51 ± 4.04 mA cm-2. This performance outperforms other results obtained on Bi-based electrodes—even most gas-diffusion electrodes under similar conditions. The excellent performance seen here is most likely attributed to its large surface area and fast transport of the reactants. This originates from the Bi dendrites catalysts and the unique network structure of the Cu mesh substrate. This work offers a facile route to obtain an efficient and robust electrode for electroreduction of CO2 to formate, which makes it easy to scale up in industrial applications.

In this study, the composition-optimized Pd–Cu catalyst for electrochemical N2O reduction in highly alkaline solution was prepared by a galvanic displacement method. The atomic ratio of Pd to Cu in Pd–Cu bimetallic catalyst, which has been known to be hardly controlled using galvanic displacement, was tailored by varying the concentration of citric acid in galvanic displacement bath. With increasing citric acid concentration, the decreased grain size, characterized by X-ray diffraction, and the increased amount of carbon in Pd–Cu catalyst, measured by energy-dispersive X-ray spectrometry, revealed the incorporation of citric acid into the catalyst, which was attributed to the tunable catalyst composition. The incorporation of citric acid into Pd–Cu deposit restrained the diffusion of Cu from Cu substrate to deposit, leading to decrease in the Cu content in Pd–Cu. The electrocatalytic activity for N2O reduction was strongly dependent on the Pd/Cu composition in Pd–Cu catalysts. Among the investigated Pd–Cu catalysts with different compositions, the highest electrocatalytic activity was obtained with Pd60Cu40 with a Tafel slope of 0.096 V dec−1. Moreover, the Pd60Cu40 catalyst showed remarkably enhanced mass-specific activity for N2O reduction, compared with a commercial Pd/C. The density functional theory (DFT) calculations revealed that the highest N2O reduction activity of Pd60Cu40 could be attributed to the facilitation of an adsorption/desorption balance for N2O reduction, resulting from the appropriately lowered d-band center of catalyst.

We present a reaction-based fluorescent probe (1) for Hg2+ and CH3Hg+, based on the displacement reaction of the arylboronic acid with the mercury species. 1 showed promising sensing properties for Hg2+ and CH3Hg+, such as high selectivity and sensitivity, turn-on response, fast response to Hg2+ (

The advantage of dendritic monodisperse macromolecules’ dual templating ability was useful in the formation of silica-supported copper nanoparticles Cun@SiO2NPs. This was acquired by the initial synthesis of a silica framework (G4-PAMAM-NH2-SiO2) as a mesoporous support using amine-terminated generation 4 PAMAM dendrimers (G4-PAMAM-NH2). The encapsulated Cun@SiO2 NPs, calcined at 500 °C, were made to undergo a displacement reaction with Au3+ generated from the equivalent molar addition of HAuCl4. This resulted in the formation of Aun@SiO2NPs upon in situ replacement at a regulated pH. The synthesized nanoparticles were characterized and examined. The catalysts were shown to be catalytically active in the hydrogenation of 4-nitrophenol, and oxidation of rhodamine B as model reactions, before oxidation of styrene using TBHP. Also, the stability of the catalyst was evaluated, and the catalytic activity was retained after three consecutive cycles.

A kind of organic microcrystal, 9,10-diphenylanthracene microcrystals (DPA MCs), was developed as a novel electrochemiluminescence (ECL) coreactant accelerator to efficiently catalyze dissolved O2 for more reactive oxygen species (ROSs) generation, achieving intense ECL for a H2O2-free luminol system. Moreover, based on this ternary ECL system, a signal "off-on" ECL biosensor for microRNA-21 (miRNA-21) detection was constructed combining a sensitive target recycling amplification strategy and an enzyme-mediated recycling strand displacement reaction (RSDR).

The objective of this study was to report the preparation of a highly efficient hematite nanorod photoanode by H2 treatment of the β-FeOOH nanorod with subsequent quenching in air at lower temperature activation for photoelectrochemical (PEC) water oxidation. The hematite nanorod photoanode (H650) prepared by thermally treating the β-FeOOH nanorod at 360 °C for 1 h under H2 flow and quenching at 650 °C for 10 min in air exhibited a remarkable photocurrent of 1.17 mA cm−2 at 1.23 V vs. RHE, which was 20 times higher than that of hematite quenched at the same temperature without H2 treatment. Such enhanced PEC performance was attributed to high Sn4+ diffusion from the fluorine doped SnO2 (FTO) substrate via H2 treatment and Sn4+ doping by subsequent lower temperature quenching. Our density functional theory (DFT) calculation supports our experimental results and proposed mechanism in that the Sn replacement reaction of magnetite (Fe3O4, H2-reduced β-FeOOH) occurs at a lower temperature and requires a smaller energy than that of akaganeite (β-FeOOH).

It is important to develop novel sensors for the simple, rapid, and quantitative detection of residual antibiotics in food, considering their potential threats to human health. Herein, we report the successful fabrication of raspberry-like nanogold (R-like Au) structures with rough surfaces and partially hollow structures for the rapid and sensitive detection of antibiotics in duck meats on a portable Raman spectrometer. The R-like Au with tunable plasmonic wavelengths was fabricated by a two-step method. Ag particles as seeds were substituted by Au particles through a replacement reaction; moreover, the surface plasmon resonances (SPRs) of R-like Au red-shifted with the increase in the Au ion concentration. The R-like Au with a diameter of about 120 nm that matched well with the 785 nm laser on the portable Raman spectrometer was used as an excellent surface-enhanced Raman spectroscopy (SERS) active platform for detecting two kinds of antibiotics, namely, nitrofurantoin (NFT) and nitrofurazone (NFZ), in spiked duck meats. Both of them have sufficient sensitivity (0.05-10 mg L-1), good linear relationship (R2 > 0.99) and high recovery in quantitative SERS analysis. The platform is simple without the need for complex pretreatment of the food samples or use of large scale Raman spectrometers, promising easy implementation for the on-site analysis of residuals of antibiotics in food.

The optical transition properties of trivalent rare earth (RE3+) doped luminescent materials have received extensive attention. The Judd–Ofelt theory is an effective tool for exploring the optical transition properties for the 4f–4f transitions of lanthanides. The aim of this work is to discover the effect of Er3+ concentration and different Ln3+ ions on the Judd–Ofelt parameters in LnOCl:Er3+ (Ln = Y, La, Gd) phosphors. Oxychloride LnOCl:Er3+ (Ln = Y, La, Gd) phosphors were produced via a single displacement reaction technique. The Judd–Ofelt calculation procedure for RE3+ doped powders was modified and then adopted to obtain the Judd–Ofelt parameters of Er3+ in the studied phosphors. Meanwhile, a new route for examining the Judd–Ofelt calculation quality was proposed and used. It was found that the Er3+ doping concentration slightly affects the optical transition properties of Er3+ in YOCl and LaOCl, but greatly affects the optical transition properties in GdOCl. Moreover, it was also found that the optical transition properties of Er3+ depend also on Ln3+ (Ln = Y, La, Gd) though the crystal structure of these compounds is similar. The Judd–Ofelt parameters of Er3+ are the smallest in LaOCl:Er3+, medium in YOCl:Er3+, but the biggest in GdOCl:Er3+ when the doping concentration is the same.

The development of high capacity, low cost, and high safety cathode materials for rechargeable aqueous zinc-ion batteries (ZIBs) is an ongoing challenge. Herein, CuV2O6 nanowires are prepared by a facile hydrothermal method to be used as a high-capacity cathode material for ZIBs. The sample displays an initial discharge capacity of 338 mA h g-1 at a current density of 100 mA g-1 and a capacity of 143 mA h g-1 remained at 5 A g-1 after 1200 cycles with a retention of ∼100% except for the initial capacity decay. Systematic structural and elemental characterization confirms that the reduction/oxidation of Cu2+/Cu0 is reversible during the electrochemical process. This work provides new prospects for designing more cathode materials based on the displacement reaction mechanism for Zn-ion batteries.

ZnSe nanodisks:Ti3C2 MXene complex was prepared for the first time. Based on its remarkable photoelectrochemical performance, combined with the enzyme-free toehold-mediated strand displacement reaction, a photoelectrochemical biosensor for the detection of the non-small-cell cancer biomarker ctDNA KRAS G12D was developed. ZnSe nanodisks were in situ grown on Ti3C2 MXene surface by two-step hydrothermal method. The high conductivity and adjustable band gap of MXene significantly enhanced the photoelectric response of ZnSe. Subsequently, the photoelectrochemical biosensor was prepared by combining with the signal amplification function of p-aminophenol and the enzyme-free toehold-mediated strand displacement reaction on the modified ITO electrode surface. Under the optimized conditions, the linear detection range is 0.5 ~ 100.0 fM, and the detection limit is 0.2 fM, which realizes the sensitive detection of KRAS G12D. The photoelectrochemical biosensor constructed opens up a new pathway for the preparation of new Mxene-based composite materials and the research of photoelectrochemical biosensor. Nucleic acid liquid biopsy with ZnSe nanodisks:Ti3C2 MXene photoelectroactive modified electrode.

Cu chips are cheaper than Ag and Au chips for practical SERS applications. However, copper substrates generally have weak SERS enhancement effects and poor stability. In the present work, Cu-based SERS chips with high sensitivity and stability were developed by a chemical reduction method. In the preparation process, Cu NPs were densely deposited onto fabric supports. The as-prepared Cu-coated fabric was hydrophobic with fairly good SERS performance. The Cu-coated fabric was able to be used as a SERS chip to detect crystal violet, and it exhibited an enhancement factor of 2.0 × 106 and gave a limit of detection (LOD) as low as 10–8 M. The hydrophobicity of the Cu membrane on the fabric is favorable to cleaning background interference signals and promoting the stability of Cu NPs to environment oxidation. However, this Cu SERS chip was still poor in its long-term stability. The SERS intensity on the chip was decreased to 18% of the original one after it was stored in air for 60 days. A simple introduction of Ag onto the clean Cu surface was achieved by a replacement reaction to further enhance the SERS performances of the Cu chips. The Ag-modified Cu chips showed an increase of the enhancement factor to 7.6 × 106 due to the plasmonic coupling between Cu and Ag in nanoscale, and decreased the LOD of CV to 10–11 M by three orders of magnitude. Owing to the additional protection of Ag shell, the SERS intensity of the Cu-Ag chip after a two-month storing maintained 80% of the original intensity. The Cu-Ag SERS chips were also applied to detect other organics, and showing wide linearity range and low LOD values for the quantitative detection.