Replacement Reaction Research Articles

Electrochemical behaviour of metal ions in ethaline-based solutions: Impact of electrode material

Deep eutectic solvents (DESs) have become increasingly important in material synthesis, particularly in electrodeposition processes. Ethaline – a DES composed of choline chloride and ethylene glycol – stands out due to its low viscosity compared to other DESs which is favourable for the electrodeposition process. Among the key factors influencing electrodeposition, the substrate material can also play a significant role in the electrochemical behaviour of metal ions and resulting deposit morphology at the early stages of film growth. This study investigates the electrochemical behaviour of various metal ions, including Co(II), Fe(II), Ni(II), In(III), Sn(II), Cu(I), and Cu(II), on four selected substrates (Pt, glassy carbon, Au, and Cu) in dried ethaline-based solutions. The research highlights the impact of different working electrode materials on deposition processes and examines the onset potentials for deposit dissolution, providing insights into predicting galvanic replacement reactions in the DES medium. The formation of the complexes of different composition between metal ions and ethaline components leads to the sequence of equilibrium potentials different from aqueous, non-complex electrolyte solutions. As a remarkable example, we demonstrate the occurrence of galvanic replacement reaction between Ni(II) ions and a more noble Sn substrate in ethaline. The findings underscore the importance of considering both the choice of substrate material and the speciation in ethaline-based DESs.

Simulated Experimental Study on the Removal of Methylene Blue-Cu(II) Composite Pollution by Magnetized Vaterite

The combined pollution of organics and heavy metals represents a significant environ-mental problem that has attracted widespread attention. This explores the treatment of methylene blue (MB) and Cu(II), which are common pollutants in dye wastewater, and the recycling of Cu. A magnetized vaterite (V-M) was synthesized using Bacillus velezensis, and its structure and magnetic performance were investigated. The effects and mechanisms of removing MB-Cu(II) composite pollution using V-M and H2O2 in combination were estimated. The results indicated that V-M is a combination of organic and inorganic substances, with 21.5 wt% organic matter and multiple organic functional groups, including O-H, -SH, and others. The combination of V-M and H2O2 can achieve a maximum removal percentage of 90% for MB-Cu(II) pollution. The analysis showed that MB was oxidized by the ·OH generated from the H2O2-based Fenton-like reaction, and was catalyzed by the Fe3O4 in V-M. The immobilization of Cu(II) by V-M was mostly realized through the binding of the organic substances on the surface of the V-M, multilayer adsorption, and a replacement reaction with Ca(II). Magnetic separation and the addition of diluted HCl were used for the recycling of the Cu(II) enriched by V-M, with a recycling percentage reaching 85%. This study introduced a novel approach to the remediation of MB-Cu(II) composite pollution, and the recycling of Cu(II).

Diffusive ex situ galvanic growth of metal nanocrystals on transmission electron microscopy grid

The uniform modification of commercial and standardized objects features considerable potential, as in the case of dip-pen lithography, biosensor kits, and disposable electrodes. In this study, we devised a dense nanoparticle array formation using the metallic mesh of a transmission electron microscopy (TEM) grid, which was formerly solely employed as a sampling stage. Incompletely oxidized cationic species generated from the galvanic replacement reaction of the metallic support mesh at the opposite side of the carbon layer diffused to the exposed top side and led to ex situ nanostar formation. A uniform nanoparticle array was obtained by immersion in an aqueous solution of replacing metal cations without reducing agents or surface energy-controlling compounds. Moreover, the array density was exclusively regulated by the incubation time. The straightforward nanoparticle array formation was successfully extended to various metal mesh TEM grids and different transition metal cations capable of spontaneous redox reactions. Cu mesh TEM grid and Mo grids could be utilized as sacrificial templates, and the growth of Au, Pd, Pt, Ag, and Rh nanostructures was confirmed.

Arsenic (III) and (V) complexes from solvent free condition and their kinetic factors leading to arsenic nanoparticles

A clear melt from catechol and sodium salts of arsenic (III and V) were obtained individually from the grinding mixing protocol (GMP). The as-obtained molten mass from exothermic reaction between catechol and arsenic salts motivated isothermal titration calorimetry (ITC) advocating the propensity of complex catecholate formation. Individual ITC results substantiated structurally two different mono-anionic complexes, one for arsenic (III) and the other for arsenic (V) ions, of catechol in water at room temperature. Then, the compositions of both the mono-anionic complexes with stoichiometry 1:2 and 1:3 (w∕w) were confirmed for arsenic (III) and (V), respectively. It was shown here for the 1st time that both the complexes supplemented two neat precursors for useful arsenic nanoparticle (As NP) preparation from pH control redox reactions. Again, galvanic replacement reaction (GRR) between As NP and HAuCl4 evolved Au NPs of comparable size as that of As NPs. Thus, thermodynamic results, binding constant (Kb) values, redox kinetic studies and ion associate formation of the two catecholates clearly differentiated the stability (labile and inert character) of As(III) and As(V) catecholates. Conclusively, electrochemistry, galvanic replacement reaction, DLS, thermal analysis, and diverse spectrometric results provided 1st hand support for the complex catecholates of arsenic, a p-block metalloid as labile and inert characters respectively in two different (III) and (V) oxidation states.

Replacing the Gallium Oxide Shell with Conductive Ag: Toward a Printable and Recyclable Composite for Highly Stretchable Electronics, Electromagnetic Shielding, and Thermal Interfaces.

Liquid metal (LM)-based composites hold promise for soft electronics due to their high conductivity and fluidic nature. However, the presence of α-Ga2O3 and GaOOH layers around LM droplets impairs conductivity and performance. We tackle this issue by replacing the oxide layer with conductive silver (Ag) using an ultrasonic-assisted galvanic replacement reaction. The Ag-coated nanoparticles form aggregated, porous microparticles that are mixed with styrene-isoprene-styrene (SIS) polymers, resulting in a digitally printable composite with superior electrical conductivity and electromechanical properties compared to conventional fillers. Adding more LM enhances these properties further. The composite achieves EMI shielding effectiveness (SE) exceeding 75 dB in the X-band frequency range, even at 200% strain, meeting stringent military and medical standards. It is applicable in wireless communications and Bluetooth signal blocking and as a thermal interface material (TIM). Additionally, we highlight its recyclability using a biodegradable solvent, underscoring its eco-friendly potential. This composite represents a significant advancement in stretchable electronics and EMI shielding, with implications for wearable and bioelectronic applications.

In Vitro Assessment of Gallium Nanoalloy Hydrogels for Antimicrobial and Wound Healing Applications.

Chronic and recurring wounds pose a significant challenge in modern healthcare, leading to substantial morbidity. These wounds allow pathogens to colonize, potentially resulting in local and systemic infections. Current interventions need to be revised and become increasingly less reliable due to the emergence of antibiotic resistance. In the present study, we aim to address these issues by fabricating hydrogels impregnated with gallium-based nanoalloys for their antimicrobial activity. Gallium liquid metal nanoparticles (approximately 100 nm in diameter) were alloyed in different combinations with bismuth and silver ions through a galvanic replacement reaction. These multimetallic hydrogels showed favorable antibacterial activity against the Gram-positive Staphylococcus aureus and the Gram-negative Pseudomonas aeruginosa, as observed with fluorescence microscopy and inhibition assays. The multimetallic hydrogels showed no toxicity against murine macrophages or human dermal fibroblasts and enhanced in vitro wound healing. The development of these innovative gallium-based hydrogels represents a promising strategy to combat chronic wounds and their associated complications, offering an effective alternative to current antimicrobial treatments amidst rising antibiotic resistance.

Strain-Controlled Galvanic Synthesis of Platinum Icosahedral Nanoframes and Their Enhanced Catalytic Activity toward Oxygen Reduction.

The unique strain distribution on the surface of a Pd icosahedral nanocrystal is leveraged to control the sites for oxidation and reduction involved in the galvanic replacement reaction. Specifically, Pd is oxidized and dissolved from the center of each {111} facet due to its tensile strain, while the Pt(II) precursor adsorbs onto the vertices and edges featuring a compressive strain, followed by surface reduction and conformal deposition of the Pt atoms. Once the galvanic reaction is initiated, the {111} facets become more vulnerable to oxidation and dissolution, as the vertices and edges are protected by the deposited Pt atoms. The site-selected galvanic reaction naturally results in the formation of Pt icosahedral nanoframes covered by compressively strained {111} facets, which show enhanced catalytic activity and durability toward oxygen reduction relative to commercial Pt/C.

Plasmonic Nanocubes with a Controllable "Crescent Arc" Facet: Tunable Hotspot Engineering for Highly Reliable and Sensitive SERS Detection.

The fine control of the nanogap and morphology of metal nanoparticles (NPs) has always been an obstacle, hindering the development and application of surface-enhanced Raman scattering (SERS) quantitative detection. Here, Au/4-mercaptobenzoic acid@Ag@Au-Ag bimetal core-shell nanocubes (NCs) with a "crescent arc" facet (C-Au/4MBA@Ag NCs) as a highly reliable and sensitive surface-enhanced Raman scattering SERS substrate is proposed for the first time. The bifunctional internal standard (IS) molecules (4MBA) govern the morphology of metal shells to maintain cubic configuration and provide calibration for SERS signals' flotation. In parallel, the controllable curvature of the C-Au/4MBA@Ag NCs is directly modulated by adjusting the relative rates of the galvanic replacement and co-reduction reaction, which generates a controllable interparticle nanogap to offer large depositing spaces for analytes and improve authoritative SERS signals' enhancement. The proposed C-Au/4MBA@Ag NCs exhibit an enhancement factor of up to 4.8 × 1010 and contribute to the ultralow RSD (7.9%). These C-Au/4MBA@Ag NCs also enable the detection of hazardous pesticide residues such as methamidophos and thiram in herbal plants with a complex matrix, with an average detection accuracy of up to 96%. In summary, this study achieves a fine control strategy of the "crescent arc" surface for improving SERS performance and explores the practical application potential for accurate and sensitive Raman detection of hazardous substances.

Chiral Symmetry Breaking in Colloidal Metal Nanoparticle Solutions by Circularly Polarized Light.

Shape symmetry breaking in the formation of inorganic nanostructures is of significant current interest. It was typically achieved through the growth of colloidal nanoparticles with adsorbed chiral molecules. Photochemical processes induced through asymmetric plasmon excitation by circularly polarized light in surface immobilized nanostructures also led to symmetry breaking. Here, we show that chiral symmetry breaking can be achieved by randomly rotating gold@silver core-shell nanobars in colloidal solution using circularly polarized illumination, where orientational averaging does not eliminate the symmetry breaking of an asymmetric plasmon-induced galvanic replacement reaction. Different morphological effects that are produced by circularly vs linearly polarized light illumination demonstrate the intricate effect of light polarization on the localized plasmonic-induced photochemical response. The essential features of this symmetry breaking, such as illumination wavelength dependence, were reproduced by simulations of circularly polarized light-excited-plasmon-induced hot-electron generation as the source for asymmetric metal deposition. The symmetry breaking becomes smaller in more symmetric geometrical shapes, such as triangular nanoprisms and nanocubes, and down to zero in spherical ones. The degree of symmetry breaking rises when the nanobars are immobilized on a substrate and illuminated from a single direction.

Improving Catalytic Performance via the Synergy of Tensile Lattice Strain and Plasmonic Enhancement in Defective AuPd@Pd Short Nanowires.

The synthesis of bimetallic nanocatalysts with strained crystal lattices has attracted considerable interest. This is because, beyond the electronic structure modifications realized through elemental doping, the strain effect offers an extra mechanism to fine-tune the electronic structures, thereby possibly improving the catalytic performances. We present a method for constructing defective AuPd@Pd short nanowires, achieved through a controlled galvanic replacement reaction between short AuCu nanowires and Pd precursors. Advanced structural analyses using spherical aberration-corrected transmission electron microscopy (AC-TEM) validated the expanded crystal lattice on the nanowire surface and also demonstrated pronounced plasmonic absorption in the UV-vis region. Leveraging both plasmonic absorption and strain effects, the AuPd@Pd short nanowires displayed a higher apparent rate constant compared to Pd nanoparticles. Integrating molecular dynamic simulations with density functional theory calculations revealed that the tensile strain on AuPd@Pd short nanowires benefited the catalytic activity by elevating the d-band center, thereby intensifying the adsorption of p-nitrophenol. The current research introduces a unique method for synthesizing noble metal nanocrystals with specific dimensions and elucidates the rational development of high-performance plasmonic nanocatalysts through synergistic exploitation of the beneficial strain effect.

Z-scheme heterostructure of ZnO@NPC/Au/ZnIn2S4 for chemical replacement reaction-mediated signal-on photoelectrochemical assay of mercury ion

Herein, an advanced Zn-based metal organic framework (Zn-MOF) derived ZnO embedded in a nitrogen-doped porous carbon (ZnO@NPC) polyhedron/Au/ three-dimensional (3D) chrysanthemum-like ZnIn2S Z-scheme heterojunction was employed for the chemical replacement reaction-mediated signal-on photoelectrochemical (PEC) sensing detection of mercury ions (Hg2+). The p-type ZnO@NPC polyhedron was initially prepared by carbonising the zeolitic imidazolate framework (ZIF)-8 polyhedron, followed by modification with Au nanoparticles (NPs) via an in situ photocatalytic reduction method. Subsequently, the ZnO@NPC/Au polyhedron was combined with n-type 3D chrysanthemum-like ZnIn2S4 through physical adsorption, forming the ZnO@NPC polyhedron/Au/3D chrysanthemum-like ZnIn2S4 Z-scheme heterostructure. The newly constructed heterostructure exhibited strong visible light–harvesting capacity, and considerably improved photoelectric conversion efficiency. The 3D chrysanthemum-like ZnIn2S4 functioned not only as a photosensitiser but also as an Hg2+ recognition probe. Importantly, the PEC sensor exhibited a considerably increased photocurrent response to Hg2+. This is presumably because the introduction of Hg2+ triggered a selective Zn-to-Hg chemical replacement reaction, leading to the in-situ formation of a ZnO@NPC/Au/ZnIn2S4/HgS heterojunction, which further improved charge separation. Consequently, Hg2+ was sensitively detected with a wide linear range from 0.5 pM to 2 μM and a low detection limit of 0.07 pM. Furthermore, the proposed sensor was validated by detecting Hg2+ in food and aqueous environments, indicating its potential application in food safety and environmental monitoring.

Plasmon-induced efficient solar-driven H2 production using bimetallic core-shell Cu@Ag:TiO2 nanocomposite photocatalyst

The nano-interface formed by bimetallic Cu@Ag nanoparticles (NPs) on a TiO2 surface enhances charge separation through plasmonic heterojunctions. These bimetallic Cu@Ag NPs were synthesized via the a galvanic replacement reaction (GRR) involving Ag+ in an aqueous medium and metallic Cu NPs on TiO2. During the GRR, Cuδ+ and Agδ+ charge pairs are generated by electron transfer from the catalyst surface. These charge pairs act as active sites, significantly enhancing photocatalytic hydrogen production. Additionally, the cubic crystalline phase of metallic Cu NPs is maintained after the GRR process with Ag ions, while the size of bimetallic Cu@Ag NPs remains constant. Consequently, Cu@Ag NPs supported on TiO2 (Cu@Ag:TiO2) exhibit increased donor charge density of 1.66 × 1020 cm−3 and facilitate rapid charge transfer. As a result, the photocatalytic hydrogen production rate of Cu@Ag:TiO2 is 20 times higher than that of pristine TiO2. Moreover, the visible-light responsive photocatalytic activity of Cu@Ag:TiO2 NPs reaches 3.4 mmol g−1 over 5 hours, which is 78 times higher than that of pristine TiO2. This remarkable enhancement is attributed to the formation of a plasmonic heterojunction with close contact between Cu@Ag and TiO2, enabling efficient charge carrier separation.

Bismuth nanosheets guided zinc deposition enabled long-life aqueous zinc-based flow batteries

The poor cycling durability and low Coulombic efficiency (CE) of zinc (Zn) anodes substantially restrict their further development, which should be attributed to the severe uneven plating and hydrogen evolution reaction (HER) across the repeated plating/stripping processes. Herein, bismuth nanosheets decorated graphite felt (BiNS/GF) is constructed for Zn anode via galvanic replacement reaction. BiNS/GF affords more robust Zn nucleation sites, lower Zn nucleation overpotential and higher HER overpotential to guide even and dense Zn deposition. In addition, a total internal reflection imaging method is employed to detect micro-bubbles generated by HER on the electrode surface, revealing that BiNS prevents the formation of micro-bubbles and thus avoids dead Zn caused by unstable Zn deposition. As a proof of concept, BiNS/GF exhibits an average CE of 99.2 % in 300 cycles and a peak power density of 295.2 mW cm−2 at a current density of 380 mA cm−2 in aqueous neutral zinc-iron flow batteries. Therefore, it is reasonably anticipated that the BiNS/GF may emerge as suitable electrode for other aqueous zinc-based flow batteries.

Investigation on the reaction progress of titanium and lead chloride in NaCl-KCl melt

The in-situ preparation of NaCl-KCl-TiClx molten salt electrolyte was investigated by replacement of PbCl2 and Ti in a NaCl-KCl melt at 750 ℃. The reaction progress of PbCl2(3.38 wt.%) with excess Ti was monitored in real-time by a series of electrochemical techniques such as cyclic voltammetry, square wave voltammetry, and open circuit chronopotentiometry. The thermodynamic calculation and electrochemical test results show that titanium ions are mainly generated in the form of Ti(III). The redox peak current of Pb(II) decreases rapidly and drops to below the detection limit of the electrochemical tests after 275 min. Simultaneously, the reduction peak current of Ti(III) increases rapidly from 0 to 75min, and reaches to the maximum value until 275 min. At this time, the replacement reaction has been completed, and the NaCl-KCl-TiClx(2≤x≤4) molten salt is obtained finally. Ti-Pb alloy was obtained by depositing at -1.0 V(vs. Ag/AgCl) for 30 min during the replacement process. Lead by-product of the replacement reaction was precipitated and collected. Electrolytic refining was carried out successfully using the NaCl-KCl-TiClx molten salt electrolyte prepared as described above. The results demonstrated that a stable NaCl-KCl-TiClx molten salt electrolyte can be obtained by the present method. The study provides a new thinking for the preparation of molten salt electrolyte containing titanium ions, and also provides theoretical references for the electrolytic refining of titanium and the preparation of titanium alloys by electrodeposition.

A Liquid Metal-Based Temperature-Responsive Low-Toxic Smart Coating for Anti-Biofouling Applications in Marine Engineering.

Titanium alloys have been widely used in marine engineering fields. However, because of high biocompatibility, they are vulnerable to biofouling. In this work, based on the micro-arc oxidation technology and spontaneous galvanic replacement reaction, a temperature-responsive low-toxic smart coating consisting of liquid metal particles is designed to control the release of Ga3+, Cu2+, and Cu1+ ions in different temperatures. This technology can ensure the full release of active ingredients within the target temperature range, intelligently maintaining the excellent anti-biofouling performance, while saving active ingredients. After being immersed in culture media with Sulfate-Reducing Bacteria (SRB) for 14 days at 10, 20, and 30°C, at the optimal activity temperature of 30°C for SRB, the best sample releases the highest amounts of Ga3+, Cu2+, and Cu1+ ions, demonstrating a 99.9% bactericidal rate. When the temperature decreases to 10°C, the activity level of SRB is very low, and the smart coating can also reduce the released ions correspondingly, still with a 97.3% bactericidal rate. The remarkable anti-biofouling performance is attributed to the physical damage and lethal ions interaction. Furthermore, the best sample exhibits good corrosion resistance. This work presents a design route for smart anti-biofouling coatings for temperature-responsive.

Rational design of stable Cu and AuCu nanoparticles for investigations of size-enhanced SERS applications

BackgroundWhile significant progress has been made to clarify the effects of Au and Ag nanoparticle size on SERS enhancement, research on the size effects of copper nanoparticles and copper-related nanoalloys on SERS enhancement remain scarce. Nanoscale copper (Cu) is important because of its unique sensing and catalytic properties; however, research on its size and compositional effects remains a significant challenge because of the intricate fabrication process and difficulty in preventing oxidation. ResultsOur study elucidated the size-dependent, surface-enhanced Raman scattering (SERS) of Cu NPs, particularly the sensing capabilities of both electromagnetic (EM) SERS at 1.5 × 103 and chemical enhancement (CE) SERS at 3.6 × 104 of approximately 58 nm Cu NPs. Additionally, a solution aging examination revealed preservation of the metal-related core structure, surface plasmon resonance, and SERS features of the PSMA/ONPG-coated Cu NPs for up to 7 days. With the introduction of galvanic replacement reactions and laser ablation syntheses, the incorporation of Au atoms enabled the fabrication of 7–75 nm AuxCuy nanoparticles by using the remaining Cu core after aging in water, which offered precise control over the Cu/Au ratio from 5/95 to 29/71. SERS measurements of the large AuxCuy nanoparticles amplified up to 1.4 × 104 of the EM-mediated vibrational signals from the adsorbed molecules. The strong Au–S chemical bonds of the Au-rich AuxCuy nanocrystals increased the CE SERS to 5.5 × 104, whereas the Au3Cu1 crystals at the AuxCuy interface decreased the CE SERS but improved the electron transfer for catalysis via SERS detection. SignificanceOur research provides further insight into the structural and size effects of Cu and AuCu alloys used as SERS enhancers and offers avenues for designing cutting-edge SERS catalytic sensors tailored to Cu-related catalytic reactive structures.For the first time, we also manipulated the Cu atomic structure and surface composition to understand the significance of surface effects on SERS substrates of the Cu series from a nanoscale analytical perspective.

Low-cost dealkalization of bauxite residue by gypsum coordinated with industrial iron salt: Mineralogical mechanisms and field practice

The sustained-release of alkalinity in bauxite residue hinders the soil formation and ecological restoration processes in disposal areas. Ferric salts (Fe3+), known for their rapid neutralization reaction process and straightforward operational simplicity, showed a synergistic advantage with gypsum (CaSO4) in the alkaline regulation of bauxite residue. Nevertheless, the mineralogical mechanisms of the reaction between Fe3+ and Ca2+ and alkaline minerals in bauxite residue remained unclear. The present study aimed to elucidate the geochemical stability mechanisms of sodalite and cancrinite, major alkaline minerals in bauxite residue, driven by Fe3+ and Ca2+ from a mineral structural perspective and the integrated restoration effect was demonstrated by the field experiment. Unreacted shrinking core model (USCM) calculations demonstrated that Fe3+ was able to enter the lattice structure of sodalite and cancrinite to replace Na+ and assisted Ca2+ in successfully replacing Na+ in cancrinite. Moreover, Fe3+ and Ca2+ facilitated the formation of insoluble coating layers on their surface. In the lattice structure of sodalite and cancrinite, the replacement reaction for Na+ was influenced by the competition between Fe3+ and Ca2+. The Ca2+ preferentially replaced Na+, while Fe3+ accumulated near the Si-O bonds, balancing the negative charges of the Si-O and Al-O tetrahedra structure and further inhibited alkaline mineral dissolution. The pH and EC of bauxite residue decreased from 10.52 to 7.60 and 712 μS/cm to 501 μS/cm, respectively, after a one-year field-scale amelioration by the integration of Fe3+ and Ca2+. These findings highlighted the synergistic roles of Fe3+ and Ca2+ in regulating the alkalinity of bauxite residue and provided a practical strategy for ecological restoration in disposal areas.

A corrosion-resistant zincophilic film enables synergistic hydrogen evolution suppression and dendrite-free deposition toward highly reversible and durable Zn anodes

Zinc ion batteries have challenges originated from the Zn dendrite growth and hydrogen evolution reaction (HER) on Zn anodes. We design an all-in-one corrosion-resistant zincophilic film (CRZF) composed of zinc halide and Cu on Zn (CRZF@Zn) through the replacement reaction of copper halides with Zn metal. The in-situ formed zinc halide with high zincophilicity in the CRZF facilitates desolvation of [Zn(H2O)6]2+ clusters and boosts ions migration, with the conspicuously decreased nucleation potential of Zn. The formed chemically inert Cu improves the corrosion-resistivity of Zn anode and enhances the HER overpotential on Zn. The stimulated charge transfer supports uniform deposition of Zn to avoid the “tip effect”, which effectively restrains dendrites formation on Zn anode. Thus this artificial surface demonstrates synergistic effect on dendrite inhibition and HER suppression. The density functional theory (DFT) calculations show that with the increase of the electronegativity of halogen atoms in the zinc halide, the adsorption energy of Zn2+ on the CRZF layer is enhanced, validating the positive correlation between ions migration and electronegativity of halogen atoms in CRZF. Our findings offer a deeper insight into the interface tuning chemistry of Zn anodes, providing opportunities for the development of dendrite-free and long-life Zn metal batteries.

An super sensitive Multi-Modal controlled release biosensor with label- and enzyme- free assisted single step simultaneously detect multiple breast cancer biomarkers

Despite the fact that homogeneous biosensing strategies have been proven to be advantageous, it remains a difficult task to identify multiple tumor biomarkers. Our proposition entails the creation of a groundbreaking biosensor that combines electrochemical and fluorescent techniques, enabling simultaneous detect multiple biomarkers with label- and enzyme-free assistance in a single step. Porous UIO-66-NH2 nanovessels loaded with 3,3′,5,5′ −tetramethylbenzidine (TMB) and methylene blue (MB) double signal dyes, along with double-stranded DNA (dsDNA) formed by the aptamer chain of human epidermal growth factor receptor-2 (HER2) and estrogen receptor (ER) and its complementary chain as a gated switch to the envelope MOFs, were utilized to create functional MOFs (dsDNA@MB@UIO and dsDNA@TMB@UIO). When HER2 and ER targets are present, the chain replacement reaction led to the formation of a biomarker-aptamer complex, resulting in the destruction of the dsDNA structure on the surface of MOF and the liberation of MB and TMB. The concentration of the two target biomarkers determines the strength of the electrochemical and fluorescent signals produced. By combining targeted biomarkers, signal enhancement, and dual-signal detection into one unified process, the amount of test error caused by the multi-step detection needed in prior studies is significantly decreased. We executed the detect HER2 and ER, achieving detection limits of 4.7 and 5.9 fg/mL in 4.7–1000 pg/mL linear range with good selectivity, stability, reproducibility, and acceptable applicability. The proposed biosensor for developing dsDNA@MB@UIO and dsDNA@TMB@UIO is promising for the early and sensitive detection of cancer biomarkers.

Multi-dimensional signals coupling of simultaneous acquisition stripping current with laser-induced breakdown spectroscopy for accurate analysis of Cd(II) in coexisting Cu(II)

BackgroundDespite significant advancements in detecting Cd(II) using nanomaterials-modified sensitive interfaces, most detection methods rely solely on a single electrochemical stripping current to indicate concentration. This approach often overlooks potential inaccuracies caused by interference from coexisting ions. Therefore, establishing multi-dimensional signals that accurately reflect Cd(II) concentration in solution is crucial. ResultsIn this study, we developed a system integrating concentration, electrochemical stripping current, and laser-induced breakdown spectroscopy (LIBS) characteristic peak intensity through in-situ laser-induced breakdown spectroscopy and electrochemical integrated devices. By simultaneously acquiring multi-dimensional signals to dynamically track the electrochemical deposition and stripping processes, we observed that replacement reactions occur between Cu(II) and Cd(II) on the surface of Ru-doped MoS2 modified carbon paper electrodes (Ru-MoS2/CP). These reactions facilitate the oxidation of Cd(0) to Cd(II) during the stripping process, significantly increasing the currents of Cd(II). Remarkably, the ingenious design of the Ru-MoS2 sensitive interface allowed for the undisturbed deposition of Cu(II) and Cd(II) during the electrochemical deposition process. Consequently, our in-situ integrated device achieved accurate detection of Cd(II) in complex environments, boasting a detection sensitivity of 8606.5 counts μM⁻1. SignificanceBy coupling multi-dimensional signals from stripping current and LIBS spectra, we revealed the interference process between Cu(II) and Cd(II), providing valuable insights for accurate electrochemical analysis of heavy metal ions in complex water environments.