Integrated logic gate for fluorescence turn-on detection of histidine and cysteine based on Ag/Au bimetallic nanoclusters-Cu²⁺ ensemble

Construction of a Dual-Mode Biosensor with Ferrocene as Both a Signal Enhancer and a Signal Tracer for Electrochemiluminescent and Electrochemical Enantioselective Recognition

We demonstrate for the first time the construction of a dual-mode biosensor for electrochemiluminescent (ECL) and electrochemical chiral recognition of l- and d-isomers of amino acids, with ferrocene (Fc) as both a signal enhancer and a signal tracer. With the dissolved oxygen as a coreactant, ZnIn2S4 acts as the ECL emitter to generate a weak cathodic ECL signal. Fc can enter into the β-cyclodextrin (β-CD) cavity on ZnIn2S4-modified electrode as a result of host-guest interaction. Since Fc can promote H2O and O2 to produce abundant reactive oxygen species (ROS) (e.g., O2·- and ·OH), the ECL signal of ZnIn2S4 can be further amplified with Fc as a coreaction accelerator. Meanwhile, Fc molecules on the β-CD/ZnIn2S4-modified electrode can be electrochemically oxidized to Fc+ to produce a remarkable oxidation peak current. When l-histidine (l-His) is present, the matching of the l-His configuration with the β-CD cavity leads to the entrance of more l-His into the cavity of β-CD than d-histidine (d-His), and the subsequent competence of l-His with Fc on the Fc/β-CD/ZnIn2S4-modified electrode induces the decrease in both Fc peak current and ZnIn2S4-induced ECL intensity. This dual-mode biosensor can efficiently discriminate l-His from d-His, and it can sensitively monitor l-His with a detection limit of 7.60 pM for ECL mode and 3.70 pM for electrochemical mode. Moreover, this dual-mode biosensor can selectively discriminate l-His from other l- and d-isomers (e.g., threonine, phenylalanine, and glutamic acid), with potential applications in the chiral recognition of nonelectroactive chiral compounds, bioanalysis, and disease diagnosis.

Near-Infrared Molecular Logic Gate for In Situ Construction and Quantification of Cell-Macromolecule Conjugates

Engineering cell surfaces with macromolecules offers the potential to manipulate and control their phenotype and function for cell-based therapies. In situ construction and real-time evaluation of cell-macromolecule conjugates are vital for characterizing their dynamics, mobility, and function but remain a great challenge. Herein, we design a near-infrared (NIR) heptamethine cyanine (LS)-bearing dibenzocyclooctyne (DBCO) and norbornene (NB) in its structure for rapid and selective bioorthogonal "click" coupling to azide-labeled cells and tetrazine-functionalized macromolecular precursors. Specifically, only orthogonal dual "click" cell-macromolecule conjugates turn on NIR fluorescence, in which LS behaves as an AND logic gate, with azide- and tetrazine-derivatives being "input" and the emission intensity as the output. LS enables in situ construction and real-time evaluation of the process and functional effects that macromolecules "graft to" cells with high cytocompatibility. This probe is tailor-made for live-cell microscopy technologies, which may open new opportunities for promoting further developments in cell-tracking and cell-based therapies.

Facile preparation of bimetallic Au-Cu nanoclusters as fluorescent nanoprobes for sensitive detection of Cr3+ and S2O82- ions

Metallic nanoclusters (NCs) have attracted special attention from researchers due to their interesting optical properties. In this experiment, we proposed a facile one-step method for the synthesis of bimetallic gold-copper nanoclusters (AuCuNCs). The prepared AuCuNCs were characterized by fluorescence spectroscopy (FL), UV-vis absorption spectrum, transmission electron microscopy (TEM), etc. The emission peak of the prepared AuCuNCs was located at 455 nm and showed blue luminescence under the excitation of 365 nm UV light. Furthermore, after the addition of Cr³⁺ and S₂O₈^2- ions, the FL emission intensity of AuCuNCs was significantly reduced at 455 nm and there was a color change of diminished blue luminescence under UV lamp. The AuCuNCs exhibited excellent linearity and sensitivity for the detection of Cr³⁺ and S₂O₈^2- ions. The limits of detection (LOD) for the Cr³⁺ and S₂O₈^2- ions were calculated to be 1.5 and 0.037 μM, respectively. Finally, the recoveries of Cr³⁺ and S₂O₈^2- ions in Runxi Lake and tap water were measured by standard addition recovery test and were 96.66 ∼ 116.29 %, 95.75 ∼ 119.4 %.

Sequential-Dependent Synthesis of Bimetallic Silver-Chromium Nanoparticles for Multichannel Sensing, Logic Computing, and 3 in 1 Information Protection

Bimetallic nanomaterials (BNMs) have been used in sensing, biomedicine, and environmental remediation, but their multipurpose and comprehensive applications in molecular logic computing and information security protection have received little attention. Herein, This synthesis method is achieved by sequentially adding reactants under ice bath conditions. Interestingly, Ag-Cr NPs can dynamically selectively sense anions and reductants in multiple channels. Especially, ClO^- can be quantitatively detected by oxidizing Ag-Cr NPs with detection limits of 98.37 nM (at 270 nm) and 31.83 nM (at 394 nm). Based on sequential-dependent synthesis process of Ag-Cr NPs, Boolean logic gates and customizable molecular keypad locks are constructed by setting the reactants as the inputs, the states of the resulting solutions as the outputs. Furthermore, dynamically selective response patterns of the Ag-Cr NPs can be converted into binary strings to exploit molecular crypto-steganography to encode, store, and hide information. By integrating the three dimensions of authorization, encryption, and steganography, 3 in 1 advanced information protection based on Ag-Cr nanosensing system can be achieved, which can enhance the anti-cracking ability of information. This research will promote the development and application of nanocomposites in the field of information security and deepen the connection between molecular sensing and the information world.

A neutral mononuclear rhenium(I) complex with a rare in situ-generated triazolyl ligand for the luminescence "turn-on" detection of histidine

A rare in situ-generated mononuclear rhenium complex [Re(bpt)(CO)₃(NH₃)] (1, bpt = 3,5-bis(2-pyridyl)-1,2,4-triazolate) can be used as a "turn-on" luminescent probe for selectively sensing L-histidine against other amino acids. Compound 1 was prepared by reacting Re₂(CO)₁₀, 2-cyanopyridine and hydrazine with an in situ formed bpt ligand through cyclization via C-N and N-N couplings with its single-side chelating mode arrayed with respect to the Re center. Compound 1 was highly stable and showed a green light MLCT emission in DMF solution at 507 nm upon excitation at 360 nm. Interestingly, the emission from 1 could be quenched by the addition of metal ions such as Ni²⁺ and Cu²⁺ but the emission efficiently recovered with the introduction of histidine. However, histidine could only be selectively detected when a combination of compound 1 and Ni²⁺ was used. Therefore, the luminescence response of the Ni²⁺-modified compound 1 could be utilized as a "turn-on" probe for the selective detection of histidine. This work provides a simple method for developing new sensing platforms of a discrete metal complex based on rare in situ generation.

Terbium (III)-based Metallacrowns with aggregation-induced emission feature coupled with cu (II) for fluorescence detection of cysteine

The Metallacrowns (MCs) composed of repeated [Metal-N-O] subunits are a type of new material, but the MCs have not been developed and utilized in analytical applications. This essay reports on a new kind of terbium(III)-based Metallacrowns (Tb-MCs) with aggregation-induced emission (AIE) feature to build a sensing platform. It is first time that Tb-MCs are able to aggregate to larger aggregates in water along with a bright green emission, so that the property makes it possible to apply in biosensing. Thereafter, the AIE of Tb-MCs can be quenched effectively by Cu²⁺. Based on the high affinity of thiol to Cu²⁺, cysteine (Cys) recovers the fluorescence of Tb-MCs in the presence of Cu²⁺. There is a good linear range varying from 0.02 to 20 μM with a low limit of detection (LOD) 9.67 nM of Cys. In the end, this novel probe is also successfully applied to the determination of Cys in human serum with satisfactory results.

Synthesis of metal nanoclusters and their application in Hg2+ ions detection: A review

Mercuric (Hg²⁺) ions released from human activities, natural phenomena, and industrial sources are regarded as the global pollutant of world's water. Hg²⁺ ions contaminated water has several adverse effects on human health and the environment even at low concentrations. Therefore, rapid and cost-effective method is urgently required for the detection of Hg²⁺ ions in water. Although, the current analytical methods applied for the detection of Hg²⁺ ions provide low detection limit, they are time consuming, require expensive equipment, and are not suitable for in-situ analysis. Metal nanoclusters (MNCs) consisting of several to ten metal atoms are important transition missing between single atoms and plasmonic metal nanoparticles. In addition, sub-nanometer sized MNCs possess unique electronic structures and the subsequent unusual optical, physical, and chemical properties. Because of these novel properties, MNCs as a promising material have attracted considerable attention for the construction of selective and sensitive sensors to monitor water quality. Hence this review is focused on recent advances on synthesis strategies, and optical and chemical properties of various MNCs including their applications to develop optical assay for Hg²⁺ ions in aqueous solutions.

Computational Characterization of the Intermixing of Iron Triade (Fe, Co, and Ni) Surfaces and Sub-nanometric Clusters with Atomic Gold

Dispersion-corrected density functional theory (DFT-D3) is applied to model iron triade (Fe, Co, and Ni) surfaces upon exchange of surface atoms with atomic gold. One first goal is to analyze the contact problem at the triade surface-Au interface and to correlate our findings with recent observations on iron triade nanoparticles (with diameters of around 5 nm) passivated by a few layers of gold. For this purpose, we analyze: (1) the energies of substitution; (2) the restructuring of the iron triade surfaces upon the atomic exchange; (3) the density of the orbitals bearing the largest projection on d(Au) atomic orbitals and, particularly, their overlap with orbitals from neighboring atoms of the triade surfaces; (4) the modification of the electronic density of states; and (5) the redistribution of the electronic density upon intermixing of Au and triade atoms. Inspite of the similarities between Ni, Co, and Fe in the condensed phase, significant differences are found in the features characterizing the exchange process. In particular, we find a better integration of the Au atom on the substitutional site of the Ni(001) surface than on those of the Fe(001) and Co(001) surfaces. This is in agreement with the fact that the electronic density of states is almost indistinguishable before and after Ni-Au intermixing. This outcome is correlated with the experimental observation on the allowing transition of Ni-Au core-shell nanoparticles before reaching the melting temperature. Our second objective is to explore the Au-triade atom intermixing process in sub-nanometric clusters, finding that it is energetically more favored than at solid surfaces yet endothermic at 0 K. This feature is explained as the result of the structural fluxionality characterizing clusters at the sub-nanometer scale. Entropy contributions make mixed Au-Ni clusters more stable than the unmixed counterpart already at 650 K while unmixed Co clusters remain energetically more favored up to 1295 K and iron clusters are predicted to be stable against intermixing over the experimentally relevant range of temperatures (up to 1100 °C). Remarkably, the net charge donated from the three triade atoms to atomic gold upon intermixing is similar in triade sub-nanometeric clusters and at extended triade surfaces. Gold clusters are prone to host Fe, Co, and Ni atoms at the center of their structures and the exchange process is predicted to be exothermic at 0 K even for a small cluster made of 13 atoms. More generally, our work highlights the importance of the polarity of the chemical bond between unlike metal atoms in alloys.

Thermally Induced Diffusion and Restructuring of Iron Triade (Fe, Co, Ni) Nanoparticles Passivated by Several Layers of Gold

The temperature-induced structural changes of Fe-, Co-, and Ni-Au core-shell nanoparticles with diameters around 5 nm are studied via atomically resolved transmission electron microscopy. We observe structural transitions from local toward global energy minima induced by elevated temperatures. The experimental observations are accompanied by a computational modeling of all core-shell particles with either centralized or decentralized core positions. The embedded atom model is employed and further supported by density functional theory calculations. We provide a detailed comparison of vacancy formation energies obtained for all materials involved in order to explain the variations in the restructuring processes which we observe in temperature-programmed TEM studies of the particles.

Photonic crystal enhanced gold-silver nanoclusters fluorescent sensor for Hg2+ ion

Luminescent nanoclusters (NCs) have attracted much attention because of their good photostability and low toxicity, however, the low quantum yield is still a deficiency, and many increasing efforts are being devoted to enhance the luminescence intensity of NCs. In this paper, a method of enhancing the fluorescent signal of gold-silver nanoclusters (AuAgNCs) by photonic crystals (PhCs) was proposed. The fluorescent intensity of AuAgNCs on PhCs can be enhanced 8.0-fold in comparison to the control sample without PhCs. Furthermore, a novel fluorescence sensor of AuAgNCs based on PhCs is used for the sensitive and selective detection of Hg²⁺ ion in the aqueous solution, the detection limit is 0.35 nM due to the PhCs enhancement effect for the fluorescence. This proposed method may not only develop a highly sensitive method for determination of Hg²⁺ ion, but also expand the application of AuAgNCs in ultra-trace analysis.

Aggregation-induced emission enhancement of adenosine monophosphate-capped bimetallic nanoclusters by aluminum(III) ions, and its application to the fluorometric determination of cysteine

The fluorescence of adenosine monophosphate-capped bimetallic gold and silver nanoclusters (type AuAgNC@AMP) is strongly enhanced and blue shifted in the presence of Al(III). As confirmed by transmission electron microscopy, the AuAgNC nanodots are converted to larger assembled spheres of type AuAgNC-Al(III). The fluorescence enhancement is attributed to aggregation-induced emission enhancement (AIEE). The fluorescence of the AuAgNC-Al(III) assembly (with excitation and emission maxima at 340 and 540 nm) is quenched by cysteine (Cys). The effect was applied to the fluorometric determination of Cys. The assay works in the 1.0 to 16.0 μM Cys concentration range and has a 50 nM limit of detection. The method was successfully applied to analyze Cys-spiked mineral waters and serum. The quenching mechanism is explored in depth. It is attributed to the partial replacement of AMP by Cys at the surface of the AuAgNC and alteration of the assembly structure from large spherical particles to a strip shape. Graphical abstractSchematic representation of the fluorescence enhancement of bimetallic nanoclusters capped with adenosine monophosphate by using Al(III), and its application in selective and sensitive determination of cysteine via ligand replacement and reassembly.

Effects of the Core Location on the Structural Stability of Ni-Au Core-Shell Nanoparticles

Structural changes of Ni-Au core-shell nanoparticles with increasing temperature are studied at atomic resolution. The bimetallic clusters, synthesized in superfluid helium droplets, show a centralized Ni core, which is an intrinsic feature of the growth process inside helium. After deposition on SiN _x , the nanoparticles undergo a programmed temperature treatment in vacuum combined with an in situ transmission electron microscopy study of structural changes. We observe not only full alloying far below the actual melting temperature, but also a significantly higher stability of core-shell structures with decentralized Ni cores. Explanations are provided by large-scale molecular dynamics simulations on model structures consisting of up to 3000 metal atoms. Two entirely different diffusion processes can be identified for both types of core-shell structures, strikingly illustrating how localized, atomic features can still dictate the overall behavior of a nanometer-sized particle.

Recent Progress on Gold-Nanocluster-Based Fluorescent Probe for Environmental Analysis and Biological Sensing

Gold nanoclusters (AuNCs) are one of metal nanoclusters, which play a pivotal role in the recent advances in the research of fluorescent probes for their fluorescence effect. They are favored by most researchers due to their strong stability in fluorescence and adjustability in fluorescence wavelength when compared to traditional organic fluorescent dyes. In this review, we introduce various synthesis strategies of gold-nanocluster-based fluorescent probes and summarize their application for environmental analysis and biological sensing. The use of gold-nanocluster-based fluorescent probes for the analysis of heavy metals and inorganic and organic pollutants is covered in the environmental analysis while biological labeling, imaging, and detection are presented in biological sensing.

A rational strategy to develop a boron nitride quantum dot-based molecular logic gate and fluorescent assay of alkaline phosphatase activity

By comparing the percentage of FL quenching and recovery of the BNQDs, a Fe³⁺-mediated FL quenching of BNQDs system was rationally designed for efficient ALP assay. Moreover, the aforementioned ensemble was exploited to newly construct a 2D-QD-based INH logic gate.

Chemical etching of pH-sensitive aggregation-induced emission-active gold nanoclusters for ultra-sensitive detection of cysteine

This study reports the utilization of thiol-induced chemical etching of aggregation-induced emission (AIE)-active Au nanoclusters (NCs) for the facile, sensitive, and selective detection of cysteine. The AIE-active Au NCs were formed in an acidic solution containing excess Au(i)-thiolate complexes. At an acidic pH (2.0), the emission of these Au NCs was enhanced by cysteine at a concentratioin below 1 mM. However, the emission was quenched by cysteine at a high concentration, e.g., 500 mM, via the thiol-induced etching of gold, although the process occurred very slowly. Interestingly, in the absence of cysteine, increasing the solution pH enhanced the emission, while the presence of cysteine remarkably accelerated the etching-induced quenching process. The complete quenching of the emission by excess cysteine at pH 2.0 and the enhancement of the emission by the increasing pH in the absence of cysteine indicated that aurophilicity might not be involved in the AIE of the Au NCs prepared using glutathione (GSH) both as the reducing and protecting reagent. On the other hand, the etching process involved the penetration of cysteine molecules through the Au(i)-thiolate complexes, which could assemble or disassemble around the embedded Au NCs in response to the solution pH to get access to the innermost Au(0) cores. Therefore, a facile, sensitive, and selective method for the detection of cysteine was established. This method exhibited an extremely wide linear range as wide as nine orders of magnitude above the cysteine concentration, including two linear regions of the relative emission intensity of the Au NCs versus the logarithm of cysteine concentration, from 10 pM to 150 μM (correlation coefficient, 0.99851) and from 150 μM to 2 mM (correlation coefficient, 0.99866). An ultra-low limit of detection of 6.3 pM (S/N = 3) was also achieved. The developed method showed superior selectivity for cysteine relative to the 19 other natural amino acids and GSH. The method was applied for the analysis of human serum samples spiked with cysteine with satisfactory results. This study demonstrates the potential of the thiol-induced chemical etching approach as a powerful tool for studying luminescent metal NCs.

A novel label-free colorimetric detection of l-histidine using Cu2+-modulated G-quadruplex-based DNAzymes

We proposed a colorimetric method for l-histidine detection based on Cu²⁺-mediated DNAzyme and G-quadruplex-hemin complex catalyzed oxidation of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS). In this system, after the addition of l-histidine, the formation of G-quadruplex-hemin complex will be disturbed, thus the colorimetric signal intensity conversely corresponds to the concentration of histidine. In this assay, a lower detection limit of l-histidine (50 nM) is addressed comparing to previously reported colorimetric methods. The cost is extremely low as the proposed design is both label-free and enzyme-free. All the more vitally, the colorimetric detection procedure is substantially straightforward with no further modification processes. By and large, the sensor can provide a promising plan for the detection of l-histidine.

Protein Fibril-Templated Biomimetic Synthesis of Highly Fluorescent Gold Nanoclusters and Their Applications in Cysteine Sensing

Biomimetic synthesis of multifunctional fluorescent gold nanoclusters (Au NCs) is of great demand because of their ever-increasing applications. In this study, we have used self-assembled bovine serum albumin (BSA) amyloid-like nanofibers as the bioinspired scaffold for the synthesis of Au NCs. The amyloid fibril stabilized gold nanocluster (Fib-Au NC) has been found to have appreciable enhancement of fluorescence emission and a large 25 nm red shift in its emission maxima when compared to its monomeric protein counterpart (BSA-Au NC). The underlying mechanism accountable for the fluorescence behavior and its spectral shift has been thoroughly investigated by a combined use of spectroscopic and microscopic techniques. We have subsequently demonstrated the use of Fib-Au NCs for cysteine (Cys) sensing both in vitro and inside live cells. Additionally, cellular uptake and postpermeation effect of Fib-Au NCs have also been ascertained by detailed flow cytometry analysis, viability assay, and real-time apoptotic gene expression profiling.

Optical sensing at the nanobiointerface of metal ion-optically-active nanocrystals

Optically-active nanocrystals (such as quantum dots and plasmonic noble metal nanoparticles) have received great attention due to their size-tunable optical properties. The indicator displacement assay (IDA) with optically-active nanocrystals has become a common practice for optical sensor development, since no sophisticated surface functionalization of nanoparticles is required. Among the IDA-based optical sensors, the use of metal ions as receptors seems to be attractive. Therefore, in this review, the research progress of optical sensing at the nanobiointerface of metal ion-optically-active nanocrystals has been summarized. In particular, metal ion-mediated selective recognition has been summarized here based on the classical Hard-Soft-Acid-Base (HSAB) principle, which has been seldom mentioned before. Most of the references were therefore categorized according to their located place based on the HSAB theory. Besides, several metal ion modulation strategies that were not related to the HSAB theory (e.g., redox modulation) were also included. Finally, due to the cross-talk of metal ions in selective recognition, we have also summarized sensor array development based on multiple metal ion receptors in IDA sensing with optically-active nanocrystals. Several interesting applications of the IDA sensing with metal ions as receptors and optically-active nanocrystals as indicators are presented, with specific emphasis on the design principles and photophysical mechanisms of these probes.

Ag-Au bimetallic nanoclusters formed from a homogeneous gas phase: a new thermodynamic expression confirmed by molecular dynamics simulation

In this work, two probabilistic and thermodynamic limits for formation of a bimetallic nanocluster from a homogeneous gas phase were obtained in order to investigate the related phenomena using molecular dynamics simulation. Therefore, by application of some simple assumptions from thermodynamics and statistical mechanics, a new expression for composition of the nanocluster was derived which depends only on the initial conditions of the system and one adjustable parameter. This expression can be easily fitted to the results of molecular dynamics and can be used as a measure of the thermodynamic contribution in the cluster formation process. Then, molecular dynamics simulations were performed for several systems containing the same total number of metallic atoms and different concentrations of Ag and Au atoms. The results of this study exhibited that depending on different initial compositions of Ag and Au types, fcc and icosahedral structures are formed. Moreover, increase of the initial Ag concentration leads to products whose compositions are more controlled by probability limits. However, longer simulation times indicated that creation of more thermodynamically favoured nanoclusters depends on the formation of more probable ones in the early stages of the simulation.

Metal-assisted selective recognition of biothiols by a synthetic receptor array

A synergistic combination of a deep cavitand host, fluorophore guests and transition metal ions can be used to sense small molecule thiols of biological interest with good efficiency and selectivity in complex aqueous media.

Carbon dots with red emission as a fluorescent and colorimeteric dual-readout probe for the detection of chromium(vi) and cysteine and its logic gate operation

A schematic illustration for assaying Cr(vi) and Cys activity by CDs with both fluorescent and colorimetric readouts.

Luminescent gold nanocluster-based sensing platform for accurate H2S detection in vitro and in vivo with improved anti-interference

Gold nanoclusters (Au NCs) are promising luminescent nanomaterials due to their outstanding optical properties. However, their relatively low quantum yields and environment-dependent photoluminescence properties have limited their biological applications. To address these problems, we developed a novel strategy to prepare chitosan oligosaccharide lactate (Chi)-functionalized Au NCs (Au NCs@Chi), which exhibited emission with enhanced quantum yield and elongated emission lifetime as compared to the Au NCs, as well as exhibited environment-independent photoluminescence properties. In addition, utilizing the free amino groups of Chi onto Au NCs@Chi, we designed a FRET-based sensing platform for the detection of hydrogen sulfide (H₂S). The Au NCs and the specific H₂S-sensitive merocyanine compound were respectively employed as an energy donor and acceptor in the platform. The addition of H₂S induced changes in the emission profile and luminescence lifetime of the platform with high sensitivity and selectivity. Utilization of the platform was demonstrated to detect exogenous and endogenous H₂S in vitro and in vivo through wavelength-ratiometric and time-resolved luminescence imaging (TLI). Compared to previously reported luminescent molecules, the platform was less affected by experimental conditions and showed minimized autofluorescence interference and improved accuracy of detection.

Au@void@AgAu Yolk-Shell Nanoparticles with Dominant Strain Effects: A Molecular Dynamics Simulation

Au@void@AgAu yolk-shell nanoparticles with different morphologies were studied by classical molecular dynamics simulation. The results indicated that all of simulated yolk-shell nanoclusters with ∼3.8 nm size and different morphologies are unstable at room temperature, and collapse of the shell atoms into the void space completely fills it and creates more stable Au@AgAu core-shell structures. Also, it was observed that thermodynamic stabilities of the created core-shell structures strongly depend on the morphology of nanocluster, for which competition between strain and surface energy effects plays the key role in this phenomenon. Within this competition, strain effect is dominant and helps the stability of the created core-shell structure. Herein, the icosahedral nanocluster with the lowest strain effect exhibits the highest thermodynamic stability. By comparing the simulation results with experimental data, it was concluded that the essential factor that controls the stability of these nanoparticles is their size.

Carbon nano-dots as a fluorescent and colorimetric dual-readout probe for the detection of arginine and Cu2+ and its logic gate operation

A new visual fluorescent probe based on carbon nano-dots (CNDs) has been facilely synthesized via one step microwave-assisted pyrolysis and utilized for sequential detection of arginine (Arg) and Cu²⁺ by fluorescent and colorimetric dual-readout assay. The fluorescence of CNDs can be effectively quenched by Arg, and recovered upon addition of Cu²⁺ due to the competitive binding of Arg and Cu²⁺ that leads Arg to escape from the surface of CNDs. The probe displayed high sensitivity and selectivity toward Arg and Cu²⁺ over other analytes with a low detection limit of 0.26 μM and 0.17 μM, respectively. Meanwhile, the CNDs can also give dual responsive signals of a visible color change (yellow-pink-light yellow). According to this phenomenon, an "AND" logic gate based on the novel CNDs has been constructed. More importantly, the probe was also extended to cellular imaging. The proposed method was simple with ease of operation, which demonstrated great potential in bio-sensing, disease diagnosis or environmental monitoring.

Au@Void@Ag Yolk-Shell Nanoclusters Visited by Molecular Dynamics Simulation: The Effects of Structural Factors on Thermodynamic Stability

Au@void@Ag yolk-shell nanoclusters were studied by molecular dynamics simulation in order to study the effects of core and shell sizes on their thermodynamic stability and structural transformation. The results demonstrated that all of simulated nanoclusters with different core and shell sizes are unstable at temperatures lower than 350 K in such a way that Ag atoms are collapsed into the void space and fill it, which leads to creation of a more stable core-shell morphology, and at the melting point, only core-shell structures with altered thickness of the shell exist. Also, at higher temperatures, Au atoms tend to migrate toward the surface, and an increase of both the core and shell sizes leads to an increase of the thermodynamic stability. Moreover, a Au₁₄₇@void@Ag₂₅₂ nanocluster with the largest core and shell and minimum void space exhibited the most thermodynamic stability and highest melting point. Generally, the core and shell sizes affect the stability and thermal behavior of yolk-shell nanoclusters cooperatively.

Cu2+-Mediated turn-on fluorescence assay for sulfide ions using glutathione-protected gold nanoclusters: enhanced sensitivity, good reusability, and cell imaging

Cu²⁺-Mediation enables turn-on fluorescence detection of S²⁻using GSH-Au NCs with good sensitivity, reusability, and applicability in cell imaging.

Ratiometric fluorescence monitoring of cerebral Cu2+ based on coumarin-labeled DNA coupled with the Cu2+-induced oxidation of o-phenylenediamine

A novel ratiometric fluorescence assay for cerebral Cu²⁺ has been developed based on coumarin-labeled single-stranded DNA coupled with the Cu²⁺-induced oxidation of o-phenylenediamine.

Fluorescent metal quantum clusters: an updated overview of the synthesis, properties, and biological applications

A brief history of metal quantum clusters, their synthesis methods, physical properties, and an updated overview of their applications is provided.

Lanthanide coordination polymer nanoparticles as a turn-on fluorescence sensing platform for simultaneous detection of histidine and cysteine

A turn-on fluorescent sensor for simultaneous detection of histidine and cysteine based on lanthanide coordination polymer nanoparticles.

Structure and dynamics of a dl-homocysteine functionalized fullerene-C60–gold nanocomposite: a femtomolar l-histidine sensor

An Au@Hcys-C₆₀ nanocomposite for l-histidine sensing.

An integrated logic system for time-resolved fluorescent "turn-on" detection of cysteine and histidine base on terbium (III) coordination polymer-copper (II) ensemble

Cysteine (Cys) and histidine (His) both play indispensable roles in many important biological activities. An enhanced Cys level can result in Alzheimer's and cardiovascular diseases. Likewise, His plays a significant role in the growth and repair of tissues as well as in controlling the transmission of metal elements in biological bases. Therefore, it is meaningful to detect Cys and His simultaneously. In this work, a novel terbium (III) coordination polymer-Cu (II) ensemble (Tb(3+)/GMP-Cu(2+)) was proposed. Guanosine monophosphate (GMP) can self-assemble with Tb(3+) to form a supramolecular Tb(3+) coordination polymer (Tb(3+)/GMP), which can be suited as a time-resolved probe. The fluorescence of Tb(3+)/GMP would be quenched upon the addition of Cu(2+), and then the fluorescence of the as-prepared Tb(3+)/GMP-Cu(2+) ensemble would be restored again in the presence of Cys or His. By incorporating N-Ethylmaleimide and Ni(2+) as masking agents, Tb(3+)/GMP-Cu(2+) was further exploited as an integrated logic system and a specific time-resolved fluorescent "turn-on" assay for simultaneously sensing His and Cys was designed. Meanwhile it can also be used in plasma samples, showing great potential to meet the need of practical application.