Diazonium Research Articles

A Simple Dispersive Liquid-Liquid Microextraction for the Determination of Copper II in the Water Samples of the Halfaya Oil Field in Maysan

Background: Copper, an important trace element for life on Earth, is crucial to many metabolic processes. This includes its role in the production and breakdown of nucleic acids and the metabolism of proteins, lipids, and carbohydrates. Objective: We aim to integrate DLLME with a spectrophotometric method to establish a novel approach for quantifying trace amounts of copper in water samples. Methods: In this study, a new ligand known as a 2-(4 aminophenol) benzimidazole azo derivative was successfully synthesized. This ligand was created by converting 2-(4-aminophenyl) benzimidazole into a diazonium salt and coupling it with 8-hydroxyquinoline in an alkaline environment. The resulting product was a brown azo dye, which served as the ligand for detecting copper (II) in aqueous samples. Results: To analyze copper (II) in both pure and aqueous samples, we developed and validated micro-extraction techniques combined with UV-Vis measurement. Specifically, we used the DLLME (dispersive liquid-liquid microextraction) method to separate, enrich, and assess copper (II) in both its pure form and in aqueous samples. UV-Vis spectroscopy at a wavelength of 503 nm was used for this purpose. We considered several variables during the experiment, including the type and volume of the dispersive solvent, the extraction solvents, the temperature, the reaction duration, and the centrifuging time. By optimizing these conditions, we achieved linear procedures within the concentration range of (1.0–25.0) and (2.0–25.0) μg/mL for spectroscopy and DLLME methods, respectively. For the spectroscopic and DLLME approaches, the coefficient of determination (R2) was found to be 0.9963 and 0.9979 for the spectrophotometric and DLLME methods, respectively. The limit of detection (LOD) for copper (II) was found to be 0.23 and 0.04 μg/mL, respectively. Moreover, the recovery of the target analyte in aqueous samples was found to be between 95.6% and 101% for the spectroscopy method and between 102.4% and 108.2% for the DLLME method. Conclusions: These results demonstrate the effectiveness and accuracy of both methods in analyzing copper (II) in aqueous samples.

Synthesis, Characterization and Analytical Study of New Azo Compounds for using as acid-base indictors

A diazotization method was used to synthesize new azo compounds, to which phenol was subsequently added to diazonium salt solution in basic medium at temperatures ranging from 0 to 5 °C and compounds were characterized by FT-IR, 1H-NMR, and 13C-NMR spectroscopy. The potential of the compounds as acid-base indicators was tested by determining their ionization and protonation constants at different pH levels (1 to 14) using a DMSO solution of the synthesized compounds. UV-Vis spectra shown as maximum wavelength (380-390 nm) observed at pH 1-7 occurs, indicating the cationic formula (protonated form of compound H2 and H4), another peak (470-530 nm) appears at pH 8-13, indicating the ionic formula (deprotonated form of compound H2 and H4), where for compound H5 observed at 560 nm at pH 1-7. Another peak appears 505 nm at pH 8-13 attributable to absorption the ionic formula (deprotonated form of compounds H5). Molecules H2, H4, and H5 showed distinct color changes when shifted to acidic and basic conditions. Furthermore, these compounds showed exceptional accuracy in drawing conclusions about the phenomenon.

Synthesis of thiophene hydrazone derivatives by Japp Klinegmann reaction method for anticancer activity against MCF-7 cell line.

The creation of novel anticancer drugs is the aim of this research. Our decision about which compounds to synthesis was aided by docking studies. Using data from the protein databank and refinement from BIOVIA discovery, the protein structure of AGF183 (PDB5IZQ). It was subjected to molecular docking investigations using PyRx 0.8 Autodock Vina software. following the creation of a novel sequence of thiophene-2,5-carbohydrazide. Final chemicals such as thiophene-2,5-carbohydrazide derivatives (G1 and G2) are produced via the Japp Klinegmann process. This reaction makes it possible to produce Schiff bases without any problems. Diethylthiophene-2,5-dicarboxylate was reacted with an aromatic diazonium salt to create the final products. When compared to the reference drug imatinib, the synthesized compounds exhibited the strongest anticancer effect. The study conducted on MCF-7 cell line demonstrated that compounds G1 and G2 demonstrated the most potent anticancer effect. Compared to the reference value of imatinib, which is 52.77 µg/ml and has G1 and G2 docking scores of -8.8, -8.6, and the standard medication methotrexate (-11.87 kcal/mol), their IC50 values were 46.52 µg/ml and 50 µg/ml. On base of characterization results above show that it Japp Klinegmann Synthesis method is useful for synthesis of thiophene hydrazone derivatives and its findings imply that the MCF-7 cells, which are utilized to potential treatment for human breast cancer.

Development of ultrasensitive genosensor targeting pathogenic Leptospira DNA detection in artificial urine

In the last decades, to access the stages of leptospirosis pathogenicity, site of infection, progression, monitor disease, and after-treatment were required especially non-invasive techniques. This becomes one of the significant goals for researchers. In this study, we developed a highly sensitive DNA-based electrochemical sensor to detect pathogenic leptospires in urine samples using a gold screen-printed electrode. The gold working electrode was electrodeposited with diazonium salt (CMA) with external carboxylic acid from the surface, and the specific Loa22 single-stranded DNA (ssDNA) probe to Leptospira interrogans was immobilized through a carbodiimide chemical reaction. The modified working electrode was characterized by contact angle measurement, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). After that, targeted DNA testing showed the EIS change in the range of 5 ag mL-1 - 16 fg mL-1 with a correlation R2 of 0.9638. The high sensitivity electrochemical sensor indicated a lower limit of detection to the attomolar level specifically 5 ag mL-1. Additionally, the developed genosensor exhibited high specificity without crossing other bacteria present in urine such as Escherichia coli, Staphylococcus aureus, and S. typhi as well as non-pathogenic leptospires L. biflexa serovar Patoc. Leptospires DNA was analyzed in both buffer solution and diluted artificial urine and detection in diluted artificial urine 1:1,000 was possible despite salt interferences. This study provides a highly sensitive lower detection platform for leptospirosis, offering potential for further development as a portable and point-of-care testing tool.

Direct Diazoarylation of [1.1.1]Propellane with Arenediazonium Salts: A Modular Assembly of Arylated Diazo Bicyclo[1.1.1]pentanes.

A mild and concise diazoarylation of [1.1.1]propellane is described, which provides a modular approach to arylated diazo bicyclopentanes (BCPs). This reaction proceeds smoothly under basic conditions without requiring other additives or catalysts. The substrate scope shows that various electron-withdrawing and electron-donating groups are tolerated, and the subsequent modifications provide a novel avenue for assembling arylamino-BCP analogs.

Tunable and Photoactivatable Mimics of Calicheamicin γ1 for DNA Cleavage.

Calicheamicin γ1 and related natural products are renowned for their potency in DNA cleavage, serving as the warheads in commercial ADCs used for treating leukemia. Their mechanism of action involves the formation of aryl radicals, which abstract hydrogen atoms from nucleic acids. However, the complex strained enediyne structure of calicheamicin γ1 presents significant challenges in synthesis, resulting in high production costs and limited structural and activity modularity for tuning the therapeutic window. This report describes the development of simple molecular mimics based on diazonium salts, synthesized in fewer than 3 steps, capable of generating aryl radicals upon green or red light irradiation. SAR studies conducted on over 30 analogues reveal a wide range of potencies in DNA cleavage, with EC50 values ranging from low nanomolar to micromolar. Forming benzenoid diradicals does not appear to be necessary for potent DNA cleavage; instead, DNA cleavage can be achieved with radicals distributed among different arenes when connected with proper linkages. The potency is influenced by electronic effects, stereochemistry, orbital orientations, the distance between multiradicals, and the number of diazonium motifs within the molecule. In addition to providing a more cost-effective, efficient, and modular alternative to calicheamicin γ1, this technology offers the potential for enhanced specificity through spatiotemporal control.

Palladium‐Catalyzed Denitrogenative Coupling of Aryldiazonium Salts with Terminal Alkynes for the Assembly of Internal Alkynes

AbstractAn N‐heterocyclic carbene palladium (NHC‐palladium)‐catalyzed denitrogenative coupling of aryldiazonium salts with terminal alkynes in ionic liquids has been accomplished. This catalytic strategy provides an effective and green synthetic protocol for the assembly of structurally diverse internal alkynes with excellent functional group compatibility and mild conditions. In the presence of 1 mol % of IMes‐Pd‐Im‐Cl2 as the catalyst, a wide range of terminal alkynes and aryldiazonium salts could be excellently tolerated. Basic ionic liquid plays a crucial role in this catalytic system, which not only acts as the green solvent, but also provides basic environment for the carbon‐carbon bond formation process. Notably, this catalytic system could be recycled up to six times and reused without significant loss of catalytic activity.

Enhanced Electrochemical Detection of Nonelectroactive Compounds Based on Surface Supramolecular Interactions on Chevron-like Graphene Nanoribbons Modified through Click Chemistry.

In this study, we have developed a nanostructured electrochemical sensor based on modified graphene nanoribbons tailored for the analysis of nonelectroactive compounds via a surface competitive assay. Stigmasterol, a nonelectroactive phytosterol, was selected as a representative case. Chevron-like graphene nanoribbons, chemically synthesized, were immobilized onto glassy carbon electrodes and covalently functionalized to allow the on-surface formation of a supramolecular complex. To this end, the nanoribbons were first modified through a diazotization process by electrochemical reduction of a 4-azidoaniline diazonium salt, leaving the electrode surface with azide groups exposed to solution. Next, the incorporation of a ferrocene group, as a redox probe, was carried out by a click chemistry reaction between ethynylferrocene and these azide groups. Finally, the recognition event leads to the formation of a supramolecular complex between ferrocene and a macrocyclic receptor on the electrode surface. To this end, the receptors cucurbit[7]uril, cucurbit[8]uril, and β-cyclodextrin were evaluated, with the better results obtained with β-cyclodextrin. Atomic force microscopy and scanning electron microscopy measurements were performed for the morphological characterization of the resulting electrochemical platform surface. The ability of β-cyclodextrin to form an inclusion complex with ferrocene or with stigmasterol allows to perform a competitive assay, which translates into the decrease and recovery of the ferrocene electrochemical signal. For stigmasterol determination, a linear concentration range between 200 and 750 μM and a detection limit of 60 μM were obtained, with relative errors and relative standard deviations less than 7.1 and 9.8%, respectively.

Development of Optical Sensors Based on Neutral Red Absorbance for Real-Time pH Measurements.

Measuring pH with an optical sensor requires the immobilization of a chemical recognition phase on a solid surface. Neutral red (NR), an acid base indicator was used to develop two different optical probe configurations. The chemistry of aryl diazonium salts was chosen for the elaboration of this chemical phase, as it enables strong covalent bonds to be established on the surface of metallized glass or metallic surfaces. It also allows the formation of a thick film required to obtain an exploitable spectral response. The surfaces of interest (metallized optical fiber and 316 L stainless-steel mirror) are modelized by flat surfaces (metallized glass plates and 316 L stainless-steel plates). The analytical characterizations carried out (IR, XPS, UV-Visible, and profilometry) show that NR was covalently grafted onto the model surfaces as well as on the surfaces of interest. The supports grafted with NR to develop optical pH probes exhibit spectral changes, particularly the values of pKa, the pH range, and the isosbestic point wavelength. The experimental results show that the optical probe can be used for pH measurements between 4 and 8.

Some New Aspects of Gold-Catalyzed Benzannulation Reaction

Introduction: The gold-catalyzed benzannulation reaction of oxo-alkynes with al-kenes or alkynes is one of the important and unique reactions in gold-catalyzed organic trans-formations. Methods: In this manuscript, many facets of this reaction have been discussed concerning reac-tivity and selectivity, along with a new self-benzannulation process. The scope of this chemistry was extended to construct a phenanthrene moiety. Results: In addition, a palladium-gold dual catalytic arylation of isobenzopyrylium salts using arene-diazonium salts as an aryl group source and a one-pot isoquinoline synthesis is reported for the first time. Conclusion: Moreover, a conductance measurement experiment was performed, which supports the formation of ionic species, most likely the isobenzopyrylium auric ate complex as an inter-mediate formed during the reaction process.

Surface Tailoring of MoS2 Nanosheets with Substituted Aromatic Diazonium Salts for Gas Sensing: A DFT Study.

Two-dimensional (2D) nanomaterials are useful for building gas sensors owing to their desirable electronic and optical properties. However, they usually suffer from selectivity, because they cannot discriminate between gas molecules. Functionalization with organic molecules can be used to tailor their surfaces to recognize a specific family of compounds. In this study, solid-state density functional theory (DFT) was used to elucidate the functionalization of MoS2 with substituted aromatic diazonium salts (R = -H, - CH3, -CO2H, -CHO, -OCH3, and -NO2). Results showed that chemical reaction with diazonium salts is favored to their physical adsorption (E ads = -0.04 to -0.38 eV vs E rxn = -1.47 to -2.20 eV), where organic cations have a preference to attach atop of sulfur atoms. Chemical functionalization induced a small variation in the bandgap energy not exceeding 0.04 eV; thus, the optical properties were well preserved. In the presence of ammonia, the substituted MoS 2 /2(a-f) responded to the target analyte through a change in the interaction energy, varying from -0.08 to -0.83 eV, where the best interaction energy was obtained for MoS 2 /2c, bearing the carboxylic acid group. In the presence of other gases such as CO2, SO2, and H2S, the interaction energy is lower (-0.14 to -0.35 eV), indicating good selectivity of the nanomaterials. Furthermore, the interaction increased in the presence of humidity, which was more realistic than that in the presence of neat NH3. This interaction was confirmed by computing the partial charges. Recovery times estimated from the interaction energies ranged from 0.31 s to several minutes, depending on the interacting molecules. Phenylcarboxyl-modified MoS2 nanosheets show great potential as candidates for the development of chemoresistive gas sensors that are specifically designed for detecting ammonia.

Radical Alkynylthiolation with Visible-Light-Sensitive S-Alkynylthio Sulfonates.

A novel kind of S-alkynylthio sulfonate, which can be directly activated under visible-light irradiation, has been developed for the radical addition of multiple bond systems and radical coupling with diazonium salts under photocatalyst-free conditions. This strategy features a broad substrate scope, high regioselectivity, excellent tolerance of functional groups, and the late-stage modification of drugs. Experimental and theoretical mechanistic investigations gave reasonable insight into the photolysis of S-alkynylthio sulfonates and C-S bond formation.

An In‐Depth Review on Recent Progress in Synthetic Approaches and Biological Activities of Thiazol‐2(3H)‐Imine Derivatives

AbstractThis review presents the in‐dept analysis of the synthetic approaches towards thiazol‐2(3H)‐imine and embarks at its various biological properties published during 2000 to 2023. The most important method of synthesis involves the reaction of substituted thioureas and α‐halo carbonyl compounds, and condensation and nucleophilic addition of 2‐amino‐1,3‐thiazoline with aldehydes. Additionally, isothiocyanate‐based multicomponent synthesis, and α‐nitroepoxides have been proved as benign precursors for this motif. Several eco‐friendly and solvent‐free synthesis from diazonium salts, acetylenes, tertiary enaminones and thiosemicarbazides have also been reported. This epitome is a unique combination of synthetic methods as well as biological activities like anti‐inflammatory, anti‐bacterial, anti‐cancer, anti‐leishmanial, anti‐microbial, herbicidal, anti‐HIV, and may be a valuable tool for researchers to tailor the synthetic procedures according to specific target structures and applications. Moreover, this review enlightens the applications of thiazol‐2(3H)‐imine as platelet GPIIB/IIIA receptor antagonists, alkaline phosphatase inhibitors, neurodegenerative drug Pifithrin‐α analogues, and skin whitening agents.

Mechanochemical Activation of Aryl Diazonium Salts: Synthesis of Polycyclic (Hetero)Aromatics.

Although the synthesis of polycyclic (hetero)aromatics via the [4 + 2] benzannulation process has been thoroughly explored, the restricted availability of energy sources (including thermal, light, and electrical energy) mandates the utilization of substantial quantities of organic solvents, inevitably leading to environmental pollution, resource wastage, and low reaction efficiency. Herein, we report a new method for the synthesis of polycyclic (hetero)aromatics from diazonium salts and alkynes under ball-milling conditions. This mechanochemical approach requires only substoichiometric amounts of DMSO as a liquid-assisted grinding additive and furnishes the desired product in a short time.

Rational synthesis of Azo ligands and copper complexes: Insights into potential therapeutic agents

In the pursuit of innovation, four distinct mono Azo dyes D1-D4 were synthesized. These dyes were crafted through a coupling reaction involving 1-naphthol, resorcinol and salicylic acid with diazonium salts derived from a diverse array of aromatic amines, including aniline and sulphanilic acid. Subsequently, they are transformed into copper Azo complexes, namely (D1CuC-D4CuC). The structural underpinnings of these mono Azo dyes and their corresponding copper complexes were unveiled using an arsenal of analytical techniques: FTIR, 1H NMR, 13C NMR, and UV-visible spectroscopy which unequivocally confirmed their synthesis. A computational protein-ligand docking approach was used to assess the binding affinity of ligands and metal complexes to an anti-oxidant receptor protein (PDB ID:2HCK) which showed excellent binding interactions. The findings from an in vitro antioxidant activity using the DPPH scavenging method exhibited: Complexes > Ligands. As an antioxidant agent, the synthesized compounds may prove to be a great therapeutic option. This research introduces a novel approach by utilizing Azo dyes as ligands, leveraging their exceptional electronic tunability and stability to form innovative copper complexes. Their pharmacological applications will be explored, potentially yielding drugs with improved efficacy and selectivity.

Novel sulfonic groups grafted sugarcane bagasse biosorbent for efficient removal of cationic dyes from wastewater

In this research, we reported the synthesis of effective sulphonated sugarcane bagasse (SCB@SA) biosorbent based on agriculture waste materials via a simple diazotization strategy for the removal of methylene blue (MB) and Bismarck Brown R(BB) dyes from waste water samples. First, the sugarcane bagasse (SCB) waste was collected, grinded, and sieved to obtain the desired size. Secondly, the SCB powder is modified with sulfanilinic acid (SA) via the formation of its diazonium salt to introduce sulfonic groups on the SCB surface. Different advanced techniques were applied to characterize the prepared materials before and after the adsorption process viz. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDS) and Thermogravimetric analysis (TGA). Different parameters affecting the adsorption process of both MB and BB were studied. Because of the higher correlation coefficient (R2 ≥ 0.999) and lower error functions, the equilibrium MB and BB adsorption isotherms for a single-dye system fit Langmuir with maximum adsorption capacity reaching to 127.48 and 166.75 mg/g for MB and BB, respectively. Moreover, the RL values obtained for both dyes lie between 0 and 1, indicating that MB and BB adsorption by SCB@SA is a favorable process. Besides, the error functions’ values of the pseudo-2nd-order are significantly lower than those of the pseudo-1st-order, implying that the adsorption MB and BB onto SCB@SA biosorbent fitted the pseudo-2nd-order kinetic model in a chemosorption manner. In the thermodynamic studies, the adsorption process is spontaneous, exothermic, and has less randomness. In addition, the SCB@SA biosorbent could be reused in five cycles maintaining on suitable adsorption efficiency. Finally, the MB and BB dyes could be adsorbed on the SCB@SA biosorbent via three mechanisms including π-π stacking, columbic attraction, and hydrogen bonding.

Diazonium-Functionalized Silicon Hybrid Photoelectrodes: Film Thickness and Composition Effects on Photoelectrochemical Behavior.

Aryl diazonium electrografting is a powerful method for imparting molecular functionality onto various substrates by forming a stable carbon-surface covalent bond. While the high reactivity of the aryl radical intermediate makes this method fast and reliable, it can also lead to the formation of an insulating and disordered multilayer film. These thick films affect electrochemical performance, especially for semiconductor substrates used in photoelectrochemical applications. We studied the effects of film thickness and composition by electrografting in situ-generated aminobenzene diazonium salts onto both n-type and p-type silicon electrodes at fixed potentials. Next, we attached ferrocene to the amine-terminated films and probed their (photo)electrochemical behavior. Cyclic voltammetry measurements showed decreased electrochemical reversibility with increasing diazonium film thickness; this reversibility was restored when ferrocene was incorporated throughout the film with a layer-by-layer deposition process. Finally, we compared the behavior of dark p-type electrodes to n-type photoelectrodes and observed differences in the electrochemical reversibility that we attribute to the change in potential drop across the two interfaces.

Enantioselective Arylation of Sulfenamides to Access Sulfilimines Enabled by Palladium Catalysis

AbstractSulfur‐containing functional groups have garnered considerable attention due to their common occurrence in ligands, pharmaceuticals, and insecticides. Nevertheless, enantioselective synthesis of sulfilimines, particularly diaryl sulfilimines remains a challenging and persistent goal. Herein we report a highly enantio‐ and chemoselective cross–coupling of sulfenamides with aryl diazonium salt to construct diverse S(IV) stereocenters by Pd catalysis. Bisphosphine ligands bearing sulfinamide groups play a crucial role in achieving high reactivity and selectivity. This approach provides a general, modular and divergent framework for quickly synthesizing chiral sulfilimines and sulfoximines that are otherwise challenging to access. In addition, the origins of the high chemoselectivity and enantioselectivity were extensively investigated using density functional theory calculations.

Eosin Y Catalyzed Photochemical Synthesis of Arylated Phenothiazones.

In the presence of Eosin Y (EY), the synthesis of substituted phenothiazones was carried out efficiently using various substituted 2-aminothiophenol, diazonium salts, and 1,4-napthaquinones (1,4-NQ) at room temperature (RT) (condition: green LED of 525 nm, 44 W; reaction time: 8 h, isolated yield: 68-90%). A fluorescence quenching experiment and density functional theory (DFT) calculations suggested that the triplet photoexcited state of EY (EY*; τT = 320 ± 10 ns) converts to EY+• via oxidative quenching by ArN2 + (-1.11 V vs SCE for EY* to EY+•) initially. Thiyl and aryl radicals were captured as TEMPO adducts in high-resolution mass spectroscopy (HRMS). The reaction was not inhibited by the addition of a singlet oxygen quencher such as 1,4-diazobicyclo [2.2.2] octane (DABCO), which suggests that singlet oxygen is not participated.

(Nanocarbons Division SES Young Investigator Award) Surface Chemistry of Nanocarbon Field-Effect Transistors: From Fundamental Physics to Biosensing

Conductive carbon nanomaterials are particularly well-suited to form field-effect biosensors (bioFETs) because they are stable in aqueous media and can be chemically coupled to biomolecules. Their reduced dimensionality, either 2D (graphene) or 1D (carbon nanotubes), is key to their sensitivity: because they are entirely surfaces, these materials present remarkable electrical transport properties that are easily altered by microscopic surface interactions. Biochemical processes occurring in close proximity to their surface can therefore be transduced as changes in their electrical conductance. Selectivity for specific biochemical events, however, must be engineered via functionalization of the nanomaterial, i.e. by modifying its surface with bioactive or biorecognition elements (e.g., antibodies, aptamers, enzymes, polymer layer). Our group recently analyzed a corpus of studies presenting graphene field-effect transistors (GFETs) as bioanalytical sensors for the quantitative detection of biomarkers in the form of nucleic acids, proteins, ions or small molecules [1]. We found a striking variance in the reported sensing performance between these studies, that could not be explained by controlling for differences in graphene material, analyte type and for evolution over the years. Our hypothesis is that the lack of microscopic control on the biointerface is likely the most important source of variation in such bioFETs, highlighting the critical need to improve our knowledge and control of the functionalization of nanocarbon materials.In this talk, I will discuss our work investigating the interplay between surface chemistry and electrical properties in nanocarbon field-effect transistors. In the first part, I will focus on covalent additions using aryldiazonium salts. I will review what we have learned on the fundamental physics of this chemistry from experiments and simulations on carbon nanotube devices [2-5], in particular on its disruptive character because of the formation of sp 3 defects in the carbon lattice. More recently, we investigated this same chemistry on GFET devices and observed a heterogeneous response in their electrical conductance. Aiming to solve this, we developed a novel approach to precisely trigger and stop the reaction in situ using the applied gate voltage [6], enabling unprecedented control on the functionalization rate and yield on GFETs. In the second part, I will describe our ongoing efforts to characterize and control the biofunctionalization of GFETs through non-covalent pyrene derivatives, using a combination of electrical measurements, microscopy and spectroscopy techniques, and theoretical simulations. Finally, I will discuss our ongoing translational projects in oncology, on adapting nanocarbon-based bioFETs in cancer diagnostics applications.[1] Béraud et al, Analyst 146 (2), 403-428 (2021)[2] Bouilly et al, Applied Physics Letters 101 (5), 053116 (2012)[3] Bouilly et al, ACS nano 9 (3), 2626-2634 (2015)[4] Bouilly et al, Nano Letters 16 (7), 4679-4685 (2016)[5] Côté et al, Physical Chemistry Chemical Physics 24 (7), 4174-4186 (2021)[6] Bazan et al, Nano Letters 22 (7), 2635-2642 (2022)