Reaction-based energy level modulation of a cyclometalated iridium complex for electrochemiluminescent detection of formaldehyde.

Formaldehyde is a toxic compound present in both the environment and living systems, and its detection is important due to its association with various pathological process. In this study, we report a new electrochemiluminescence (ECL) probe based on a cyclometalated iridium complex (IrHAA) for the selective detection of formaldehyde. The homoallylamine moiety in IrHAA reacts with formaldehyde, undergoing a 2-aza-Cope-rearrangement reaction to form a formyl group. Significant changes in the electronic properties and molecular orbital energies of the iridium complex through the functional group transformation result in enhanced ECL and radiometric phosphorescence changes, enabling the quantitative and selective detection of formaldehyde. The energetic requirements for ECL sensing were investigated, highlighting the importance of the excited state energy for achieving efficient ECL. The sensing mechanism was elucidated using NMR spectroscopy and MALDI-TOF analysis.

A photoluminescent and electrochemiluminescent probe based on an iridium(III) complex with a boronic acid-functionalised ancillary ligand for the selective detection of mercury(II) ions.

Exposure to mercury(II) ions (Hg2+) can cause various diseases such as Minamata disease, acrodynia, Alzheimer's disease, and Hunter-Russell syndrome, and even organ damage. Therefore, real-time and accurate monitoring of Hg2+ in environmental samples is crucial. In this study, we report a photoluminescent (PL) and electrochemiluminescent (ECL) probe based on a cyclometalated Ir(III) complex for the selective detection of Hg2+. The introduction of a reaction site, o-aminomethylphenylboronic acid, on the ancillary ligands allowed a prompt transmetalation reaction to take place between Hg2+ and boronic acid. This reaction resulted in significant decreases of the PL and ECL signals due to the photo-induced electron transfer from the Ir(III) complex to the Hg2+ ions. The probe was applied to the selective detection of Hg2+, and the signal changes revealed a linear correlation with Hg2+ concentrations in the range of 0-10 µM (LOD = 0.72 µM for PL, 8.03 nM for ECL). The designed probe allowed the successful quantification of Hg2+ in tap water samples, which proves its potential for the selective detection of Hg2+ in environmental samples.

Molecular Engineering for Enhanced Thermoelectric Performance of Single-Walled Carbon Nanotubes/π-Conjugated Organic Small Molecule Hybrids.

Hybridizing single-walled carbon nanotubes (SWCNTs) with π-conjugated organic small molecules (π-OSMs) offers a promising approach for producing high-performance thermoelectric (TE) materials through the facile optimization of the molecular geometry and energy levels of π-OSMs. Designing a twisted molecular structure for the π-OSM with the highest occupied molecular orbital energy level comparable to the valence band of SWCNTs enables effective energy filtering between the two materials. The SWCNTs/twisted π-OSM hybrid exhibits a high Seebeck coefficient of 110.4 ± 2.6 µV K-1 , leading to a significantly improved power factor of 2,136 µW m-1 K-2 , which is 2.6 times higher than that of SWCNTs. Moreover, a maximum figure of merit over 0.13 at room temperature is achieved via the efficient TE transport of the SWCNTs/twisted π-OSM hybrid. The study highlights the promising potential of optimizing molecular engineering of π-OSMs for hybridization with SWCNTs to create next-generation, efficient TE materials.

Electrochemiluminescence of dimethylaminonaphthalene-oxazaborine donor-acceptor luminophores.

Donor-acceptor (D-A) type molecules with a skeleton consisting of a dimethylaminonaphthalene donor and an oxazaborine acceptor were designed as efficient electrochemiluminescence (ECL) luminophores with tunable intramolecular charge transfer (ICT). The D-A ECL luminophores demonstrated that the ICT characteristics play a critical role in the electrochemistry and ECL of luminophores in the presence of tri-n-propylamine, which was rationalised experimentally and computationally. Furthemore, dual-peaked ECL-potential behaviours of the luminophores were rationalised using two competitive pathway ECL mechanisms, elucidated through the use of spooling ECL spectroscopy.

Ambient-Stable n-Type Carbon Nanotube/Organic Small-Molecule Thermoelectrics Enabled by Energy Level Control.

The stability of n-type organic and hybrid thermoelectric materials is limited in terms of their practical application to p-n parallel thermoelectric devices. We demonstrate the ambient stability of an n-type single-walled carbon nanotube/organic small-molecule (SWNT/OSM) hybrid by deepening the lowest occupied molecular orbital energy level. This hybrid exhibited the best figure of merit (0.032) among n-type SWNT/OSM hybrid thermoelectrics and an enhanced power factor of 291.0 µW m-1 K-2. Furthermore, we observed that the n-type thermoelectric stability of a hybrid of SWNT and pip containing two N-ethylpiperidinyl groups on both sides of a naphthalenediimide core was retained at 87% over 7 months (220 days) under ambient conditions without encapsulation.

Gp05, a Prophage-Encoded Virulence Factor, Contributes to Persistent Methicillin-Resistant Staphylococcus aureus Endovascular Infection.

Persistent methicillin-resistant Staphylococcus aureus (MRSA) endovascular infections represent a serious public health threat. We recently demonstrated that the presence of a novel prophage ϕSA169 was associated with vancomycin (VAN) treatment failure in experimental MRSA endocarditis. In this study, we assessed the role of a ϕSA169 gene, ϕ80α_gp05 (gp05), in VAN-persistent outcome using gp05 isogenic MRSA strain sets. Of note, Gp05 significantly influences the intersection of MRSA virulence factors, host immune responses, and antibiotic treatment efficacy, including the following: (i) activity of the significant energy-yielding metabolic pathway (e.g., tricarboxylic acid cycle); (ii) carotenoid pigment production; (iii) (p)ppGpp (guanosine tetra- and pentaphosphate) production, which activates the stringent response and subsequent downstream functional factors (e.g., phenol-soluble modulins and polymorphonuclear neutrophil bactericidal activity); and (iv) persistence to VAN treatment in an experimental infective endocarditis model. These data suggest that Gp05 is a significant virulence factor which contributes to the persistent outcomes in MRSA endovascular infection by multiple pathways. IMPORTANCE Persistent endovascular infections are often caused by MRSA strains that are susceptible to anti-MRSA antibiotics in vitro by CLSI breakpoints. Thus, the persistent outcome represents a unique variant of traditional antibiotic resistance mechanisms and a significant therapeutic challenge. Prophage, a critical mobile genetic element carried by most MRSA isolates, provides their bacterial host with metabolic advantages and resistance mechanisms. However, how prophage-encoded virulence factors interact with the host defense system and antibiotics, driving the persistent outcome, is not well known. In the current study, we demonstrated that a novel prophage gene, gp05, significantly impacts tricarboxylic acid cycle activity, stringent response, and pigmentation, as well as vancomycin treatment outcome in an experimental endocarditis model using isogenic gp05 overexpression and chromosomal deletion mutant MRSA strain sets. The findings significantly advance our understanding of the role of Gp05 in persistent MRSA endovascular infection and provide a potential target for development of novel drugs against these life-threatening infections.

Energy Level Modulation of Small Molecules Enhances Thermoelectric Performances of Carbon Nanotube-Based Organic Hybrid Materials.

Although numerous thermoelectric materials based on single-walled carbon nanotubes (SWNTs) and organic semiconductors have been reported during the past decade, the correlation between energy levels of organic semiconductors and thermoelectric performances of their hybrids is still ambiguous. In this study, we demonstrate that simultaneous modulation of the bandgap and highest occupied molecular orbital levels in organic small molecules (OSMs) largely improves the Seebeck coefficient and thus maximizes the figure of merit (ZT) of SWNT/OSM hybrids. SWNT/CzS with an enlarged bandgap and reduced barrier energy exhibited a synergistic increment in the Seebeck coefficient (108.7 µV K-1) and power factor (337.2 µW m-1 K-2), with the best ZT of 0.058 at room temperature among dopant-free carbon nanotube-hybridized thermoelectrics. The efficient charge carrier transport and reduced thermal conductivity of SWNT/CzS provided enhanced thermoelectric performance. Our strategy based on energy level modulation could be broadly applied for performance enhancement of organic and hybrid thermoelectric materials.

Efficient blue organic electrochemiluminescence luminophore based on a pyrenyl-phenanthroimidazole conjugate.

A pyrenyl-phenanthroimidazole (Py-PI) conjugate emitted strong blue electrochemiluminescence (ECL) emission via the reductive-oxidation co-reactant pathway, with an ECL efficiency 3.3 times higher than that of the 9,10-diphenylanthracene (DPA) reference compound.

Highly Selective Electrochemiluminescence Chemosensor for Sulfide Enabled by Hierarchical Reactivity.

Hydrogen sulfide (H2S) is a well-known toxic gas with the odor of rotten eggs. Several reaction-based electrochemiluminescence (ECL) chemosensors for H2S have been developed; however, no homogeneous ECL probe with high selectivity toward H2S in aqueous media has been reported. Herein, we report an iridium(III) complex-based ECL chemodosimetric probe employing two 7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD) groups known as a photo-induced electron transfer quencher and a reaction site for the selective detection of H2S; the detection mechanism involves H2S being clearly distinguished from biothiols based on the different cleavage rates of the two NBD groups and extremely weak ECL interferences caused by reaction by-products. The probe was rationally designed to improve selectivity toward H2S within the ECL analysis platform by enabling the removal of nonspecific background signals observed via fluorescence analysis. This analytical system exhibited remarkable selectivity toward H2S, a rapid reaction rate, and high sensitivity (LOD = 57 nM) compared to conventional fluorescence methods. Furthermore, the probe could successfully quantify H2S in tap water samples and commercial ammonium sulfide solutions, which demonstrates the effectiveness of this probe in field monitoring.

Click-To-Twist Strategy To Build Blue-to-Green Emitters: Bulky Triazoles for Electronically Tunable and Thermally Activated Delayed Fluorescence.

Discovery of a new chemical moiety is the foundation to build new functional materials. For charge-transfer-type thermally activated delayed fluorescence (TADF) emitters, donor, acceptor, and π-spacer are the three key structural components. We invented a "click-to-twist" strategy to prepare a triazole-based acceptor unit that allows for a systematic modulation of the electronic and steric properties to control the excited-state photophysics. Taking the modular approach, six different emitters were prepared by varying the donor strength and π-spacer sterics for mix-and-match. These materials display deep blue to sky blue emissions in solutions, as well as apparent TADF characteristics in doped films. Organic light emitting diodes fabricated with these new TADF materials exhibit high external quantum efficiencies of up to 20.7% and maximum luminance of 6823 cd m-2. Building upon an intuitive and operationally straightforward method to build sterically congested molecules, this work showcases a new strategy to diversify TADF emitters by a mechanism-based design and modular synthesis.

Supramolecular Functionalization for Improving Thermoelectric Properties of Single-Walled Carbon Nanotubes-Small Organic Molecule Hybrids.

Single-walled carbon nanotube (SWCNTs-P)-small organic molecule hybrid materials are promising candidates for achieving high thermoelectric (TE) performance. In this study, we synthesized rod-coil amphiphilic molecules, that is, tri(ethylene oxide) chain-attached bis(bithiophenyl)-terphenyl derivatives (1 and 2). Supramolecular functionalization of SWCNTs-P with 1 or 2 induced charge-transfer interactions between them. Improved TE properties of the supramolecular hybrids (SWCNTs-1 and SWCNTs-2) are attributed to increased charge-carrier concentration (electrical conductivity), interfacial phonon scattering (thermal conductivity), and energy difference between the transport and Fermi levels (ETr - EF; Seebeck coefficient). SWCNTs-2 exhibited a ZT of 0.42 × 10-2 at 300 K, which is 350% larger than that of SWCNTs-P. Furthermore, 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ)-doped SWCNTs-2 showed the highest ZT value of 1.96 × 10-2 at 300 K among SWCNTs-P/small organic molecule hybrids known until now. These results demonstrated that the supramolecular functionalization of SWCNTs-P with small organic molecules could be useful for enhancement of TE performance and applications in wearable/flexible thermoelectrics.

Electrochemiluminescent detection of glucose in human serum by BODIPY-based chemodosimeters for hydrogen peroxide using accelerated self-immolation of boronates.

BODIPY-based ECL chemodosimeters were developed for the detection of hydrogen peroxide. The reactivity of boronate towards hydrogen peroxide was enhanced by adjacent fluorine atoms. In combination with glucose oxidase, a fluorine-substituted probe successfully quantified the glucose level in human serum, providing its potential as a versatile tool in point-of-care testing applications.

The Stringent Response Contributes to Persistent Methicillin-Resistant Staphylococcus aureus Endovascular Infection Through the Purine Biosynthetic Pathway.

Persistent methicillin-resistant Staphylococcus aureus (MRSA) endovascular infections represent a significant clinical-therapeutic challenge. Of particular concern is antibiotic treatment failure in infections caused by MRSA that are "susceptible" to antibiotic in vitro. In the current study, we investigate specific purine biosynthetic pathways and stringent response mechanism(s) related to this life-threatening syndrome using genetic matched persistent and resolving MRSA clinical bacteremia isolates (PB and RB, respectively), and isogenic MRSA strain sets. We demonstrate that PB isolates (vs RB isolates) have significantly higher (p)ppGpp production, phenol-soluble-modulin expression, polymorphonuclear leukocyte lysis and survival, fibronectin/endothelial cell (EC) adherence, and EC damage. Importantly, an isogenic strain set, including JE2 parental, relP-mutant and relP-complemented strains, translated the above findings into significant outcome differences in an experimental endocarditis model. These observations indicate a significant regulation of purine biosynthesis on stringent response, and suggest the existence of a previously unknown adaptive genetic mechanism in persistent MRSA infection.

Potential-Dependent Electrochemiluminescence for Selective Molecular Sensing of Cyanide.

Although tremendous efforts have been devoted to providing specificity for molecular sensors, most of the methods focus on the structural variation of the binding or reaction site to improve selectivity. Herein, we report a new approach in which a chemical probe, possessing a mediocre recognition site, can successfully discriminate a target among various interferences only with electrochemical manipulation. The synthetic probe (1) was designed to react with a cyanide anion (CN-), and its dicyanovinyl group has selectivity toward CN- along with sulfides and biothiols resulting in similar adducts. However, the binding adduct between 1 and CN- (1-CN-) has significantly different energy levels that are only able to undergo electrochemical oxidation under ∼1.2 V (vs Ag/AgCl), generating strong electrochemiluminescence (ECL). The ECL emission from 1-CN- successfully discriminates CN- without any interferences from other analytes including sulfides and thiols and exhibits a linear correlation with CN- in a range of 1-400 µM (LOD = 0.04 µM, n = 5). Density functional theory (DFT) calculations and electrochemical studies supported the mechanism of CN- discrimination. The approach was finally applied to direct trace analysis of CN- in tap water (≥1 µM) and showed excellent performance suggesting a new, versatile, and rapid determination method for molecular toxins in real samples.

Enhanced Humid Reliability of Organic Thermoelectrics via Crosslinking with Glycerol.

Poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) has shown significant achievements in organic thermoelectrics (TEs) as an alternative for inorganic counterparts. However, PEDOT:PSS films have limited practical applications because their performance is sensitive to humidity. Crosslinking additives are utilized to improve the reliability of PEDOT:PSS film through enhancing hydrophobicity; among these, polyethylene glycol (PEG) is a widely-used additive. However, ether groups in PEG induce water molecules in the film through the hydrogen bond, which deteriorates the TE reliability. Here, we enhance the TE reliability of the PEDOT:PSS film using glycerol as an additive through the crosslinking reaction between the hydroxyl group in glycerol and the sulfonic acid in PEDOT:PSS. The TE reliability (1/Power factor (PF)) of PEG solution-treated PEDOT:PSS film (PEG solution-treated film) was 57% of its initial absolute value (0 h), after 288 h (two weeks) in a humid environment (95% relative humidity, 27 °C temperature). On the other hand, the glycerol solution-treated PEDOT:PSS film (glycerol solution-treated film) exhibited superior TE reliability and preserved 75% of its initial 1/PF. Furthermore, glycerol vapor treatment enabled the film to have stronger TE humid reliability, maintaining 82% of its initial 1/PF, with the same condition. This enhancement is attributed to the increased hydrophobicity and lower oxygen content of the glycerol vapor-treated PEDOT:PSS film (glycerol vapor-treated film), which provides little change in the chemical composition of PEDOT:PSS.

Molecular Recognition of Pyrophosphate with Extended Bis(Zn(II)-DPA) Derivatives.

A series of pyrophosphate (PPi) receptors were synthesized, and their binding affinities toward both PPi and adenosine triphosphate were evaluated in N-(2-hydroxyethyl)piperazine-N'-ethanesulfonic acid-buffered solution. The presence of two hydrogen bond donors slightly retarded the reaction rate of anionic guest exchange, while four had a significant retardation effect. A macrocyclic receptor, 17, exhibited superior selectivity toward PPi compared with acyclic receptors, presumably due to effective steric interactions. Isothermal titration calorimetry experiments and potentiometric titration experiments revealed the effect of the substituent structure on the degree of anion guest stabilization and the deprotonation of water molecules bound to zinc(II) ions, as well as the guest binding thermodynamics.

Photoluminescence and Electrochemiluminescence Dual-Signaling Sensors for Selective Detection of Cysteine Based on Iridium(III) Complexes.

Cysteine (Cys) is important in biosynthesis, detoxification, and metabolism. The selective detection of Cys over structurally similar homocysteine (Hcy) or glutathione (GSH) remains an immense challenge. Although there are many methods for detecting Cys, photoluminescence (PL) and electrochemiluminescence (ECL) techniques are well-suited for clinical diagnostics and analytical technology because of their high sensitivities. Herein, we report PL and ECL dual-channel sensors using cyclometalated iridium(III) complexes for the discrimination of Cys from Hcy and GSH. The sensors react with cysteine preferentially because of kinetic differences in intramolecular conjugate addition/cyclization, enabling phosphorescence enhancement and ECL decrease in the blue-shifted region. Sensor 1 shows ratiometric PL turn-on and ECL turn-off for Cys. In addition, unique ECL-enhancing behavior of sensor 1 toward GSH enables discrimination between Cys and GSH. Sensor 1 was successfully applied to the detection of Cys in human serum by the ECL method. We demonstrate the first case of a Cys-selective PL and ECL dual-channel chemodosimetric sensor based on cyclometalated iridium(III) complexes and expect that the rational design of efficient PL and ECL dual-channel sensors will be useful in diagnostic technology.

Iridium(iii) complex-based electrochemiluminescent probe for H2S.

Since abnormal levels of hydrogen sulphide (H2S) correlate with various diseases, simple methods for its rapid and sensitive detection are highly required. Herein, we introduce a new electrochemiluminescent probe 1 for H2S based on a cyclometalated iridium(iii) complex. o-(Azidomethyl)benzoate ester groups on the main ligands of probe 1 react selectively with H2S, resulting in cascade reactions involving H2S-mediated reduction and intramolecular cyclization/ester cleavage. With this structural change induced by H2S, the intrinsic electrochemiluminescence (ECL) of 1 decreased greatly due to the unfavourable electron transfer of a tripropylamine (TPA) radical. Probe 1 showed a high ECL turn-off ratio and good selectivity for H2S over various anions and biothiols. The sensing mechanism of H2S was elucidated using 1H NMR spectroscopy and MALDI-TOF mass spectrometry analyses.

Electrogenerated Chemiluminescent Chemodosimeter Based on a Cyclometalated Iridium(III) Complex for Sensitive Detection of Thiophenol.

Thiophenol is the simplest aromatic thiol that is utilized for various applications in industry and agriculture. However, it should be used with care because thiophenol is readily absorbed into the human body by inhalation and ingestion, which leads to serious internal injuries. Thus, there is an urgent need for real-time and accurate monitoring of thiophenol. Despite remarkable advantages of electrogenerated chemiluminescence (ECL) analysis, ECL thiophenol probes have never been reported. Herein, a new strategy for the rapid detection of thiophenol by use of an ECL turn-on chemodosimeter based on a cyclometalated Ir(III) complex is described. This analytical system showed superior sensitivity [limit of detection (LOD) value, 3.8 nM] in comparison to the conventional fluorescence method. In addition, our system exhibited remarkable selectivity and reaction rate toward thiophenol over other analytes. Moreover, it was successfully applied to quantify thiophenol in real water samples, providing a new proof-of-concept for field monitoring based on ECL.

Ir(iii) complex-based phosphorescence and electrochemiluminescence chemodosimetric probes for Hg(ii) ions with high selectivity and sensitivity.

Mercury, one of the most prevalent toxic metal elements, poses severe risks to human health and the environment. Several molecular probes have been developed for colorimetric and fluorometric detection of Hg(ii) ions. Nevertheless, development of a rapid, selective, and sensitive probe for Hg(ii) ions remains important. Herein, we report three Ir(iii) complex-based phosphorescence and electrochemiluminescence chemodosimeters for the selective detection of Hg(ii) ions. The acetylacetonate ancillary ligand of probe 1 reacts selectively with the Hg(ii) ion, inducing phosphorescence enhancement with a concomitant blue-shift. Meanwhile, the Hg(ii) ion selectively quenches the phosphorescence of probe 2. Probes 1 and 2 showed low detection limits (LOD) of 73 and 160 nM, respectively. In addition, the Hg(ii) ion level was successfully monitored by the electrochemiluminescence decrement of probe 9 with a good linear correlation between 0 and 40 µM, with a detection limit of 170 pM.