Ultrasensitive self-powered biosensor with facile chemical signal amplification strategy using hydrogen peroxide-triggered silver oxidation reaction.

The amplification strategies used for self-powered biosensor based on biofuel cell (BFC-SPB) need to be further developed. Because the currently developed strategies utilized the complicated hybridization of DNA or poorly readable current signal of capacitors for amplification, which limits the practical application in public health emergencies. Here, we present a facile chemical amplification strategy for BFC-SPB. The 5-min amplification was triggered by simply adding H2O2 solution dropwise to the sensing cathode after the formation of the immune sandwich. The Ag NP of immunoprobe were oxidized to Ag(I), which can be served as the electron acceptor of the cathode. The amount of immunoprobe was positively correlated with that of the antigen, resulting in corresponding and high concentration of Ag(I) after the amplification, which enhanced the ability of the cathode as the electron acceptor. Meanwhile the glucose oxidation reaction (GOR) was performed on the bioanode modified with glucose oxidase (GOx). After assembling the bioanode and sensing cathode, the open circuit voltage of the BFC-SPB, measured by digital multimeter, distinctly rised with the elevated concentration of the antigen. To demonstrate the proof of concept, immunoglobulin G (IgG), selecting as a model analyte, was sensitively detected using this method. Result indicated that the limit of detection was 4.4 fg mL-1 (0.03 amol mL-1) in the linear range of 1 pg mL-1-10 µg mL-1. This work initiates a brand-new way of chemical amplification strategy for BFC-SPB, and offers a promising platform for practical applications.

Quantification of Glycated Hemoglobin in Total Hemoglobin by a Simultaneous Dual-Signal Acquisition Approach.

The glycated hemoglobin (HbA1c) level, which is defined as the ratio of HbA1c to total hemoglobin (tHb, including glycated and unglycated hemoglobin), is considered one of the preferred indicators for diabetes monitoring. Generally, assessment of the HbA1c level requires separate determination of tHb and HbA1c concentrations after a complex separation step. This undoubtedly increases the cost of the assay, and the loss or degradation of HbA1c during the separation process results in a decrease in the accuracy of the assay. Therefore, this study explored a dual-signal acquisition method for the one-step simultaneous evaluation of tHb and HbA1c. Quantification of tHb: graphene adsorbed carbon quantum dots and methylene blue were utilized as the substrate material and linked to the antibody. tHb was captured on the substrate by the antibody. The unique heme group on tHb catalyzed the production of •OH from H2O2 to degrade methylene blue on the substrate, and a quantitative relationship between the tHb concentration and the methylene blue oxidation current signal was constructed. Quantification of HbA1c: complex labels with HbA1c recognition were made of ZIF-8-ferrocene-gold nanoparticles-mercaptophenylboronic acid. The specific recognition of the boronic acid bond with the unique cis-diol structure of HbA1c establishes a quantitative relationship between the oxidation current of the label-loaded ferrocene and the concentration of HbA1c. Thus, the HbA1c level can be assessed with only one signal readout. The sensor exhibited extensive detection ranges (0.200-600 ng/mL for tHb and 0.100-300 ng/mL for HbA1c) and low detection limits (4.00 × 10-3 ng/mL for tHb and 1.03 × 10-2 ng/mL for HbA1c).

CRISPR/Cas9-mediated knockout of a male accessory glands-specific gene takeout1 decreases the fecundity of Zeugodacus cucurbitae female.

BACKGROUND: The melon fly, Zeugodacus cucurbitae (Coquillett), is an invasive Tephritidae pest with robust fertility. The male accessory glands (MAGs) form a vital organ that ensures insect reproductive efficiency. Most of the secreted proteins by MAGs exhibit a male bias expression. Takeout, one of these proteins, is abundantly present in the MAGs of many insects. RESULTS: In this study, we identified 32 takeout genes in Z. cucurbitae. The phylogenetic analysis and multiple sequence alignment results showed that Zctakeout1 is the most related homolog to the MAGs-specific takeout in Tephritidae. The real-time quantitative PCR results showed that Zctakeout1 was exclusively expressed in the male adult stage, and its expression level gradually increased with the increase in age and then remained stable at the sexually matured stage. The distribution among tissues demonstrated the specific expression of Zctakeout1 in the MAGs, and fluorescence immunohistochemical results confirmed the presence of Zctakeout1 in close proximity to binuclear cells of the mesoderm epidermal MAGs. In continuation, CRISPR/Cas9-mediated genome editing was employed, resulting in successfully generating a homozygous strain with an +8 bp insertion. The mating experiments with the Zctakeout1-/- males resulted in significant reductions in both the mating rate and egg production of females. CONCLUSION: These findings prove that the MAGs-specific Zctakeout1 is essential in regulating fecundity in female Z. cucurbitae fruit flies. Our data suggests its utilization in future essential insect-specific gene-directed sterility insect technique (SIT) by the genetic manipulation to keep these important Tephritidae populations under control. © 2024 Society of Chemical Industry.

A Recyclable Electrochemical Reduction of Aldehydes and Ketones to Alcohols Using Water as the Hydrogen Source and Solvent.

There are several challenging problems such as the usage of combustible and hazardous hydrogen sources and severe environmental pollution in the conventional reduction of aldehydes/ketones to alcohols. We report here a practical, safe, and green electrochemical reduction, which solves these problems to a large extent. Through an undivided cell, Zn(+) and Sn(-) as the electrode, tetrabutylammonium chloride (TBAC) as the electrolyte, water as the solvent and hydrogen source, a wide range of aldehydes and ketones are converted into the corresponding alcohols in mild conditions. Furthermore, the electrolytes and water can be recycled, and reductive deuteration can be achieved by simply using D2O as the solvent. Finally, the reduction can be smoothly scaled up to a kilogram level.

Two heat shock cognate 70 genes involved in spermatogenesis regulate the male fertility of Zeugodacus cucurbitae, as potential targets for pest control.

The melon fly Zeugodacus cucurbitae Coquillett (Diptera: Tephritidae) is an agricultural quarantine pest threatening fruit and vegetable production. Heat shock cognate 70 (Hsc70), which is a homolog of the heat shock protein 70 (Hsp70), was first discovered in mice testes and plays an important role in spermatogenesis. In this study, we identified and cloned five Hsc70 genes from melon fly, namely ZcHsc70_1/2/3/4/5. Phylogenetic analysis showed that these proteins are closely related to Hsc70s from other Diptera insects. Spatiotemporal expression analysis showed that ZcHsc70_1 and ZcHsc70_2 are highly expressed in Z. cucurbitae testes. Fluorescence in situ hybridization further demonstrated that ZcHsc70_1 and ZcHsc70_2 are expressed in the transformation and maturation regions of testes, respectively. Moreover, RNA interference-based suppression of ZcHsc70_1 or ZcHsc70_2 resulted in a significant decrease of 74.61% and 63.28% in egg hatchability, respectively. Suppression of ZcHsc70_1 expression delayed the transformation of sperm cells to mature sperms. Meanwhile, suppression of ZcHsc70_2 expression decreased both sperm cells and mature sperms by inhibiting the meiosis of spermatocytes. Our findings show that ZcHsc70_1/2 regulates spermatogenesis and further affects the male fertility in the melon fly, showing potential as targets for pest control in sterile insect technique by genetic manipulation of males.

A facile electrochemical immunosensor based on EDTA-Pb2+ complexation reaction.

The sensitivity of electrochemical (EC) sensors has been improved through the development of multiple approaches. However, the majority of EC sensors were limited in their practical application by high costs or tedious procedures. Herein, based on ethylenediaminetetraacetic acid (EDTA)-Pb2+ complexation reaction, a facile and affordable immunosensor was designed. Pb2+-magnesium silicate hydrate was served as the sensing substrate. The immunorecognition process was carried out in the Eppendorf tube, and antibody-functionalized Pb2+-polydopamine was utilized as immunoprobe. In the tube, the quantitative and appropriate excess of EDTA was introduced to complex with Pb2+ on the immunoprobes. The remaining EDTA was added to the sensing substrate surface to coordinate with some Pb2+ in it. This leaded to the reduction of the EC signal of Pb2+, which was related to the antigen concentration. Using prostate-specific antigen as the model analyte, the sensitive detection was realized with a low limit of detection (30.49 fg mL-1). Remarkably, the assay results were available within 24 min, sensibly faster than the most existing EC sensors.

Overexpression of miR-927-5p suppresses stalky expression and negatively reduces the spermatid production in Zeugodacus cucurbitae.

BACKGROUND: The melon fly, Zeugodacus cucurbitae Coquillett, is one of the major pests attacking Cucurbitaceae crops. Identifying critical genes or proteins regulating fertility is essential for sustainable pest control and a research hotspot in insect physiology. MicroRNAs (miRNAs) are short RNAs that do not directly participate in protein translation, but instead function in post-transcriptional regulation of gene expression involved in male fertility. RESULTS: We found that miR-927-5p is highly expressed in the testes and investigated its function in spermatogenesis in Z. cucurbitae. Fluorescence in situ hybridization (FISH) showed miR-927-5p in the transformation and maturation region of the testis, and overexpression of miR-927-5p reduced the number of sperms by 53%. In continuation, we predicted 12 target genes of miR-927-5p using bioinformatics combined with transcriptome sequencing data, and found that miR-927-5p targets the new gene Stalky in insects, which was validated by quantitative real-time PCR, RNA pull-down and dual luciferase reporter assays. FISH also confirmed the co-localization of miR-927-5p and the transcript Stalky_1 in the testis. Moreover, silencing of Stalky_1 by RNA interference reduced the number of sperms by 32% and reduced sperm viability by 39% in physiologically mature male adults. Meanwhile, the silencing of Stalky_1 also resulted in low hatchability. CONCLUSION: Our work not only presents a new, so far unreported mechanism regulating spermatogenesis by miR-927-5p targeting a new unknown target, Stalky, which is providing new knowledge on the regulatory network of insect spermatogenesis, but also lays a foundation for the development of SIT against important tephritid fly pests. © 2024 Society of Chemical Industry.

Novel dual-responsive hydrogel composed of polyacrylamide/Fe-MOF/zinc finger peptide for construction of electrochemical sensing platform.

Responsive hydrogels have received much attention for improving the detection performance of electrochemical sensors because of their special responsiveness. However, current responsive hydrogels generally suffer from long response times, ranging from tens of minutes to several hours. This situation severely limits the detection performance and practical application of electrochemical sensors. Here, an electrochemical sensing platform was constructed by employing dual-responsive polyacrylamide/zinc finger peptide/Fe-MOF hydrogel (PZFH) as the silent layer, sodium alginate-Ni2+-graphene oxide hydrogel as the signal layer. GOx@ZIF-8, as the immunoprobe, catalyzed glucose to H2O2 and gluconic acid, resulting in the cleavage of immunoprobe as the pH decreased and subsequent release of Zn2+ ions. During the process of Fe-MOF converting from Fe3+ to Fe2+, free radicals were generated and used to destroy the structure of the PZFH. Cysteine and histidine in the zinc finger peptide can specifically bind to Zn2+ to create many pores in PZFH, exposing the signal layer. These synergistic effects rapidly decreased the impedance of PZFH and increased the electrochemical signal of Ni2+. The electrochemical sensing platform was used to detect pro-gastrin-releasing peptide with response times as short as 7 min of PZFH, a wide linear range from 100 ng mL-1 to 100 fg mL-1, and an ultra-low limit of detection of 14.24 fg mL-1 (S/N = 3). This strategy will provide a paradigm for designing electrochemical sensors.

Schiff base fluorescent sensor with aggregation induced emission characteristics for the sensitive and specific Fe3+ detection.

An aggregation induced emission based compound ((E)-4-((2-hydroxy-5-methoxybenzylidene)amino)benzoic acid) was synthesized through facile Schiff base condensation and characterized by various spectral techniques. The as-prepared compound represented a typical aggregation induced emission behavior in aqueous solution and exploited as a turn-off fluorescent sensor for Fe3+ detection in THF-H2O system (3:7, v/v) with high sensitivity and selectivity. The mechanism of the fluorescence quenching was intensively studied, which was attributed to both dynamic quenching and inner filter effect. The fluorescence probe displayed a highly broad dynamic response range (0.5-500 µM) for selective detection of Fe3+ with a limit of detection of 0.079 µM. The proposed method was successfully employed for detection and quantification of Fe3+ in human urine samples and proved to have potential for practical applications in biological field.

Faraday cage-type self-powered immunosensor based on hybrid enzymatic biofuel cell.

Self-powered immunosensors (SPIs) based on enzymatic biofuel cell (EBFC) have low sensitivity and poor stability due to the high impedance of the immune sandwich and the vulnerability of enzymes to environmental factors. Here, we applied the Faraday cage-type sensing mode on a hybrid biofuel cell (HBFC)-based SPI for the first time, which exhibited high sensitivity and stability. Cytokeratin 19 fragment (CYFRA 21-1) was used as a model analyte. Au nanoparticle-reduced graphene oxide (Au-rGO) composite was used as the supporting matrix for immunoprobe immobilized with detection antibody and glucose dehydrogenase (GDH), also the builder for Faraday cage structure on the bioanode in the presence of antigen. After the combination of immunoprobe, antigen, and the antibody on the bioanode, the Faraday cage was constructed in case the AuNP-rGO was applied as a conductive cage for electron transfer from GDH to the bioanode without passing through the poorly conductive protein. With the assistance of the Faraday cage structure, the impedance of the bioanode decreased significantly from 4000 to 300 Ω, representing a decline of over 90%. The sensitivity of the SPI, defined as the changes of open circuit voltage (OCV) per unit concentration of the CYFRA 21-1, was 68 mV [log (ng mL-1)]-1. In addition, Fe-N-C was used as an inorganic cathode material to replace enzyme for oxygen reduction reaction (ORR), which endowed the sensor with 4-week long-term stability. This work demonstrates a novel sensing platform with high sensitivity and stability, bringing the concept of hybrid biofuel cell-based self-powered sensor.

Anti-Fouling Strategies of Electrochemical Sensors for Tumor Markers.

The early detection and prognosis of cancers require sensitive and accurate detection methods; with developments in medicine, electrochemical biosensors have been developed that can meet these clinical needs. However, the composition of biological samples represented by serum is complex; when substances undergo non-specific adsorption to an electrode and cause fouling, the sensitivity and accuracy of the electrochemical sensor are affected. In order to reduce the effects of fouling on electrochemical sensors, a variety of anti-fouling materials and methods have been developed, and enormous progress has been made over the past few decades. Herein, the recent advances in anti-fouling materials and strategies for using electrochemical sensors for tumor markers are reviewed; we focus on new anti-fouling methods that separate the immunorecognition and signal readout platforms.

Electrochemical sensing interface based on the oriented self-assembly of histidine labeled peptides induced by Ni2+ for protease detection.

To construct an electrochemical sensing interface which was convenient for protease recognition and cleavage, we designed a strategy for directed self-assembly of histidine-tagged peptides on the electrode led by Ni2+ ions for electrochemical detection of prostate specific antigen (PSA). The electrode surface was first functionalized using carboxylated multiwalled carbon nanotubes and then modified with the metal ion chelating agent (5 S)-N-(5-Amino-1-carboxypentyl) iminodiacetic acid (NIA). After the Ni2+ was captured by NIA, the designed immune-functional peptide could be oriented assembly to the electrode interface through the imidazole ring of histidine at the tail, completing the construction of the recognition layer. Therefore, by adding the analyte PSA to identify and shear the immune-functional peptide, the ferrocene in its head was released, resulting in a reduction in the electrical signal, enabling sensitive detection. In addition, the self-assembly layer could be removed by pickling to realize the reconstruction of the recognition layer. Under optimal conditions, the electrochemical sensor had an ultralow detection limit of 11.8 fg mL-1 for PSA, with a wide detection range from 1 pg mL-1 to 100 ng mL-1. In this work, an electrochemical sensing interface based on the histidine-tagged peptide induced by Ni2+ was formed to enable controllable oriented assembly on the electrode surface, and the recognition layer could be reconstructed via pickling, providing a potential approach for the design of repeatable interfaces.

Universal and High-Speed Zeptomolar Protein Serum Assay with Unprecedented Sensitivity.

The accurate detection of trace protein biomarkers is critical for disease diagnosis, healthcare, and pathology research. Currently, the main predicaments of techniques are low sensitivity, prolonged procedures, and the need for specialized devices. Moreover, multistep handling and nonspecific biofouling can lead to high background noise and false positives. To overcome these barriers, a novel ultrasensitive electrochemical platform was developed by combining an electrochemistry approach with the silver mirror reaction to detect proteins at the zeptomolar level. This assay can be accomplished in about only 18 min. As a proof of the concept, human immunoglobulin G (h-IgG) as a model analyte exhibited an ultralow detection limit of 6.31 ag mL-1 (0.04 zeptomoles mL-1). This strategy can be exploited as a universal approach for the ultrasensitive detection of various proteins in clinical diagnostics and point-of-care testing.

Expression and Role of Vitellogenin Genes in Ovarian Development of Zeugodacus cucurbitae.

Vitellogenin (Vg) genes encode the major egg yolk protein precursor in arthropods. In this study, four Vgs were identified in Zeugodacus cucurbitae (Coquillett). Sequence analysis showed that four ZcVgs had the conserved Vg domain. Phylogenetic analysis indicated that four ZcVgs were homologous to the Vgs of Tephritidae insects. The temporal and spatial expression patterns of ZcVgs were analyzed by quantitative real-time polymerase chain reaction (RT-qPCR), and the four ZcVgs showed high expression levels in female adults, especially in the fat body. The expression of ZcVg1 and ZcVg3 was down-regulated by a low dosage (0.5 µg) of 20-hydroxyecdysone (20E), and ZcVg2, ZcVg3, and ZcVg4 were up-regulated by a high dosage (1.0 and 2.0 µg) of 20E. The expression of ZcVg1 and ZcVg2 was up-regulated by 5 µg of juvenile hormone (JH), while all of the ZcVgs were down-regulated by a low and high dosage of JH. Expression of ZcVgs was down-regulated after 24 h of starvation and recovered to normal after nutritional supplementation. After micro-injection of the gene-specific double-stranded RNA, the ZcVgs' expression was significantly suppressed, and ovarian development was delayed in Z. cucurbitae females. The results indicate that RNA interference of reproduction-related genes is a potential pest control method that works by manipulating female fertility.

A dual-channel indicator of fish spoilage based on a D-π-A luminogen serving as a smart label for intelligent food packaging.

Advances in food monitoring benefit tremendously from the naked-eye observation and device-miniaturization of colorimetric and fluorometric methods. Intelligent food packaging, containing a built-in sensor inside food bags, is capable of real-time monitoring of food quality by visibly discernible out-put signals, which effectively ensures food safety. We synthesized a donor-π-acceptor (D-π-A) compound DPABA, and disclosed its fluorescence response to amines. According to quantum chemical calculations, DPABA is apt to D-A coupling in aggregated state, causing the formation of exciplex/excimer together with intermolecular charge/energy transfer to the disadvantage of light emission; while the evasion of amine vapors would decouple the intermolecular D-A interactions to induce stronger emission with shorter wavelength. Utilizing the amine vapor generated by fish, DPABA can serve as an indicator for freshness monitoring. To create an intelligent food package, the compound was made into cellulose film, which was further cut into smart labels to be encapsulated into food bags. The as-prepared smart label exhibits red color under ambient light and glows weak red emission under UV light, while it turns into faint yellow color in response to putrid fish, and its emission changes to bright cyan. The output signals can be accurately recorded by instrument, and detected by naked eye, suggesting high signal contrast. In addition, the smart label exhibits different changing scope in response to different degree of freshness, showing high potential for in-field detection.

Proton-responsive annunciator based on i-motif DNA structure modified metal organic frameworks for ameliorative construction of electrochemical immunosensing interface.

Reformative exploitation for metal organic frameworks (MOFs) has been a topic subject in electrochemical sensing, in which the loading of electroactive species is always introduced to enable them to generate electrochemical signal. However, insulation shielding of MOFs and flimsy combination method interfere with the signal readout of electroactive dyes when they are co-immobilized on electrode surface, indicating that an amelioration is imperatively proposed to solve these issues. Herein, a proton-activated annunciator for responsive release of methylene blue (MB) based on i-motif DNA structure modified UIO-66-NH2 was presented to design electrochemical immunosensor (Squamous cell carcinoma antigen was used as the model analyte). With the catalysis of a ZIF-8 immunoprobe contained glucose oxidase (GOx) to glucose in test tube, protons are produced in ambient solution and then they can be used as the key to unlock the i-motif functionalized UIO-66-NH2, releasing the loaded MB molecules to be readout on an improved electrode. This stimuli-responsive mode not merely eliminates the insulation effect of MOFs but also provides a firm loading method for electroactive dyes. Under the optimal conditions, the proposed immunoassay for SCCA had displayed excellent performance with a wide linear range from 1 µg mL-1 to 1 pg mL-1 and an ultralow detection limit of 1.504 fg mL-1 (S/N = 3) under the optimal conditions.

Responsive-released strategy based on lead ions-dependent DNAzyme functionalized UIO-66-NH2 for tumor marker.

Signal labeling on electrode interface is an important step during the construction of immunosensor and most signal substances are directly affixed on the immunoprobe or substrate so that some problems such as flimsy labeling method and interference of insulating proteins on electrode surface have been existed to affect their readout. In order to solve above problems in electrochemical immunoassay, a lead ions-decodable autocephalous signal integrator based on UIO-66-NH2 was proposed for the detection of prostate specific antigen (PSA). Briefly, a lead ions-dependent DNAzyme functionalized UIO-66-NH2, in which methylene blue was encapsulated, was independently dispersed in solution phase to be closely associated with the lead sulfide labeled sandwich bioconjugates, and internal methylene blue molecules can be sustained released once a cationic exchange reaction was occurred between lead sulfide label and adscititious silver ions. Based on this designing, immunoassay for PSA was effectively connected with the dynamic behavior of methylene blue molecules through the cleavage of DNAzyme on MOFs surface and performed a wide linear range from 1 pg mL-1 to 10 ng mL-1 and a satisfactory detection limit with 0.34 pg mL-1. The proposed strategy was expected to offer more valuable information for the application of MOFs in early and accurate cancer diagnosis.

In situ growth of electroactive polymers via ATRP to construct a biosensing interface for tumor marker.

A novel biosensing interface for tumor markers was designed based on the atom transfer radical polymerization (ATRP) of poly(isopropenylphenol) (PPPL) in situ initiated by the fixing of p-chloromethyl benzoic acid on the surface of amino-modified electrodes. It was found that the electrochemical activity of PPPL itself can provide sufficient signals for these biosensors, which can avoid signal leakage and streamline the interface modification process. Cu(II) ions absorbed on the carbon spheres and then were released via acid stimulation to act as a catalyst to participate in the interface polymerization with ATRP. As the concentration of targets increased, more Cu(II) ions were released, and the electrochemical signal of polymers was enhanced. Therefore, the sensitive detection of carbohydrate antigen 19-9 (CA19-9) as a model target was achieved, with an ultralow limit of detection of 39 µU mL-1 and wide detection range from 100 µU mL-1 to 100 U mL-1 under optimal conditions. Furthermore, this method achieved satisfying performance in human blood serum with good inter-assay precision (RSD < 6%) and satisfactory recovery of ~ 99-105%. According to the results, this work is of great significance for constructing biosensor interfaces via in situ polymerization. A novel biosensing interface for tumor marker was designed based on atom transfer radical polymerization (ATRP), which poly(isopropenylphenol) with electrochemical signal was fabricated in situ on electrode.

A novel electrochemical sensor based on process-formed laccase-like catalyst to degrade polyhydroquinone for tumor marker.

Methods to improve the sensitivity of electrochemical sensors based on catalytic reactions generally require adscititious or pre-modified catalysts, which make the sensitive detection of sensors extremely challenging. This is because the activity of the catalyst is susceptible to the storage and modification process, such as aggregation during storage or loss of active sites during multi-step modification, which impairs the performance of the sensor. To solve this thorny issue, a novel electrochemical sensor based on a process-formed laccase-like catalyst was constructed for sensitive detection of tumor markers. Cu2+-polydopamine (CuPDA) combined with antibody (Ab2) were employed as copper-containing immunoprobe, which released Cu(Ⅱ) ions under acidic stimulation. Cu(Ⅱ) ions coordinate with the self-assembly cationic diphenylalanine-glutaraldehyde nanospheres (CDPGA) to form a laccase-like catalyst, which had stronger catalytic activity than laccase. The freshly formed catalyst was immediately used to degrade the polyhydroquinone-reduced graphene oxide (PHQ-rGO) composite, resulting in a significant reduction in the current signal. The PHQ-rGO composite plays dual roles of signal substance and substrate on the sensing interface. The proposed electrochemical sensor demonstrated wide linearity for the determination of a model analyte, human epididymis protein 4 (HE4), from 1 pg mL-1 to 100 ng mL-1, and the detection limit was as low as 0.302 pg mL-1 (S/N = 3), which had good consistency with that of electrochemiluminescence method. This process-formed catalyst approach will have potential reference significance for the construction of other sensors.

A new application of terahertz time-domain absorption spectra in luminescent complexes: characterization of the C-Hπ weak interactions in Cu(I) complexes.

Six Cu(i) complexes, [Cu(2,3-f)(bdppmapy)]BF4 (1), [Cu(2,3-f)(bdppmapy)]ClO4 (2), [Cu(2,3-f)(bdppmapy)]CF3SO3 (3), [Cu(imidazo[4,5-f])(bdppmapy)]BF4 (4), [Cu(imidazo[4,5-f])(bdppmapy)]ClO4 (5), and [Cu(imidazo[4,5-f])(bdppmapy)]CF3SO3·MeOH (6·MeOH) (bdppmapy = N,N-bis[(diphenylphosphino)methyl]-2-pyridinamine, 2,3-f = pyrazine[2,3-f][1,10]-phenanthroline, and imidazo[4,5-f] = 1H-imidazo[4,5-f][1,10]-phenanthroline), have been synthesized to explore the effects of counteranions on their crystal structures, photophysical properties, and terahertz (THz) spectra. Time-dependent density functional theory (TD-DFT) shows that the luminescence performance of these complexes is attributed to the metal-to-ligand charge transfer (MLCT) in combination with ligand-to-ligand charge transfer (LLCT). In complexes 1-3, the characteristic peak at 1.4 THz is mainly related to the C-Hπ interaction formed by the H atom on the 4#/5# position of 2,3-f and the benzene ring from the bdppmapy on the adjacent asymmetric unit. The common C-Hπ interaction enhances the rigidity of the structure and has non-negligible influence on the photoluminescence quantum yields (PLQYs): the stronger the C-Hπ interaction is, the higher the quantum yield (QY) is. In complexes 4-6, similar absorption peaks (1.10-1.30 THz) are mainly related to the C-Hπ interactions, and strong absorption peaks (1.50-1.90 THz) are affected by the typical hydrogen bonds N-HF/O and O-HO. These results show that some weak interactions can be characterized by THz time-domain spectroscopy (THz-TDS). So, the THz spectroscopy method would make it possible to tune some of the weak interactions in complex structures to regulate the luminescence of materials.