Hydrazine (N2H4) is a crucial chemical raw material extensively utilized in chemical production. However, due to its volatility, water solubility, and high toxicity, both the gaseous form and aqueous solution of N2H4 pose significant environmental risks by causing severe pollution that can adversely impact plants, microorganisms, and human health. Therefore, accurate detection of N2H4 in the environment is imperative for safeguarding public health. In this study, we synthesized a ratiometric fluorescent probe (BCaz-Cy2) based on Carbazole and Hemicyanine groups. This probe exhibits simple synthesis procedure, rapid response time, high sensitivity and selectivity as well as remarkable detection signals. It enables effective detection of N2H4 in various matrices such as water, food, soil and plant samples thereby significantly expanding the scope of applications for N2H4 probes.

The development of high-performance sensors for rapidly detecting acetylacetone (AP) in water samples is necessary because its release into the environment can result in many vital problems for human health and environment. Herein, we first designed a hybrid by integrating HOF with ZIF-8 through a sequential growth strategy. By separately introducing blue-emitting SiQDs and green- and red-emitting Tb3+ and Eu3+ into ZIF-8 and HOF, the resultant ZIF-8@SiQDs@HOF@Eu3+@Tb3+ comprised three emission peaks at 484, 545 and 620 nm, all of which could be employed as switch-off responsive peaks to low concentrations of AP with a detection limit of 0.79 ppm. However, in environments with high concentrations of AP, a turn-on signal at 484 nm was observed. Thereupon, the ratiometric fluorescence intensity of the ternary emission varied within different concentration ranges, accompanied by the fluorescence color evolution from red to salmon to plum to purple to final blue. Moreover, a portable sensing film was fabricated for rapid warning, sensitive and visual determination of AP in complicated environments. Therefore, this triple-emission sensor with wide color variations and strong anti-interference advantages could promote further research to improve the selectivity, sensitivity and inherent self-correction of multimodal fluorescence detection and the ease of sensing operation.

BACKGROUND: As cyanide (CN-) is a significant hazard to the environment and human health, it is essential to monitor cyanide levels in water and food samples. Moreover, real-time visualization of CN-could provide an additional understanding of its critical physiological and toxicological roles in living cells. The fluorescence approach based on small organic probes is an effective way for the detection of CN-. In this approach, a triphenylamine-xhantane conjugate was applied to detect in many samples such as sewage water, soil, sprouted potato, apricot seed, and living cells.
RESULTS: We report a new ratiometric near-infrared fluorescent probe based on a triphenylamine-xhantane derivative for CN-sensing in many samples. The probe displays high selectivity for only CN- ions among a series of analytes. The addition of cyanide to the dicyanovinyl moiety of the probe disrupts π-conjugation followed by the interruption of internal charge transfer. Consequently, the emission peak of the probe shifts hypsochromically from 655 to 495 nm. There is a linear correlation between the emission intensity (I495) and cyanide level, with a detection limit of 0.036 μM. The probe has many advantages over many probes, such as NIR fluorescence, ratiometric response, low cytotoxicity (85.0 % cell viability up to 50.0 μM of the probe), good membrane permeability, fast response time (4.0 min), high selectivity, good photostability, and anti-interference capability.
CONCLUSIONS: Although various probes have been reported in the literature, the use of triphenylamine-xhantane unit as CN- probe has yet to be explored. The probe can detect trace levels of cyanide in many samples such as sewage water, soil, sprouted potatoes, and apricot seeds. Furthermore, it is successfully utilized for the ratiometric fluorescent bioimaging of cyanide in living cells.

Buprofezin (BUP) is an insect growth regulator widely used in agriculture to control hemipteran pests, particularly the melon aphid, Aphis gossypii, due to its efficiency and low toxicity. Although approved by the Chinese government, its maximum residue limit (MRL) in food is strictly regulated, and conventional techniques for detecting BUP have several limitations. Our study reports successful BUP detection using a supramolecular fluorescent probe DP@ALB, constructed with chalcone-based fluorescent dye DP and albumin as the host. The probe offers advantages such as low cost, visual signal output with high fluorescence color variation, rapid response, and high sensitivity. Additionally, portable test strips enable convenient on-site BUP detection and simplifying field monitoring of spiked real samples. The study achieves precise qualitative and quantitative BUP analysis in grape fruit, groundwater, and soil with satisfactory recoveries. Further, the biological applicability of sensor for the in vitro detection of BUP in L929 living cells was demonstrated. This research breakthrough overcomes the limitations of traditional analytical methods, offering an efficient and reliable approach for food and environmental monitoring and pesticide residue detection.

The development of a fluorescent probe for pyriproxyfen (PPF) is crucial due to its potential threat to human health. However, the chemical inertness and low solubility of PPF present significant challenges for the detection of PPF in aqueous solutions using fluorescent probes. Herein, we have originally proposed a complex based on 2-(4-(dimethylamino)phenyl)-3-hydroxy-6,7-dimethoxy-4 H-chromen-4-one (HOF) and serum albumin (SA) as a dual-mode fluorescent probe, HOF@SA. This probe utilizes an indicator displacement assay (IDA) to release the dye HOF from the probe at low PPF concentrations (< 10 µM) and embeds the free dye HOF into the micelle of PPF at high concentrations (> 10 µM). This results in dual-mode fluorescent response characteristics for PPF: a turn-off response at low concentrations and a ratiometric response at high concentrations. An investigation of sensing behavior of HOF@SA for PPF detection exhibits rapid response (< 60 s), high sensitivity (LOD ∼4.7 ppb), high selectivity, and excellent visual detection capability (from cyan to yellow). Moreover, with the aid of a portable device, this method enables to analyze PPF in environmental and food samples. These results promote the advancement of a fluorescent probe approach for PPF analysis in environment and food.

Hypochlorous acid (HClO) as a kind of reactive oxygen species (ROS) plays a vital role in many biological processes. Organic fluorescence probes have attracted great interests for the detection of HClO, due to their relatively high selectivity and sensitivity, satisfactory spatiotemporal resolution and good biocompatibility. Constructing fluorescence probes to detect HClO with advantages of large Stokes shift, wide emission gap, near infrared emission and good water solubility is still challenging. In this work, a new ratiometric fluorescence probe (named HCY) for HClO was developed. FRET-based HCY was constructed by bonding a coumarin and a flavone fluorophore. In absence of HClO, HCY exists FRET process, however, FRET is inhibited in the presence of HClO because the conjugated double bond broke. Due to the good match of the emission spectrum of the donor and the absorption spectrum of the acceptor, the FRET system appears favorable energy transfer efficiency. HCY showed high sensitivity and rapid response time. The linearity between the ratios of fluorescence intensity and concentration of HClO was established with a low limit of detection. What\'s more, HCY was also applied for fluorescence images of HClO in RAW264.7 cells.

The identification and quantification of melatonin (MT) are crucial for early diagnosis of disorders associated with circadian rhythm disruption. Herein, novel blue-emissive carbon dots (BCDs) were synthesized through an improved hydrothermal treatment using serine and malic acid as reductant and carbon source. The excellent optical properties of the as-obtained BCDs were used for ratiometric sensing by strategically constructing a MT sensing system integrating BCDs with C3N4 nanosheets loaded with platinum/ruthenium nanoparticles (PtRu/CN). In this system, H2O2 activated the peroxidase-like activity of PtRu/CN to generate •OH and 1O2 for oxidizing the colorless o-phenylenediamine (OPD) into yellow 2,3-diaminophenazine (DAP) with fluorescence emission at 565 nm. Concurrently, the fluorescence emission of BCDs at 439 nm was quenched by the generated DAP via the static quenching and inner filter effect (IFE) process. However, MT rapidly scavenged the generated free radicals to reverse the ratio fluorescence signal. The developed BCDs/PtRu/CN/OPD/H2O2 sensing platform enabled quantitative analysis of MT at concentrations ranging from 0.06 to 600 μmol/L with a low detection limit of 23.56 nmol/L. Moreover, smartphone-based RGB sensing of MT was successfully developed for rapid visualization and portable processing. More broadly, novel insights into the preparation of carbon dots with sensitive fluorescence sensing properties were presented, promising for future considerations.

Herein, a novel ratiometric strategy for ultra-sensitive detection of o-phenylenediamine (OPD) was proposed based on combinatorial reactions of in-situ fluorogenic reaction and in-situ formation of red fluorescent dithiothreitol-copper nanoparticles (DTT-CuNPs). Here, Cu2+ is used both as an oxidant and as a precursor. Dehydroascorbic acid (DHAA) is formed via redox reaction of AA and Cu2+. Then, DHAA reacts with OPD to yield blue fluorescent quinoxaline (OXD) with emission peak at 434 nm through in-situ fluorogenic reaction. Red emitting DTT-CuNPs with emission peak at 666 nm is instantly generated due to the coordination reaction between DTT and the residual Cu2+ which is not consumed by AA. The fluorescence intensity (FI) of OXD at 434 nm is closely relied on the concentration of OPD, which can be used as a response signal for OPD detection. Meanwhile, FI of DTT-CuNPs at 666 nm has no significant change, which can be used as a reference signal for OPD detection. Thus, the ratio (F434/F666) of the Cu2+/AA/DTT sensing system is successfully employed to quantify OPD, exhibiting a wide linear range from 0.2 µM to 60 µM, with LOD of 0.09 µM.

A novel high-precision aptasensor of microcystin-RR (MC-RR) is developed based on a ratiometric self-powered photoelectrochemical platform. In detail, the defective MoS2/Ti3C2 nanocomposite with good photoelectric activity was designed to serve as the photoanode of the sensor for enhancing the signal and improving the detection sensitivity. In order to effectively eliminate external interferences, the key point of this ratiometric device is the introduction of the spatial-resolved technique, which includes the detection section and the reference section, generating reference signals and response signals, respectively. Moreover, output power was used as the detection signal, instead of the traditional photocurrent or photovoltage. Further, potassium persulfate was introduced as electron acceptor, which was beneficial for improving the electron transport efficiency, hindering electron-hole recombination, and significantly promoting the performance of the sensor. Finally, aptamer was adopted as recognition element to capture MC-RR molecules. The prepared sensor had a linear range from 10-12 to 10-6 M, and the detection limit was 5.6 × 10-13 M (S/N = 3). It has good precision, selectivity, and sensitivity, which shows great prospects in the on-site accurate analysis of samples with high energy output in the self-powered sensing field.

Rapid and accurate identification of tumor boundaries is critical for the cure of glioma, but it is difficult due to the invasive nature of glioma cells. This paper aimed to explore a rapid diagnostic strategy based on a label-free surface-enhanced Raman scattering (SERS) technique for the quantitative detection of glioma cell proportion intraoperatively. With silver nanoparticles as substrate, an in-depth SERS analysis was performed on simulated clinical samples containing normal brain tissue and different concentrations of patient-derived glioma cells. The results revealed two universal characteristic peaks of 655 and 717 cm-1, which strongly correlated with glioma cell proportion regardless of individual differences. Based on the intensity ratio of the two peaks, a ratiometric SERS strategy for the quantification of glioma cells was established by employing an artificial neuron network model and a polynomial regression model. Such a strategy accurately estimated the proportion of glioma cells in simulated clinical samples (R2 = 0.98) and frozen samples (R2 = 0.85). More importantly, it accurately facilitated the delineation of tumor margins in freshly obtained samples. Taken together, this SERS-based method ensured a rapid and more detailed identification of tumor margins during surgical resection, which could be beneficial for intraoperative decision-making and pathological evaluation.