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In this paper, we first introduce the explicit analytical formulas for the expected values of the Gutman and Schultz indices for a random cyclooctane chain COCn. Meanwhile, the explicit formulas of the variances of the Gutman and Schultz indices for a random cyclooctane chain are determined and we prove these two indices are asymptotically subject to normal distribution. Furthermore, we are surprised to find the expected values of the Sombor index SOCOCn, the reduced Sombor index RSOCOCn, the modified Sombor index mSOCOCn and the reduced and modified Sombor index mRSOCOCn for a random cyclooctane chain. [ABSTRACT FROM AUTHOR]

Let Hn be the molecular graph of a linear polyacene chain. In this paper, we introduce a kind of linear polyacene cylinder graph H n 2 , which is the strong product of two automorphism polyacene graphs Hn and H n ′. Next, we obtain that the Laplacian spectrum of H n 2 consists of the eigenvalues of symmetric matrices LA and LS of order 4 n + 2 according to the decomposition theorem of Laplacian characteristic polynomial. Furthermore, by applying the relationship between the roots and coefficients of the characteristic polynomials of the above two matrices, we study the Kirchhoff index and the number of spanning trees, and derive their explicit expressions in terms of n for the graph H n 2. [ABSTRACT FROM AUTHOR]

The study of topological indices of some special chemical graphs has become a hot topic in chemical theory. Let Ln be the dicyclobutadieno derivative of linear phenylene which consists of n hexagons and (n + 1) quadrangles and let Ln2 be the strong prism of the dicyclobutadieno derivative of linear phenylenes. Firstly, we obtain that the normalized Laplacian spectrum of Ln2 consists of the eigenvalues of symmetric matrices LA and LS according to the decomposition theorem of normalized Laplacian characteristic polynomial. Then, by taking full advantage of the relationship between the roots and coefficients of the characteristic polynomials of the above two matrices, we determine the explicit expressions of the multiplicative degree‐Kirchhoff index and the number of spanning trees of the graph Ln2. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess the imaging features of urethral and peri-urethral masses on transvaginal or transperineal ultrasound (US) in a cohort of 95 women. In this retrospective study, medical records of 95 female patients with 98 asymptomatic or symptomatic urethral and peri-urethral masses were retrospectively reviewed. Data regarding patient demographic characteristics, symptoms, signs, imaging features on 2-D and 3-D transvaginal or transperineal US, diagnostic tests and physical and intra-operative findings were extracted. The US imaging features and clinicopathologic characteristics of each urethral or peri-urethral mass were compared. On ultrasound, 39 masses (in 39 patients) were diagnosed as urethral diverticula, which manifested mostly as complex cystic masses (24/39, 61.5%); 35 masses (in 33 patients) were diagnosed as para-urethral cysts, which manifested mostly as simple cystic masses (19/35, 54.3%); 13 hypo-echoic solid masses (in 12 patients) exhibiting blood flow signals on color Doppler imaging were diagnosed as urethral leiomyomas; hypo-echoic or heterogeneous solid masses (in 8 patients) exhibiting blood flow signals on color Doppler imaging were diagnosed as urethral caruncles, including one complicated by malignant transformation; solid masses with mixed echogenicity (in 2 patients) exhibiting blood flow signals on color Doppler imaging were diagnosed as urethral squamous cell carcinoma or adenocarcinoma, and a hypoechoic solid mass (in one patient) with blood-flow signals on color Doppler imaging was diagnosed as urethral condyloma associated with human papillomavirus infection. This study confirmed transvaginal or transperineal 2-D and 3-D ultrasonography to be a valid, non-invasive, cost-effective diagnostic modality for the differential diagnosis of urethral and periurethral masses. [ABSTRACT FROM AUTHOR]

• Single-phase Cu doped c -oriented ε -Fe 2–3 N films with manipulable magnetic and transport properties are synthesized. • The saturation magnetizations decrease with increasing Cu doping amount, which are attributed to the weaken of Fe-Fe ferromagnetic coupling by Cu doping. • The resistivity variations with changing temperature are weakened by Cu doping, which may be ascribed to the more hybridization of 3d states with N 2p states. c -oriented Cu doped ε -Fe 2 – 3 N films are fabricated on c -Al 2 O 3 by magnetron sputtering. It is found that the crystal constant c decreases with increasing Cu doping amount, which is due to the smaller radius of Cu atoms. The XPS peaks of Fe 2p and Cu 2p are confirmed with Fe-N and Cu-N binding energy determined. The saturation magnetizations decrease with increasing Cu doping amount, which are attributed to the weakening of Fe-Fe ferromagnetic coupling by Cu doping. Furthermore, the temperature dependences of (R T –R 300 K)/R 300 K indicate that the resistivity variations with changing temperature are weakened by Cu doping. The manipulable magnetic and transport properties by Cu doping may provide a new method of designing spintronic devices. [ABSTRACT FROM AUTHOR]

This work extends the conventional back-propagation neural network (BPNN) to the classification of Chinese liquors of different flavors according to their Raman spectra. Conformal prediction is applied to assign reliable confidence measures for each classification and support an effective framework to make the machine learning on classification trustable. The BPNN can be used to predict the flavors of Chinese liquors according to their Raman spectra, and a classification rate of 88.96% can be achieved. In order to evaluate each classification, a non-conformity score is defined to generate a P -value for each classification. Moreover, the validity of conformal prediction in online mode is discussed. The number of cumulative errors in the conformal prediction is much less than that without conformal prediction. The relationship between the cumulative error and confidence levels shows that a high confidence level leads to low cumulative errors, but many cumulative errors will occur under a very high confidence level. The result implies that conformal prediction is a useful framework, which can employ classification satisfying a certain level of confidence. Meanwhile, the conformal prediction can improve our classification using a BPNN, when the number of data points is limited. [ABSTRACT FROM AUTHOR]

• A simple method to compare two liquors is developed. • The spectral distance was used to measure the differences of liquors quantitatively. • One method to predict years of finished Chinese liquors was presented. • The flavor of liquors can be considered without analysis of components in liquors. We propose a distance to measure differences of Chinese liquors quantitatively through comparing their three-dimensional fluorescence spectra. This distance can be easily computed with value ranges from 0 to 2. We use this distance to build a forecasting model to predict years of mixed liquors. The result shows that this model possesses high accuracy with the mean error around 0.3 year. Furthermore, since three-dimensional fluorescence spectra of Chinese liquors contain the information of all florescent substances inside of them, we suggest a method to classify flavors of original year Chinese liquors based on this distance. It gives a relatively correct classification on these samples in the sense of their flavors. [ABSTRACT FROM AUTHOR]

Rapid recruitment of small fish after biomanipulation in warm lakes may delay the reestablishment of submerged macrophytes, not least at high nutrient concentrations. Success has recently been obtained in controlling phosphorus (P) loading to many lakes, but nitrogen (N) inputs often remain high. To determine the interactive effects of N loading and the abundance of small-sized fish on the growth of the submerged macrophyte Vallisneria natans , we conducted an outdoor mesocosm experiment with a factorial design on the north shore of Lake Taihu, China. The experiment involved two densities of small crucian carp – low (10 g m − 2 ) and high (40 g m − 2 ) – crossed with two levels of N loading – present-day external nutrient loading (P: 5 μg L − 1 day − 1 , N: 130 μg L − 1 day − 1 ) and P: 5 μg L − 1 day − 1 with a three times higher N loading (N: 390 μg L − 1 day − 1 ). The results showed that nitrogen-fish interactions significantly hindered the growth of V. natans , particularly at the high N loading. At low N loading, high densities of fish decreased the relative growth rate, mean leaf length, leaf mass and root mass of V. natans by 16%, 5%, 8%, and 23%, respectively, compared with these measures at low fish densities. The effect of fish was even stronger when N loading was high, with decreases of 232%, 32%, 57%, and 47% for the respective plant growth measures. The stronger effect at high N loading was attributed to higher turbidity due to enhanced phytoplankton biomass and to increased consumption or damage of plants by the fish in response to the more nutrient-enriched plant tissue. Our results indicate that high abundance of small crucian carp in warm lakes may reduce the resilience of submerged macrophytes to external N loading, thereby lowering the chances of successful restoration by biomanipulation. [ABSTRACT FROM AUTHOR]

Reestablishment of submerged macrophytes is considered important when restoring shallow eutrophic lakes. To improve water clarity and consequently the growth conditions of macrophytes, removal of plankti-benthivorous fish has been used. In sub-tropical shallow lakes, however, rapid recruitment of small fish, especially benthivores during restoration, may hamper early reestablishment of submerged macrophytes. Crucian carp ( Carassius carassius ) and Vallisneria natans are common species dominated in sub-tropical shallow lakes. To investigate the effect of small benthivorous fish on the growth of Vallisneria natans , a 28-day outdoor controlled experiment was undertaken in 12 mesocosms with three densities of Carassius carassius − low (10 g m −2 ), high (40 g m −2 ) and no fish (all in four replicates). The results showed that the fish significantly increased chlorophyll- a concentrations and periphyton biomass in both fish treatments, most significantly at high density for Chl a . This concurs with an increase in nutrient concentrations, likely mediated by fish sediment disturbance and excretion, and a reduction of zooplankton biomass (less algal grazing). Increased concentrations of inorganic suspended solids with increasing fish density further enhanced turbidity, causing shading of the macrophytes. Accordingly, the relative growth rate, ramet number and root/leaf ratio of V. natans decreased significantly at low and high fish density compared with the controls, but the effects did not depend on fish density. However, mean leaf length rose with increasing fish density, likely to allow the plants to obtain more light. Overall, our results show that not only large-bodied carp, as demonstrated frequently, but also small-sized crucian carp posed a constraint on submerged macrophyte reestablishment, and we conclude that crucian carp may hamper restoration efforts in sub-tropical shallow lakes. Restoration by biomanipulation should therefore target also small-sized crucian carp. [ABSTRACT FROM AUTHOR]

[Display omitted] • The β-CD-AgNPs substrate can selectively combine with NFX. And the proposed method can be applied in the detection of real milk samples. • The "host–guest" interaction of NFX and β-CD-AgNPs was verified by the UV–Vis absorption spectroscopy, fluorescence spectroscopy, Zeta potential and DLS. • This developed SERS method is simple and sensitive, the LOD of NFX was 3.214 pmol/L in standard solution and 5.327 nmol/L in milk. The norfloxacin (NFX) residue in milk will increase human resistance to drugs and pose a threat to public health. In this work, a highly sensitive method for detection of NFX was developed based on surface enhanced Raman spectroscopy (SERS) using β-cyclodextrin functionalized silver nanoparticles (β-CD-AgNPs) as substrate. The unique spatial size and hydrophilicity of β-CD on the surface of AgNPs could selectively capture the target molecule (NFX) through some weak interactions, including hydrogen-bond interaction, electrostatic interaction, etc. The interactions were characterized by the UV–Vis absorption spectroscopy, fluorescence spectroscopy, Zeta potential and DLS. The Raman signal of NFX is largely enhanced when anchored by β-CD on the surface of AgNPs due to SERS effect. Through a series of experiments and analysis, the limit of detection (LOD) in standard solution and spiked milk were calculated to be 3.214 pmol/L and 5.327 nmol/L. The correlation coefficients (R2) were 0.986 and 0.984, respectively. For milk sample determination of NFX, the recovery was 101.29% to 104.00% with the relative standard deviation (RSD) from 2.986% to 9.136%. To sum up, this developed SERS strategy is sensitive and specific to detect NFX in milk, it has practical application value and prospects. [ABSTRACT FROM AUTHOR]

We define a (pseudo-)distance between graphs based on the spectrum of the normalized Laplacian. Since this quantity can be computed easily, or at numerically estimated, it is suitable for comparing in particular large graphs. Numerical experiments demonstrate that the spectral distance provides a practically useful measure of graph dissimilarity. The asymptotic behavior of the Laplacian spectrum furthermore yields a tool for classifying families of graphs in such a way that the distance of two graphs from the same family is bounded by O ( 1 / n ) in terms of size n of their vertex sets. [ABSTRACT FROM AUTHOR]

By assigning a probability measure via the spectrum of the normalized Laplacian to each graph and using L p Wasserstein distances between probability measures, we define the corresponding spectral distances d p on the set of all graphs. This approach can even be extended to measuring the distances between infinite graphs. We prove that the diameter of the set of graphs, as a pseudo-metric space equipped with d 1 , is one. We further study the behavior of d 1 when the size of graphs tends to infinity by interlacing inequalities aiming at exploring large real networks. A monotonic relation between d 1 and the evolutionary distance of biological networks is observed in simulations. [ABSTRACT FROM AUTHOR]

There has been an upsurge of research on complex networks in recent years. The purpose of this paper is to study the mathematical properties of the random pentagonal chain networks PE C n with the help of graph theory. Based on the networks PE C n , we first obtain the expected value expressions of the Gutman index, Schultz index, multiplicative degree-Kirchhoff index, and additive degree-Kirchhoff index, and then, we get the explicit expression formulas of their variances. Finally, we find that their limiting distributions all have the probabilistic and statistical significance of normal distribution. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we try to propose a toy model, which follows the majority rule with the Fermi function, to uncover the role of the heterogeneous interaction between individuals in opinion formation. In order to do this, we define the impact factor , says individual , as the exponential function of its connectivity with the tunable parameter . also shows the public information that can be collected by individuals in the system. We realize our model in scale-free networks with mean connectivity . We find that much more public information ( ) and less public information ( ) cannot let either of the two opinions be the majority during the opinion formation. Furthermore, is a constant and equal to , and decreases as a power-law function of the mean connectivity of the network. Our work can provide some perspectives and tools to understand the diversity of opinion in social networks. [Copyright &y& Elsevier]

We introduce the variant rate and white noise into the susceptible-infected-removed (SIR) model for epidemics, discuss the epidemic dynamics of a multiple-compartment system, and describe this system by using master equations. For both the local epidemic spreading system and the whole multiple-compartment system, we Snd that a threshold could be useful in forecasting when the epidemic vanishes. Furthermore, numerical simulations show that a model with the variant infection rate and white noise can improve fitting with real SARS data. [ABSTRACT FROM AUTHOR]

We study message spreading on a scale-free network, by introducing a novel forget-remember mechanism. Message, a general term which can refer to email, news, rumor or disease, etc, can be forgotten and remembered by its holder. The way the message is forgotten and remembered is governed by the forget and remember function, F and R, respectively. Both F and R are functions of history time t concerning individual's previous states, namely being active (with message) or inactive (without message). Our systematic simulations show at the low transmission rate whether or not the spreading can be efficient is primarily determined by the corresponding parameters for F and R. [ABSTRACT FROM AUTHOR]

Nitrogen, boron co-doped carbon quantum dots (gCQDs), and a coloration probe (PPD-NPs) with response to cobalt ions (Co2+) were prepared by using 4-hydroxyphenylboric acid as the common precursor, with ethylenediamine and p-phenylenediamine (PPD) adopted as nitrogen-doped reagents, respectively. A noticeable brown-to-purple color change can be observed with the addition of Co2+, and a broad absorption band emerges at 535 nm. At the same time, gCQDs, which is introduced as the fluorescence signal source, will be significantly quenched due to the enhanced inner filtration effect, induced by the overlap between the emission spectrum of gCQDs and the emerging absorption band. Therefore, a colorimetric/fluorescent dual-mode sensing probe for Co2+ is constructed by combining the recognition unit PPD-NPs and the fluorescent gCQDs into PPD-NP/gCQD. Under the optimized experimental conditions, the calculated limits of detection are 1.51 × 10−7 M and 3.75 × 10−7 M for the colorimetric mode and the fluorescence mode, respectively, well qualified for the determination of Co2+ maximum permitted level in drinking water. The feasibility of the proposed method has been verified in tap water, lake water, and black tea samples. [ABSTRACT FROM AUTHOR]

This meta-analysis aims to clarify the correlations between cognitive reappraisal, expressive suppression, and life satisfaction. We searched the literature using eight databases and set a deadline of April 19, 2021. A total of 33 studies (66 effect sizes) were obtained, and random-effect models were also used to evaluate the relationships between the two strategies and life satisfaction. Additionally, the moderating effects of age, gender, and regional cultural values of participants were analyzed. The results showed that cognitive reappraisal was moderately positively correlated with life satisfaction, whereas expression suppression was not. The relationships between the two strategies and life satisfaction were not affected by age and gender, and only the regional cultural values of the participants moderated the relationship between expression suppression and life satisfaction. The relationship between expression suppression and life satisfaction in Western cultural values is significantly negative, while the relationship in Eastern cultural values is non-significant. We examined the relationships between cognitive reappraisal, expressive suppression, and life satisfaction, and demonstrated that regional cultural values had a moderating effect on the relationship between expression suppression and life satisfaction. [ABSTRACT FROM AUTHOR]

With the expansion of human activities, the consequent influx of mercury (Hg) into the food chain and the environment is seriously threatening human life. Herein, nitrogen and sulfur co-doped fluorescent carbon quantum dots (yCQDs) were prepared via a hydrothermal method using o-phenylenediamine (OPD) and taurine as precursors. The morphological characteristics as well as spectral features of yCQDs indicated that the photoluminescence mechanism should be the molecular state fluorophores of 2, 3-diaminophenothiazine (oxOPD), which is the oxide of OPD. The as-synthesized yCQDs exhibited sensitive recognition of Hg2+. According to the investigation in combination of UV-Vis absorption spectra, time-resolved fluorescence spectra and quantum chemical calculations, the abundant functional groups on the surface of yCQDs allowed Hg2+ to bind with yCQDs through various interactions, and the formed complexes significantly inhibited the absorption of excitation light, resulting in the static fluorescence quenching of yCQDs. The proposed yCQDs was utilized for Hg2+ sensing with the limit of detection calculated to be 4.50 × 10− 8 M. Furthermore, the recognition ability of yCQDs for Hg2+ was estimated in tap water, lake water and bottled water, and the results indicated that yCQDs have potential applications in monitoring Hg2+. [ABSTRACT FROM AUTHOR]

Background: Malignant transformation of endometriosis in the rectovaginal septum is rare and usually misdiagnosed as a colorectal or gynecological tumor. We report a rare case of primary endometrioid adenocarcinoma of the rectovaginal septum with invasion of the rectum. Case presentation: A 57-year-old overweight woman presented with vaginal bleeding and self-reported left lower abdominal pain during the previous 2 weeks. Preoperative imaging showed a large pelvic mass with invasion of the rectum, suggestive of a gynecologic malignancy. Multiple endoscopic biopsies and immunohistochemical analyses of specimens was performed. The patient received joint gynecological-surgical laparotomy, and there were no intra- or postoperative complications. The histopathological diagnosis was rectovaginal endometrioid adenocarcinoma with rectum infiltration. The patient received adjuvant chemotherapy and achieved good treatment response, with no early complications. At 12 months after surgery, there was no evidence of recurrence. Conclusions: A high index of clinical suspicion is required for the diagnosis of endometrioid adenocarcinoma in the rectovaginal septum. Surgery combined with additional chemotherapy or radiotherapy seems to be a standard treatment, and hormonal therapy is optional. The efficacies of other therapies, including targeted medication and immunotherapy, are unknown. [ABSTRACT FROM AUTHOR]

Tetracycline, an animal antibiotic, may remain in milk to cause harm to human health. For economic reasons, the abuse of antibiotics is becoming more and more common. Therefore, the abuse of tetracycline has alarmed the dairy industry and many countries such as New Zealand, China, and the USA have proposed strict standards. Surface-enhanced Raman scattering (SERS) is an emerging detection method which has been applied in food detection with the advantages of no complex pretreatment, fast detection, and weak water environment interference. Considering the abuse of antibiotics in dairy industry, we used polydimethylsiloxane (PDMS) plasma cavity as SERS substrate to detect tetracycline in milk. We found that the enhancement ability of PDMS substrate is affected by addition of 4-amino-1-butanol and complex interplay in the milk--tetracycline system. The modified PDMS plasma cavity has high SERS sensitivity that allows us to achieve low detection limit of 0.28 μ g/L. The correlation coefficient was 0.987. The detection of tetracycline in milk using PDMS substrate is quick (within 10 min) and it provides a possible method for in-site detection of tetracycline. [ABSTRACT FROM AUTHOR]

Amaranth red is usually used as a food colorant in carbonated drinks, but long-term excess consumption of amaranth red in carbonated drinks may lead to the loss of zinc in the human body, thus causing kidney dysfunction. In this study, we developed a simple method to combine cysteamine (Cys) and silver nanoparticles (AgNPs), the surface of AgNPs was modified with Cys at room temperature, and then the amino-functionalized SERS substrate was obtained, which was applied to the determination of amaranth red in carbonated drinks. The characteristic peak in Raman spectra of amaranth red showed obvious SERS enhancement at 1570 cm−1, whose intensity had a good linear relationship with the concentration of amaranth red in carbonated drinks. The limits of detection (LOD) in water and carbonated drinks were calculated to be 1.49 μg/L and 4.13 μg/L, and the adjusted correlation coefficients (R2) were 0.992 and 0.990, respectively. In addition, the average recovery rate of amaranth red in carbonated drinks was 95.11–105.48%, and the relative standard deviation (RSD) was 4.37–8.09%. This work provides a simple and fast method for detecting amaranth red in carbonated drinks. [ABSTRACT FROM AUTHOR]

Eutrophic shallow lakes have a high content of organic matter in the sediment that may be frequently resuspended. Whilst it is generally accepted that inorganic suspended matter has a negative effect on filtering-feeding bivalves in streams, it is unclear whether resuspended sediment in lakes with a high organic content will inhibit or support bivalve growth, the latter reflecting that resuspended sediment can increase food availability for Asian clams directly but also through release of nutrients, promoting the growth of phytoplankton. We conducted two experiments assessing the impact of different concentrations of total suspended solids (TSS) on the growth and feeding behaviour of Asian clams. We found that the growth rates in the low, medium and high treatments increased 12%, 36% and 53% respectively, when compared with the control with no sediment added. The effect on clearance rates of Asian clams differed amongst suspended fractions, and the clams showed significant preference for diatoms over other algae at high TSS. We conclude that an increase in TSS stimulated rather than reduced the growth of Asian clams, suggesting that eutrophication in shallow lakes provides more favourable conditions for the population expansion of Asian clams, an invasive species in many water bodies outside Asia. [ABSTRACT FROM AUTHOR]

The secondary inner filter effect on the fluorescence excitation spectra of rhodamine 6G aqueous solutions with concentration was demonstrated in this paper. The peak of fluorescence excitation spectrum stays at 525 nm at low concentrations, while it breaks up and turns into valley at high concentrations. The threshold concentration was determined to be 3.16 mg/L by the second derivative spectroscopy. A mathematical model was proposed to explain the inflection point of fluorescence excitation spectrum caused by the secondary inner filter effect. On the basis of it, the threshold concentration was calculated to be 2.86 mg/L, approaching to the experimental result. [ABSTRACT FROM AUTHOR]

• The novel Ag-COF-COOH substrates provide huge SERS hot spots, EF = 9.72 × 106. • The SERS method in this work is sensitive and the LOD is 0.68 μg/L in milk. • The SERS method in this work requires only one step of pretreatment. Melamine, a nitrogen-containing organic molecule, has received widespread attention as it had been illegally added in dairy products to increase the content of nitrogen, leading to kidney stones in healthy people after long-term ingestion. Based on SERS technology and Covalent Organic Framework (COF) materials, we developed carboxyl-functionalized Ag-COF-COOH materials as SERS substrates for the detection of melamine adulteration. Using COF material as a ligand can effectively reduce the influence of interferents in milk. In addition, we investigated two causes of melamine SERS enhancement: the ordered arrangement of Ag NPs and the strong interaction between the substrate and the melamine. The linear range was 1–20 μg/L and the limit of detection (LOD) was 0.68 μg/L in liquid milk due to the high sensitivity and reliability of this method. The results show that this new SERS substrate has great potential for applications in the food surveillance industry. [ABSTRACT FROM AUTHOR]

The Raman spectra of nine monohydroxy alcohols have been obtained by confocal Raman spectrometer at room temperature. Based on the Raman spectra, the density functional theory was used to analyze the characteristic Raman bands of monohydric alcohols. Through the discussion of the characteristic Raman bands and their corresponding assignment, four major Raman bands were selected to identify nine monohydric alcohols using principal component analysis and Euclidean distance. Finally, nine saturated monohydroxy alcohols can be distinguished exactly, and the recognition rate is 100%. [ABSTRACT FROM PUBLISHER]

The objectives of the present study were to investigate the mitigation of lead (Pb), cadmium (Cd), and arsenic (As) in a multi-metal contaminated soil and their accumulation in rice plants (Oryza sativaL., cv II You 93) using a combined amendment (CMF, calcium carbonate + metakaolin + fused calcium–magnesium phosphate fertilizer). The results showed that application of CMF was effective in reducing the acid-extractable concentrations of soil Pb and Cd. The exchangeable concentrations of soil As showed an initial decrease followed by a gradual increase. The application of 0.2% CMF notably reduced the concentrations of Pb, Cd, and As in brown rice by 46.5%, 43.6%, and 32.0%, respectively. The concentration of As in brown rice was 0.179 mg kg−1at 0.2% CMF, which met the maximum levels of contaminants in foods of China (MLs) (the ML of Pb, Cd, and As is 0.2 mg kg−1according to the China national standard GB 2762-2012). At 1.6% CMF, the concentrations of Pb and Cd in brown rice were 0.002 and 0.185 mg kg−1, respectively, i.e., reductions of 99.6% and 74.1%, and these values also fell within the MLs. [ABSTRACT FROM AUTHOR]

Introduction: Low birth weight infants remain a significant public health problem in many developing countries. Poor nutrition recognized as an important cause, which is associated with a short- term and long-term adverse consequences, carrying relatively greater risks of perinatal and neonatal morbidity and mortality. Methods: The nutritional status was assessed prospectively on 170 LBWI in neonatology ward of Guangxi medical university, Nanning, China, from January 2007 to December 2008; with infant's birth weight, the most obvious day age of weight lost, the lowest weight percentage and the age recovering to birth weight. Mounla's method was based on the excess time expressed in percent beyond the allocated time for an infant to gain the birth weight and the excess drop in weight expressed in percent beyond the allowed drop of weight. Results: There were61.8% male and38.2% female with gestational age at the time of admission is 28 ~ 37 (33.7±1.9) week; birth weight of 1180~ 2480 (1952±316) gram. The most obvious day age of weight lost was 21~10 (3.7±1.4) days and the regain of the birth weight is 2~23 (7.8±3.8) days. The incidence of malnutrition was 52.3% based on Mounla's method. Conclusion: Mounla's method used to assess nutritional status of LBWI provides certain reference for the clinical support in nutrition of the infants. [ABSTRACT FROM AUTHOR]

The re‐establishment of submerged macrophytes is crucial in shallow lake restoration transforming a turbid into a clear water system, but it might be inhibited by juvenile omni‐benthivorous fish. These fishes disturb the sediment, and even uproot new sprouts, creating turbid water through sediment resuspension and release of nutrients stored in the sediment. Lanthanum modified bentonite (LMB), an in‐situ capping material, can immobilise phosphate and consolidate sediments, potentially weakening the negative effects of juvenile omni‐benthivorous fish.We hypothesised that applying LMB would improve water quality and promote the growth of submerged macrophytes by eliminating or weakening the increase of suspended solids, nutrient concentration, and algal reproduction due to juvenile omni‐benthivorous fish disturbance. To test our hypothesis, a two‐by‐two factorial mesocosm experiment with two densities of juvenile crucian carp (absence and 10 g/m3) and two doses of LMB (absence and 800 g/m2) was conducted.Juvenile crucian carp significantly inhibited the growth and reproduction of the macrophyte Vallisneria natans by reducing the underwater light and direct effects such as uprooting. No significant inhibition or promotion by LMB on the growth of V. natans in the absence of juvenile crucian carp was observed. However, LMB significantly inhibited the fish‐induced sediment resuspension and nutrients increases. Consequently, algal production was reduced and underwater light conditions were improved, which promoted the growth and reproduction of V. natans, e.g., more ramets, biomass, and leaves of V. natans.Our results indicated that submerged macrophytes could benefit from LMB application under high intensity disturbance by juvenile omni‐benthivorous fish, thereby conducive to the maintenance of a clear water state in shallow lakes. [ABSTRACT FROM AUTHOR]

[Display omitted] • This is the first time that carbon dots have been synthesized using ammonium citrate and glutamic acid as precursors. • The fluorescence stability of carbon dots is fully explored, facilitating their use in real-world environments. • This method achieves high selectivity and sensitivity in the trace detection range. • Monitoring Cd2+ ions in tap water and lake water. In this study, fluorescent carbon dots were synthesized for the first time using ammonium citrate and glutamic acid as precursors via a one-pot hydrothermal method. The synthesized carbon dots emit blue fluorescence at 436 nm (excited at 320 nm) and demonstrate excellent photobleaching resistance and fluorescence stability in high salt environments. Within the range of 1–25 μM, the fluorescence of CDs gradually increases with the increasing concentration of Cd2+, reaching a limit of detection as low as 13 nM. This phenomenon could be ascribed to the chelation-enhanced fluorescence, a result of Cd2+ forming complexes with the abundant surface functional groups such as CN–, –COOH, –OH, –NH 2 in CDs. Furthermore, this turn-on fluorescent probe has been successfully used for the detection of Cd2+ in tap water and lake water, providing an efficient and sensitive method for the analysis of environmental metals. [ABSTRACT FROM AUTHOR]

[Display omitted] • COF (covalent-organic framework) capped with sliver nanoparticles (Ag NPs) were first developed as SERS substrate for detection of benzoic acid in liquid milk. • This detection method has high sensitivity and reliability that allows us to achieve LOD of 0.13μg/mL in milk and 0.00372μg/mL in water. • The proposed method can be applied in the detection of real milk samples. Benzoic acid, which has a pivotal role in food additive, is prohibited to add as a preservative in dairy products. China, Brazil, and other countries have proposed standard methods to detect the addition of benzoic acid in food. Surface-enhanced Raman scattering (SERS) is an upcoming spectral detection technique, which has been widely used in the field of material analysis with the advantages of non-invasive, fast detection speed and complex environment with little interference. To detect the illegal use of benzoic acid in dairy industry, we developed Ag-COF (covalent-organic framework) material as SERS substrate to detect benzoic acid in liquid milk. The great enhancement ability of Ag-COF substrate is controlled by the addition of acetic acid and complex interplay between COF material and benzoic acid. This detection method has high sensitivity and reliability that allows us to achieve limit of detection (LOD) of 0.13 μg/mL in milk and 0.00372 μg/mL in water by applying this method. In experiment on recovery rate of real samples, the detection time is less than 15 minutes and the relative standard deviation (RSD) ranged from 2.82% to 5.69%. Therefore, this method has practical significance of the detection of benzoic acid in dairy products. [ABSTRACT FROM AUTHOR]

Herein, we developed a sophisticated dual-mode sensor that utilized 3-aminophenylboric acid functionalized carbon dots (APBA-CDs) to accurately detect uric acid (UA). Our innovative process involved synthesizing APBA-CDs that emitted at 369 nm using a one-step hydrothermal method with 3-aminophenylboric acid and L-glutamine as precursors, ethanol and deionized water as solvents. Once UA was introduced to the APBA-CDs, the fluorescence of the system became visibly quenched. The results of Zeta potential, Fourier transformed infrared (FTIR) spectra, fluorescence lifetime, and other characteristics were analyzed to determine that the reaction mechanism was static quenching. This meant that after UA was mixed with APBA-CDs, it combined with the boric acid function on the surface to form complexes, resulting in a decrease in fluorescence intensity and a blue shift in the absorption peak at about 295 nm in the Ultraviolet–visible (UV–vis) absorption spectra. We were pleased to report that we have successfully used the dual-reading platform to accurately detect UA in serum and human urine. It provided a superior quantitative and visual analysis of UA without the involvement of enzymes. We firmly believe that our innovative dual-mode sensor has immense potential in the fields of biosensing and health monitoring. [ABSTRACT FROM AUTHOR]

Herein, a fluorescent “on-off-on” nanosensor based on N,S-CDs was developed for highly precise and sensitive recognition of Hg2+ and ampicillin (AMP). Nitrogen and sulfur co-doped carbon dots with blue fluorescence were synthesized by one-pot hydrothermal method using ammonium citrate and DL-methionine as precursors. N,S-CDs exhibited a surface abundant in -OH, -COOH, and -NH2 groups, aiding in creating non-fluorescent ground state complexes when combined with Hg2+, leading to the suppression of N,S-CDs’ fluorescence. Subsequent to additional AMP application, the mixed system’s fluorescence was restored. Based on this N,S-CDs sensing system, the thresholds for detection for AMP and Hg2+ were discovered to be 0.121 µM and 0.493 µM, respectively. Furthermore, this methodology proved effective in identifying AMP in real samples of tap and lake water, yielding satisfactory results. Consequently, in the area of bioanalysis in intricate environmental sample work, the sensing system showed tremendous promise. [ABSTRACT FROM AUTHOR]

In this paper, fluorescent carbon dots were prepared by hydrothermal method using 3,5-dihydroxybenzoic acid and l -Arginine as precursors. The synthesized CDs have excitation-dependent emission with emission peaks at 354 nm and 460 nm, corresponding to the optimal excitation wavelengths of 295 nm and 330 nm, respectively. CDs have good dispersion and resistance to photobleaching in aqueous solution, and can maintain stable fluorescence in highly concentrated salt environment. Based on the inner filter effect, Cr(VI) with strong absorption can shield the excitation light of CDs at 295 nm and absorb the emission fluorescence at 354 nm simultaneously. Due to the intermolecular electrostatic interaction, Hg(II) can coordinate with CDs surface groups and cause static quenching, which significantly reduces the fluorescence intensity of CDs emitted at 460 nm. The linear ranges were 0.1–2 μM and 0.4–5 μM for Cr(VI) and Hg(II) detection, respectively, and limits of detection were 0.024 μM and 0.084 μM. Additionally, the probe was successfully applied to tap water and lake water samples. With high sensitivity and spectral selectivity, this sensing strategy realized the detection of two heavy metal ions by a single fluorescent probe, demonstrating its great potential in the field of environmental metal analysis. [Display omitted] • First synthesis of carbon dots with spectral selectivity using 3,5-dihydroxybenzoic acid and l -arginine as precursors. • Separate detection of Cr(VI) and Hg(II) ions using the same carbon dots under different excitations. • This method achieves high selectivity and sensitivity in the trace detection range. • Monitoring Cr(VI) and Hg(II) ions in tap water and lake water. [ABSTRACT FROM AUTHOR]

In this paper, we obtained nitrogen and phosphorus co-doped carbon dots through a hydrothermal method using o-phenylenediamine and citric acid in a 40% phosphoric acid environment. The carbon dots emitted fluorescence at 476 nm under excitation at 408 nm and exhibited good selectivity and high sensitivity towards mercury ions. These carbon dots showed excellent dispersibility in water and maintained stable fluorescence even in high concentration salt environments. The interaction between mercury ions and functional groups on the carbon dots surface through electrostatic interaction resulted in static quenching. Simultaneously, by detecting the lifetime and transient absorption spectra of the carbon dots, we observed that the coordination of mercury ions with the carbon dots broadened the band structure of the carbon dots, and the existing photoinduced electron transfer process increased the non-radiative transition channel. The combined effect of dynamic quenching and static quenching significantly reduced the fluorescence intensity of the carbon dots at 476 nm. The carbon dots exhibited linear detection of mercury ions in the range of 0.01-1 µM, with a detection limit as low as 0.0245 µM. In terms of practical water environmental detection applications, these carbon dots were able to effectively detect mercury ions in tap water and lake water, demonstrating their broad application prospects in the field of environmental metal analysis. [ABSTRACT FROM AUTHOR]

In this work, the possible molecular association structure in isopropanol-water solution has been analyzed by density functional theory (DFT) calculations. The properties of the isopropanol-water clusters with different number of water molecules, including optimal structure, intermolecular hydrogen bonding, binding energy and theoretical Raman spectra, are particularly investigated in the gas phase with B3LYP/6–31 + G (d, p) basis set. According to the simulated optimal structure, we found that the influence of hydration in the molecular configuration of isopropanol is mainly reflected in the O–H bond, which increases with the augment of water molecules. Meanwhile, in terms of the most stable structure, isopropanol-(H2O)5 will show the transition from a two-dimensional planar ring structure to a three-dimensional cage structure. In addition, the position and intensity of intermolecular hydrogen bonds interaction between the isopropanol and water molecules have been investigated by atoms in molecule (AIM) analysis and reduced density gradient (RDG) methods. The theoretical Raman spectra of isopropanol-(H2O)n (n = 1–5) clusters show the redshifts of the O–H bond tensile peak, which indicates that the O–H tensile strength is weakened and the hydrogen bonds interaction is strengthened with the increase in water molecules. [ABSTRACT FROM AUTHOR]

Melamine has been illegally adulterated in dairy food because of the rich nitrogen content and stable chemical properties in recent years. Therefore, the detection of melamine is of great significance for food safety supervision and human health protection. As melamine is a weak fluorescent substance, it is difficult to detect melamine directly by fluorescence spectroscopy. In this work, we found that melamine can significantly enhance the emission of the tetracycline–europium (EuTC) complex at 616 nm. Therefore, we took EuTC complex as a fluorescent probe to detect melamine. According to the characterizations of absorption spectra, molecular electrostatic potential distribution, and the time-resolved spectra, we speculated that tetracycline and melamine may form a complex through hydrogen bonding interaction in the melamine-EuTC reaction system, causing the melamine closer approach to Eu3+ and reducing the non-radiative energy loss of water molecules to Eu3+, which significantly enhanced the fluorescence intensity of EuTC. The fluorescence intensity of EuTC complex with melamine concentration in the range of 0.5–40.0 μM shows a good linear relationship, and the correlation coefficient is 0.9951 with the detection limit of 7.85 × 10−8 M. It shows a high sensitivity for the EuTC complex as a fluorescent probe to detect melamine, which provides a supplement and extension for the detection of melamine by fluorescence spectroscopy. Graphical Abstract [ABSTRACT FROM AUTHOR]

In this paper, multifunctional nitrogen-doped carbon dots (N-CDs) were synthesized from 3,5-diaminobenzonitrile by a simple one-step hydrothermal method. The N-CDs have a high quantum yield of 67.0% in ethanol with great water solubility, temperature stability, light stability and resistance to ion interference. Experiments showed that pH has an effect on the fluorescence intensity and emission wavelength of N-CDs. Especially, the switchable fluorescence of N-CDs caused by changes of pH value could be distinguished to the naked eye. Additionally, the multifunctional N-CDs also showed a selective response to tetracycline. We studied the influence of tetracycline on the luminescence intensity of N-CDs in the concentration range of 0–1000 μ g/L. A linear equation was established in the range of 10–80 μ g/L with a limit of detection (LOD) of 3.5 μ g/L. Based on the above excellent characteristics, N-CDs are expected to be applied in the field of sensing. In this study, nitrogen-doped carbon dots (N-CDs) were synthesized from 3,5-diaminobenzonitrile by a simple one-step hydrothermal method. The N-CDs have good water solubility and high quantum yield. More importantly, the diverse and sensitive responses of N-CDs to pH and tetracycline indicate that N-CDs can be used as good probe. [ABSTRACT FROM AUTHOR]

• Ultrafast photo-physical properties of DASPA are studied by the TA spectra. • Simulated results suggest multiple binding locations between DASPA and protons. • TA results indicate a solvation relaxation rather than a state-to-state transition. • An energy model is proposed to demonstrate the relaxation mechanism. The ultrafast photophysical properties of dimethyl amino styryl pyridine acetonitrile (DASPA) were studied by the femtosecond transient absorption spectra (TA). The results show no evidence of state-to-state relaxation. The excited energy is released by the interaction between DASPA and solvent molecules. The solvation relaxation in protic solutions is faster than that in aprotic solutions, which results in a rapid decay of fluorescence. An energy diagram is finally proposed to interpret the relaxation mechanism. [ABSTRACT FROM AUTHOR]

A rapid, selective and sensitive method for the detection of caffeine in tea infusion and tea beverages are proposed by using 3,5-diaminobenzoic acid as a fluorescent probe. The 3,5-diaminobenzoic acid emits strong fluorescence around 410 nm under the excitation of light at 280 nm. Both the molecular electrostatic potential analysis and fluorescent lifetime measurement proved that the existence of caffeine can quench the fluorescence of 3,5-diaminobenzoic acid. Under the optimal experimental parameters, the 3,5-diaminobenzoic acid was used as a fluorescent probe to detect the caffeine aqueous solution. There exists a good linear relationship between the fluorescence quenching of the fluorescent probe and the concentration of caffeine in the range of 0.1–100 μM, with recovery within 96.0 to 106.2%, while the limit of detection of caffeine is 0.03 μM. This method shows a high selectivity for caffeine. The caffeine content in different tea infusions and tea beverages has been determined and compared with the results from HPLC measurement. [ABSTRACT FROM AUTHOR]

[Display omitted] • This paper presents a sensitive and label-free SERS method that requires no pre-derivatization and adjustment of pH for L-Hyp detection. • The mechanism of this work provides inspiration for detecting molecules with small Raman cross-section. • The proposed SERS method has a low LOD of 8.18 ng/mL in aqueous solution and 0.13 μg/mL in milk. The detection of non-protein nitrogen adulterants is a major challenge in dairy testing. As a marker molecule of animal hydrolyzed protein, the presence of non-edible L-hydroxyproline (L-Hyp) molecules can be used to identify low-quality milk containing components of animal hydrolyzed protein. However, it is still difficult to detect L-Hyp directly in milk. The Ag@COF-COOH substrate in this paper can be used to realize label-free L-Hyp sensitive detection based on the hydrogen bond transition mechanism. To explore the mechanism, the binding sites of hydrogen bond interaction have been verified experimentally and computationally, and the charge transfer process was also explained in terms of HOMO/LOMO energy level. In conclusion, the quantitative models for L-Hyp in an aqueous environment and in milk were developed. The limit of detection (LOD) of L-Hyp in an aqueous environment could reach 8.18 ng/mL, with R2 of 0.982. The linear range of quantitative detection in milk was 0.5–1000 μg/mL and the LOD was as low as 0.13 μg/mL. In this work, a hydrogen bond interaction based Surface-enhanced Raman spectroscopy (SERS) method for the label-free detection of L-Hyp was proposed, which complemented the application of SERS technology in the detection of dairy products. [ABSTRACT FROM AUTHOR]

Quinolone antibiotics have good antibacterial properties and are commonly used antibiotics in the dairy industry. Currently, the problem of excessive antibiotics in dairy products is very serious. As an ultra-sensitive detection technology, Surface-Enhanced Raman Scattering (SERS) was applied to the detection of quinolone antibiotics in this work. In order to classify and quantify three antibiotics (Ciprofloxacin, Norfloxacin, Levofloxacin) with highly similar molecular structures, a combination of magnetic COF-based SERS substrate and machine learning algorithms (PCA-k-NN, PCA-SVM, PCA-Decision Tree) was used. The classification accuracy of the spectral dataset could reach 100% and the results of LOD calculation were: CIP: 5.61 × 10−9M, LEV: 1.44 × 10−8M, NFX: 1.56 × 10−8M. This provides a new method for the detection of antibiotics in dairy products. [Display omitted] • This method realized the detection of three quinolone antibiotics with one SERS substrate. • This method can classify three quinolone antibiotics with highly similar molecular structures with 100% accuracy. • The proposed SERS method has low LODs in milk: CIP: 5.61 × 10−9M, LEV: 1.44 × 10−8M, NFX: 1.56 × 10−8M. [ABSTRACT FROM AUTHOR]

[Display omitted] • This is the first time that carbon dots were synthesized using cysteine and ethylenediamine as precursors. The synthesis method is green and simple, and the prepared N -CDs have good fluorescence stability. • The developed experimental conditions for the detection of Fe3+ using nitrogen-doped carbon dots as fluorescent probes have been fully optimized to significantly improve the sensitivity. • The method is simple, sensitive and highly feasible, with LOD as low as 0.069 μM in deionized water. And, linear models were also constructed in tap water and lake water with LOD of 0.21 μM and 0.59 μM, respectively. In this study, we synthesized stable nitrogen-doped carbon dots by a simple and economical one-step hydrothermal method using l -cysteine and anhydrous ethylenediamine as precursors. The prepared carbon dots have bright and stable blue light emission near 383 nm and can be used as fluorescent probes to detect the concentration of Fe3+ in environmental waters. It was demonstrated that due to intermolecular electrostatic interaction, a non-fluorescent complex N -CDs/Fe3+ is formed by coordination of Fe3+ with amino and carboxyl functional groups on the surface of carbon dots. Therefore, in combination with internal filtration effect, the fluorescence of carbon dots can be quenched in the presence of Fe3+, and the degree of quenching is linearly related to the concentration of Fe3+. The limit of detection in deionized water was as low as 0.069 μM with R2 of 0.998 and a linear range of 0.3 to 20 μM. In addition, satisfactory recoveries were achieved for the determination of Fe3+ in environmental water samples. The method is reliable, with highly sensitivity and selectivity, and has potential for practical applications in environmental metal analysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • The intermolecular hydrogen bonds in uric acid aqueous solution were studied. • The configuration search and geometry optimization of uric acid–water cluster were carried out. • Position and intensity of interaction are discussed by AIM and RDG analyses. Cluster structures that may be associated between uric acid molecules and different numbers of water molecules were studied in detail using density functional theory (DFT) at the B3LYP-D3(BJ)/6–31 + G (d, p) level. When the number of water molecules increases from one to three, the cluster configuration changes from planar single-ring structure to double-ring structure. At the same time, the weak interactions were analyzed by atomic analysis (AIM) and reduced density gradient (RDG) methods. Finally, the theoretical Raman spectra show that the N–H Raman peak in the uric acid molecule is redshifted and the hydrogen bond interaction is enhanced. [ABSTRACT FROM AUTHOR]

The main objectives of the present study were to investigate the levels of arsenic (As) in 23 vegetable species planted on As-polluted soil and assess the human health risks of contaminated vegetable consumption. The target hazard quotient (THQ) and target cancer risk (TR) methods were employed to evaluate the human health risks posed by exposure to As through vegetable consumption. Our results indicate substantial As contamination of the experimental soil. Significant differences were detected in the concentrations of total and inorganic As in the edible parts of the various vegetables grown on contaminated soil, which were generally in the following order: leafy vegetables > stem vegetables > root vegetables > melon and fruit vegetables. The total THQ value for As due to vegetable consumption for children (4.81) was higher than that for adults (3.66), the TR values for As due to vegetable ingestion for adults (1.65 × 10−3) and children (2.17 × 10−3) were significantly beyond the range of acceptable risk (10-6–10-4) recommended by the US Environmental Protection Agency and the maximum acceptable risk value (5.0 × 10−5) recommended by the International Commission on Radiation Protection, which clearly poses a dangerous health risk for residents consuming vegetables in the long-term in the study area. [ABSTRACT FROM AUTHOR]

[Display omitted] • The AgNPs-4MPBA composite structure was first designed as SERS substrate for detection of fructose in urine. • This method achieve the LOD of fructose to be 0.535 µmol/L in urine. • This method realizes rapid fructose detection in less than 10 min. The accurate detection of fructose in human urine can help prevent and screen for diseases such as fructokinase deficiency and hereditary fructose intolerance. Surface-enhanced Raman spectroscopy (SERS) is an analytical technique with selectivity and high sensitivity, which has been widely applied to the detection of targets with complex backgrounds. In this work, 4-mercaptophenylboronic acid (4-MPBA) was modified on the surface of silver nanoparticles (AgNPs) under mild conditions to obtain a boronic acid-functionalized SERS substrate for the detection of fructose in artificial urine. The detection mechanism was based on the deboronization reaction of 4-MPBA on the surface of AgNPs, which was induced by fructose, and the Raman signal of the generated thiophenol (TP) molecules was significantly enhanced by the silver nanoparticles, with a linear increase in SERS peak intensity at 1570 cm−1. We achieved the detection limits of 0.084 µmol/L in water and 0.535 µmol/L in urine by this method. The relative standard deviation (RSD) in the recovery experiments of urine ranged from 1.01 % to 2.22 %, and the whole detection time was less than 10 min, which indicated that this method is highly reliable for fructose detection and has a good prospect in bioassay and clinical medicine. [ABSTRACT FROM AUTHOR]

Cavitation is a common phenomenon in diesel injector and has a strong influence on the internal flow. However, studies so far have focused on cavitation characteristics inside the nozzle. Its influence on the flow during control valve opening remains still unclear. In the paper, a computational study focused on the flow and cavitation phenomena within control valve has been reported and the effects of control valve’s structure parameters (including rounded edge, seal cone angle and outflowing control-orifice structure) on the flow and cavitation characteristics have been investigated in detail. Firstly the 3D model has been validated in terms of single injection quantity and fuel injection duration, showing a good consistency. And then, the development from sheet cavitation to cloud cavitation and the relationship between cavitation, pressure and velocity has been discussed. Based on the numerical results obtained, it is shown that not only the variation of pressure but also the velocity is the important factor which affects cavitation. The increase of the flow velocity reduces the pressure within the flow field which can aggravate the development of cavitation. As cavitation region increases, the fuel flow is hindered and the flow velocity decreases. However, the decrease of flow velocity has suppressed the development of cavitation. All of those variations form a cyclical process. [ABSTRACT FROM AUTHOR]

[Display omitted] • Carbon nanodots (CNDs) were synthesized through a facile microwave method. • The fluorescence of CNDs was selectively quenched by gold nanoparticles (AuNPs). • Once introduced, thiourea triggered the reversion of quenched fluorescence. • Effective applications in environmental water and compound fruit-vegetable juice. Illegal abuse results in the presence of thiourea (TU) in soil, wastewater, and even fruits, which is harmful for the environment and human health. It has urgent practical significance to design an efficient and reliable probe for TU detection. Herein, a sensitive fluorescent probe with off–on response for harmful TU was reported. The probe was designed with fluorescent carbon nanodots (CNDs) and gold nanoparticles (AuNPs) based on fluorescence resonance energy transfer (FRET) effect. Firstly, the CNDs were pre-combined with AuNPs and the fluorescence of CNDs was quenched due to the FRET effect. Upon addition of TU, the fluorescence of CNDs recovered due to the unbinding of CNDs and AuNPs, since the coordination interaction between TU and AuNPs is stronger than the electrostatic interaction among CNDs and AuNPs. Under the optimum parameters, a linear relationship was found between the relative fluorescence intensity of the probe and the concentration of TU in the range of 5.00 × 10-8-1.00 × 10-6 M (R2 = 0.9958), with the limit of detection (LOD) calculated to be 3.62 × 10-8 M. This proposed method is easy to operate and has excellent selectivity and sensitivity for TU, which can be effectively applied in environmental water and compound fruit-vegetable juice. [ABSTRACT FROM AUTHOR]