Remembering Olivier Guillot-Noël

Graphene quantum dots were synthesized by control carbonization of citric acid and utilized for selective determination of dopamine in the presence of ascorbic and uric acids. The prepared graphene quantum dots were characterized by X-ray diffraction, transmission electron microscopy, and Fourier transform infrared, ultraviolet–visible and fluorescence spectroscopy. The results revealed that dopamine could quench the fluorescence of graphene quantum dots through a dynamic quenching mechanism. Under the optimized conditions, the linear concentration range was obtained within 0.01–50.0 µM, with the correlation coefficient of 0.9983 and a limit of detection of 8.2 nM. This method does not show any interference with respect to coexisting foreign substances, even at the presence of 500-fold of ascorbic acid and uric acid.     

Facile Synthesis of Carbon Dots from Biomass Material and Multi-Purpose Applications

Selective and sensitive water content measurement in organic solvents is extremely significant for both industrial use and laboratory preparation. Carbon nanodots are promising carbon nanomaterials with unique and novel properties and thus have drawn growing attention. However, the hydrothermal approach for the preparation of carbon dots always uses water as solvent, and consequently, the development of carbon dots from biomass materials for fluorescence detection of water content remains unexplored. Here, carbon dots were prepared from gallic acid via a cheap and facile one-step method. The as-prepared carbon dots present excellent sensitivity and selectivity toward water content and exhibits good linear relationships with water content in range of 0–10%. The carbon dots demonstrated a strong antioxidation capacity and colour-reaction of Fe³⁺ like gallic acid. The carbon dots also showed solid-state lighting.

     

Recovery of β-carotene from pumpkin using switchable natural deep eutectic solvents

The aim of the present research was to develop green and sustainable extraction procedure for β-carotene recovery from pumpkin. A series of hydrophobic natural deep eutectic solvents (NADESs) based on fatty acids were prepared to establish high extraction efficiency of β-carotene and to increase stability of extracted carotenoids from the pumpkin. To intensify extraction process, NADES composed of C8 and C10 fatty acids (3:1) was selected and coupled with ultrasound assisted extraction. Response surface methodology and artificial neural network model (ANN) model was adopted to analyze significance of extraction parameters demonstrating high prediction levels of the β-carotene yield, experimentally confirming the maximum β-carotene content of 151.41 µg/mL at the optimal process condition. Extracted carotenoids in the optimal NADES extract have shown high stability during the storing period of 180 days. A switchable-hydrophilicity eutectic solvent system has been introduced as a successful way to recover extracted carotenoids from the NADES solvent. It was capable of precipitating 90% of carotenoids present in the extract. The proposed procedure is simple, easily scalable and has minimal impact on operators and the environment.     

Investigation of Solvent Effects on Photophysical Properties of New Aminophthalimide Derivatives-Based on Methanesulfonate

Novel aminophthalimide derivatives were synthesized starting from (3aR,7aS)-2-(2-hydroxypropyl)-3a,4,7,7a–tetrahydro-1H-isoindole-1,3(2H)-dione (9) , and solvent effects on the photo-physical properties of these newly synthesized aminophthalimide derivatives (compounds 14 and 15) were investigated using UV-Vis absorption spectroscopy, steady-state and time-resolved fluorescence measurements. Both absorption and fluorescence spectra exhibited bathochromic shift with the increased polarity of the solvents for both molecules. Solute-solvent interactions were analyzed using the Lippert-Mataga and Bakhshiev polarity functions, and Kamlet-Taft and Catalan multiple linear regression approaches. The results revealed that these two molecules experienced specific interactions. Furthermore, photo-physical parameters were calculated for both molecules in all of the solvents, such as the fluorescence quantum yield, fluorescence lifetime, radiative (k_r) and non-radiative (k_nr) rate constant values. It was observed that the fluorescence quantum yield values decreased linearly with increasing solvent polarity. This study proved the new dyes including isopropyl methanesulfonate group displayed different behavior from previous studies of aminophthalimide derivatives in water. It was recommended that these new dyes having interesting properties by changing solvent can be used various applications such as environmentally sensitive fluorescent probes, labels in biology, laser industry.     

Composition and antioxidant activity of anthocyanins from Aronia melanocarpa extracted using an ultrasonic-microwave-assisted natural deep eutectic solvent extraction method

A time-saving, efficient, and environmentally friendly ultrasonic-microwave-assisted natural deep eutectic solvent (UMAE-NADES) extraction method was developed for the extraction of anthocyanins from Aronia melanocarpa. Eight different natural eutectic solvents were screened initially, and choline chloride-glycerol was selected as the extraction solvent. The extraction conditions were optimized using the response surface methodology, and the extraction rate of anthocyanins was higher than those achieved using the traditional ethanol method, natural deep eutectic solvent extraction method, and ultrasonic-microwave-assisted ethanol method. Six anthocyanins, including cyanidin-3-O-galactoside, cyanidin-3-O-glucoside, cyanidin-3-O-arabinoside, cyanidin-3-O-xyloside, cyanidin-3,5-O-dihexoside, and the dimer of cyanidin-hexoside were identified and extracted at a purity of 448.873 mg/g using high performance liquid chromatography-mass spectrometry (HPLC-MS). The compounds extracted using UMAE-NADES had higher antioxidant capacities than those extracted by the other three methods. The UMAE-NADES demonstrated significant efficiency toward the extraction of bioactive substances and has potential utility in the food and pharmaceutical industries.     

Determination of Protoporphyrin IX Disodium Salt Based on Fluorescence Quenching of Glutathione-Capped Cadmium/Tellurium Quantum Dots

ABSTRACT

Aqueous glutathione-capped cadmium/tellurium quantum dots with a diameter of about 3 nm were synthesized. The fluorescence was quenched in the presence of protoporphyrin IX disodium salt, with the excitation wavelength at 320 nm. Under the optimal conditions, the quenched fluorescence intensity was linear in the range of 0.096–16 µg · mL^?1 with a concentration of protoporphyrin IX disodium salt, and the detection limit (3σ) was 2.8 × 10^?2 µg · mL^?1. The proposed method has been applied to the determination of protoporphyrin in serum samples with satisfactory results. The interaction mechanism was investigated.     

Highly sensitive and selective detection of glutathione using ultrasonic aided synthesis of graphene quantum dots embedded over amine-functionalized silica nanoparticles

Glutathione (GSH) is the most abundant antioxidant in the majority of cells and tissues; and its use as a biomarker has been known for decades. In this study, a facile electrochemical method was developed for glutathione sensing using voltammetry and amperometry analyses. In this study, a novel glassy carbon electrode composed of graphene quantum dots (GQDs) embedded on amine-functionalized silica nanoparticles (SiNPs) was synthesized. GQDs embedded on amine-functionalized SiNPs were physical-chemically characterized by different techniques that included high resolution-transmission electron microscopy (HR-TEM), X-ray diffraction spectroscopy (XRD), UV–visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), and Raman spectroscopy. The newly developed electrode exhibits a good response to glutathione with a wide linear range (0.5–7 µM) and a low detection limit (0.5 µM) with high sensitivity(2.64 µA µM⁻¹). The fabricated GQDs-SiNPs/GC electrode shows highly attractive electrocatalytic activity towards glutathione detection in the neutral media at low potential due to a synergistic surface effect caused by the incorporation of GQDs over SiNPs. It leads to higher surface area and conductivity, improving electron transfer and promoting redox reactions. Besides, it provides outstanding selectivity, reproducibility, long-term stability, and can be used in the presence of interferences typically found in real sample analysis.     

Synchronous Fluorescence as a Green and Selective Method for the Simultaneous Determination of Cetirizine and Azelastine in Aqueous Humor

A green, simple, quick and economical method is implemented for the first time for the simultaneous estimation of cetirizine (CTZ) and azelastine (AZE) as co-administered eye drops. The method relies on synchronous spectrofluorimetry with ?λ?=?60 nm. Cetirizine can be estimated at 231 nm and AZE can be measured at 294 nm, each at the other’s zero crossing point. All factors affecting the method were studied and properly optimized. Good correlation was obtained in the range of 0.1–2 µg mL^?1 for both drugs. The limits of detection were 0.014 and 0.010 µg mL^?1 and limits of quantitation were 0.043 and 0.029 µg mL^?1 for CTZ and AZE, respectively. Moreover, ICH guidelines were carried out to validate the adopted method. The method was suitable for the analysis of CTZ and AZE in synthetic mixtures, eye drops and aqueous humor. The mean percentage of recoveries of CTZ and AZE in spiked aqueous humor were 99.83 and 99.37, respectively. Furthermore, Green Analytical Procedure Index (GAPI) and analytical Eco-scale approaches were used to evaluate the greenness of the suggested method.

     

A Novel Benzimidazole-Based Chemosensor for Fluorometric Determination of Zinc Ions

A simple and novel Schiff base chemosensor (BMHM) based on benzimidazole was synthesized. In ethanol–water (1:1, v/v) medium on varying concentrations of Zn²⁺ chemosensor exhibited a strong and quick turn on fluorescence response. The Zn²⁺ recognition was based on the Chelation–enhanced fluorescence effect. The binding constant and limit of detection for BMHM-Zn²⁺ complexation were estimated to be 7.99?×?104 M^?1 and 0.148 µM, respectively. The extreme fluorescent enhancement caused by Zn²⁺ binding in chemosensor BMHM occurred at a pH range of 6–7. The practical use of chemosensor BMHM was tested by determination of Zn²⁺ in real water samples and comparing the results with the data obtained using high resolution inductively coupled plasma mass spectrometry.

     

Detection of Fe3+ and Hg2+ Ions by Using High Fluorescent Carbon Dots Doped With S And N as Fluorescence Probes

In this paper, carbon quantum dots (N-S-CDs) containing sulfur and nitrogen were synthesized using citric acid and thiourea. The average particle size of N-S-CDs is 8 nm. The N-S-CDs surface contains various of functional groups, which has good water solubility. The fluorescence quantum yield of N-S-CDs is as high as 36.8%. N-S-CDs emits strong blue fluorescence in aqueous solution and has good photostability in neutral and alkaline NaCl solution. N-S-CDs has unique selectivity and high sensitivity to Fe³⁺ and Hg²⁺ ions, and the lowest detection limits are 1.4 μM and 0.16 μM, respectively. Under the interference of other metal ions, Fe³⁺ and Hg²⁺ ions can still effectively and stably quench the fluorescence of N-S-CDs. In addition, in the detection of actual samples, N-S-CDs can effectively detect Fe³⁺ and Hg²⁺ ions in tap water and lake water.

     

A sonochemical assisted synthesis of hollow sphere structured tin (IV) oxide on graphene oxide sheets for the low-level detection of environmental pollutant mercury in biological samples and foodstuffs

In modern approaches for nanomaterials synthesis, ultrasonication plays an important role in providing the larger surface area and smaller crystalline size properties that are favorable to electrochemical techniques. Herein, we report the tin (IV) oxide on graphene oxide nanoparticles were synthesized (SnO₂@GO NPs) by ultrasonic methodology (UZ SONOPULS HD 3400 Ultrasonic homogenizer) with the total power of 400 W and the (frequency of 20 kHz; 140 W/dm³). The formation of as-prepared SnO₂@GO NPs and its surface morphology were scrutinized over XRD, XPS, TEM, and FESEM. Besides, the sonochemically prepared SnO₂@GO NPs were employed for the determination of environmental hazardous mercury (Hg). As a result, the modified electrode acquired a very low-level detection limit of 1.2 nM with a wider range of 0.01–10.41-µM and 14.52–225.4-µM for the detection of Hg. Finally, the practical applicability of SnO₂@GO NPs in spiked human blood serum and tuna fish samples shows appreciable found and recovery values..     

温度对低共熔溶剂影响的二维拉曼光谱研究

低共熔溶剂（DES）作为一种新式的绿色溶剂，在多种化学过程中表现出色，因此在诸多热门范畴都展现出良好的发展潜力。对DES的光谱分析通常局限在一维光谱技术上，但其分辨率低、谱峰重叠严重等缺点，导致光谱数据存在误差。运用二维拉曼光谱（2D Raman），能够明显提高光谱分辨率，并发现重叠峰位置，获得在外扰条件下不同谱峰的变化顺序及其相互作用等重要信息，以实现对复杂体系的精确分析。以氯化胆碱（ChCl）和ZnCl₂合成的DES为例，利用显微共焦激光拉曼光谱仪分别对ChCl和DES进行拉曼实验，发现与ChCl相比，DES中各处峰的整体强度显著下降，原有的谱峰未消失，说明Zn2+的加入没有破坏ChCl的骨架结构。287 cm-1处出现一个新的特征峰，推测有Zn-Cl配位键的伸缩振动。对DES进行升温拉曼实验，发现随着温度的升高，NC₄的不对称伸缩振动峰强度逐渐减小，峰宽变大，峰形变缓，Zn-Cl配位键伸缩振动峰强度逐渐降低，峰位置基本不变，峰形有明显重叠。运用2D Raman技术对溶液内NC₄和Zn-Cl特征峰的变化进行研究，结果表明，随着温度的升高，溶液中发生ChCl向Ch+的解离过程，Zn2+与Cl-形成了多种配合物，ZnCl-₃，Zn₂Cl-₅，Zn₃Cl-₇之间存在相互转化。不同位置的特征峰随温度的变化顺序不同，将特征峰与团簇进行一一归属，得出了各个团簇对温度的敏感程度。基于量子化学中的密度泛函理论，对推测的物质结构进行构型优化和参数计算，证实了其存在的可能性，同时也验证了2D Raman的分析结果准确可行。这些结果将为DES的后续研究提供理论参考，拓展了二维光谱技术的应用范围。     

One step synthesis of ultra-high quantum yield fluorescent carbon dots for “on-off-on” detection of Hg2+ and biothiols

In this paper, the carbon dots (CDs) with strong blue fluorescence were synthesized through hydrothermal method, which using folic acid, ammonium citrate and ethylenediamine as precursors. The prepared CDs with a high absolute quantum yield of 81.94% and showed excellent stability in high concentration salt solution and different pH conditions. With the addition of Hg²⁺, the signal of CDs was selectively quenched. At the same time, the CDs-Hg²⁺ system could be recovered after the introduction of biothiols. Moreover, the fluorescence of CDs showed a good linear relationship with Hg²⁺ (1–15 µM), and the detection limit as low as 0.08 µM. In addition, the prepared CDs with low toxicity could be used to detect Hg²⁺ in living cells and actual water samples.

     

Sensitive Fluorescent Determination of Cobalt by Microwave Assisted Synthesized TPTZ Functionalized Carbon Dots

Novel fluorescent carbon dots (CDs) for cobalt ions sensing were synthesized from 2,4,6-tris(2′-pyridyl)-s-triazine (TPTZ) and citric acid by microwave-assisted method in one pot. This sensor was water soluble, simple, sensitive and cheap. The size of the CDs was determined from transmission electron microscope image and was in the range of 10 nm. Under optimized experimental conditions, this luminescent system had stable response for Co (II) over a concentration range from 0.4 to 50 µM with a detection limit as low as 230 nM. The proposed method showed good sensitivity and selectivity with respect to interference ions. Finally, this system was used for Co (II) determination in tap water, river water and mineral water and B₁₂ ampoule samples.     

溶剂对石墨烯量子点荧光性质的影响

采用柠檬酸热解法制备了石墨烯量子点(GQDs),研究了非极性溶剂戊烷,极性溶剂乙醇、丙酮、乙二醇对GQDs荧光性质的影响。透射电子显微镜(TEM)和原子力显微镜(AFM)图像表明,制备的GQDs尺寸分布在2~12 nm(平均尺寸为4.9 nm),分散均匀,高度分布在0.5~2 nm。吸收光谱表明,GQDs具有明显的紫外吸收特性,吸收峰位于259 nm和274 nm。光致发光谱表明,GQDs的发光具有明显的溶剂依赖性。GQDs在极性溶剂乙醇、丙酮、乙二醇中,发光峰的位置依赖于激发波长,发射波长在可见光区。而在非极性溶剂戊烷中,GQDs表现出对激发波长不依赖的荧光性能,且发射波长在近紫外。     

Ultrasound-aided synthesis of gold-loaded boron-doped graphene quantum dots interface towards simultaneous electrochemical determination of guanine and adenine biomolecules

To acquire substantial electrochemical signals of guanine-GUA and adenine-ADE present in deoxyribonucleic acid-DNA, it is critical to investigate innovative electrode materials and their interfaces. In this study, gold-loaded boron-doped graphene quantum dots (Au@B-GQDs) interface was prepared via ultrasound-aided reduction method for monitoring GUA and ADE electrochemically. Transmission electron microscopy-TEM, Ultraviolet–Visible spectroscopy-UV–Vis, Raman spectroscopy, X-ray photoelectron spectroscopy-XPS, cyclic voltammetry-CV, and differential pulse voltammetry-DPV were used to examine the microstructure of the fabricated interface and demonstrate its electrochemical characteristics. The sensor was constructed by depositing the as-prepared Au@B-GQDs as a thin layer on a glassy carbon-GC electrode by the drop-casting method and carried out the electrochemical studies. The resulting sensor exhibited a good response with a wide linear range (GUA = 0.5–20 μM, ADE = 0.1–20 μM), a low detection limit-LOD (GUA = 1.71 μM, ADE = 1.84 μM), excellent sensitivity (GUA = 0.0820 µAµM⁻¹, ADE = 0.1561 µAµM⁻¹) and selectivity with common interferents results from biological matrixes. Furthermore, it seems to have prominent selectivity, reproducibility, repeatability, and long-lasting stability. The results demonstrate that the fabricated Au@B-GQDs/GC electrode is a simple and effective sensing platform for detecting GUA and ADE in neutral media at low potential as it exhibited prominent synergistic impact and outstanding electrocatalytic activity corresponding to individual AuNPs and B-GQDs modified electrodes.     

Optimization in Solvent Selection for Chlorin e6 in Photodynamic Therapy

The photophysical properties of chlorin e6 (Ce6) in twelve different protic, aprotic and non-polar solvents were investigated using ultraviolet–visible and fluorescence spectroscopic methods. Solvatochromic effects were determined by the changes in quantum yield, Stokes shift, fluorescence half-life and excited state dipole moments of Ce6 in the different solvents. The absorption shifts observed in different solvents were further analyzed using the Kamlet-Abboud-Taft model and the nature of solute-solvent interactions between Ce6 and different protic and aprotic solvents was elucidated. The quantum yields were found highest in protic solvents (except water), followed by aprotic and non-polar solvents. Solvent polarity parameters showed a linear increasing trend with Stokes shift and fluorescence half-life, which indicated the presence of Ce6-solvent interaction. Using the Kamlet-Abboud-Taft model, a direct correlation between the solvent polarity parameters and absorption shift was observed, which substantiated the existence of Ce6-solvent interaction by hydrogen bond formation. The excited state dipole moments in specific protic and aprotic solvents were found to be higher than the ground state dipole moments, implying a more polar nature of Ce6 during excited state transition.     

Synthesis and Characterization of Large PbSe Colloidal Quantum Dots

Large colloidal quantum dots of PbSe (first excitonic peak position >2 µm) are synthesized under different conditions of temperature, the concentration of precursors and their ratio, and concentration of oleic acid and diphenylphosphine. The dependence of the optical properties, grain size dispersity, and process yield on the processing conditions is systematically explored and discussed. The Ostwald ripening process and how it affects grain growth is demonstrated. Finally, the results for the dependence of the absorption wavelength on the grain diameter for large nanocrystals are compared to the relationships reported in the literature for smaller nanocrystals.     

氘代溶剂对丙烯酰胺溶剂化作用的NMR研究

用¹H NMR谱研究了丙烯酰胺（AM）分别在氘代氯仿（CDCl₃）和氘代二甲基亚砜（DMSO-d₆）溶剂以及在不同比率的混合溶剂中,AM的烯键C上的反式两个质子的谱峰位置开始相向移动,重叠,后又反向交错以致形成“类似镜像”的现象,用溶剂化作用讨论了成因;混合溶剂中,随着DMSO-d₆摩尔分数的增加,－NH₂质子和溶剂残余水质子的化学位移逐渐都向低场移动,这与－NH₂和DMSO之间形成氢键,－NH₂和水质子之间既有氢键生成又有质子交换有关.     

Layered nanocomposite of zinc sulfide covered reduced graphene oxide and their implications for electrocatalytic applications

Herein, we have synthesized zinc sulfide nanospheres (ZnS NPs) encapsulated on reduced graphene oxide (RGO) hybrid by an ultrasonic bath (50 kHz/60 W). The physical and structural properties of ZnS NPs@RGO hybrid were analyzed by TEM, XRD, EIS and EDS. As-prepared ZnS NPs@RGO hybrid was applied towards the electrochemical determination of caffeic acid (CA) in various food samples. The ZnS NPs@RGO hybrid modified electrode (GCE) exhibited an excellent electrocatalytic performance towards caffeic acid detection and determination, when compared to other modified electrodes. Therefore, the electrochemical sensing performance of the fabricated and nanocomposite modified electrode was significantly improved owing to the synergistic effect of ZnS NPs and RGO catalyst. Furthermore, the hybrid materials provide highly active electro-sites as well as rapid electron transport pathways. The proposed electrochemical caffeic acid sensor produces a wide linear range of 0.015–671.7 µM with a nanomolar level detection limit (3.29 nM). In addition, the real sample analysis of the proposed sensor has applied to the determination of caffeic acid in various food samples.