First principles studies on the adsorption of rare base-pairs on the surface of B/N atom doped γ-graphyne.

Rare base-pairs consists of guanine (G) paired with rare bases, such as 5-methylcytosine (5-meCyt), 5-hydroxymethylcytosine (5-hmCyt), 5-carboxylcytosine (5-caCyt), and 5-formylcytosine (5-fCyt), have become the focus of epigenetic research because they can be used as markers to detect some chronic diseases and cancers. However, the correlation detection of these rare base-pairs is limited, which in turn limits the development of diagnostic tests and devices. Herein, the interaction of rare base-pairs adsorbed on pure and B/N-doped γ-graphyne (γ-GY) nanosheets was explored using the density functional theory. The calculated adsorption energy showed that the system of rare base-pairs on B-doped γ-GY is more stable than that on pure γ-GY or N-doped γ-GY. Translocation time values indicate that rare base-pairs can be successfully distinguished as the difference in their translocation times is very large for pure and B/N-doped γ-GY nanosheets. Meanwhile, sensing response values illustrated that pure and B-doped γ-GY are the best for G-5-hmCyt adsorption, while the N-doped γ-GY is the best for G-Cyt adsorption. The findings indicate that translocation times and sensing response can be used as detection indexes for pure and B/N doped γ-GY, which will provide a new way for experimental scientists to develop the biosensor components.

The Asymmetric Total Synthesis of the Female-Produced Sex Pheromone of the Tea Tussock Moth.

The tea tussock moth is a pest that damages tea leaves, affecting the quality and yield of tea and causing huge economic losses. The efficient asymmetric total synthesis of the sex pheromone of the tea tussock moth was achieved using commercially available starting materials with a 25% overall yield in 11 steps. Moreover, the chiral moiety was introduced by Evans' template and the key C-C bond construction was accomplished through Julia-Kocienski olefination coupling. The synthetic sex pheromone of the tea tussock moth will facilitate the subsequent assessment and implementation of pheromones as environmentally friendly tools for pest management.

A Series of Lanthanide Coordination Polymers as Luminescent Sensors for Selective Detection of Inorganic Ions and Nitrobenzene.

Seven new lanthanide coordination polymers, namely [Ln(cpt)3H2O)]n(Ln = La (1), Pr (2), Sm (3), Eu (4), Gd (5), Dy (6), and Er (7)), which were synthesized under hydrothermal conditions using 4'-(4-(4-carboxyphenyloxy)phenyl)-4,2':6',4'-tripyridine (Hcpt) as the ligand. The crystal structures of these seven complexes were determined using single-crystal X-ray diffraction, and they were found to be isostructural, crystallizing in the triclinic P1- space group. The Ln(III) ions were nine-coordinated with tricapped trigonal prism coordination geometry. The Ln(III) cations were coordinated by carboxylic and pyridine groups from (cpt)- ligands, forming one-dimensional ring-chain structures. Furthermore, the luminescent properties of complexes 1-7 were investigated using fluorescent spectra in the solid state. The fluorescence sensing experiments demonstrated that complex 4 exhibits high selectivity and sensitivity for detecting Co2+, Cu2+ ions, and nitrobenzene. Moreover, complex 3 shows good capability for detecting Cu2+ ions and nitrobenzene. Additionally, the sensing mechanism was also thoroughly examined through theoretical calculations.

A DFT/TDDFT Investigation on Fluorescence and Electronic Properties of Chromone Derivatives.

The development of quick and precise detection technologies for active compounds in vivo is critical for disease prevention, diagnosis and pathological investigation. The fluorescence signal of the fluorophore usually defines the probe's sensitivity to the chemical being examined. Many natural compounds containing flavone and isoflavone scaffolds exhibit a certain amount fluorescence, albeit with poor fluorescence quantum yields. Therefore, we used density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations to investigate the fluorescence characteristics of chromium-derived fluorophores in more depth. Different substituents are introduced at different positions of the chromone. As weak electron donor groups, alkyl and aromatic groups were discovered to have varying quantum yields on the fluorophore scaffold, and longer alkyl chains are favorable to enhance fluorescence quantum yield. In comparison to the amino group, substituted amino group can avoid group rotation, and the introduction of cyclic amines such as pyrrolidine and heterocyclic amines can improve optical characteristics. The electron-donating methoxy group at position 6 helps to increase the fluorescence quantum yield.

Ratiometric Sensing of Intracellular pH Based on Dual Emissive Carbon Dots.

Accurate monitoring of intracellular pH in living cells is critical for developing a better understanding of cellular activities. In the current study, label-free carbon dots (p-CDs), which were fabricated using a straightforward one-pot solvothermal treatment of p-phenylenediamine and urea, were employed to create a new ratiometric pH nanosensor. Under single-wavelength excitation (λex = 500 nm), the p-CDs gave dual emission bands at 525 and 623 nm. The fluorescent intensity ratio (I525/I623) was linearly related to pH over the range 4.0 to 8.8 in buffer solutions, indicating that the ratiometric fluorescence nanoprobe may be useful for pH sensing. In pH measurements, the p-CDs also demonstrated outstanding selectivity, reversibility, and photostability. Owing to the advantages outlined above, the nanoprobe was used to monitor the pH of HeLa cells effectively. The label-free CD-based ratiometric nanoprobe features comparatively easy manufacturing and longer excitation and emission wavelengths than the majority of previously reported CD-based ratiometric pH sensors, which is ultimately beneficial for applications in biological imaging.

Ab initio studies on graphyne (GY) for the detection of rare bases in DNA.

Graphyne (GY) and functionalized GY have become cutting-edge research materials for the scientific community. In the present work, the adsorption of rare bases -cytosine (Cyt), 5-methylcytosine (5-meCyt), 5-hydroxymethylcytosine (5-hmCyt), 5-formoxylcytosine (5-fCyt), and 5-carboxylcytosine (5-caCyt) on pristine, B- and N-doped γ-GY was investigated by the first-principles density functional method; methods were designed to distinguish these rare bases by the translocation time and sensitivity. Initially, the stability of pristine, B- and N-doped γ-GY was ascertained by the cohesion energy, and the electronic properties were also analyzed by the energy gap and density of state (DOS). When adsorbing over pristine γ-GY, the translocation times of rare bases were 1.34 × 101, 4.71 × 101, 1.19 × 104, 3.77 × 10-1 and 1.93 × 101 s, respectively. The sensitivities were 2.19%, 0.88%, 0.22%, 2.41%, and 0.88%, respectively, which indicates that they were not clearly separated. By doping the impurity atom, the electronic properties can be fine-tuned to change their selectivity. When adsorbing on the B-doped γ-GY, these rare bases showed sensitivities of 24.69%, 27.20%, 43.32%, 29.97%, and 32.24%, respectively. The rare bases showed sensitivities of 10.15%, 9.02%, 17.29%, 0.38%, and 3.76%, respectively, when adsorbing over the N-doped γ-GY, which greatly increases selectivities for recognization. Thus, these results indicate that pristine and doped γ-GY, as the electrical sensing material, can be used to detect rare bases.

CO adsorption, oxidation and carbonate formation mechanisms on Fe3O4 surfaces.

By means of density functional theory calculations that account for the on-site Coulomb interaction via a Hubbard term (DFT+U), we systematically investigated CO adsorption on Fe3O4 surfaces at different coverages. It has been found that more than one CO can coadsorb on one surface iron atom on both Fetet1 and Feoct2 terminations of Fe3O4(111). The uncapped oxygen atom is the active site for CO oxidation on both Fetet1 and Feoct2 terminations of Fe3O4(111). For Fe3O4(110), two CO molecules prefer to coadsorb on one surface iron atom on the A layer; CO prefers to adsorb at the bridge site of the surface octahedral iron atoms at low coverage, while CO prefers to adsorb at the surface tetrahedral iron atom at high coverage on the B layer. It has been found that the surface oxygen atom which is not coordinated to the tetrahedral iron atom is the active site for CO oxidation on the B termination of Fe3O4(001). On the Fe3O4 surfaces, the formation of carbonate has been found to be very stable thermodynamically, which agrees well with experiments. The adsorption mechanism has been analyzed on the basis of projected density of states (PDOS).

Formic acid catalyzed isomerization of protonated cytosine: a lower barrier reaction for tautomer production of potential biological importance.

Tautomerism in nucleotide bases is one of the possible mechanisms of DNA mutation. In spite of numerous studies on the structure and energy of protonated cytosine tautomers, little information is available on the process of their intra- and intermolecular tautomerizations. The catalytic ability of H2O, HCOOH, and the HCOOHH2O group to facilitate the tautomerism of the Cyt2t+ to CytN3+ isomer has been studied. It is shown that the activation free energies of tautomerism in the gas phase are 161.17, 58.96, 26.06, and 15.69 kJ mol-1, respectively, when the reaction is carried out in the absence and presence of H2O, HCOOH, or the HCOOHH2O group. The formation of a doubly hydrogen bonded transition state is central to lowering the activation free energy and facilitating the intramolecular hydrogen atom transfer that is required for isomerization. In the aqueous phase, although the solvent effects of water significantly decrease the activation free energy of intramolecular tautomerization, the isomerization of the Cyt2t+ to CytN3+ isomer remains unfavorable, and the HCOOH and HCOOHH2O group mediated mechanisms are still more favorable. Meanwhile, conventional transition state theory (CTST) followed by Wigner tunneling correction is then applied to estimate the rate constants. The rate constant with Wigner tunneling correction for direct tautomerization is obviously smaller than that of HCOOH-mediated tautomerization, which is the most plausible mechanism. Finally, another important finding is that the product complex (CytN3+HCOOH) is in the rapid tautomeric equilibrium with the reaction complex (Cyt2t+HCOOH) (τ99.9% = 3.84 × 10-12 s), which is implemented by the mechanism of the concerted synchronous double proton transfer. Its lifetime of the formed CytN3+HCOOH complex (τ = 8.33 × 10-9 s) is almost one order of magnitude larger than the time required for the replication machinery to forcibly dissociate a base pair into the monomers during DNA replication (several ns), which is further dissociated into the CytN3+ and HCOOH monomers. The results of the present study demonstrate the feasibility of acid catalysis for DNA base isomerization reactions that would otherwise be forbidden.

Correction: Formic acid catalyzed isomerization of protonated cytosine: a lower barrier reaction for tautomer production of potential biological importance.

Correction for 'Formic acid catalyzed isomerization of protonated cytosine: a lower barrier reaction for tautomer production of potential biological importance' by Lingxia Jin et al., Phys. Chem. Chem. Phys., 2017, 19, 13515-13523.

Can a single water molecule really affect the HO2 + NO2 hydrogen abstraction reaction under tropospheric conditions?

The effect of a single water molecule on the HO2 + NO2 hydrogen abstraction reaction has been investigated by employing B3LYP and CCSD(T) theoretical approaches with the aug-cc-pVTZ basis set. The reaction without water has three types of reaction channels on both singlet and triplet potential energy surfaces, depending on how the HO2 radical approaches NO2. These correspond to the formation of trans-HONO + O2, cis-HONO + O2 and HNO2 + O2. Our calculated results show that triplet reaction channels are favorable and their total rate constant, at 298 K, is 2.01 × 10(-15) cm(3) molecule(-1) s(-1), which is in good agreement with experimental values. A single water molecule affects each one of these triplet reaction channels in the three different reactions of H2O···HO2 + NO2, HO2···H2O + NO2 and NO2···H2O + HO2, depending on the way the water interacts. Interestingly, the water molecule in these reactions not only acts as a catalyst giving the same products as the naked reaction, but also as a reactant giving the product of HONO2 + H2O2. The total rate constant of the H2O···HO2 + NO2 reaction is estimated to be slower than the naked reaction by 6 orders of magnitude at 298 K. However, the total rate constants of the HO2···H2O + NO2 and NO2···H2O + HO2 reactions are faster than the naked reaction by 4 and 3 orders of magnitude at 298 K, respectively. Their total effective rate constant is predicted to be 1.2 times that of the corresponding total rate constant without water at 298 K, which is in agreement with the prediction reported by Li et al. (science, 2014, 344, 292-296).

A new insight into the 5-carboxycytosine and 5-formylcytosine under typical bisulfite conditions: a deamination mechanism study.

5-Methylcytosine (5-MeCyt) can be converted to 5-hydroxymethylcytosine (5-hmCyt) in mammalian DNA by the ten-eleven translocation enzymes. The conventional bisulfite sequencing cannot discriminate 5-hmCyt from 5-MeCyt, whereas the oxidation products of 5-hmCyt, 5-carboxycytosine (5-caCyt) and 5-formylcytosine (5-fCyt) enable them to be identified in bisulfite sequencing. This mechanism likely involves the decarboxylation of 5-caCyt and deformylation of 5-fCyt to cytosine (Cyt) before deamination. Another possibility could be a direct bisulfite-induced deamination reaction followed by decarboxylation and deformylation. Here the HSO3(-)-induced direct hydrolytic deamination of 5-caCytN3(+)-SO3(-) (paths A and B) and 5-O(+)fCytN3(+)-SO3(-) (paths C and D) has been explored at the MP2/6-311++G(3df,3pd)//B3LYP/6-311++G(d,p) level. The activation free energy (ΔG(s≠) = 54.16 kJ mol(-1)) of the direct hydrolytic deamination of 5-caCytN3(+)-SO3(-) path A is much lower than the ΔG(s≠) of CytN3(+)-SO3(-) (100.91 kJ mol(-1)) under bisulfite conditions, implying that 5-caCyt may firstly involve a process of deamination. Meanwhile, the ΔG(s≠) (103.84 kJ mol(-1)) of the HSO3(-)-induced direct hydrolytic deamination of 5-O(+)fCytN3(+)-SO3(-) path C is in close proximity to our previous theoretical data for CytN3(+)-SO3(-), indicating that the deamination of 5-fCyt is also likely to occur in the presence of bisulfite. Meanwhile, the HSO3(-)-induced direct hydrolytic deamination of 5-caCytN3(+)-SO3(-) path A and 5-O(+)fCytN3(+)-SO3(-) path C is represented and has been further explored in the presence of one and two water molecules. The results show that both in the gas and aqueous phases, the participation of one and two water molecules makes the HSO3(-)-induced direct hydrolytic deamination of 5-caCytN3(+)-SO3(-) path A unfavorable, whereas the contribution of one and two water molecules facilitates the HSO3(-)-induced direct hydrolytic deamination of 5-O(+)fCytN3(+)-SO3(-) path C.

Is the contribution of cis and trans protonated 5-methylcytosine-SO3(-) isomers equal in the conversion to thymine-SO3(-) under bisulfite conditions? A theoretical perspective.

Cytosine (Cyt) can be converted to 5-methylcytosine (5-MeCyt) in CpG sequences of DNA. Conventional bisulfite sequencing can discriminate Cyt from 5-MeCyt, however inappropriate conversion of 5-MeCyt to thymine and a failure to convert Cyt to uracil always occur when Cyt and 5-MeCyt are treated with bisulfite, which would lead to erroneous estimates of DNA methylation densities. Here, the direct hydrolytic deamination of cis (paths A-C) and trans (paths A'-C') 5-MeCytN3(+)-SO3(-) isomers with bisulfite have been explored at the MP2/6-311++G(3df,3pd)//B3LYP/6-311++G(d,p) level. The activation free energies (ΔG(s-a≠)) of the cis and trans 5-MeCytN3(+)-SO3(-) isomers' paths exhibit no obvious differences, implying both isomers may make an equal contribution to the hydrolytic deamination of 5-MeCyt under bisulfite conditions. It is greatly expected that these results could aid experimental scientists to explore new methods to avoid the formation of the deaminated reactants (5-MeCytN3(+)-SO3(-)). Meanwhile, the HSO3(-)-induced direct hydrolytic deamination of cis and trans 5-MeCytN3(+)-SO3(-) isomers is represented by paths A and A', respectively, and has been further explored in the presence of two water molecules. It was found that the contribution of two water molecules renders the HSO3(-)-induced direct hydrolytic deamination of cis and trans 5-MeCytN3(+)-SO3(-) isomers by paths A and A' favourable. In addition, the ΔG(s-a≠) values (85.74-85.34 kJ mol(-1)) of the rate-limiting steps of the two water-mediated paths A and A' are very close to that of the theoretical value for CytN3(+)-SO3(-) (88.18 kJ mol(-1)), implying that the free barrier gap between Cyt and 5-MeCyt is very small under bisulfite conditions. This further suggests that bisulfite sequencing technology may be easily influenced by the external environment.

Screening novel candidates of ZL003-based organic dyes for dye-sensitized solar cells by modifying auxiliary electron acceptors: A theoretical study.

In this work, a series of ZL003-based free-metal sensitizers with the donor-acceptor-π- conjugated spacer-acceptor (D-A-π-A) structure were designed by modifying auxiliary electron acceptors for the potential application in dye-sensitized solar cells. The energy levels of frontier molecular orbitals, absorption spectra, electronic transition, and photovoltaic parameters for all studied dyes were systematically evaluated using density functional theory (DFT)/time-dependent DFT calculations. Results illustrated that thienopyrazine (TPZ), selenadiazolopyridine (SDP), and thiadiazolopyridine (TDP) are excellent electron acceptors, and dye sensitizers functionalized by these acceptors have smaller HOMO-LUMO gaps, obviously red-shifted absorption bands and stronger light harvesting. The present study revealed that the photoelectric conversion efficiency (PCE) of ZL003 is around 13.42 % with a JSC of 20.21 mA·cm-2, VOC of 966 mV and FF of 0.688 under the AM 1.5G sun exposure, in good agreement with its experimental value (PCE = 13.6 ± 0.2 %, JSC = 20.73 ± 0.20 mA·cm-2, VOC = 956 ± 5 mV, and FF = 0.685 ± 0.005.). With the same procedure, the PCE values for M4, M6, and M7 were estimated to be as high as 19.93 %, 15.38 %, and 15.80 % respectively. Hence, these three dyes are expected to be highly efficient organic sensitizers applied in practical DSSCs.

The conversion of protonated cytosine-SO3(-) to uracil-SO3(-): insights into the novel induced hydrolytic deamination through bisulfite catalysis.

The induced ability of bisulfite to facilitate the hydrolytic deamination of the protonated cytosine-SO3(-) has been studied at the MP2/6-311++G(3df,3pd)//B3LYP/6-311++G(d,p) level and CBS-QB3 approach, respectively. In the gas phase, two distinct groups of mechanisms were explored, the direct hydrolytic deamination (path A) and HSO3(-)-induced hydrolytic deamination (paths B-D), and it indicates that the direct hydrolytic deamination of protonated cytosine-SO3(-) (path A) is unlikely because of the high activation free energy involved in the rate-limiting step, whereas the presence of bisulfite (paths B-D) significantly contributes to decreasing the activation free energy. In the aqueous phase, although the solvent effects of water significantly decrease the activation free energy of path A, the direct hydrolysis reaction remains unfavorable and the HSO3(-)-induced mechanism is still more favorable, which is in agreement with previous experimental data. The pseudo-first-order rate constant (k') for direct hydrolysis is obviously smaller than that of HSO3(-)-induced hydrolytic deamination, which is the most plausible mechanism, where the calculated the k' (1.99-3.81 × 10(-5) s(-1)) is in close proximity to the experimentally determined the pseudo-first-order rate constant (26.2 × 10(-5) s(-1)). Furthermore, the results also manifest that there is a positive correlation between the k' and temperature, and the ratio of reaction rates between direct hydrolysis reaction and HSO3(-)-induced hydrolytic deamination increases with the increase of the bisulfite concentration at a given temperature.

A simple indanone-based red emission fluorescent probe for the rapid detection of cysteine in vitro and in vivo.

Cysteine is a vital biothiols that plays an important role in numerous physiological and pathological processes. The development of simple molecule tools for detection and analysis Cys in subcellar environment is significant for further exploring their pathophysiological. In this work, a simple but activated fluorescent probe AMIA was constructed with a donor-π-accepter (D- π -A) structure, which using an indanone as the electron-withdrawing unit acting as the fluorophore, dimethylamino group attached to the position 4 of the benzene ring as the electron-donating, two double bonds as the linker group, and the acryloyl ester group as the trigger and response unit. This probe AMIA was exhibited highly selective and sensitive response to Cys over other amino acids and ions under physiological conditions. It was found that AMIA showed a red turn-on fluorescence response at 630 nm towards Cys with a large stroke shift of 170 nm and a very low detection limit of 26.3 nM. HRMS, 1H NMR and TD-DFT calculation further confirmed that the response mechanism is the Cys triggered the addition-cyclization reaction between AMIA' acryloyl group and Cys' sulfhydryl and amino unit, leading to the release of a red fluorescent dye AMIA-OH, which can be identified by naked eyes. Furthermore, AMIA was successfully applied for simultaneous determination of Cys in living cells and zebrafish with lower cytotoxicity and good cell permeability. We hope that this novel indanone-based probe AMIA will provide a new reference for visualized Cys in other complex biological system.

A simple "turn-on" fluorescent probe capable of recognition cysteine with rapid response and high sensing in living cells and zebrafish.

Cysteine (Cys), an essential biological amino acid, participates several crucial functions in various physiological and pathological processes. The sensitive and specific detection of Cys is of great significance for understanding its biological function to disease diagnosis. Herein, we designed and synthesized a simple fluorescence sensor 2-(benzothiophen-2-yl)-4-oxo-4H-chromen-3-yl acrylate (BTCA) composed of a flavonol skeleton as the fluorophore and acrylic ester group as the recognition receptor. Probe BTCA displayed high selectivity and extremely fast response toward Cys in phosphate buffer solution in the presence of other competitive species even Homocysteine (Hcy) and Glutathione (GSH) owing to a specific conjugate addition-cyclization reaction between the acrylate moiety and Cys. The photoluminescence mechanism of probe BTCA toward Cys was modulated by excited state intramolecular proton transfer (ESIPT) process. The sensing property for Cys was studied by UV-Visible, fluorescence spectrophotometric analyses and time-dependent density functional theory (TD-DFT) calculations, those results indicated that probe BTCA possessed excellent sensitivity, higher specificity, dramatically "naked-eye" fluorescence enhancement (30-fold), high anti-interference ability, especially immediate response speed (within 40 s). Additionally, the practicability of sensor BTCA in exogenous and endogenous Cys imaging in living cells and zebrafish was elucidated as well, suggesting that it has remarkedly diagnostic significance in physiological and pathological process.

N-{2-[(2-chlorothieno[3,2-d]pyrimidin-4-yl)amino]ethyl}-3-methoxybenzamide: design, synthesis, crystal structure, antiproliferative activity, DFT, Hirshfeld surface analysis and molecular docking study.

The compound N-{2-[(2-chlorothieno[3,2-d]pyrimidin-4-yl)amino]ethyl}-3-methoxybenzamide (8) was synthesized by the condensation of 3-methoxybenzoic acid (7) with N1-(2-chlorothieno[3,2-d]pyrimidin-4-yl)ethane-1,2-diamine (6). This intermediate was prepared from methyl 3-aminothiophene-2-carboxylate (1) by the condensation with urea, chlorination with phosphorus oxychloride and then condensation with ethane-1,2-diamine. The crystal structure of the title compound was determined and the crystal of the title compound belongs to the tetragonal system, space group P4(3) with a = 9.4694(10) Å, b = 9.4694(10) Å, c = 18.886(3) Å, α = 90°, ß = 90°, γ = 90°. The optimized geometric bond lengths and bond angles obtained by using density functional theory (DFT) have been compared with X-ray diffraction values. The calculated HOMO and LUMO energies showed the character of the title compound. The molecular electrostatic potential (MEP) surface map of the related molecule was investigated with theoretical calculations at the B3LYP/6-311 + G(d,p) levels. A quantitative analysis of the intermolecular interactions in the crystal structures has been performed using Hirshfeld surface analysis. In addition, the title compound possesses marked inhibition against the proliferation of human colon cancer cell line HT-29 (IC50 = 1.76 µM), human lung adenocarcinoma cell line A549 (IC50 = 1.98 µM) and human gastric cancer cell line MKN45 (IC50 = 2.32 µM), displaying promising anticancer activitiy. The molecular docking studies revealed that the title compound may exhibit activity inhibiting PDB:3D15.Communicated by Ramaswamy H. Sarma.

Highly efficient red-emitting carbon dots as a "turn-on" temperature probe in living cells.

Nanothermometers, which can precisely detect the intracellular temperature changes, have great potential to solve questions concerning the cellular processes. Thus, the temperature sensors that provide fluorescent "turn-on" signals in the biological transparency window are of highly desirable. To meet these criteria, this work reported a new "turn-on" carbon dot (CD)-based fluorescent nanothermometry device for sensing temperature in living cells. The CDs that emit bright red fluorescence (R-CDs; λmax = 610 nm in water) were synthesized with o-phenylenediamine as carbon precursor via a facile solvothermal method. The R-CDs in water were almost nonfluorescent at 15 °C. As the temperature increased, the fluorescence intensity of R-CDs exhibited a gradual increase and the final enhancement factor was greater than 21-fold. The fluorescence intensity exhibited a linear response to temperature and a high-sensitive variation of ≈13.3 % °C-1 was detected within a broad temperature range of 28-60 °C. Moreover, the R-CD thermal sensors also exhibited high storage stability, excellent response reversibility and superior photo- and thermo-stability. Due to its good biocompatibility and "intelligent" response to external temperature, the nanothermometer could be applied for sensing temperature changes in biological media.

Efficient ß-Carboline Alkaloid-Based Probe for Highly Sensitive Imaging of Endogenous Glutathione in Wheat Germ Tissues.

Discriminative detection of GSH is achieved by employing a highly sensitive and selective fluorescent probe (KL-DN) that bears ß-carboline alkaloid as a potential fluorophore and an azide group as the recognition unit. A rapid fluorescence off-on change is caused by special redox reaction; KL-DN has the capability of monitoring endogenous GSH in wheat germ tissues, indicating that this probe holds great potential for biological applications in plant tissues.

One-step synthesis of yellow-emissive carbon dots with a large Stokes shift and their application in fluorimetric imaging of intracellular pH.

A new nanoprobe based on yellow-emissive carbon dots (Y-CDs) was developed for sensing full-range intracellular pH values. By using o-phenylenediamine as the raw material, Y-CDs with a quantum yield of 31% were prepared through a one-pot solvothermal carbonization method. The Y-CDs exhibited a distinctive fluorescence emission peak at 570 nm with excitation at 450 nm, showing a very large Stokes shift (120 nm). Notably, the nanoprobe revealed a linear relationship between fluorescence intensity and pH value within the range of pH 4.0 to 8.2, exhibiting the ability of this probe to monitor full-range intracellular pH variations. In addition, the nanosensor possessed excellent photostability and fluorescence reversibility in pH measurements and showed excellent selective detection of the influences of other biological species. The CD-based nanoprobe was successfully used to perform quantitative fluorescence imaging of intracellular pH variation, demonstrating its promise for application in cellular systems.