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Scanning tunneling microscopy/spectroscopy (STM/S) is a powerful experimental tool to understand the electronic structure of materials at the atomic scale, with energy resolution down to the microelectronvolt range. Such resolution requires a low-vibration laboratory, low-noise electronics, and a cryogenic environment. Here, we present a thorough enumeration and analysis of various noise sources and their contributions to the noise floor of STM/S measurements. We provide a comprehensive recipe and an interactive python notebook to input and evaluate noise data, and to formulate a custom step-by-step approach for optimizing the signal-to-noise ratio in STM/S measurements. [ABSTRACT FROM AUTHOR]

Recent experiments on FeSe films grown on SrTiO3 (STO) suggest that interface effects can be used as a means to reach superconducting critical temperatures (Tc) of up to 80 K (ref. ). This is nearly ten times the Tc of bulk FeSe and higher than the record value of 56 K for known bulk Fe-based superconductors. Together with recent studies of superconductivity at oxide heterostructure interfaces, these results rekindle the long-standing idea that electron pairing at interfaces between two different materials can be tailored to achieve high-temperature superconductivity. Subsequent angle-resolved photoemission spectroscopy measurements of the FeSe/STO system revealed an electronic structure distinct from bulk FeSe (refs , ), with an energy gap vanishing at around 65 K. However, ex situ electrical transport measurements have so far detected zero resistance-the key experimental signature of superconductivity-only below 30 K. Here, we report the observation of superconductivity with Tc above 100 K in the FeSe/STO system by means of in situ four-point probe electrical transport measurements. This finding confirms FeSe/STO as an ideal material for studying high-Tc superconductivity. [ABSTRACT FROM AUTHOR]

Abstract: A productive synthesis of benzo[a]phenoxazine derivative SSJ-183 (1), a promising lead for antimalarial agents, was developed using a one pot procedure. Furthermore, N-deethylated metabolite 3 and bis-N,N-deethylated metabolite 4 were synthesized by the application of the method. The metabolites 3 and 4 showed comparable and ∼2-fold increased activities against drug-sensitive and drug-resistant Plasmodium falciparum parasites. [Copyright &y& Elsevier]

Abstract: A series of symmetric phenoxazinium chlorides, which have good solubility in polar solvents and good thermal stability, were evaluated in acetonitrile solution for third-order nonlinear optical properties at 532 nm using nanosecond and picosecond Z-scan techniques. The title compounds exhibit strong reverse saturable absorption and nonlinear refraction. The third-order nonlinear optical properties under nanosecond laser beam irradiation and picosecond laser beam irradiation were obtained. The nonlinear mechanism is revealed as excited-state nonlinearity by a picosecond pump-probe response experiment for one of the compounds. [Copyright &y& Elsevier]

Abstract: A series of 5-phenyliminobenzo[a]phenoxazine derivatives were synthesized. The in vitro antiprotozoal activities were evaluated against Plasmodium falciparum K1, Trypanosoma cruzi, Leishmania donovani and Trypanosoma brucei rhodesiense. N,N-Diethyl-5-((4-methoxyphenyl)imino)-5H-benzo[a]phenoxazin-9-amine shows IC50 =0.040μmolL−1 with a selective index of 1425 against Plasmodium falciparum K1. [Copyright &y& Elsevier]

Abstract: A ratiometric, near-infrared, and fully water-soluble probe, a phenoxazinium-based chemosensor bearing an anilino thiaazacrown, was successfully synthesized and characterized. The use of this probe for the selective ratiometric detection of Hg2+ in pure water is reported. The probe shows good selectivity for Hg2+, and a large blue shift (75nm) of the complex’s absorption maximum was observed. [Copyright &y& Elsevier]

Abstract: A new series of unsymmetrical phenoxazinium chlorides, featuring a heterocyclic aromatic π-bridge with dialkylamino donors, were evaluated in acetonitrile solution for third-order nonlinear optical properties at 532nm using a Z-scan technique. The title compounds exhibit strong reverse saturable absorption and nonlinear refraction. The third-order nonlinear optical properties were obtained under nanosecond and picosecond laser beams. The nonlinear mechanism is revealed by the excited-state nonlinearity, as observed from a picosecond pump-probe response experiment for one of the compounds. They are potential nonlinear optical materials because they also have good solubility in polar solvents and good thermal stability. [Copyright &y& Elsevier]

Abstract: A series of phenothiazinium chlorides, which have good solubility in polar solvents and good thermal stability, were evaluated in dimethyl sulfoxide solution for third-order nonlinear optical properties at 532nm using a nanosecond and picosecond Z-scan technique. The title compounds exhibit strong reverse saturable absorption and nonlinear refraction. The third-order nonlinear optical properties were obtained under irradiation with either a nanosecond or picosecond laser. The nonlinear mechanism is revealed as excited-state nonlinearity by a picosecond pump-probe response experiment for one of the compounds. The absorption and emission maxima, Stokes shift and quantum yield are also reported. [ABSTRACT FROM AUTHOR]

A series of novel acrylate monomers bearing stilbene segments with D-π -A structure, 4-methacrylate-4'-nitro stilbene (NS), 4-(6-methacrylate)hexyl-4'-nitro stilbene (HNS) and 4-(6-methacrylate)hexyl-2,3-dimethoxy-4'-nitro stilbene (DMHNS), were synthesized by the Witting reaction and polymerized by free radical polymerization. These stilbene-containing monomers and polymers were fully characterized, and their fluorescent properties in solution and solid state were also investigated. The emission band of monomers and corresponding polymers in solution also showed a remarkable effect with increasing polarity of the solvent. More importantly, the fluorescence emission could be adjusted from green to orange and even red regions by forming donor-π -acceptor (D-π -A) construction. [ABSTRACT FROM AUTHOR]

Abstract: In vivo antimalarial drug candidates screening test was carried out on a series of water-soluble 3,7-bis(dialkylamino)phenoxazin-5-ium derivatives. Among them, 3-(diethylamino)-7-(piperidin-1-yl)phenoxazin-5-ium chloride (SSJ-206) showing highest efficacy was chosen for further pharmcodynamics and pharmacokinetics study. It was supported from these data that the phenoxazinium salts, SSJ-206, would be one of hopeful candidates as an oral antimalarial drug. [Copyright &y& Elsevier]

Abstract: Zinc chloride-free 3,7-bis(dialkylamino)phenoxazinium salts carrying different anions (chloride, bromide, hydrosulfate, tosylate, perchlorate and nitrate) were synthesized with the yields up to 84%. Their structures were determined by spectroscopy and elemental analyses. [Copyright &y& Elsevier]

Taking advantage of the excellent host–guest complexation ability between an auxochrome (adamantane group) and CB[7], the fluorescence emission performance of dyes in water was effectively improved with the addition of two equivalents of CB[7], which provided an efficient method for increasing fluorescence intensity in aqueous environments. Furthermore, these dyes with the host were successfully used in cell imaging. [ABSTRACT FROM AUTHOR]

Abstract: A selective, sensitive probe for Hg(II) ions, 7-(diethylamino)-3-methyl-2H-benzo[b][1,4] oxazine-2-thione (1), is developed. Compound 1 behaves as a ratiometric probe, exhibiting a large blue shift of 100nm in its absorption spectra upon exposure to Hg(II) ions. The dramatic color change of the solution made ‘naked-eye’ detection of Hg(II) ions possible. Emission spectra of 1 displayed a selective enhancement in intensity in the presence of Hg(II) ions. ESI+-MS analysis indicated that Hg2+-induced desulfurization caused the large absorption response. [ABSTRACT FROM AUTHOR]

The idea that preformed Cooper pairs could exist in a superconductor at temperatures higher than its zero-resistance critical temperature (Tc) has been explored for unconventional, interfacial, and disordered superconductors, but direct experimental evidence is lacking. We used scanning tunneling noise spectroscopy to show that preformed Cooper pairs exist up to temperatures much higher than Tc in the disordered superconductor titanium nitride by observing an enhancement in the shot noise that is equivalent to a change of the effective charge from one to two electron charges. We further show that the spectroscopic gap fills up rather than closes with increasing temperature. Our results demonstrate the existence of a state above Tc that, much like an ordinary metal, has no (pseudo)gap but carries charge through paired electrons. [ABSTRACT FROM AUTHOR]

The fluorescence of functional dyes was generally quenched in aqueous solution, which hindered their application in water‐bearing detections. In this work, a novel strategy based on host‐guest interaction was provided for the purpose of fluorescence enhancement in aqueous solution and cell imaging. Three adamantane‐modified fluorescent dyes (Coum‐Ad, NP‐Ad, NR‐Ad) with coumarin, 1,8‐naphthalimide and Nile Red as fluorophores were initially designed and prepared. The ((adamantan‐1‐yl)methyl)amino group, as the auxochrome of those dyes, complexed with methylated β‐cyclodextrin (M‐β‐CD) via supramolecular interaction, and then fluorescent supramolecular nanoparticles (FSNPs) were formed by self‐assembly in water. The inclusion equilibrium constant (K) could be as high as 3.94×104 M−1. With the addition of M‐β‐CD, fluorescence quantum yields of these dyes were separately improved to 69.8 %, 32.9 % and 41.3 %. Inspired by the above satisfactory results, six adamantane‐modified probes organelle‐NPAds with organelle‐targeting capability were further obtained. As the formation of hydrogen bonds between organelle‐NPAd2 and M‐β‐CD verified by theoretical calculation, K of organelle‐NPAd2 (5.13×104 M−1~4.53×105 M−1) with M‐β‐CD was higher than that of organelle‐NPAd1 (1.15×104 M−1~3.66×104 M−1) and their fluorescence quantum yields increased to 32.8 %~83.6 % in aqueous solution. In addition, fluorescence enhancement was realized in cell imaging with the addition of M‐β‐CD. [ABSTRACT FROM AUTHOR]

A series of viscosity probes targeting different organelles were obtained using a single hemicyanine dye as the matrix structure. Specifically, probes 1a–d were obtained by introducing four amines (6-amino-2H-chromen-2-one, N-(2-aminoethyl)-4-methylbenzenesulfonamide, dodecan-1-amine and N,N diphenylbenzene-1,4-diamine) into the indole hemicyanine dye of the carboxylic acid with a D–π-A structure. Their maximum absorption wavelengths were in the range 570–586 nm and they had relatively large molar absorption coefficients, while their maximum emission wavelengths in the red light region were in the range 596–611 nm. Moreover, their fluorescence intensity in glycerol was 35–184 times higher than that in phosphate buffer solution (PBS). The lg(Fl) and lg η of probes 1a–d showed good linearity with high correlation coefficients according to the Förster–Hoffman equation. In addition, cell staining experiments demonstrated that 1a–c could target lysosomes, endoplasmic reticulum and mitochondria, respectively. They could also undergo viscosity-detectable changes in the corresponding organelles under the action of the corresponding ion carriers. [ABSTRACT FROM AUTHOR]

Two chromenoquinoline-based fluorescent probes 1a-b have been synthesized and investigated. Photofading behaviors of compounds 1a-b showed that at least 89% absorption remained after 6 h irradiating, meanwhile, many of ions and amino acids had negligible impacts on their fluorescence intensity, which meant they had excellent photostability and selectivity. Probes 1a-b exhibited strong absorption and emission in organic solvents with large fluorescence quantum yields, even in water probe 1a still had a relatively large fluorescence quantum yield (20%). Combined with DFT calculation, the influence of alkylation on optical properties of 1b was elucidated. In addition, the fluorescence intensity of probe 1b with red emission enhanced by 5.4-fold and 5.3-fold after DNA and RNA added, and the fluorescence quantum yield increased from 3% to 17% and 14%, respectively, but the neutral molecule 1a had no response to nucleic acid. Furthermore, confocal microscopy imaging of probes 1a-b showed that 1a targeted lipid droplets while the methylated probe 1b to nucleus in living HeLa cells. The results indicated that the subcellular targeting zone could be changed by alkylation of nitrogen atom on chromenoquinoline-based conveniently, which provided a new idea for designing and synthesizing new subcellular labeled probes. [ABSTRACT FROM AUTHOR]

Polarity and viscosity, as important microenvironment parameters, play an essential role in cell metabolism. Therefore, 9-acridine carboxaldehyde reacted with cyano compounds to obtain polarity-sensitive probes 1a–b and viscosity-sensitive probes 1c–d. Among them, with the increase in solvent polarity, the maximum emission wavelength of acridine-dicyanoisophorone-based probe 1a red-shifted from 553 nm to 594 nm, the fluorescence quantum yield increased from 0.5% to 35.6%, and the fluorescence intensity enhanced 38 fold. The acridine-cyanofuranone based probe 1b also has a polarity response similar to 1a. Nevertheless, when the solution viscosity increased from 0.89 cP (100% water) to 856 cP (1% water), the fluorescence intensity of the acridine-tricyanodihydrofuran based probe 1c at 430 nm enhanced 5.6 times. The acridine-cyanobenzothiazole based probe 1d also had a viscosity response similar to 1c. In addition, probes 1a–b were used for further HeLa cell imaging experiments due to their good photostability and the results suggested that probe 1a could locate lipid droplets and probes 1b–c could stain lysosomes. Moreover, probes 1a–b could dynamically monitor the changes in intracellular polarity. [ABSTRACT FROM AUTHOR]

The neutral fluorescent probes 1a-1c based on D-π-A-π-D structure, with benzopyranoquinoline as the fluorophore and the electron-donating groups at both ends, were developed, which emitted dual-channel fluorescence in different pH environments. Among them, probe 1a with both N,N -diethyl group and morpholine ring as electron-donating groups exhibited the best fluorescence performance, showing a red shift of 85 nm in dual emission at 505 nm and 590 nm, and a Stokes shift of 95 nm in both channels. The neutral 1a displayed green fluorescence specifically targeting mitochondria, while the protonated form 1a+H + resulting in red fluorescence localized in lysosomes. The ability to distinguish healthy and pathological cells such as cancer or inflammation could be achieved by observing the differences in red fluorescence within lysosomes. Probe 1a could migrate and retarget between mitochondria and lysosomes, and it was discovered by the physiological effects of chloral hydrate experiments. In addition, the dynamic changes in morphology and movement of mitochondria and lysosomes during cellular autophagy through the variation of fluorescence intensity in green and red channels induced by rapamycin and starvation conditions had been investigated deeply. [Display omitted] • Novel pH sensitive probes 1a-1c based on D-π-A-π-D structure with ICT mechanism are introduced. • Probe 1a enables distinction between healthy and pathological cells through lysosomal pH monitoring. • The dual-channel strategy of probe 1a allows independent targeting of mitochondria and lysosomes, with organelle migration capability. • Probe 1a enables long-term observation of coordinated interactions between mitochondria and lysosomes during cellular autophagy. [ABSTRACT FROM AUTHOR]

[Display omitted] • The photooxidation of thiocarbonyl photosensitizers were further studied. • It provides a feasible way to solve the photosensitizer residues problem in small molecule level. • The heavy-atom-free photosensitizer 1a mitochondrial targeting ability was verified. Photodynamic therapy (PDT) has been successfully applied in clinical treatment several years. However, after finished treatment process the residual photosensitizer will spread throughout body, which forces patients stay in the dark room to avoid exposure in sunlight several weeks. Therefore, develop degradable photosensitizer could effectively eliminate this inconvenience. In the past, researchers have developed degradable photosensitizers based on supramolecular structure. In this study, we achieved the same effect in small molecule level. Three thiocarbonyl photosensitizers (PS) have high photogenerated 1O 2 quantum yield and can be photodegraded by laser irradiation within 15 min. And due to its high phototoxicity and low toxicity, thiocarbonyl PS still maintains its high phototoxicity. Especially, mitochondrial targeting PS 1a has better properties than many BODIPY or cyanine heavy-atom-free photosensitizers. It only needs 1 μM to reduce HeLa cell activity to 30%. Finally the thiocarbonyl PS provided a convenient way to solve the PS residue problem without sacrificing PDT efficiency. [ABSTRACT FROM AUTHOR]

Abstract: The molecular electrostatic potential (ESP) properties were used for the explanation of organic electric memory ability. Several chalcone compounds, owning a negative ESP region locates at the oxygen atom, were selected in this paper to validate the selection of compounds for organic memory materials. The synthesis, characterization, fabrication of the organic memory devices and the electrical properties for them were reported, and they were shown as WORM (write once read many times) type memory devices. The molecular geometries were optimized by the addition of a changeable electric field in the x direction inside the molecules using FF-DFT (Finite Field-Density Functionary Theory) method. The relationship between ESP of the molecules under different electric field and the property was discussed, and the mechanisms associated with the memory effect were also elucidated from DFT calculation results. [Copyright &y& Elsevier]

As a special form of autophagy, mitophagy is a pivotal mechanism governing cellular metabolism and physiology. Viscosity monitoring is an important aspect for real-time visualization of the mitophagy process. Hence, the development of high-performance viscosity probes is crucial for investigating dynamic pathological processes related to mitophagy. This study presents the discovery of mitochondria near-infrared and aggregation-induced emission probes with neutral structure. Probes 1a - 1b were connected quinoline/naphthidine malononitrile and coumarin units with a double bond, the absorption maxima were at 433–471 nm; emission maxima were at 605–720 nm with large Stokes shifts of 170–279 nm in solvents of different polarity. As the environmental viscosity increases from 0.89 cP to 856 cP, the fluorescence intensity of probe 1a and probe 1b is enhanced by 418-fold and 769-fold, respectively, which due to the restricted rotation and inhibited twisted intramolecular charge transfer in high viscosity systems. In addition to excellent NIR, hypotoxicity, and mitochondrial targeting capabilities, probes 1a - 1b were successfully applied to detect changes in mitochondrial viscosity during starvation or rapamycin-induced mitophagy. These remarkable features make probes 1a - 1b as promising candidates for investigating dynamic pathological processes related to mitophagy with significant potential for biological applications. [Display omitted] • Two electroneutral, NIR and AIE probes with exhibit mitochondrial targeting abilily. • These probes nearly showed dramatic "OFF–ON" fluorescent response with viscosity increasing. • These probes can monitor the viscosity changes of starvation and drug-induced mitophagy in real time. [ABSTRACT FROM AUTHOR]

Abstract: A series of unsymmetric pentamethine cyanine dyes featuring benzoxazolyl and benzothiazolyl groups were synthesized, the structures were characterized by 1H NMR, UV–vis absorption spectroscopy and mass spectrometry. The dyes with different anions such as chloride, tetraphenylborate and tetra(4-fluorophenyl)borate were also obtained and their solubility can be changed by the choice of the anion part. The third-order nonlinear optical properties were measured by the Z-scan technique with a picosecond laser beam at 532 nm in DMF solution. The third-order nonlinear optical susceptibilities χ (3) and the second-order hyperpolarizabilities γ'' were obtained. The results reveal that these dyes exhibit strong reverse saturable absorption and nonlinear refraction. [Copyright &y& Elsevier]

Abstract: GalNAc-T14 was identified as a novel IGFBP-3 binding partner in previous studies. Here, we furtherly confirmed the interaction between them by confocal microscopy, and identified the binding domain and probable interaction sites of GalNAc-T14 with IGFBP-3. The result of subcellular localization indicated that GalNAc-T14 was distributed in the cytosol, whereas IGFBP-3 existed in the cytosol and nucleolus. Confocal analyses demonstrated that IGFBP-3 and GalNAc-T14 colocalized in the cytosol. The result from yeast two hybrid assay showed that the C terminus of GalNAc-T14 (408–552aa) was essential for the interaction between GalNAc-T14 and IGFBP-3, especially Tyr408, Pro409, and Glu410 of GalNAc-T14 may play key roles in the interaction with IGFBP-3. In conclusion, these studies demonstrated that IGFBP-3 and GalNAc-T14 are colocalized in MCF-7 cells and confirmed the interaction between IGFBP-3 and GalNAc-T14. This interaction may play an important role in the functional regulation of IGFBP-3. [Copyright &y& Elsevier]

Abstract: Six symmetrical and unsymmetrical trimethine cyanine dyes bearing benzothiazolyl and benzoxazolyl groups were synthesized. Their linear optical properties were studied. It was found that the variation of hetero atoms play an important role in the spectral properties of the dyes. Sequential replacement of the oxygen atom by the sulfur atom resulted in a change in shade from yellow to purple. In order to understand the relationship between the molecular structures and the spectral properties of these dyes, theoretical calculations were made using the Gaussian programme. Key parameters related to absorption and emission spectra were reported and discussed. [Copyright &y& Elsevier]

Abstract: Six new compounds: [M(dps)(dca)2]∞ (1, M=Cd; 2, M=Fe), [Cu(dps)(dca)2(CH3OH)2]∞ (3), [M(dps)2(SCN)2(H2O)2]∞ (4, M=Cd; 5, M=Fe), [Cu(dps)4(SCN)2]∞ (6), (dps=4,4′-dipyridyl sulfide, dca=dicyanamide) were synthesized, characterized by FT-IR, element analysis and TG. Their structures were determined by single crystal X-ray diffraction. According to the structure analysis, compounds 1 and 2 are three-dimensional microporous frameworks constructed by Cu–dps–Cu and Cu–dca–Cu bridges; compound 3 shows a zigzag chain constructed by a Cu–dps–Cu bridge; compounds 4 and 5 show double-stranded chains constructed by a Cu–(dps)2–Cu bridge while thiocyanate anions act as terminal groups; compound 6 is a mononuclear compound. Moreover, compound 1 shows visible yellow luminescence under UV light irradiation and such phenomenon is mainly attributed to inter-ligand transitions. [Copyright &y& Elsevier]

Abstract: Tropical diseases are serious infectious diseases caused by protozoan parasites in tropical and subtropical regions. Novel, effective, safe, and inexpensive drugs are required to treat the parasites and contribute to the global goal of eradication. A series of phenothiazinium chlorides were synthesized and evaluated for in vitro activities against Plasmodium falciparum, Trypanosoma cruzi, Trypanosoma brucei rhodesiense, and Leishmania donovani. Notably, 3,7-bis(piperidinyl)phenothiazinium chloride showed IC50 of 0.097 μmol L−1 against T. cruzi and 3,7-bis(benzyl(methyl)amino)phenothiazinium chloride exhibited IC50 of 0.081 μmol L−1 against L. donovani, although the cytotoxicities of these compounds against L-6 cells were observed at low concentration. [ABSTRACT FROM AUTHOR]

Abstract: The third-order nonlinear optical properties of a series of resonance benzo[a]phenoxazinium salts in acetic acid solution were studied using the Z-scan technique employing a Nd:YAG nanosecond laser at 532 nm. The compounds displayed strong reverse absorption with third-order nonlinear optical coefficients of 0.42–1.20 × 10−11 esu and second hyperpolarizabilities of 2.75–7.29 × 10−29 esu, respectively. Quantum chemical calculations showed that the compound with more stable highest occupied molecular orbital energy also displayed highest second hyperpolarizability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Probes 1a-b for detection of thiophenols by ESIPT mechanism were constructed with diethylcoumarin–salicylaldehyde units. • They showed large Stokes shift (greater than100 nm) and one of them displayed NIR-emitting (670 nm) when detecting thiophenols. • Probes 1a-b could form inclusion complexes with M-β-CD. • The presence of M-β-CD reduced the detection limits of probes 1a - b towards thiophenols. Thiophenol and its derivatives are compounds with high toxicity to organisms and environmental pollution, so it is necessary to detect the level of thiophenols in the environment and biological samples. The probes 1a-b were obtained by introducing the 2,4-dinitrophenyl ether group into diethylcoumarin–salicylaldehyde based compounds. And they can form host-guest compounds with methylated β-cyclodextrin (M-β-CD), the association constants of inclusion complexes are 49.2 M−1, 125 M−1 respectively. The fluorescence intensities of probes 1a-b at 600 nm (1a) and 670 nm (1b) increased significantly in thiophenols detection. Meanwhile, with the addition of M-β-CD, the hydrophobic cavity of M-β-CD significantly increased the fluorescence intensity of probes 1a-b , thus the detection limits of probes 1a-b to thiophenols were reduced from 410 nM, 365 nM to 62 nM, 33 nM respectively. Whereas, the good selectivity and short response time of probes 1a-b towards thiophenols was not affected in the presence of M-β-CD. Moreover, probes 1a-b were used for further water sample detection and HeLa cell imaging experiments due to their good response to thiophenols and the results suggested that probes 1a-b had the potential to detect the content of thiophenols in water samples and living cells. [ABSTRACT FROM AUTHOR]

In this paper, several novel nitrogen-containing heterocycle dyes 1a-c with large conjugated planar structures based on naphthyridine derivatives were designed and synthesized, which had excellent optical properties and biological applications. Optical test showed the maximum absorption wavelengths of 1a-c were in the range of 443–485 nm, while the maximum emission wavelengths located at 523–610 nm in difference solvents. Furthermore, they exhibited polarity related fluorescence intensity changes with high fluorescence quantum yields, even up to 88% (1a in THF). Moreover, the transient absorption spectra revealed the excited-state lifetime of dye 1a became shorter with the increase of solvent polarity. Density functional theory calculations are also used to help explain the effect of the polarity of solvents on their fluorescence properties. Interestingly, the dyes 1a-c were somewhat toxic to cancer cells, while had an obvious growth-promoting effect on normal cells. Additionally, 1a-c with excellent lipid droplet (LD) targeting could be used for long-term observation of targeted cellular lis) hysiological activity and further applied to dynamic monitoring of changes in LDs polarity stimulated by TLR4 activator (LPS) in living cells. Overall, the excellent optical properties and biocompatibility of 1a-c indicate that they can serve as fluorescent probes for biological applications, and the results have important implications for understanding the physiological functions of LDs, especially in terms of morphological and polar changes. [Display omitted] • The dibenzo[c,f] [2,7]naphthyridine skeleton have been first applied in the field of cell imaging. • Dyes 1a-c possess high fluorescence quantum yield and excellent polarity response. • Dyes 1a-c are somewhat toxic to cancer cells, while have a growth-promoting effect on normal cells. • Dyes 1a-c can sensitively target lipid droplets with a low concentration, and dynamically monitor their polarity changes. [ABSTRACT FROM AUTHOR]

As a key parameter affecting the biochemical reaction of cells, the change of polarity also affects some important biological processes of cells. However, there are very few polarity probes for Golgi apparatus. In this work, coumarin or 1,8-naphthalimide were chosen as the fluorophores for their excellent optical property. Based on the combination of amide and long carbon chain, three Golgi polarity probes with different emission regions were designed and synthesized. Among them, Golgi-Blue and Golgi-Green inherited the blue and green fluorescence of the parents, respectively; while after the introduction of dicyanoisophorone unit to the 1,8-naphthalimide, Golgi-Red achieved near infrared emission (700–750 nm). Moreover, the three probes were sensitive to the polarity of solution. Interestingly, the fluorescence of Golgi-Blue and Golgi-Green decreased whereas that of Golgi-Red first enhanced gradually and then weakened with the increase of polarity, which was caused by the configuration change of the ground and excited state to induce twisted intramolecular charge transfer (TICT) in 1,4-dioxane and elucidated by means of density functional theory. Cell experiments showed that the three probes could quickly and accurately target Golgi apparatus and monitor the changes of Golgi polarity. The results may help in the early diagnosis of polar-related diseases. [Display omitted] • Three coumarin or 1,8-naphthalimide derivatives were synthesized. • The three probes could rapidly target to the Golgi apparatus and test polarity. • The red polarity probe had the opposite property to the other two. • This work filled the gap in the blue and green channels of Golgi polarity probes. [ABSTRACT FROM AUTHOR]

Three hydrogen sulfide (H 2 S) probes based on an azonia–cyanine skeleton were successfully designed and prepared. Probe 1a , containing 4-chloro-7-nitro-1,2,3-benzoxadiazole connected to the cyanine dye, had an emission at 660 nm that was enhanced 4.5-fold by the reduced photoinduced electron transfer process when reacting with H 2 S. Probes 1b and 1c were constructed from cyanine dyes with electron withdrawing 2,4-dinitrophenyl and 7-nitrobenzo[c] [1,2,5]oxadiazol-4-yl groups, respectively. Probes 1b and 1c gave off−on type responses with 169- and 17-fold fluorescent enhancements at 639 nm with H 2 S. Their emission properties were influenced by intramolecular hydrogen bonds and intramolecular charge transfer processes. The detection limits of probes 1a – 1c were calculated at 178, 121, and 9.6 nM, respectively. The intracellular imaging experiments with HeLa cells indicated probe 1a was a mitochondria-targeting H 2 S probe, while probes 1b and 1c were lysosome-targeting H 2 S probes. Image 1 • The cyanine dyes had possess different organelles targetablities with different drivatives. • OFF-ON fluorescent probes were designed based on the elimination and recovery of hydrogen bonds. • Three fluorescent probes all have good selectivity to hydrogen sulfide, and one probe has a lowest detection limit as 9.6 nM. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Five probes (1a-e) have excellent photo stability. • Four probes (1a-d) exhibit "OFF–ON" fluorescent responses towards nucleic acids. • Probe 1a can image mitochondrial nucleic acid. • Probe 1a was a low-toxic probe for live HeLa cells. Abstract Five cyanine dyes (1a-e) with azonia unit have been prepared by the reaction of pyrido[1,2−a]pyrimidinium ions and suitable aldehydes. Before further research, their photo and thermal stabilities were determined in the first place. At least 88% absorption remained after 5 h irradiating illustrated all of these dyes had excellent photo stability. Meanwhile, the decomposition temperature of dyes was around 200 °C which demonstrated they had good thermal stability. Therefore, the good photo and thermal stability made them possible to be probes. Subsequently, the optical properties of probes toward nucleic acids had been measured. TheirOFF–ON fluorescent responses (1a - d) towards nucleic acids were investigated. In addition, confocal microscopy imaging of probe 1a in live HeLa cells indicated that probe 1a could image mitochondrial nucleic acid. [ABSTRACT FROM AUTHOR]

Abstract The emission of organic fluorophores is usually quenched in water solution. In this paper, strong emission of 7-hydroxyindazolo[2,3- b ]isoquinolin-12(7 H)-one derivatives were disclosed in aqueous solution. The absorption and fluorescence spectra of the ten derivatives were reported, they show absorption at 349–374 nm and emission at 409–483 nm. Among of them, the fluorescence quantum yield of 1c with alkyl groups is up to 85.9% in water; Compound 1g with benzyl group showed the maximum fluorescence intensity at 486 nm in water, which was attributed to S 1 →S 0 transition and intramolecular hydrogen bond. While the fluorescence of 1j with m -methoxyphenyl group was quenched by photo-induced electron transfer process. The fluorescence intensities of selected compounds were stable in pH 3.0–9.0. Thus this work expands the study of new fluorophores which produce strong fluorescence in aqueous condition. Graphical abstract Image 1 Highlights • The optical properties of 7-hydroxyindazolo[2,3- b ]isoquinolin-12(7 H)-one derivatives are reported. • Strong emission in water solution. • The fluorescence quantum yields are up to 85.9%. [ABSTRACT FROM AUTHOR]

To evaluate the lysosome targetability of different nitrogen-containing basicity groups, seven fluorescent probes based on phenoxazinium connected different nitrogen-containing basicity groups were prepared. Probe 8b containing N , N -dimethylphenyl, 8c containing N , N -diethylphenyl group and 8d containing quinolin-8-yl group exhibited obvious emission responses at 675 nm with pH ranging from 2.4 to 5.6, 3.4–7.6 and 1.8–4.2, and their calculated p K a were 3.99, 5.57 and 2.46 respectively. While probe 8a containing morphoyl group, probe 8e containing pyridine-4-yl, probe 8f containing pyridine-3-yl and probe 8g containing pyrimidine group showed no significant changes of emission intensity when pH changes from 2.0 to 8.0. Moreover, three probes 8b , 8c and 8d showed good selectivity for hydrogen ion. Fluorescent imaging experiments indicated that probes 8c and 8d were lysosome biomarkers for Ges-1 and HeLa cells. [ABSTRACT FROM AUTHOR]

In order to improve lysosome targetability of probes, fluorescent probes based on benzo[ a ]phenoxazine attaching different length oligoethyleneoxy chains were designed and prepared. Probes 2a – c containing N -pyridineium-3-yl exhibited almost ON-OFF near-infrared emission responses at 697–701 nm from pH 2.8 to 7.2, and the calculated p K a values of 2a – c were 4.90, 4.92 and 5.03 respectively. More importantly, fluorescent imaging experiments indicated that probes 2a – c were all lysosome biomarkers for Ges-1 and HeLa cells, which was because the introduction of oligoethyleneoxy groups improved the biocompatibility of probes, so that the probes 2a – c were better transported to lysosomes via the endocytosis pathway of the cells. Moreover, the probe 2a was selected as a representative, which not only showed good reversibility and selectivity, but used to successfully image lysosomal pH increases induced by chloroquine. [ABSTRACT FROM AUTHOR]

Two rosamine-based probes (1a–b) with pyronine-pyridinium skeleton were designed and prepared. Probe 1a bearing boron ester unit was oxidized and eliminated upon addition of hydrogen peroxide (H2O2), and the emission spectrum exhibited OFF–ON response accompanied by 33-fold fluorescent enhancement. In contrast, the fluorescence intensity of probe 1b enhanced 58 times after the dinitrophenyl ether part within the probe was removed by nucleophilic substitution with hydrosulfide (H2S). The design concept was based on the d-PET process in pyronine-pyridinium structures, and free 4-pyridinyl-substituted pyronine dye showing strong fluorescence was released followed by elimination. Furthermore, as biocompatible molecules, probes 1a–b have been successfully applied for imaging in live HeLa and Ges-1 cells, and all of them can serve as mitochondrial targetable probes in red channel for detecting independent species. [ABSTRACT FROM AUTHOR]

In this paper, a new compound ( 3 ) with pyronine-pyridine skeleton had a strong fluorescence at pH 5.0−9.0, while the emission turned off at pH = 1.0–2.0. It was a mitochondrial biomarker in cancer cells (KB, 4T1, HeLa) and normal cells (Ges-1, L929, WS1). Based on these above results, probe 1 with pyronine-pyridinium skeleton was further designed and prepared to detect nitroreductase (NTR). The nitrofuran group of probe 1 was reduced and eliminated upon addition of NTR and nicotinamide adenine dinucleotide (NADH) to produce compound 3 , and the d-PET process could be allowed in the pyronine-pyridinium structure of probe 1 but it was prohibited in the pyronine-pyridine skeleton of compound 3 after detection, hence probe 1 showed a nearly turn-on signal in red light region at 565–800 nm with emission maxima at 604 nm. The detection limit was calculated as low as 2.2 ng/mL. Furthermore, fluorescence imaging experiments with live HeLa and Ges-1 cells were performed, and probe 1 could serve as a mitochondrial targetable probe to detect nitroreductase in red channel. [ABSTRACT FROM AUTHOR]

The cyanine dye ( 1 ) with three arms of one chromenyl group and two indol groups was synthesized in this paper; and the proposed synthetic mechanism was also mentioned. It has excellent photostability compared to three typical cyanine dyes. Dye 1 gives high chemical activity and nearly turn-on fluorescent response towards hydrosulfide at 600–800 nm, it also has good selectivity towards hydrosulfide over other species; the detection reaction mechanism was proved by 1 H NMR analysis, and the emission responses was elucidated by time dependent density functional theory (TDDFT) calculation. The in cellular fluorescent imaging application of the dye 1 was successfully performed for the hydrosulfide imaging of HeLa cells. [ABSTRACT FROM AUTHOR]

Three phenoxazinium compounds attached with o -nitrophenyl ( 3a ), m -nitrophenyl ( 3b ) and p -nitrophenyl ( 3c ) groups were prepared, and the pH promoted emission spectra were used to evaluate the deprotonated-protonated equilibrium between phenoxazinium and phenoxazine. They showed nearly ON-OFF emission responses at 650–850 nm around pH 8.0–10.8, and the fluorescence related p K a s of 3a–c were 8.7, 9.2, and 8.9, respectively. Two phenoxazinium compounds attached with pyridinyl groups ( 7a–b ) were further prepared, the pH promoted emission spectra were influenced by both the deprotonated-protonated equilibrium between phenoxazinium and phenoxazine, and the equilibrium between pyridinyl group and pyridinumyl group. They exhibited more strong red and near-infrared emission at 600–850 nm, probe 7a gave p K a ,1 = 3.71 and p K a ,2 = 9.68, and that of probe 7b was 2.75. Moreover, the fluorescent imaging experiment indicated that probe 7a was a lysosome biomarker for V79 and HeLa cells. [ABSTRACT FROM AUTHOR]

Oxazinium derivatives have recently played an important role in bioanalysis attributing to the distinguished properties, thus a detailed study of the structure-property relationship is especially significant. Herein, pH-sensitive optical properties of Nile Blue ( 1a), N-monoalkyl-Nile Blue ( 1b) and Azure A ( 1c) have been carried out in extreme acid and base conditions. Dyes 1a and 1c showed colorimetric changes by the protonation of nitrogen atom in strong acidic condition (pH < 2.0), and dyes 1a − c exhibited colorimetric changes by equilibrium between amino and imide groups in very strong basic case (pH > 7.6). Besides, their fluorescent properties were closed to ON − OFF and OFF − ON emissions at 640-820 nm under strong acidic and basic conditions. Moreover, the absorption and emission properties were reversible, and there were no remarkable optical intensity changes of dyes 1a − c under subacidic and neutral solutions (pH = 3.0-7.0). The (TD) DFT calculations were used to optimize the most stable structures of their corresponding protonated and deprotonated forms, and their absorption and emission properties were also explained. Their fluorescent properties nearly ON-OFF and OFF − ON in strong acidic and basic conditions at near-infrared region will give the possible application in pH detection for extreme conditions. [ABSTRACT FROM AUTHOR]

A near-infrared fluorescent probe based on benzo[a]phenoxazine containing o -phenylenediamine group as reactive site was designed and synthesized. The titration experiment showed that the probe gave colorimetric response towards sodium nitrite with the absorption maxima at 630 nm and 542 nm in pH = 5.0 disodium hydrogen phosphate-citric acid buffers containing 30% DMSO; its emission was located in 590–820 nm with the 9.1-fold fluorescent enhancement under excitation at 580 nm. Moreover, the probe can detect nitrite quantitatively in a concentration range of 0.0–26.0 μM and the detection limit is as low as 45 nM. The salient features of this method are high sensitivity and selectivity, fast detection and low detection limit. Fluorescence confocal imaging experiments with V79 and HeLa cells indicate that the probe has the potential application in quantitative detection exogenous nitrite level for in cellular imaging. [ABSTRACT FROM AUTHOR]

Two hemicyanine dyes ( 1a–b ) linked with tetraalkyl ammonium group were prepared, and they were evaluated as near-infrared probes for the detection of nucleic acid. Fluorescent responses were observed from 643 to 850 nm when probes 1a–b was titrated with commercially available DNA and RNA. The dimethylaminophenyl containing hemicyanine ( 1a ) gave a 32.8-fold and 33.5-fold emission enhancement towards DNA and RNA, while the dimethylaminonaphthalen containing hemicyanine ( 1b ) gave a 33.0-fold and 38.8-fold emission enhancement respectively. They also show large fluorescence Stokes shifts. The fluorescence of 1a–b distinguishes clear nucleoli staining accompanied by faint cytoplasm in cellular environment, and nucleic acid digest test of ribonuclease indicates their markedly higher affinity for RNA. These results prove that probes 1a – b are very attractive staining reagents for visualizing RNA in fixed cells. [ABSTRACT FROM AUTHOR]

The fluorescent pH probes, 3,11-diamino-7-(4-(diethylamino)-phenyl)- dibenzo[c,h]xanthen-14-ium trifluoromethanesulfonate ( 1a ) and 3,11-bis-(diethylamino)-7-(4-(diethylamino)phenyl)dibenzo[c,h]xanthen-14-ium trifluoromethanesulfonate ( 1b ), were reported as pH probes worked in strong acidic conditions. Probes 1a – b were prepared by one-step condensation with 4-diethylaminobenzaldehyde and aminonaphthalen-1-ol derivatives, their absorption maxima gave slight changes between neutral and acidic conditions, and they exhibited pH-dependent near-infrared OFF–ON emission in the range of pH 2.0–5.0 with increasing fluorescent intensities of 272 and 114 folds, the calculated p K a values were 3.28 and 3.24 for probe 1a and probe 1b , respectively. The probes also showed excellent selectivity toward proton over other interferents in the selectivity and competition assays. The photoinduced electron transfer effect from diethylaminophenyl group to dibenzoxanthenium skeleton was proposed and further verified by theoretical calculation. The work indicates that dibenzoxanthenium would be a near-infrared fluorophore for probe design. [ABSTRACT FROM AUTHOR]

In this paper, the design of a lysosome-targetable pH probe that has a fluorescent OFF (pH = 4) to ON (pH = 5–6) response is described to identify lysosomes in normal cells. The mechanism of photoinduced electron transfer with a fluorophore-based reaction (FBR-PET) was proposed. Benzo[ a ]phenoxazines with electro-donating aryl groups were selected, its (2,5-dimethoxyphenyl)imino-, (2-hydroxyphenyl)imino- and (2-hydroxy-5-methoxyphenyl)- imino-derivatives (probes 1a−c ) were prepared and their optical responses towards pH were evaluated; their fluorescence pH titration experiments gave regularly changes with the increasing electro-donating abilities at the linked aryl groups, the (2-hydroxy-5-methoxyphenyl)iminobenzo[ a ]phenoxazine (probe 1c ) exhibited a nearly OFF−ON response at 580–800 nm. All probes were reversible, and they showed excellent selectivity toward the proton over other competitive species. Fluorescence confocal images were performed with HeLa, KB cancer cells and V79 normal cells, probes 1a−c are all lysosome-targetable pH probes, and benzo[ a ]phenoxazine with (2-hydroxy-5-methoxyphenyl)imino-group (probe 1c ) has potential applications in selective differentiation of normal cells from cancer cells. [ABSTRACT FROM AUTHOR]

As an important organelle, the main function of the Golgi apparatus is to further modify and deliver proteins synthesized by the endoplasmic reticulum (ER). Dyshomeostasis of the Golgi appartus can cause many serious diseases. Therefore, monitoring the normal functioning of the Golgi appartus is particularly important. However, only a few commercially Golgi markers are available till now. In this work, three 1,8-naphthalimide related Golgi markers (4a - c) with the combination of amide and long carbon chain were designed and synthesized, their maximum emission wavelengths could reach 500–575 nm with high fluorescence quantum yields. Moreover, they possessed low cytotoxicity (cell viabilities >82%). Cell experiments exhibited that dyes 4a - c could rapidly and accurately mark the Golgi apparatus. To discuss the origin of their targeting ability, compounds 5–7 with independent amide or long carbon chain were additionally prepared. With the separation of amide and long carbon chain in compound 5 – 7 , the targeting ability was lost. The experiments showed that the targeting ability of 4a - c resulted from the combination of amide and long carbon chain structure. Also, the results may provide a new idea for designing organelle markers. [Display omitted] • Synthesis of three 1,8-naphthalimide derivatives with the combination of amide and long carbon chain. • All three dyes can quickly locate in the Golgi apparatus and not located to other organelles. • All three dyes can image at a low concentration. • The Golgi targeting ability may be attributed to the combination of amide and long carbon chain structure. [ABSTRACT FROM AUTHOR]

In this paper, oxazolepyridine and coumarin units were combined to prepare cell membrane fluorescent probe (PM-A) through aldol condensation reaction. PM-A had long wavelength emission (665–739 nm), high molar extinction coefficient (around 3.14 × 104 M−1cm−1) and large Stokes shift (150–219 nm). The photo-stability test showed that PM-A had a high relative residual absorption (93%) after 6 h of continuous illumination. In addition, the supramolecular interaction between PM-A and β-cyclodextrin was evaluated and applied to cell imaging. Probe PM-A had no fluorescence in water, but had obvious fluorescence signal in β-cyclodextrin solution. With the addition of β-cyclodextrin (0–800 eq), the fluorescence quantum yield of PM-A increased from 0% to 45%. Laser confocal experiments showed that when only PM-A was added, the probe concentration needed to be 15 μM to image the cell membrane obviously. In sharp contrast, with the help of β-cyclodextrin solution, the concentration of probe PM-A only needed 0.5 μM to quick and high specificity image cell membranes. Moreover, PM-A had high photo-bleaching resistance and long retention time after adding β-cyclodextrin. These excellent properties of PM-A were of great significance to the study of cell membrane. [Display omitted] • A near-infrared fluorescent probe (PM-A) with oxazolepyridine and coumarin units was prepared for the imaging of cell membrane at 15 μM. • The supramolecular interaction between probe PM-A and β-cyclodextrin was evaluated. • Probe PM-A showed rapid and high specificity of cell membrane imaging at the concentration of 0.5 μM with the help of β-cyclodextrin. [ABSTRACT FROM AUTHOR]

To improve self-targeting abilities towards organelles, four fluorescent dyes (1a-1d) were designed by connection of dicyanoisophorone to phenylpiperidinol (1a), naphthalenol (1b), indazole (1c) and pyrene (1d) unit with a double bond. Their absorption maxima were located at 423–517 nm; and emission maxima were at 565–682 nm with large Stokes shifts of 142–191 nm. Moreover, their fluorescence intensities increased 11–117 fold in glycerol compared to phosphate buffer solution, which might be due to the long excited state lifetimes (up to 1 ns) by transient absorption spectra. Furthermore, laser confocal experiments with HeLa cells proved that dyes 1a-1d were self-target fluorescent markers at 10–20 μM for lysosomes, endoplasmic reticulum, mitochondria and lipid droplets respectively; and they could be used for the fluorescent probes at 2 μM for viscosity detection within corresponding organelles by influence of ionophores. In addition, these dyes were able to detect viscosity changes in a Parkinson's disease model with PC-12 cells. [Display omitted] • Four Dicyanoisophorone derivatives can self-target multiple organelles. • These probes can detect viscosity change within corresponding organelles by influence of ionophores. • These dyes were able to detect viscosity changes in a Parkinson's disease model. [ABSTRACT FROM AUTHOR]

In this paper, phenoxazinium was used as a fluorophore for the design of pH probes by the photoinduced electron transfer (PET) mechanism. Phenoxazinium with an aliphatic morpholinyl group (probe 1a) gave increased emission at 665 nm with pH ranging from 7.4 to 4.4; meanwhile, the other one with an aromatic diethylaminophenyl group (probe 1b) gave nearly OFF–ON emission at 679 nm with pH ranging from 7.4 to 4.2. They both were reversible pH probes with good selectivity. Their optical properties, especially the PET mechanism, were illustrated by (TD)DFT theory. Fluorescence confocal imaging of probes 1a–b and a typical phenoxazinium dye (Oxazine 1) was also performed, and the results indicated that probes 1a–b are lysosome-targetable biomarkers. [ABSTRACT FROM AUTHOR]

The optical films based on poly(4-vinylphenol) and benzo[α]phenoxazinium dye with a long alkyl chain were obtained by spin-coating, and their optical properties are reported in this paper. UV–vis absorptions of the optical films showed that the absorption maxima were shifted about 40 nm by the influence of dye aggregation with increasing dye ratio. The third-order nonlinear optical properties of films were tested by Z-scan technique with a picosecond laser beam at 532 nm. The third-order nonlinear optical susceptibilities and second hyperpolarizabilities were up to 10 − 10 and 10 − 32 esu respectively. Meanwhile, the third-order nonlinear absorptions transformed from reverse saturated absorptions to saturated absorptions with increasing ratios of dye in doped films. The result of aggregation induced adjustable third-order nonlinear absorption can be confirmed from their TEM images. [ABSTRACT FROM AUTHOR]