Search

We report a novel approach based on non-covalent interactions for the functionalization of carbon nano-onions (CNOs) with fluorophores. The assembly of pyrene–BODIPY conjugates on the CNO surface by means of π–π-stacking results in fluorescent carbon nanoparticles that are successfully uptaken by HeLa cancer cells with no cytotoxicity observed. The ability to functionalize carbon-based nanomaterials by using mild conditions will pave the way for future clinical application of these versatile nanomaterials.

Multishell fullerenes, known as carbon nano-onions (CNOs), are an interesting class of carbon-based nanomaterials. They display several unique properties, such as a large surface area to volume ratio, a low density, and a graphitic multilayer morphology, which have made them appealing for several applications in many fields, including biology. Chemical functionalization of CNOs dramatically enhances their solubility and attenuates their inflammatory properties, thereby increasing their applicability especially in the fields of biology and medicine. CNOs functionalized with fluorescent probes can be used for cellular imaging. In this article, detailed surface characterization of CNOs functionalized with a zinc porphyrin (ZnTPP) as the fluorescent probe is presented. In particular, time-of-flight secondary ion mass spectrometry and x-ray photoelectron spectroscopy provide a detailed surface characterization of the organic functionalities introduced via "click chemistry" and clearly demonstrate the success of the CNOs functionalization process. XPS data reveal the presence of Zn and N, whilst ToF-SIMS is able to identify specific fragments related to the presence of the ZnTPP, such as the quasimolecular mass peak [C32N4H20Zn](+) and the molecular mass peak [C44N4H28Zn](+). Moreover, ions fragments deriving from the triazole ring formed by the click chemistry reaction have been identified by ToF-SIMS analysis, proving unambiguously the covalent binding of the fluorescent molecules to the CNOs surfaces.

A series of π-extended distyryl-substituted boron dipyrromethene (BODIPY) derivatives with intense far-red/near-infrared (NIR) fluorescence was synthesized and characterized, with a view to enhance the dye's performance for fluorescence labeling. An enhanced brightness was achieved by the introduction of two methyl substituents in the meso positions on the phenyl group of the BODIPY molecule; these substituents resulted in increased structural rigidity. Solid-state fluorescence was observed for one of the distyryl-substituted BODIPY derivatives. The introduction of a terminal bromo substituent allows for the subsequent immobilization of the BODIPY fluorophore on the surface of carbon nano-onions (CNOs), which leads to potential imaging agents for biological and biomedical applications. The far-red/NIR-fluorescent CNO nanoparticles were characterized by absorption, fluorescence, and Raman spectroscopies, as well as by thermogravimetric analysis, dynamic light scattering, high-resolution transmission electron microscopy, and confocal microscopy.

Carbon-based nanomaterials functionalized with fluorescent and water-soluble groups have emerged as platforms for biological imaging because of their low toxicity and ability to be internalized by cells. The development of imaging probes based on carbon nanomaterials for biomedical studies requires the understanding of their biological response as well as the efficient and safety exposition of the nanomaterial to the cell compartment where it is designed to operate. Here, we present a fluorescent probe based on surface functionalized carbon nano-onions (CNOs) for biological imaging. The modification of CNOs by chemical oxidation of the defects on the outer shell of these carbon nanoparticles results in an extensive surface functionalization with carboxyl groups. We have obtained fluorescently labelled CNOs by a reaction involving the amide bond formation between fluoresceinamine and the carboxylic acids groups on the surface of the CNOs. The functionalized CNOs display high emission properties and dispersability in water due to the presence of high surface coverage of carboxylic acid groups that translate in an efficient fluorescent probe for in vitro imaging of HeLa cells, without significant cytotoxicity. The resulting nanomaterial represents a promising platform for biological imaging applications due to the high dispersability in water, its efficient internalization by cancer cells and localization in specific cell compartments.

Carbon based nanomaterials have emerged over the last few years as important agents for biomedical fluorescence and Raman imaging applications. These spectroscopic techniques utilize either fluorescently labelled carbon nanomaterials or the intrinsic photophysical properties of the carbon nanomaterial. In this review article we present the utilization and performance of several classes of carbon nanomaterials, namely carbon nanotubes, carbon nanohorns, carbon nanoonions, nanodiamonds and different graphene derivatives, which are currently employed for in vitro as well as in vivo imaging in biology and medicine. A variety of different approaches, imaging agents and techniques are examined and the specific properties of the various carbon based imaging agents are discussed. Some theranostic carbon nanomaterials, which combine diagnostic features (i.e. imaging) with cell specific targeting and therapeutic approaches (i.e. drug delivery or photothermal therapy), are also included in this overview.

Carbon-based nanomaterials have attracted much interest during the last decade for biomedical applications. Multimodal imaging probes based on carbon nano-onions (CNOs) have emerged as a platform for bioimaging because of their cell-penetration properties and minimal systemic toxicity. Here, we describe the covalent functionalization of CNOs with fluorescein and folic acid moieties for both imaging and targeting cancer cells. The modified CNOs display high brightness and photostability in aqueous solutions and their selective and rapid uptake in two different cancer cell lines without significant cytotoxicity was demonstrated. The localization of the functionalized CNOs in late-endosomes cell compartments was revealed by a correlative approach with confocal and transmission electron microscopy. Understanding the biological response of functionalized CNOs with the capability to target cancer cells and localize the nanoparticles in the cellular environment, will pave the way for the development of a new generation of imaging probes for future biomedical studies.

Applications of single-wall carbon nanotubes (SWNT) are severely restricted, as they exist in rope-like bundles. Many methods have been suggested to de-bundle SWNTs, including both covalent and noncovalent funtionalisation with surfactants, acids, polymers and macromolecules. However, these strategies are unsatisfactory because they result in either the chemical modification of the nanotube or the presence of residual dispersion agents. What is required is the demonstration of stable, exfoliated SWNT dispersions in common solvents. In this work we have demonstrated debundling of single-wall nanotubes by diluting nanotubes dispersions in the solvent N-methyl-2-pyrrolidinone (NMP). Atomic-force-microscopy measurements show a steady decrease in bundle diameter distribution as the concentration is decreased. Photoluminescence and Raman spectroscopy confirmed the presence of individual nanotubes in NMP dispersion.

We have identified viable operating principles for the modulation of optical signals under the influence of optical stimulations. They are based on the overlap between the emission bands of a fluorescent compound and the absorption bands of one of the two forms of a bistable photochromic switch. Under these conditions, the photoinduced interconversion of the two states of the photochrome modulates efficiently the emission intensity of the fluorophore. We have implemented this mechanism for intermolecular fluorescence modulation with multilayer structures. They consist of two quartz plates sandwiching two overlapping polymer layers. One of the polymers is doped with a fluorescent benzofurazan. The other contains a photochromic spiropyran. The multilayer assembly is operated with two light sources. One of them is centered at the excitation wavelength of the fluorophore, where neither of the two states of the photochrome absorbs. The other light source is switched between ultraviolet and visible wavelengths to induce the interconversion between the two states of the photochrome. The light emitted by the fluorescent component has to propagate through the photochromic layer before reaching a detector. It can do so efficiently for only one of the two states of the photochrome. It follows that a measurement of the light intensity reaching the detector can read the state of the photochromic switch, which in turn is written and erased with optical stimulations. Thus, our strategy for all-optical processing can be used to store and retrieve binary digits, as well as to implement optical inversion, with the aid of engineered molecule-based components.

The identification of strategies to establish communication between independent molecules is an essential requirement for the development of operating principles to manipulate information at the molecular level. In this context, we have devised a strategy to exchange signals between pairs of complementary molecular switches. It is based on the photoinduced ring closing of a merocyanine to produce a spiropyran with the concomitant release of a proton. The liberated proton is captured by either one of two pyridine derivatives with the formation of their conjugate acids. This transformation induces a significant increase in chemical shift for the resonances of the pyridyl protons and, in one instance, also a pronounced color change. The overall process is fully reversible and the pair of communicating molecules reverts to the original state in the dark. Relying on this mechanism, an optical input is transduced into a detectable spectroscopic output after the controlled intermolecular exchange of protons. A simple analysis of the signal transduction operated by the communicating molecular switches reveals that a binary digit is passed unaltered from the input to the output even although the nature of the signal carrying the information changes at each step. Furthermore, the different nature of input and output implies that the state of the ensemble of molecules can be probed non-destructively at any point in time. The timescales of the switching steps, however, are seriously limited by the slow reaction kinetics. The photoinduced transformation occurs within minutes, but the thermal reaction reverts the switch state only after several hours.

[structure: see text] Chemical and optical stimulations control the interconversion of a three-state molecular switch trapped inside a silica monolith. The resulting absorbance changes in the visible region can be exploited to reproduce a sequential logic operator with one optical input and one optical output. This strategy to transfer operating principles for digital processing from bulk solutions to rigid materials can lead to the development of chemical logic gates based on functional solid components.

Certain molecular switches respond to input stimulations producing detectable outputs. The interplay of these signals can be exploited to reproduce basic logic operations at the molecular level. The transition from simple logic gates to complex digital circuits requires the design of chemical systems able to process multiple inputs and outputs. We have identified a three-state molecular switch that responds to one chemical and two optical inputs producing two optical outputs. We have encoded binary digits in its inputs and outputs applying positive logic conventions and demonstrated that this chemical system converts three-digit input strings into two-digit output strings. The logic function executed by the three-state molecular switch is equivalent to that of a combinational logic circuit integrating two AND, two NOT, and one OR gate. The three states of the molecular switch are a colorless spiropyran, a purple trans-merocyanine, and its yellow-green protonated form. We have elucidated their structures by X-ray crystallography, (1)H NMR spectroscopy, COSY and NOE experiments, as well as density functional calculations. The three input stimulations controlling the interconversion of the three states of the molecular switch are ultraviolet light, visible light, and H(+). The two outputs are the absorption bands in the visible region of the two colored states of the molecular switch. We have monitored the switching processes and quantified the associated thermodynamic and kinetic parameters with the aid of (1)H NMR and visible absorption spectroscopies.

A gradual transition from electrical to optical networks is accompanying the rapid progress of telecommunication technology. The urge for enhanced transmission capacity and speed is dictating this trend. In fact, large volumes of data encoded on optical signals can be transported rapidly over long distances. Their propagation along specific routes across a communication network is ensured by a combination of optical fibers and optoelectronic switches. It is becoming apparent, however, that the interplay between the routing electrical stimulations and the traveling optical signals will not be able to support the terabit-per-second capacities that will be needed in the near future. Electrical inputs cannot handle the immense parallelism potentially possible with optical signals. Operating principles to control optical signals with optical signals must be developed. Molecular and supramolecular switches are promising candidates for the realization of innovative materials for information technology. Binary digits can be encoded in their chemical, electrical, or optical inputs and outputs to execute specific logic functions. We have developed a simple strategy to gate optical signals with optical signals by using a photoactive molecular switch. We have demonstrated that NAND, NOR, and NOT operations can be implemented exclusively with optical inputs and optical outputs coupling from one to three switching elements. Our remarkably simple approach to all-optical switching might lead to the development of a new generation of devices for digital processing and communication technology.

Carbon nano-onions (CNOs) are an exciting class of carbon nanomaterials, which have recently demonstrated a facile cell-penetration capability. In the present work, highly fluorescent boron dipyrromethene (BODIPY) dyes were covalently attached to the surface of CNOs. The introduction of this new carbon nanomaterial-based imaging platform, made of CNOs and BODIPY fluorophores, allows for the exploration of synergetic effects between the two building blocks and for the elucidation of its performance in biological applications. The high fluorescence intensity exhibited by the functionalized CNOs translates into an excellent in vitro probe for the high resolution imaging of MCF-7 human breast cancer cells. It was also found that the CNOs, internalized by the cells by endocytosis, localized in the lysosomes and did not show any cytotoxic effects. The presented results highlight CNOs as excellent platforms for biological and biomedical studies due to their low toxicity, efficient cellular uptake and low fluorescence quenching of attached probes.

This review focuses on the development of multi-layer fullerenes, known as carbon nano-onions (CNOs). First, it briefly summarizes the most important synthetic pathways for their preparation and their properties and it gives the reader an update over new developments in the recent years. This is followed by a discussion of the published synthetic procedures for CNO functionalization, which are of major importance when elucidating future applications and addressing drawbacks for possible applications, such as poor solubility in common solvents. Finally, it gives an overview over the fields of application, in which CNO materials were successfully implemented.

[structure: see text]. Efficient strategies for the communication of signals between molecules must be identified for the development of molecule-based nanoprocessors. We have demonstrated that photoinduced proton transfer can be exploited to implement intermolecular digital transmission. Light inputs operate a three-state molecular switch inducing the transfer of a proton to or from a two-state molecular switch. The signal transduction protocol of the two communicating molecular switches is equivalent to that of a sequential logic circuit incorporating three logic gates.

The sequential combination of native chemical ligation and thiol–ene radical chemistry (NCL-TEC) on the resulting cysteine thiol has been investigated as a methodology for rapidly accessing functionalized peptides. Three sequential cycles of native chemical ligation and subsequent thiyl radical reactions (including a free-radical-mediated desulfurization reaction) were carried out on a peptide backbone demonstrating the iterative nature of this process. The versatility of the thiyl radical reaction at cysteine was demonstrated through the introduction of a number of different side chains including an amino acid derivative, a carbohydrate group, and an alkyl azide. Conditions were developed that allowed the sequential NCL-TEC process to proceed in high yield.

The inflammatory effects of carbon nanoparticles (NPs) are highly disputed. Here it is demonstrated that endotoxin-free preparations of raw carbon nanotubes (CNTs) are very limited in their capacity to promote inflammatory responses in vitro, as well as in vivo. Upon purification and selective oxidation of raw CNTs, a higher dispersibility is achieved in physiological solutions, but this process also enhances their inflammatory activity. In synergy with toll-like receptor (TLR) ligands, CNTs promote NLRP3 inflammasome activation and it is shown for the first time that this property extends to spherical carbon nano-onions (CNOs) of 6 nm in size. In contrast, the benzoic acid functionalization of purified CNTs and CNOs leads to significantly attenuated inflammatory properties. This is evidenced by a reduced secretion of the inflammatory cytokine IL-1β, and a pronounced decrease in the recruitment of neutrophils and monocytes following injection into mice. Collectively, these results reveal that the inflammatory properties of carbon NPs are highly dependent on their physicochemical characteristics and crucially, that chemical surface functionalization allows significant moderation of these properties.

This critical review focuses on the development of photochromic compounds as sensors for cations, anions, and biologically important molecules. The review commences with a brief description of photochromism and the strategies to exploit photochromic molecular switches' properties for sensing application. This is followed by a summary of photoswitchable receptors emerged to date and classified according to the photochromic structure they are based on. These include azobenzenes, fulgides, dithienylethenes, dihydroindolizines, chromenes and spiropyrans.

Surface enhanced Raman spectroscopy (SERs) of functionalization HiPco single wall carbon nanotubes are performed. SWCNTs with covalently bonded amine groups were investigated using SERs assessing the impact of altering the electronic arrangement of the nanotube surface. The Raman frequencies of tangential, disorder modes and radial breathing modes have been used to make comparison between SWCNTs conjugated with Fluoresceinamine. Excitation of nanotube samples at wavelengths in resonance with both metallic and semiconductor nanotubes was undertaken.

The sections in this article are Introduction – Nanotoxicology: Should We Worry? Toxicity of Carbon Nanotubes Challenges in the Assessment of CNT Toxicity Interaction with Dispersing Medium Interaction with Cytotoxicity Assays Effect of Impurities Effect of Dispersion Dermal Exposure to CNTs Dermal Cytotoxicity In Vivo Dermal Toxicity Pulmonary Response to CNTs Pulmonary Cytotoxicity In Vivo Pulmonary Toxicity Toxic Response to CNTs in the Intra-Abdominal Cavity CNT Cytotoxicity in the Intra-Abdominal Cavity In Vivo CNT Toxicity in the Intra-Abdominal Cavity CNTs and Immunity Recognition of CNTs by Macrophages In Vitro Responses of Macrophages Exposed to CNTs CNTs and Immunity In Vivo Local Immune Responses Allergic Immune Responses Systemic Immune Alterations CNT Interactions with the Cardiovascular Homeostasis In Vitro Interactions In Vivo CNT Toxicity to Cardiovascular Homeostasis Genotoxicity and Mutagenicity of CNTs In Vitro Studies In Vivo Studies Biodistribution and Pharmacokinetics of CNTs Internalization of CNTs into Mammalian Cells Biodegradation of CNTs Biocompatibility of CNT-Based Biomaterials Conclusions – Are CNTs safe? Abbreviations Keywords: carbon nanotubes; toxicity; nanotoxicology; green chemistry

This critical review focuses on the development of photochromic compounds as sensors for cations, anions, and biologically important molecules. The review commences with a brief description of photochromism and the strategies to exploit photochromic molecular switches' properties for sensing application. This is followed by a summary of photoswitchable receptors emerged to date and classified according to the photochromic structure they are based on. These include azobenzenes, fulgides, dithienylethenes, dihydroindolizines, chromenes and spiropyrans.

A series of four spiropyrans bearing different substituents on the indolic nitrogen were synthesized and their capability of binding mono and bivalent transition metal cations in solution was assessed via UV-visible absorption spectroscopy. All the compounds responded selectively to the presence of Cu(ii) ions producing intense absorption bands in the visible region of their spectra. Bidimensional (1)H-NMR and MALDI-TOF MS spectroscopies revealed the formation of SP dimers mediated by Cu(ii). This is the first example of cross-coupling mediated by copper(ii) in mild conditions causing the symmetric dimerization of spiropyran dyes.

Surface enhanced resonance Raman scattering (SERRS) has been applied to investigate defects in purified and carboxylated single-walled carbon nanotubes (SWCNTs). For both samples SERRS spectra with temporal fluctuating peak intensities and positions in the range of 1000 to 1350 cm-1 have been observed. A series of peaks in this window were observed to coincide with peak positions that have been assigned to arise from Stone-Thrower-Wales and heptagonal-pentagonal intramolecular junction defects on the nanotubes surface. Two possible origins for these fluctuating spectral features are discussed ie the presence of Stone-Thrower-Wales defects in SWCNTs or amorphous carbon impurities. Author has checked copyright 07/08/13 RB Longer version of title (Surface-Enhanced Raman Scattering from small numbers of purified and oxidised single-walled carbon nanotubes: Evidence for Stone-Thrower-Wales defects or amorphous carbon impurities) at the heading of article submitted. RB

Two different lipophilic guanosine derivatives (LipoGs) have been used for the disaggregation of single walled carbon nanotubes (SWCNTs) in chloroform. UV–vis–NIR spectrophotometry, Raman spectroscopy and NIR-photoluminescence measurements as well as AFM and SEM highlight a well debundling of SWCNTs while fluorescence measurements show the adsorption of LipoGs onto SWCNT surface. The ability of LipoGs to disperse SWCNTs has been demonstrated to depend on their tendency to self-assemble into ribbon-like supramolecular structures. In turn, the super-organization of these supramolecular structures appears to control the homogeneity of the dispersion.

The 1-hexadecyl-3-vinylimidazolium bromide (hvimBr), a water-soluble long-chain imidazolium ionic liquid (IL) with surfactant properties, showed the ability to produce stable homogeneous aqueous dispersions of pristine Single-Walled Carbon Nanotubes (SWNTs). The purpose of this study is the improvement of SWNT dispersing ability by assessing the effect of different groups in position 3 of the imidazole ring. In this regard structural analogues were synthesized and, after characterization, their capability to dissolve SWNTs in water was investigated. Molecular Dynamics (MD) simulations have been performed to provide a semi-quantitative indication of the affinity of each dispersing agent toward SWNT and to attempt an explanation of the experimental results.

Nanoparticles have enormous potential in diagnostic and therapeutic studies. We have demonstrated that the amyloid beta mixed with and conjugated to dihydrolipoic acid- (DHLA) capped CdSe/ZnS quantum dots (QDs) of size approximately 2.5 nm can be used to reduce the fibrillation process. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) were used as tools for analysis of fibrillation. There is a significant change in morphology of fibrils when amyloid β (1–42) (Aβ (1–42)) is mixed or conjugated to the QDs. The length and the width of the fibrils vary under modified conditions. Thioflavin T (ThT) fluorescence supports the decrease in fibril formation in presence of DHLA-capped QDs.

Oxidized single-walled carbon nanotubes (SWNTs) have been prepared following a widely reported two-step purification/oxidation procedure in the presence or absence of a treatment with base (NaOH). The oxidized nanotube samples washed with solvents or base appear close to identical with respect to both appearance and properties. Efficient removal of both metal and carbonaceous impurities and introduction of –COOH groups on the nanotube surface have been demonstrated by AFM, Raman and FTIR spectroscopy. Furthermore, persistence of optical properties was confirmed using UV-vis/NIR absorption and NIR photoluminescence spectroscopies.

A chemical treatment for preparing high purity selectively oxidised SWNTs while preserving optical/electronic properties of the material has been developed. Efficient removal of both metal and carbonaceous impurities has been demonstrated by AFM, TEM, Raman and absorption spectroscopy, while XPS confirmed quantitative conversion of oxidised defects to functionalisable carboxylic acid groups. Furthermore persistence of the characteristic optical properties was confirmed using absorption and NIR photoluminescence spectroscopy, thus indicating preservation of the electronic structure. This chemical treatment thus paves the way for the preparation of high purity, covalently functionalised SWNTs enhancing their potential for use in high-performance optical/electronic applications. A comparison with commonly used purification protocols that utilize nitric acid and sodium hydroxide followed by piranha solution treatments or simple solvent washing is made, highlighting the advantages of the reported method for the production of SWNT starting materials ideal for efficient chemical modifications.

The presence of carboxylated carbonaceous material in nitric acid-treated single-walled carbon nanotube (SWNT) samples has recently brought renewed focus on the processes by which covalent functionalization of such materials are carried out. Using a widely reported 2-step purification/oxidation procedure, we have investigated the effect of basic treatment and solvent washing on the functionalization and final properties and behavior of SWNTs. We have demonstrated, using a number of spectroscopic techniques, that in the absence of NaOH treatment, COOH functionality is introduced directly onto SWNTs, and not only onto carbonaceous material present in the sample. Covalent functionalization of the oxidized materials was also investigated by attachment of a fluorescent probe, and ultimately, whether treated with base or solvent washed, the resulting materials are close to identical with respect to both their appearance and properties. In addition, we have demonstrated that using either of these purification/ox...

Single-walled carbon nanotubes (SWNTs) are suitable for many applications in molecular imaging because of their intrinsic near-infrared (NIR) photoluminescence. Nevertheless, several important issues, such as the SWNTs low biocompatibility, still need to be overcome for the effective use of carbon nanotubes in molecular imaging. In this study, we employ a two-step oxidation procedure with the aims of (1) removing the toxic metal impurities, (2) decreasing the lengths of the tubes, and (3) introducing functional oxygenated groups on the SWNT surface to enable the future development of a multifunctional SWNT-based nanoplatform. Since the presence of defect sites on the SWNT surface is known to quench the optical properties of carbon nanotubes, we have established what effect these two chemical treatments have on the NIR photoluminescence (PL) of the tubes. Our results show that purified and oxidized SWNT samples still display structured emission features in the NIR when dispersed in surfactant aqueous solution, with a residual emission efficiency of 30%. Two-dimensional (2D) fluorescence lifetime imaging (FLIM) of aggregates of purified and oxidized SWNTs in dimethylformamide (DMF) showed an average lifetime of 1.3 and 1.2 ns, respectively. These results demonstrate the relevance of SWNT purification and oxidation in the development of novel NIR probes with reduced toxicological impact on human health and with potential for further functionalization with multiple bioactive species.

PUBLISHED, We present three new crystal structures of members from the photochromic spiropyran family, including a rare example of an open (merocyanine) form. The molecular structures are systematically compared with existing crystallographically relevant data, and a new avenue for stabilizing open spiropyran forms in the solid-state is postulated., We are grateful for financial support from Science Foundation Ireland (PIYRA 07/YI2/I1052, and SURE), Trinity College Dublin (Trinity Award to MN) and ACS-PRF (#46011-AC1).

Complete spectroscopic, structural, and anion-binding properties are reported for a special class of calixphyrins, namely, 5,10-disubstituted porphodimethenes (PDMs). The crystal structure clearly shows that PDMs exhibit nonplanar (distorted) structures with both sp(2)- and sp(3)-hybridized meso carbon centers. We were able to obtain and characterize the diacid form [H(4)(PDM)][X](2) upon addition of several acids to PDMs, where X denotes anions of different acids: HCl, HBr, MeSO(3)H, CF(3)CO(2)H, and HClO(4). We found that the PDM dications generated were more conjugated and thus more stable than their corresponding porphyrins. Their potential to coordinate anions was clearly shown by using (1)H NMR spectroscopy. In addition, we found that when HClO(4) was used to protonate PDMs, the conversion occurs through an intermediate species, which has been assigned to the elusive monoacid derivative on the basis of UV-vis and (1)H NMR experiments.

Since carbon nanotubes (CNTs) display unique structures and remarkable physical properties, a variety of applications have emerged in both materials and life sciences. In terms of applications, the functionalisation of nanotubes is extremely important, as it increases their solubility and processability, and combines the unique properties of single-walled carbon nanotubes (SWCNTs) with those of other classes of materials. A number of methods have been developed, which can be divided into two major approaches: (1) non-covalent supramolecular modifications, and (2) covalent functionalisation. In this tutorial review, we survey the covalent modification of SWCNTs with organic moieties, and illustrate the major analytical techniques routinely used to characterise the functionalised materials. © 2009 The Royal Society of Chemistry.

International audience; The emerging applications of functionalized carbon nanotubes (CNTs) in various research domains necessitate the use of many different analytical techniques to confirm their structural modifications in a fast and reliable manner. Thus far, NMR spectroscopy has not been among the main tools for characterization of organically modified carbon nanostructures. (1)H analysis is limited because the signals in these derivatives are typically weak and broad, resulting in uncertainties of a few parts per million, and because of the strong interference of residual solvent signals. To overcome these limitations, we investigated the applicability of proton NMR spectroscopy based on gradient-edited diffusion pulse sequences (1D diffusion-ordered spectroscopy, DOSY) in the characterization of CNT derivatives. In general, diffusion NMR experiments allow the separation of NMR signals of different species present in a mixture, according to their own diffusion coefficients, merging spectroscopy information with size analysis. In the present study, a selected set of CNT derivatives was synthesized and analyzed using 1D DOSY experiments by applying strong magnetic field gradients (up to 42.6 G cm(-1)). Colorimetric tests (i.e., Kaiser test) and TGA analysis support the NMR findings, which are related to isolated and/or bundled short SWNTs, on the basis of TEM and AFM characterization. The overall results show that the diffusion-based NMR spectroscopy is a fast and promising approach for the characterization of covalently modified CNT derivatives.

Carbon nanotubes have been applied in several areas of nerve tissue engineering to probe and augment cell behaviour, to label and track subcellular components, and to study the growth and organization of neural networks. Recent reports show that nanotubes can sustain and promote neuronal electrical activity in networks of cultured cells, but the ways in which they affect cellular function are still poorly understood. Here, we show, using single-cell electrophysiology techniques, electron microscopy analysis and theoretical modelling, that nanotubes improve the responsiveness of neurons by forming tight contacts with the cell membranes that might favour electrical shortcuts between the proximal and distal compartments of the neuron. We propose the 'electrotonic hypothesis' to explain the physical interactions between the cell and nanotube, and the mechanisms of how carbon nanotubes might affect the collective electrical activity of cultured neuronal networks. These considerations offer a perspective that would allow us to predict or engineer interactions between neurons and carbon nanotubes.

Transcranial magnetic stimulation (TMS) has been extensively studied as a treatment for Major Depression. However, no data are available about the role of genetic variables on the response to this treatment. We analysed the role of two polymorphisms that influence the response to antidepressants: the polymorphisms of the serotonin transporter promoter region (SERTPR) and of the 5-HT(1A) serotonergic receptor promoter region (-1019C/G). Ninety-nine patients from two double-blind, randomised, sham-controlled TMS trials were enrolled. There was a significant influence (p=0.016) of the SERTPR polymorphism on treatment outcome, without differences between active and sham stimulation. Conversely, there was a significant (p=0.014) interaction between 5-HT(1A) genotype and type of stimulation: C/C patients showed a higher difference between active and sham stimulation, indicating that these patients benefited more by TMS than C/G and G/G subjects. Our sample has not the power to control for the possible influence of different medications on these results.

An immunoassay based upon photoluminescent gold quantum dots aimed at detecting human IgG in aqueous solution from micromolar to nanomolar concentrations is described.

We present a study of tetraphenylporphyrin composites formed with single-walled carbon nanotubes (SWNTs). Stable porphyrin/SWNT composite solutions were obtained by non-covalent bonding between the carbon nanotubes and conjugated tetraphenylporphyrin molecules. Transmission electron microscopy reveals porphyrin molecules adhering to the nanotube surface. We report on the first complete linear and nonlinear optical characterization of these nanocomposite materials. The composite solutions were found to be superior optical limiters to nanotubes alone, and to all porphyrin systems studied, including metalloporphyrins.

Large-scale debundling of single-walled nanotubes has been demonstrated by dilution of nanotube dispersions in the solvent N-methyl-2-pyrrolidone (NMP). At high concentrations some very large (approximately 100 s of micrometers) nanotube aggregates exist that can be removed by mild centrifugation. By measurement of the absorbance before and after centrifugation as a function of concentration the relative aggregate and dispersed nanotube concentrations can be monitored. No aggregates are observed below CNT approximately 0.02 mg/mL, suggesting that this can be considered the nanotube dispersion limit in NMP. After centrifugation, the dispersions are stable against sedimentation and further aggregation for a period of weeks at least. Atomic force microscopy (AFM) studies on deposited films reveal that the bundle diameter distribution decreases dramatically as concentration is decreased. Detailed data analysis suggests the presence of an equilibrium bundle number density and that the dispersions self-arrange themselves to always remain close to the dilute/semidilute boundary. A population of individual nanotubes is always observed that increases with decreasing concentration until almost 70% of all dispersed objects are individual nanotubes at a concentration of 0.004 mg/mL. The number density of individual nanotubes peaks at a concentration of approximately 10(-2) mg/mL. Both the mass fraction and the partial concentration of individual nanotubes can also be measured and behave in similar fashion. Comparison of the number density and partial concentration also of individual nanotubes reveals that the individual nanotubes have average molar masses of approximately 700,000 g/mol. The presence of individual nanotubes in NMP dispersion was confirmed by photoluminescence spectroscopy. Concentration dependence of the photoluminescence intensity confirms that the AFM measurements reflect the diameter distributions in situ. In addition, Raman spectroscopy confirms the presence of large quantities of individual nanotubes in the deposited films. Finally, the nature of the solvent properties required for dispersion are discussed.

Background/objective Repetitive transcranial magnetic stimulation (rTMS) has been mainly studied as adjunctive treatment for drug-resistant patients. We assessed the effectiveness of rTMS started concomitantly with antidepressant medications in non-drug-resistant major depressive disorder patients. We also evaluated if, among the 3 antidepressants administered, one had a better synergy with rTMS. Method In this 5-week, double-blind, randomized, sham-controlled study, we recruited 99 inpatients suffering from a major depressive episode (DSM-IV criteria). They were randomly assigned to receive venlafaxine, sertraline, or escitalopram in combination with a 2-week period of sham or active 15-Hz rTMS on the left dorso-lateral prefrontal cortex. Data were gathered from February 2004 to June 2005. Results The active rTMS group showed a significantly faster reduction in Hamilton Rating Scale for Depression (HAM-D) scores compared with the sham group (p = .0029). The response and remission rates were significantly greater in the active rTMS group after the stimulation period (p = .002 and p = .003, respectively), but not at the endpoint. We found no significant difference in HAM-D score reduction among the 3 drugs administered, either in the active or in the sham group. Conclusion These findings support the efficacy of rTMS in hastening the response to antidepressant drugs in patients with major depressive disorder. The effect of rTMS seems to be unaffected by the specific concomitantly administered drug.

Single-wall carbon nanotubes (SWCNT) are severely restricted in their applications, as they exist in rope-like bundles. Recently, J. Coleman et al. demonstrated a spectroscopic method to monitor bundle dissociation in low concentration NT-polymer composites. The method relies on the measurement of the ratio of free-polymer to the nanotube-bound polymer in the SWCNT-polymer solutions via luminescent spectroscopy. A theory has been developed to transform this data into the bundle surface area, which is of course related to the bundle size. This method clearly shows that individual, isolated SWCNT are stable in low concentration dispersions. The main aim of this work is to better understanding of the physics behind polymer-SWCNT interactions, the binding scheme, and the magnitude of the polymer-SWCNT binding energy. In an effort to broaden the understanding of the physical processes governing the NT de-bundling a wide range of suitable polymers and short-chain molecules have been examined. We found a strong dependence of the concentration at which individual NTs become stable with the nature of the dispersant molecule.

The implementation of single‐walled carbon nanotubes (SWNTs) into a wide array of applications is hindered by the formation of bundles. Many methods have been suggested to de‐bundle the SWNTs, including both covalent and non‐covalent funtionalisation with surfactants, polymers and macromolecules. These methods have their advantages but the ideal situation must be to dissolve and de‐bundle the SWNTs in an appropriate solvent at concentrations that are useful for their implementation in applications. In this work we have concentrated on the amide solvent N‐methyl‐2‐pyrrolidone (NMP). This solvent has been shown to be a good dispersant of SWNTs and we have analytically characterised the dispersing and de‐bundling process. Optical absorbance based studies allowed the determination of the concentration at which these dispersions deviate from the Lambert Beer law. This concentration is thought to correspond to that where individual SWNTs are held in solution. Atomic force microscopy was carried out on all solutions confirming excellent dispersion and significant debundling even at high SWNT concentration.

We have identified a strategy to communicate a chemical signal between two independent molecular components. One of them is a photoactive merocyanine that switches to a spiropyran, releasing a proton, when stimulated with visible light. The other is a 4,4'-pyridylpyridinium monocation that captures the released proton, producing an electroactive 4,4'-bipyridinium dication. Under the irradiation conditions employed, the photoinduced transformation requires ca. 15 min to reach a photostationary state. In the dark, the ensemble of communicating molecules reequilibrates to the original state in ca. 5 days. These processes can be monitored following the photoinduced enhancement and thermal decay, respectively, of the current for the monolectronic reduction of the 4,4'-bipyridinium dication. The pronounced difference in time scale for the current enhancement and decay steps can be exploited to implement a memory element with a bit retention time of 11 h. A bit of information can be written optically in the chemical system and it can be read electrically and nondestructively. The memory can be reset, extending its permanence in the dark beyond the bit retention time. A binary logic analysis of the signal transduction operated by the communicating molecules reveals the characteristic behavior of sequential logic operators, which are the basic components of digital memories.

[see reaction]. Ultraminiaturized processors incorporating molecular components can be developed only after devising efficient strategies to communicate signals at the molecular level. We have demonstrated that a three-state molecular switch responds to ultraviolet light, visible light, and H+, attenuating the emission intensity of a fluorescent probe. Intermolecular communication is responsible for the transduction of three input signals into a single optical output. The behavior of the communicating ensemble of molecules corresponds to that of a logic circuit incorporating seven gates.