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Titanium dioxide based photocatalysis is a well-established advanced oxidation process (AOP) that recently has expanded its borders comprising advanced reduction processes (ARPs) as well. To enhance the photocatalytic activity, titania heterostructures embedding semiconductors, or clays, or plasmonic metals can be proposed as very promising solutions. In this study, carbon quantum dots (C-QDs) prepared hydrothermally, were successfully combined with titania (TiO2). The photocatalytic activity of the C-QDs/TiO2 heterostructures was successfully tested in the photocatalytic reduction of 4-nitrophenol (PNP) and hexavalent chromium (Cr+6) pollutants. Moreover, the composite thin films were also effectively used in photocatalytic degradation of characteristic dye contaminants, thus confirming their high potential for photoinduced oxidation reactions. The mechanisms of the photocatalytic reactions were studied using appropriate scavengers and it was demonstrated that electrons (e-) are at the origin of the photocatalytic reduction of Cr+6 and 4-NP, while holes (h+) are the main active species for the photocatalytic oxidation reactions.

In this work, we investigate the photoluminescence mechanisms of N-doped, CQD-based nanocomposites, in the form of aqueous suspensions as well as the transition to thin films, in order to facilitate their use for solid-state applications. The products of two different synthetic routes have been investigated for their optical response in the form of aqueous suspensions and thin films. In addition, dialysis was utilized to purify and separate the as-synthesized material into different fractions, which were then studied separately. The PL spectra revealed two optical centers identified as H-aggregates of citrazinic acid derivatives and 4-hydroxy-1H-pyrrolo[3,4-c]pyridine-1,3,6(2H,5H)-trione (HPPT). The materials were further studied with FTIR and UV–Vis spectroscopy, as well as TEM microscopy, in order to acquire a better understanding of these optical centers. The optical centers were found to be excitation-independent emitters, sensitive to ambient pH conditions and able to interact with each other by an energy transfer mechanism in the solid state.

Carbon dot-based fluorescent nanocomposite compounds were obtained following microwave assisted thermal treatment of an aqueous mixture consisting of citric acid and urea. Thin film deposition of nanocomposites on SiO2 (100) substrates is followed by annealing, in order to render the films dissolution-resistant and processable. Optical lithography and O2 plasma etching are utilized to pattern the deposited films in the desired shapes and dimensions and a solid-state relative humidity sensor is fabricated on the SiO2 substrate. Spectroscopy and microscopy techniques are employed to characterize and monitor the whole process throughout the fabrication steps. The patterned films retain the functional groups introduced during their synthesis and continue to display hydrophilicity and PL properties. Successful patterning of these nanocomposites opens the way for the fabrication of solid-state, carbon dot-based optical and electrical devices that take advantage of the properties of carbon quantum dots.

Refined mixed fullerenes were used as a reagent in known organic reactions instead of the pure fullerene C60 with aim to find an alternative, low-cost method for the synthesis of fullerene derivatives potentially exhibiting photoconductive properties. The isolation of C60 or C70 in clean form without admixtures requires the use of large quantities of toluene or other nonpolar solvents, polluting the environment and multiplying the production cost. 1,3-Dipolar cycloaddition of azomethine ylide to fullerite was chosen because this reaction is one of the most widely used for fullerene functionalization, producing material possibly presenting photoinducing behavior. The data showed that the use of the cheaper mixed fullerenes instead of pure C60 leads to the isolation of the same expected products with similar yields. The photoelectric properties of mixed fullerenes and their organic derivatives were also examined. A slightly semiconductive behavior was confirmed as well as a noticeable photoresponse...

Three fulleropyrrolidine derivatives, characterized by the presence of positive charges, were introduced in the interlayer space of montmorillonite. The composites were characterized by powder X-ray diffraction and differential thermal and thermogravimetric (DTA-TGA) analysis, in conjunction with FTIR, UV-Vis, Raman, and Fe-57-Mossbauer spectroscopies. Organophilic derivatives were intercalated into organically modified clays, while water-soluble fulleropyrrolidines were introduced into the clay galleries through ion exchange. The experiments, complemented by computer simulations, show that not all the clay-clay platelets are intercalated by the fullerene derivatives and that a sizable amount of charge transfer takes place between the host and the guests. J Am Chem Soc

Absorption spectra of the pyrrolidine N -mTEG (mTEG=CH 2 CH 2 OCH 2 CH 2 OCH 2 CH 2 OCH 3 ) mono-adduct and eight bis-adducts of C 60 were studied in the 230–800 nm spectral range. The five-membered ring adducts contain an apex nitrogen atom. A theoretical discussion in terms of the effective electronic structures and transitions of these species shows that a filiation between spectra of C 60 , and its pyrrolidine mono- and bis-adduct derivatives can be expected and rationalised. Allowed transitions in the ultraviolet are related to fullerene core electronic transitions and are observed to be little affected in energy and in transition strength by the mono-adduct, apart from band splitting or broadening associated with the lowered molecular symmetry with respect to C 60 , whereas in the visible region, the transitions related to C 60 forbidden transitions are significantly modified by the adduct. The bis-adducts have similar general spectral behaviour to that of the mono-adduct, with differences that reflect the relative position of the two addends but are found to be not dependent on membership of any of the three formal symmetry groups into which the bis-adducts can be classified. The second pyrrolidine adduct reinforces the perturbation of the forbidden and, to a lesser extent, the allowed transitions of the fullerene core. From a comparison with the spectra of C 60 [C(COOEt) 2 ] and its bis-adducts, it was concluded that the N atom in the pyrrolidine five-membered ring adduct is a less efficient blocker of through-bond and/or through-space communication than the sp 3 carbon atom in Bingel–Hirsch methanofullerenes.

For a group of seven isomeric N-mTEG[60]fulleropyrrolidine bis-adducts (mTEG = CH2CH2OCH2CH2OCH2CH2OCH3), the quantum yields of singlet oxygen (O2, 1Δg) production and the maximum triplet molar absorption coefficients were found to be separately correlated with the shortest distances and with the number of bonds connecting the two addends on the fullerene sphere.

We present optical spectroscopy measurements of a supramolecular assembly C60–H2TPP in poly-vinylbutyral (PVB) and compare its photophysical properties to separated C60 and H2TPP in PVB. Optical absorption and emission from the supramolecular assembly mainly appears as resulting from a superposition of the respective properties of the fullerene and porphyrin moieties. However, emission features unique to the supramolecule assembly are found and reported. Spectral hole-burning properties of the supramolecule are similar to those observed for separated C60 and H2TPP. This demonstrates that the phototautomerisation induced in the porphyrin moiety and thought to be responsible for the formation of the spectral hole is largely unaffected by the presence of the fullerene. r 2002 Elsevier Science B.V. All rights reserved.

1,3-Dipolar cycloaddition of azomethine ylides to C 60 generates a family of fullerene derivatives, colloquially termed fulleropyrrolidines. In this paper, we report the synthesis and the electrochemical properties of fulleropyrrolidine and fulleropyrrolidinium ion derivatives. Cyclic voltammetry measurements, performed using ultramicroelectrodes at −60°C with scan rates as high as 50 V/s, allowed, for the first time in fullerene derivatives, the observation of six fullerene-centered reductions. These derivatives also exhibit enhanced electron-accepting properties with respect to both the parent fulleropyrrolidine derivatives and C 60 . Bulk electrolysis carried out at the stage of the first reduction potential, gives rise to a stable zwitterion, with both anion and cation located on the fullerene derivatives.

Refined mixed fullerenes were used as a reagent in known organic reactions instead of the pure fullerene C60 with aim to find an alternative, low-cost method for the synthesis of fullerene derivatives potentially exhibiting photoconductive properties. The isolation of C60 or C70 in clean form without admixtures requires the use of large quantities of toluene or other nonpolar solvents, polluting the environment and multiplying the production cost. 1,3-Dipolar cycloaddition of azomethine ylide to fullerite was chosen because this reaction is one of the most widely used for fullerene functionalization, producing material possibly presenting photoinducing behavior. The data showed that the use of the cheaper mixed fullerenes instead of pure C60 leads to the isolation of the same expected products with similar yields. The photoelectric properties of mixed fullerenes and their organic derivatives were also examined. A slightly semiconductive behavior was confirmed as well as a noticeable photoresponse...

1,3-Dipolar cycloaddition of azomethine ylides to C60 leads to the isolation of a family of fullerene derivatives, named fulleropyrrolidines. Such derivatives are useful building blocks in the design and synthesis of new materials. The combination of the fullerene properties with those of other interesting units such as polymers, photo and electroactive groups, may produce useful derivatives with new applications in materials science.

The fabrication of high quality, robust and photoactive ITO electrodes—in the form of well-defined two- and three-dimensional films—is reported following the Langmuir–Schafer (LS) and the layer-by-layer (LBL) methods. In the LS approach C60-NiP multilayers were transferred from the air–water interface, while the LBL approach utilizes electrostatic and van der Waals interactions for the step-by-step deposition of individual C60-NiP molecules out of solution. These complementary techniques allow control over the thickness and composition of the films at a molecular level and guarantee the specific alignment and the orientation of the incorporated donor–acceptor system. Modified ITO electrodes were probed in photocurrent experiments, in which the LBL-modified electrodes reveal smaller photon to current conversion efficiencies relative to the LS-modified electrodes.

Thin films consisting of a fulleropyrrolidine derivative 1 and a novel water-soluble porphyrin 2 were prepared by the Langmuir–Sh+fer (LS, horizontal lifting) method. In particular, a solution of 1 in chloroform and dimethyl sulfoxide was spread on the water surface, while porphyrin 2 (bearing peripheral anionic groups) was dissolved into the aqueous subphase. To the best of our knowledge, such a versatile method of film fabrication for fullerene/porphyrin mixed composite films has never been used before. Evidence of the effective interactions between the two moieties at the air– water interface was obtained from the analysis of the floating layers by means of surface pressure versus area per molecule Langmuir curves, Brewster angle microscopy and UV-visible reflection spectroscopy. The characterisation of the LS films by UV-visible spectroscopy reveals that the two constituents behave as discrete and weakly interacting p systems. The use of polarised light suggests the existence of a preferential direction of the macrocyclic rings with an edge-on arrangement with respect to the substrate surface. Finally, photoaction spectra were recorded from films deposited by only one horizontal lifting onto indium–tin– oxide (ITO) electrodes and the observed photocurrent increased notably with increasing transfer surface pressure.

The third-order nonlinear optical properties of fulleropyrrolidine and its salt as well as their reduced forms are investigated. Upon reduction, the response increases by up to, and sometimes more than, three orders of magnitude, giving values comparable to the largest ever reported. Calculations and experiments provide a coherent picture for the nonlinear optical properties of these new materials.

The cyclic voltammetric (CV) study of a series of novel bisfulleropyrrolidines (3) and bisfulleropyrrolidinium ions (4) is reported. The eight possible stereoisomers of each series were systematically investigated under strictly aprotic conditions that allowed the observation of up to four and five subsequent reversible reductions in 3 and 4, respectively. Because of the stabilizing effect of positive charges, a significant enhancement of the electronegative properties was observed in 4. In fact, 4-trans-2 and 4-trans-1 result among the strongest reversible electron-accepting C(60) oligoadducts. Furthermore, the study evidenced that, in both 3 and 4, the CV pattern, and in particular the potential separation between the second and third reductions, changes significantly with the addition pattern. A sequential pi-electron model that simulates the effect of subsequent reductions of C(60) bis-adducts gives a good correlation (r > 0.96) with the cyclic voltammetry data when the molecules are divided in two sets dependent on the location of the addends in the same or in opposite hemispheres.

A very general and versatile method for functionalizing different types of carbon nanotubes is described, using the 1,3-dipolar cycloaddition of azomethine ylides. Approximately one organic group per 100 carbon atoms of the nanotube is introduced, to yield remakably soluble bundles of nanotubes, as seen in transmission electron micrographs. The solubilization of the nanotubes generates a novel, interesting class of materials, which combines the properties of the nanotubes and the organic moiety, thus offering new opportunities for applications in materials science, including the preparation of nanocomposites.

A novel biosensor for the amperometric detection of glutathione is proposed in which glutathione reductase is coupled to a pyrrolofullerene bis-adduct playing the role of redox mediator between electrode and enzyme. The adoption of a simple procedure for realizing the immobilization of the redox mediator, together with the enzyme, within a polypyrrole film cast onto a glassy carbon electrode, was made possible by the amphiphilic properties of the fullerene derivative. The biosensor showed a fast and reproducible response to glutathione and, because of its lower sensitivity, a wider linear range with respect to a similar device based on a diffusional redox mediator.

We report the synthesis of three novel, versatile fullerene intermediates whose main feature is the presence of an amino end group. Simple condensation reactions of these intermediates under standard conditions produce new derivatives that are useful for applications in materials science and medicinal chemistry.

We report the isolation and characterization of bisadducts of fulleropyrrolidine derivatives. The compounds were characterized by means of a variety of spectroscopic techniques, including ES-MS, UV-vis, (1)H NMR, and (13)C NMR. The whole series of bisadducts was separated for the first time in the case of the bispyrrolidines, and the determination of their structure was obtained by NMR spectroscopy with the help of HMQC and HMBC techniques.

1,3-Dipolar cycloaddition of azomethine ylides to C60 leads to the isolation of a family of fullerene derivatives, named fulleropyrrolidines. Such derivatives are useful building blocks in the design and synthesis of new materials. The combination of the fullerene properties with those of other interesting units such as polymers, photo and electroactive groups, may produce useful derivatives with new applications in materials science.

Fullerene derivatives exhibit absorption throughout the UV/Vis region up to 750nm. This feature is important for easy excitation. Once excited, fullerenes may become both electron and energy acceptors. The distinction between these two pathways depends strongly on the partner involved (donor) and on the conditions employed (solvent, etc.).

Interpenetrating networks of polythiophenes and fullerene derivatives give rise to charge transfer after irradiation with visible light. The resulting radical ion pairs have been studied by time-resolved EPR spectroscopy. At low temperatures (20 K), the radical pairs are spin correlated and locked at a distance of 27.1 A, whereas an increase of temperature causes the electron and the hole to move further away from each other.

The radical anions of two C60 Nteg-fulleropyrrolidine (teg = 3,6,9-trioxadecyl) adducts, the monoadduct and the trans1-bisadduct have been studied in liquid solution and glassy matrix of 2-MeTHF by...

The family of fullerene derivatives obtained by 1,3-dipolar cycloaddition of azomethine ylides to C 60 is colloquially termed fulleropyrrolidines. In this paper, we report the synthesis and the electrochemical properties of a series of fulleropyrrolidine derivatives. All compounds are characterized by the presence of a solubilizing mTEG group. In addition, a derivative containing a thiophene moiety, covalently attached to the pyrrolidine ring has been studied. Cyclic voltammetry measurements, performed also at low temperatures, allowed the observation of five fullerene-centered reductions for all the species. Adsorption phenomena, however, were found associated to the last reduction processes in the thiophene–fulleropyrrolidine conjugate. Moreover, thanks to the increased solubility of the latter species in polar solvents (acetonitrile–dichloromethane mixtures) its anodic polymerization was carried out, leading to a conducting film still retaining the redox properties of the fullerene derivative.

The effect of the orientating potential in the E7 liquid crystal on a series of fulleropyrrolidine bisadducts has been examined. Photoexcited triplet states, populated by spin−orbit promoted intersystem crossing, have been used as spin probes to determine the preferential orientations of the guest molecules in the anisotropic medium. Time-resolved electron paramagnetic resonance (TREPR) spectroscopy has been applied and spectra with the external magnetic field set parallel or perpendicular to the director n of the mesophase have been measured. Spectrum analysis has enabled us to determine the preferred orientation of n with respect to the principal axis frame of the dipolar interaction and to calculate the order parameters by using the orientational distribution function obtained by spectral simulation. It has been found that the macroscopic order degree induced by the mesophase on the guest molecules varies from one bisadduct to another. Bisadducts with D2h symmetry have exhibited triplet spectra due to ...