Targeted delivery combined with controlled drug release has a pivotal role in the future of personalized medicine. This review covers the principles, advantages, and drawbacks of passive and active targeting based on various polymer and magnetic iron oxide nanoparticle carriers with drug attached by both covalent and noncovalent pathways. Attention is devoted to the tailored conjugation of targeting ligands (e.g., enzymes, antibodies, peptides) to drug carrier systems. Similarly, the approaches toward controlled drug release are discussed. Various polymer-drug conjugates based, for example, on polyethylene glycol (PEG), N-(2-hydroxypropyl)methacrylamide (HPMA), polymeric micelles, and nanoparticle carriers are explored with respect to absorption, distribution, metabolism, and excretion (ADME scheme) of administrated drug. Design and structure of superparamagnetic iron oxide nanoparticles (SPION) and condensed magnetic clusters are classified according to the mechanism of noncovalent drug loading involving hydrophobic and electrostatic interactions, coordination chemistry, and encapsulation in porous materials. Principles of covalent conjugation of drugs with SPIONs including thermo- and pH-degradable bonds, amide linkage, redox-cleavable bonds, and enzymatically-cleavable bonds are also thoroughly described. Finally, results of clinical trials obtained with polymeric and magnetic carriers are analyzed highlighting the potential advantages and future directions in targeted anticancer therapy.

Efficient and selective methods for covalent derivatization of graphene are needed because they enable tuning of graphene’s surface and electronic properties, thus expanding its application potential. However, existing approaches based mainly on chemistry of graphene and graphene oxide achieve only limited level of functionalization due to chemical inertness of the surface and nonselective simultaneous attachment of different functional groups, respectively. Here we present a conceptually different route based on synthesis of cyanographene via the controllable substitution and defluorination of fluorographene. The highly conductive and hydrophilic cyanographene allows exploiting the complex chemistry of −CN groups toward a broad scale of graphene derivatives with very high functionalization degree. The consequent hydrolysis of cyanographene results in graphene acid, a 2D carboxylic acid with pKa of 5.2, showing excellent biocompatibility, conductivity and dispersibility in water and 3D supramolecular assemblies after drying. Further, the carboxyl groups enable simple, tailored and widely accessible 2D chemistry onto graphene, as demonstrated via the covalent conjugation with a diamine, an aminothiol and an aminoalcohol. The developed methodology represents the most controllable, universal and easy to use approach toward a broad set of 2D materials through consequent chemistries on cyanographene and on the prepared carboxy-, amino-, sulphydryl-, and hydroxy- graphenes.

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SACs) (see also reviews [11][12][13] ). SACs could offer ultimate atom economy and make every active site accessible, like homogeneous catalysts but being recyclable, which is a subject of paramount importance. [14] Major challenges in the field though encompass: i) the development of materials with precise functionalities for robust metal ion binding and ii) metal cooperativity in heterometallic and mixed-valence SACs, as identified in the recent topical perspective. [12] Meeting the first challenge could facilitate higher metal contents avoiding clustering and leaching upon reaction and catalyst recycling. This is also a prerequisite for the second challenge (metal-metal cooperation), since low metal content translates into large intermetallic distances. [6] Cooperation between two metal ions linked by a single-frame ligand has shown enormous potential in homogeneous catalysis. [15] For example, biocatalysts (metalloenzymes) use binuclear [16] and mixed-valence metal centers [17] for effective catalysis. Therefore, the development of heterogeneous catalysts with cooperativity between metal centers, keeping all the salient features of SACs, could offer a platform for the development of the next generation of catalysts.Graphene-based 2D materials have contributed to the development of SACs, [10,[12][13][14][18][19][20][21][22][23][24][25][26][27] in which metal ions are tetracoordinated in porphyrinic-like vacancies. Although only low contents of metal atoms can be achieved (up to ≈1 wt%), [10,12,14,18,[22][23][24][25][26] Single-atom catalysts (SACs) aim at bridging the gap between homogeneous and heterogeneous catalysis. The challenge is the development of materials with ligands enabling coordination of metal atoms in different valencestates, and preventing leaching or nanoparticle formation. Graphene functionalized with nitrile groups (cyanographene) is herein employed for the robust coordination of Cu(II) ions, which are partially reduced to Cu(I) due to graphene-induced charge transfer. Inspired by nature's selection of Cu(I) in enzymes for oxygen activation, this 2D mixed-valence SAC performs flawlessly in two O 2 -mediated reactions: the oxidative coupling of amines and the oxidation of benzylic CH bonds toward high-value pharmaceutical synthons. High conversions (up to 98%), selectivities (up to 99%), and recyclability are attained with very low metal loadings in the reaction. The synergistic effect of Cu(II) and Cu(I) is the essential part in the reaction mechanism. The developed strategy opens the door to a broad portfolio of other SACs via their coordination to various functional groups of graphene, as demonstrated by successful entrapment of Fe III /Fe II single atoms to carboxy-graphene. Single-Atom CatalysisThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.201900323.

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In this work we report on the preparation of some aqueous graphene oxide (GO) dispersions and the investigation of their nonlinear optical response under visible (532 nm) and infrared (1064 nm), picosecond and nanosecond laser excitation. The GO colloids were prepared under specific and well-defined conditions resulting in finely dispersed heavily oxidized large GO sheets. In all cases, GO colloids were found to present large nonlinear absorption and negligible nonlinear refraction. The physical mechanisms responsible for their nonlinear optical response are discussed. In addition, the so-prepared GO dispersions were found to exhibit large broadband optical power limiting action for both pulse durations, comparable to that of C 60 for visible laser pulses and much superior for infrared ones.

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We describe the synthesis of Gd(III)-doped carbon dots as dual fluorescence-MRI probes for biomedical applications. The derived Gd(III)-doped carbon dots show uniform particle size (3-4 nm) and gadolinium distribution and form stable dispersions in water. More importantly, they exhibit bright fluorescence, strong T1-weighted MRI contrast and low cytotoxicity.In the past several years semiconductor quantum dots have been the subject of intense research due to their scientific and technological importance. 1 Recently, carbon dots (C-dots) have emerged as environmentally friendly complements to calcogenide-based quantum dots. 2,3 The strong fluorescence and low toxicity of C-dots make them attractive materials for a variety of biomedical applications, such as biosensing and bioimaging. 2 However, the origin of fluorescence of C-dots is not completely understood. 3a Their optical behaviors can be partially explained in terms of recombination of excitons on the Cdot surface and/or by polyaromatic fluorophores originating from the preparation. 3a,4 For several applications, materials that combine fluorescence with additional functionality (e.g., magnetic response) in a single platform can be highly advantageous. To this end, we recently reported a series of magneto/fluorescent core-shell hybrids by decorating magnetic nanoparticles with C-dots. 5a Srivastava et al. also reported magnetic nanocomposites by thermal decomposition of organic precursors in the presence of Fe 3 O 4 nanoparticles. 5b Here we report the first Gd-doped C-dots that combine fluorescence with a strong MRI contrast. Sun and co-workers have reported previously Zn-doped C-dots with high photoluminescence (comparable to semiconductor quantum dots) but no reports exist for direct incorporation of various dopants especially to impart additional functionality. 6 Furthermore, the incorporation of the Gd compound into solid matrices brings extra advantages to T1 contrast enhancement in comparison to a ''free'' T1 contrast agent. The r 1 relaxivity is increased due to the slowing of tumbling of the Gd complex caused by attachment to a solid support. 7 Also, nanoparticles based on inorganic Gd compounds (i.e., Gd 2 O(CO 3 ) 2 , Gd 2 O 3 ) show a good T1 contrast enhancement. 8 However, these materials do not have high payloads of magnetic centers because of high diameters. Since our general synthesis approach is based on pyrolysis of molecular precursors, 9 dopants can be mixed in prior to the thermal treatment avoiding post-synthesis steps. The Gd-doped C-dots are uniform in size and highly dispersible in water. Moreover, in addition to their fluorescence they exhibit strong T1-weighted MRI contrast (comparable to commercial Gadovist) and low cytotoxicity. These features make them very promising candidates for biomedical applications as dual fluorescence-MRI probes. 10 The Gd-containing C-dots were synthesized by mixing gadopentetic acid into tris(hydroxymethyl)aminomethane (Tris base) and betaine hydrochloride followed by pyrolysis in air at 250 C. In th...