The comparative study of sorption of polar substances acetonitrile and water into powders and membranes (>10 μm thick) of modified Hummers (HGO) and Brodie (BGO) graphite oxides was performed using isopiestic method (IM) and differential scanning calorimetry (DSC). Additional sorption data were obtained for pyridine and 1-octanol. Sorption measurements were accompanied by conventional XRD and XPS control. Electron paramagnetic resonance (EPR) was additionally used to characterize ordering of the membranes. The impact on sorption of synthetic procedure (Brodie or Hummers), method of making membranes, chemical nature of the sorbent, and method of sorption was systematically examined. It was demonstrated that variations in synthetic procedures within both Hummers and Brodie methods did not lead to changes in the sorption properties of the corresponding powders. Sorption of acetonitrile and pyridine was reduced by approximately half when switching from powders to membranes at ambient temperature. DSC measurements at a lower temperature gave equal sorption of acetonitrile into HGO powder and membranes. Water has demonstrated unique sorption properties. Equal sorption of water was measured for HGO membranes and powders at T = 298 K and at T = 273 K. It was demonstrated that lowering the orientational alignment of the membranes led to the increase of sorption. In practice this could allow one to tune sorption/swelling and transport properties of the GO membranes directly by adjusting their internal ordering without the use of any composite materials.

This paper reports novel techniques for the preparation of aerogels based on graphite oxide (GO) and nanocomposites of GO and superparamagnetic iron oxide nanoparticles (GO/Fe3O4) and discusses specific features of the synthesized materials as sorbents of doxorubicin from aqueous solutions. Sorption efficiency of the aerogel based on GO and superparamagnetic iron oxide nanoparticles (GO/Fe3O4) and the GO aerogel has been determined to be about 50 and 85 W(τ ) = W(∞ )( 1 - e^ - kτ), where W is sorption efficiency, the rate constant is k = 0.042 ± 0.004 min–1 for graphite oxide and 0.0832 ± 0.018 min–1 for the GO/Fe3O4 nanocomposite. The GO/Fe3O4 composite saturates about a factor of 2 more rapidly than pure GO. Sorption by the magnetic aerogel is an exothermic process. The highest efficiency of sorption from a solution with a concentration of 40 mg/L was 95

В статье рассматриваются новые методики получения аэрогелей на основе оксида графита (GO) и его нанокомпозитов с суперпарамагнитными наночастицами оксидов железа (GO/Fe 3 O 4 ), а также обсуждаются особенности полученных материалов в качестве сорбентов доксорубицина из водных растворов. Установлено, что эффективность сорбции аэрогелем на основе GO и суперпарамагнитных наночастиц оксида железа (GO/Fe 3 O 4 ) и аэрогелем GO составляет около 50 и 85% соответственно. В то же время, к преимуществам магнитного аэрогеля следует отнести возможность извлечения сорбента при помощи внешнего магнитного поля. Показано, что при формальном описании сорбции уравнением кинетики псевдопервого порядка: \(W(\tau ) = W(\infty )\left( {1 - {{{\text{e}}}^{{ - k\tau }}}} \right),\) где W – эффективность сорбции, константы достигают значений k = 0.042 ± 0.004 мин –1 для оксида графита и 0.0832 ± 0.018 мин –1 для нанокомпозита GO/Fe 3 O 4 . Для композита GO/Fe 3 O 4 насыщение наступает примерно в 2 раза быстрее, чем для чистого GO, а процесс сорбции магнитным аэрогелем является экзотермическим, максимальная эффективность сорбции из раствора с концентрацией 40 мг/л при 25°C составила 95%, при 40°C – 60%. Полученные результаты перспективны для использования магнитных графитовых аэрогелей в качестве сорбентов и матриц для терапевтических противоопухолевых препаратов пролонгированного действия.

Reversible phase transformation in the Brodie graphite oxide-acetonitrile system, which is intercalation or release of part of the sorbed liquid from the interplanar space accompanied by an increase or a decrease in interplanar distances, is commonly observed in twice-oxidized materials. We observed this phenomenon for once-, twice- and thrice-oxidized materials using the EPR spin probe technique, DSC, and temperature programmed XRD. It was shown that all materials under study formed similar low temperature (LT) and high temperature (HT) swollen structures with acetonitrile. The phase transformation of these structures is observed for materials with different oxidation levels in the same temperature range (∼20 K). The twice- and thrice-oxidized Brodie graphite oxides form swollen structures with the same parameters, while the once-oxidized material sorbs less acetonitrile at lower temperatures, but shows the same interplanar distances as those in twice- and thrice-oxidized materials. The spin probe technique has proven its sensitivity to the appearance of small amounts of the new forming swollen structures, which makes this method useful in studies of phase transformations.

A nitroxyl spin probe is introduced into graphite oxide membranes from a solution in supercritical carbon dioxide in various modes. It is shown that a slow pressure release makes it possible to introduce the probe without destroying the orientational order of graphene layers, i.e., without destroying the internal structure of a membrane.

Solvothermal reduction of graphene oxide performed up to a sp(2)/sp(3) ratio of 20 was demonstrated. The presence of chemical and structural defects was minimized by varying the treatment conditions and reduction agents to reduce their impact on electronic and optical properties. Using the interphase deposition technique both graphene oxide and reduced graphene oxide films were transferred onto ITO-coated glass substrates or SITAL for further analysis. The analysis of the electric characteristics of the reduced graphene oxide films showed high sheet resistance originated from grain boundary resistance. The optical transmittance of the films reached 30% for the most uniform coatings.

Статья посвящена созданию многофункционального нанокомпозита состава GO@Fe3O4@DOX, содержащего оксид графита, наночастицы суперпарамагнитного оксида железа и лекарственный препарат доксорубицин. Созданный материал сочетает функцию двойного магнитного и молекулярного нацеливания на опухолевые ткани. Первоначально для создания композита на поверхность оксида графита (GO) химически осаждали суперпарамагнитные наночастицы Fe 3 O 4 , при этом получали двойной композит GO@Fe 3 O 4 . Затем полученный материал связывали с противоопухолевым лекарственным препаратом доксорубицином (DOX) и получали тройной композит состава GO@Fe 3 O 4 @DOX. Для характеристики морфологии, фазового состава, магнитных и оптических свойств синтезированных в работе образцов были использованы методы термогравиметрического и рентгенофазового анализа, измерения магнитной восприимчивости, просвечивающей электронной микроскопии, УФвидимой и спектроскопии комбинационного рассеяния (КР). В результате проведенного исследования найдено оптимальное соотношение оксида графита, оксида железа и доксорубицина для создания материала, который может быть прообразом нового лекарственного препарата. В работе доказано вхождение лекарственного препарата доксорубицина и оксида железа в композит, что делает возможным использование внешнего магнитного поля для адресной доставки лекарства к пораженным тканям. Показано, что композит стабилен в течение месяца в растворах с физиологическим значением рН.

This work is dedicated to the synthesis of a GO@Fe 3 O 4 @DOX multifunctional nanocomposite composed of graphite oxide, superparamagnetic iron oxide nanoparticles, and the drug doxorubicin. The final product combines double magnetic and molecular targeting to tumor tissues. Superparamagnetic Fe 3 O 4 nanoparticles are first chemically deposited onto a surface of graphite oxide (GO) with the acquisition of a double GO@Fe 3 O 4 composite. The material is then bound with the antitumor drug doxorubicin. The morphology, phase composition, and magnetic and optical properties of synthesized samples are characterized via thermal gravimetry, X-ray diffraction, magnetic susceptibility measurements, transmission electron microscopy, and via UV-visible and Raman spectroscopy. The optimal ratio of graphite oxide, iron oxide, and doxorubicin for the creation of a potential precursor of the new drug is established. The presence of doxorubicin and iron oxide in the composite is confirmed, making it possible to use an external magnetic field for targeted drug delivery towards the affected tissues. It is also shown that the composite retains its stability for a month in solutions with physiological pH values.