Self-assembly, a process in which molecules, polymers, and particles are driven by local interactions to organize into patterns and functional structures, is being exploited in advancing silicon electronics and in emerging, unconventional electronics. Silicon electronics has relied on lithographic patterning of polymer resists at progressively smaller lengths to scale down device dimensions. Yet, this has become increasingly difficult and costly. Assembly of block copolymers and colloidal nanoparticles allows resolution enhancement and the definition of essential shapes to pattern circuits and memory devices. As we look to a future in which electronics are integrated at large numbers and in new forms for the Internet of Things and wearable and implantable technologies, we also explore a broader material set. Semiconductor nanoparticles and biomolecules are prized for their size-, shape-, and composition-dependent properties and for their solution-based assembly and integration into devices that are enabling unconventional manufacturing and new device functions.

This article provides a brief overview of recent progress in the synthesis and functionalization of magnetic nanoparticles and their applications in the early detection of malignant tumors by magnetic resonance imaging (MRI). The intrinsic low sensitivity of MRI necessitates the use of large quantities of exogenous contrast agents in many imaging studies. Magnetic nanoparticles have recently emerged as highly efficient MRI contrast agents because these nanometer-scale materials can carry high payloads while maintaining the ability to move through physiological systems. Superparamagnetic ferrite nanoparticles (such as iron oxide) provide excellent negative contrast enhancement. Recent refinement of synthetic methodologies has led to ferrite nanoparticles with narrow size distributions and high crystallinity. Target-specific tumor imaging becomes possible through functionalization of ferrite nanoparticles with targeting agents to allow for site-specific accumulation. Nanoparticulate contrast agents capable of positive contrast enhancement have recently been developed in order to overcome the drawbacks of negative contrast enhancement afforded by ferrite nanoparticles. These newly developed magnetic nanoparticles have the potential to enable physicians to diagnose cancer at the earliest stage possible and thus can have an enormous impact on more effective cancer treatment.

Carbon capsules with hollow macroporous core/mesoporous shell were synthesized using sacrificial submicrometer-size solid core/mesoporous shell (SCMS) silica spheres as templates. Size of the hollow macroporous core and thickness of the mesoporous shell can be easily controlled by the choice of silica spheres and the amount of TEOS/C18-TMS mixture, respectively.

New preparative methods for the synthesis of nanoporous carbons using silica particles as templates will be presented. Gellation of resorcinol and formaldehyde in the presence of silica sol particles generated RF gel-silica nanocomposite. Carbonization followed by HF etching of silica templates generated nanoporous carbons with pore size ranging 10 ∼ 100 nm. When silica particles stabilized with surfactant were used as templates, uniform ∼ 10 nm pore-sized carbons have been formed. These nanoporous carbons exhibited excellent adsorption capacity for dyes.

We have developed a new synthetic procedure to fabricate mesoporous carbons using mesoporous inorganic materials as templates. Mesoporous carbons with regular 3-dimensionally interconnected ∼ 2 nm pore arrays have been synthesized using aluminum substituted MCM-48 and HMS mesoporous silicas as templates. The polymerization of phenol and formaldehyde inside the nanopores of the mesoporous silica templates generated phenol-resin/luminosilicate nanocomposites. The carbonization followed by the removal of silicate templates generated mesooporous carbons with regular pore dimensions. The mesoporous carbons exhibited excellent performance for electrochemical double layer capacitors (EDLC). They revealed ideal rectangular shaped cyclovoltammograms up to the high scan rate of 20 mV/sec, which is important for the future applications.

Bimetallic catalysts have been studied intensively because of their unique activity and selectivity. Unsupported alloy catalysts, however, are usually of limited value due to their very small surface areas. We have now developed a sonochemical synthesis of bimetallic alloys that provides both high surface areas and high catalytic activity. We have produced Fe-Co alloys by ultrasonic irradiation of mixed solutions of Fe(CO)5 and Co(CO)3(NO) in hydrocarbon solvents. The alloy composition can be controlled simply by changing the ratio of precursor concentrations. After treatment at 673K under H2 flow for 2 hours, we obtain nearly pure alloys. BET results show that the surface areas of these alloys are large (10-30 m2/g). TEM and SEM show that the alloy particles are porous agglomerates of particles with diameters of 10-20 nm. Sonochemically prepared Fe, Co, and Fe-Co powders have very high catalytic activity for dehydrogenation and hydrogenolysis of cyclohexane. Furthermore, sonochemically prepared Fe-Co alloys show high catalytic selectivity for dehydrogenation of cyclohexane to benzene; the 1:1 ratio alloy has much higher selectivity for dehydrogenation over hydrogenolysis than either pure metal.

Molybdenum hexacarbonyl in hexadecane was irradiated with high intensity ultrasound under argon at 90°C to yield face centered cubic molybdenum carbide, Mo2C. After thermal treatment, oxygen and excess carbon were removed to give stoichiometric Mo2C. SEM micrographs showed that the surface was extremely porous. TEM micrographs showed that the solid was an aggregate of particles with diameters of ≈ 2 nm. This material has a very high surface area, 188 m2/g as determined by BET gas adsorption. Catalytic studies have been conducted on the dehydrogenation of cyclohexane and the hydrogenolysis of ethane. The sonochemically prepared Mo2C shows good catalytic activity for the dehydrogenation of cyclohexane with 100% selectivity for formation of benzene without hydrogenolysis to methane. The material revealed poor catalytic activity for the hydrogenolysis of ethane.