The structure, chemistry, and charge of interfaces between materials and aqueous fluids play a central role in determining properties and performance of numerous water systems. Sensors, membranes, ...sorbents, and heterogeneous catalysts almost uniformly rely on specific interactions between their surfaces and components dissolved or suspended in the waterand often the water molecules themselvesto detect and mitigate contaminants. Deleterious processes in these systems such as fouling, scaling (inorganic deposits), and corrosion are also governed by interfacial phenomena. Despite the importance of these interfaces, much remains to be learned about their multiscale interactions. Developing a deeper understanding of the molecular- and mesoscale phenomena at water/solid interfaces will be essential to driving innovation to address grand challenges in supplying sufficient fit-for-purpose water in the future. In this Review, we examine the current state of knowledge surrounding adsorption, reactivity, and transport in several key classes of water/solid interfaces, drawing on a synergistic combination of theory, simulation, and experiments, and provide an outlook for prioritizing strategic research directions.
We propose a new type of surfactants, namely, tetrazole derivatives which can be controllably removed from the nanoparticle surface. Tetrazoles are a peculiar class of heterocyclic compounds. The ...presence of four nitrogen atoms in the tetrazole ring determines their interesting physical and chemical properties. Tetrazoles show high thermal stability below 200C while decomposing at higher temperature with formation of gaseous products and no or very little solid residue. Moreover, the tetrazole group is known as an important ligand in coordination chemistry. Its donor nitrogen atoms can bind to various metal ions leading to stable complexes with diverse coordination modes of the heteroring. We report the synthesis of CdS NPs capped with 1-R-5-thiotetrazoles using two different synthetic schemes: solution-phase and solventless single precursor approaches. In both synthetic procedures cadmium thiotetrazolates were used as cadmium precursors and sources of surfactant.
Semiconductor nanocrystals can be synthesized using inexpensive, scalable, solution-based techniques, and their utility as tunable light emitters has been demonstrated in various applications, ...including biolabeling and light-emitting devices. By contrast, the use of colloidal nanocrystals for optical amplification and lasing has been limited by the high input power densities that have been required. In this work, we show that colloidal nanoplatelets (NPLs) produce amplified spontaneous emission (ASE) with pump-fluence thresholds as low 6 uJ/cm2 and gain as high as 600 cm-1, both a 4-fold improvement over the best reported values for colloidal nanocrystals; in addition, gain saturation occurs at pump fluences two orders of magnitude higher than the ASE threshold. We attribute this exceptional performance to large optical cross-sections, slow Auger recombination rates, and the narrow emission linewidth of the NPL ensemble. The NPLs bring the advantages of quantum wells as an optical gain medium to a colloidal system, opening up the possibility of producing high-efficiency, solution-processed lasers.
We present the first time-resolved cryogenic observations of Förster energy transfer in large, monodisperse lead sulfide quantum dots with ground-state transitions near 1.5 µm (0.8 eV), in ...environments from 160 K to room temperature. The observed temperature-dependent dipole−dipole transfer rate occurs in the range of (30−50 ns)−1, measured with our confocal single-photon counting setup at 1.5 µm wavelengths. By temperature-tuning the dots, 94% efficiency of resonant energy transfer can be achieved for donor dots. The resonant transfer rates match well with proposed theoretical models.
Large surface to volume ratios of semiconductor nanocrystals cause susceptibility to charge trapping, which can modify luminescence yields and induce single-particle blinking. Optical spectroscopies ...cannot differentiate between bulk and surface traps in contrast to spin-resonance techniques, which in principle avail chemical information on such trap sites. Magnetic resonance detection via spin-controlled photoluminescence enables the direct observation of interactions between emissive excitons and trapped charges. This approach allows the discrimination of two functionally different trap states in CdSe/CdS nanocrystals underlying the fluorescence quenching and thus blinking mechanisms: a spin-dependent Auger process in charged particles; and a charge-separated state pair process, which leaves the particle neutral. The paramagnetic trap centers offer control of energy transfer from the wide-gap CdS to the narrow-gap CdSe, i.e. light harvesting within the heterostructure. Coherent spin motion within the trap states of the CdS arms of nanocrystal tetrapods is reflected by spatially remote luminescence from CdSe cores with surprisingly long coherence times of >300 ns at 3.5 K.
Organization of uniform objects into periodic structures can be found in many natural systems, such as atomic and molecular solids, opals, sponges and bacterial colonies — self-assembly is the ...fundamental phenomenon that generates structural organization on all scales 1. In this chapter we discuss the structures spontaneously formed by nanoparticles which attracted significant interest from different branches of science and technology. The progress in colloidal synthesis of inorganic nanomaterials enabled preparation of different materials (metals, semiconductors, magnetic and ferroelectric materials) in the form of uniform nanometer-size crystals with amazing levels of size and shape control 2. Nowadays colloidal synthesis allows for creation of nanostructures where composition, size, shape and connectivity of multiple parts of a multicomponent structure can be tailored in an independent and predictable manner (Fig. 1). In many nanoscale materials size and shape control provides additional degrees of freedom for designing physical and chemical properties. Thus, the effect of quantum confinement allows fine-tuning of the optical and electronic properties of semiconductor nanoparticles through varying particle size 3. Exchange-biased ferromagnetism 4, size-dependent magnetic and catalytic properties of sub-20 nm particles are all examples of how material properties can be tailored by size and shape engineering at the nanoscale 5, 6.
We present the first time-resolved cryogenic observations of Forster energy transfer in large, monodisperse lead sulphide quantum dots with ground state transitions near 1.5 um (0.83 eV), in ...environments from 160 K to room temperature. The observed temperature-dependent dipole-dipole transfer rate occurs in the range of (30-50 ns)^(-1), measured with our confocal single-photon counting setup at 1.5 um wavelengths. By temperature-tuning the dots, 94% efficiency of resonant energy transfer can be achieved for donor dots. The resonant transfer rates match well with proposed theoretical models.
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