Hierarchical and other advanced materials have attracted increasing attention due to their unique physical and chemical properties, which strongly depend on morphology and size [Reference Wright, Gabaldon, Burckel, Jiang, Tian, Liu, Brinker and Fan1, Reference Zhang, Cui, Page, Pearce, Bowden, Graham, Shen, Li, Wang, Kerisit, N’Diaye, Clark and Rosso2]. These materials have been applied in important technological fields such as energy, catalysis, optical devices, water purification, pollutant removal, CO2 sequestration, and biomedicine [Reference Yang, Fan, Malloy, Brinker and Sigmon3, Reference Sun, Bai, Wu, Boye and Fan4, Reference Cho, Chen, Forman, Kim, Rao, Jaramillo and Zheng5, Reference Huang, Hou, Zhang, Rosso and Zhang6, Reference Yang, Wang, Shen, Yao, Wang, Chen, Xie, Li, Hu, Yang and Dong7]. Particle-based crystallization and self-assembly of molecules are important pathways to synthesize advanced materials of complex structures [Reference De Yoreo, Gilbert, Sommerdijk, Penn, Whitelam, Joester, Zhang, Rimer, Navrotsky, Banfield, Wallace, Michel, Meldrum, Colfen and Dove8, Reference Colfen and Antonietti9, Reference Nakouzi, Soltis, Legg, Schenter, Zhang, Graham, Rosso, Anovitz, De Yoreo and Chun10, Reference Jehannin, Rao and Colfen11]. Unlike monomer-by-monomer addition or Ostwald ripening, particle-based crystallization occurs via particle-by-particle addition, to form larger crystals or clusters [Reference De Yoreo, Gilbert, Sommerdijk, Penn, Whitelam, Joester, Zhang, Rimer, Navrotsky, Banfield, Wallace, Michel, Meldrum, Colfen and Dove8, Reference De Yoreo and Whitelam12]. To date, numerous advanced materials have been synthesized in the lab using particle-based crystallization. Examples include metals such as Pt, Pd, Au, Ag, and Cu [Reference Fang, Du, Lebedkin, Li, Kruk, Kappes and Hahn13]; alloys such as Pt–Ni, Pt–Cu, Pt–Fe, and Au–Ag [Reference Yu, Wang, Peng and Li14]; metal oxides such as ZnO, TiO2, CuO, and α-Fe2O3, Fe3O4 [Reference Pacholski, Dipl.-Ing and Weller15, Reference Penn and Banfield16, Reference Meng, Chen, Chen, Zhou, Peng and Li17, Reference Niederberger and Colfen18, Reference Sun, Gebauer and Colfen19]; and metal sulfides such as PbS, PbSe, ZnS, and CdS [Reference Cho, Talapin, Gaschler and Murray20, Reference Bian, Li and Fan21]. In addition, particle aggregation-based crystallization has been observed in nature, such as in various geological and biological minerals including calcite, collagen, and others [Reference Jiang, Pacella, Athanasiadou, Nelea, Vali, Hazen, Gray and McKee22, Reference Gehrke, Cölfen, Pinna, Antonietti and Nassif23, Reference Hochella, Mogk, Ranville, Allen, Luther, Marr, McGrail, Murayama, Qafoku, Rosso, Sahai, Schroeder, Vikesland, Westerhoff and Yang24]. Different from the particle-based crystallization, self-assembly of molecules has also been used to build advanced materials such as molecular clusters and nanoparticles. For instance, advanced luminescent materials have been prepared by aggregation-induced emission (AIE) of intrinsically non-emissive molecules [Reference Hong, Lam and Tang25, Reference Shi, Kwok, Liu, Tang and Liu26]. One of the challenges facing this fast-growing field of advanced materials is to develop a fundamental understanding of the interactions between particles or molecules in a growth medium and the resulting response dynamics.
This Focus Issue will cover a broad range of topics about building advanced materials via particle aggregation and molecular self-assembly, from experiment and theory to application. One topic covers the synthesis of advanced materials via particle-based crystallization and self-assembly of molecules and their application in energy, catalysis, water purification, pollutant removal, etc. For example, several papers will introduce novel methods to synthesize diamondoids nanowire-cluster arrays [Reference Wang, Qiu and Wang27], hierarchical Au-loaded SnO2 nanoflowers, multi-branched gold nanostructures [Reference He, Cao, Gao and Yang28], graphene oxide coated popcorn-like Ag nanoparticles [Reference Zhang, Chen, Wang, Zheng and Wang29], hierarchically porous poly(lactic acid)/poly(ε-caprolactone) monolithic composites [Reference Chen, Qian, Sun, Chen, Uyama and Wang30], 3-dimensional-graphene/Cu/Fe3O4 composite, as well as others, and the application of hierarchical materials in surface-enhanced Raman scattering [Reference He, Cao, Gao and Yang28], Cr(VI), organic dyes, and oxytetracycline removal [Reference Zhang, Ge, Zhu, Tang, Xing and Li31, Reference Zhang, Meng, Liu, Gu, Zhao, Dong, Zhang, Hou and Guo32], photocatalysis [Reference Wang, Hu, Xu, Zhu, Ding and Deng33], supercapacitor, bisphenol A detection, and gas sensing. Another topic includes investigations of growth mechanisms, such as exploring the growth mechanism of WO3 nanocubes [Reference Wang, Hu, Xu, Zhu, Ding and Deng33]. The most important topic concentrates on understanding the driving forces for particle and molecular aggregation. Particle aggregation strongly depends on the interparticle interactions such as van der Waals (vdW), electrostatic, ion-correlation, hydration, and magnetic forces [Reference Zhang, He, Sushko, Liu, Luo, De Yoreo, Mao, Wang and Rosso34]. Understanding these interaction forces could aid in developing methods to control their aggregation behaviors and then build advanced hierarchical structures. Recently, advanced techniques have been developed to directly measure the interactions between nanoparticles, and the results have clearly shown the roles of vdW and hydration forces on the nanoparticle aggregation [Reference Zhang, He, Sushko, Liu, Luo, De Yoreo, Mao, Wang and Rosso34, Reference Zhang, He, Liu, Bowden, Kovarik, Mao, Wang, De Yoreo and Rosso35, Reference Zhang, Shen, Liu, Kerisit, Bowden, Sushko, De Yoreo and Rosso36]. An invited review in this Focus Issue summarizes these force measurement techniques, and also highlights the theories and simulations on the driving forces for particle aggregation [Reference Sushko37]. The final topic considers building materials with aggregation-induced emission (AIE) and their applications. Several manuscripts discuss the synthesis of small organic molecules containing diphenylmethylene, carbazole and malononitrile units, and polymers and how their AIE properties are used for cell imaging [Reference Huang, Wang, Chen, Liu, Mao, Yuan, Tao, Wei and Zhang38, Reference Shi, Zhang, Huo, Wang, Yu, Shi and Tang39]. The aim of this Focus Issue is to provide a platform for interdisciplinary researchers from physics, chemistry, geology, biology, engineering, and material science to share their approaches to understand and control molecular and particle-based mechanisms of advanced material formation in order to design novel functionalized materials.
Finally, we are very grateful to both the authors and reviewers of the many high-quality manuscripts submitted to this JMR Focus Issue on Building Advanced Materials via Particle Aggregation and Molecular Self-Assembly.
On the cover
The cover of this Focus Issue shows a novel kind of high performance coaxial wire-shaped supercapacitors (WSSCs) with ionogel electrolyte was assembled. Highly flexible WSSCs can be woven into wearable fabrics and devices clearly suggests the possible potential utilization of the textile structures for commercial usage in the future. This method can be utilized in industrial scale to fabricate a device to store and supply energy to portable electronic appliances during a power outage in the grid lines as this device can be charged using wind power.