The development of new, appealing metal-free photocatalysts is of great significance for photocatalytic hydrogen evolution. Herein, an electrostatic self-assembly method to form a unique core−shell architecture of a colloid of carbon spheres with graphitic carbon nitride (g-C 3 N 4 ) has been developed by a one-step chemical solution route. The chemical protonation of g-C 3 N 4 solids with strong oxidizing acids (such as HNO 3 ) is an efficient pathway toward the sol procedure of stable carbon nitride colloids, which can cover the surface of carbon spheres via electrostatic adsorption. On account of the unique polymeric matrix of g-C 3 N 4 and reversible hydrogen bonding, the carbon@g-C 3 N 4 derived from the sol solution showed high mechanical stability with broadened light absorption and enhanced conductivity for charge transport. Thus, the carbon@g-C 3 N 4 core−shell structure exhibited remarkably enhanced photoelectrochemical performance. This polymer system is envisaged to hybridize with desirable functionalities (such as carbon nanorods) to form unique architectures for various applications.

A humido-responsive free-standing film has been created using layer-by-layer assembly technique. Polyethylenimine (PEI) at high pH was assembled with poly(acrylic acid) (PAA) at low pH on a Teflon substrate to yield a micro-nanostructured surface that can be made superhydrophobic after being coated with a low surface energy compound. The resulting asymmetric free-standing film with one surface being superhydrophobic while the other is hydrophilic after detachment from the substrate can undergo reversible bending/unbending shape transitions when the environmental humidity is changed. The bending/unbending movement of the free-standing film can be ascribed to the different responses of these two surfaces to humidity.

Dye-sensitized solar cells (DSSCs) have attracted extensive attention as one of the promising alternatives to silicon solar cells.

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