We suggest that silver nanocube (AgNC) aggregates within cylindrical pores (PAM-AgNC) can be employed as efficient nanostructures for highly efficient, robust, tunable, and reusable surface-enhanced Raman scattering (SERS) substrates for trace level organic vapor detection which is a challenging task in chemical detection. We demonstrate the ability to tune both the detection limit and the onset of signal saturation of the substrate by switching the adsorption behavior of AgNCs between highly aggregated and more disperse by varying the number of adsorption-mediating polyelectrolyte bilayers on the pore walls of the membrane. The different AgNC distributions show large differences in the trace vapor detection limit of the common Raman marker benzenethiol (BT) and a widely used explosive binder Nmethyl-4-nitroaniline (MNA), demonstrating the importance of the large electromagnetic field enhancement associated with AgNC coupling. The SERS substrate with highly aggregated AgNCs within the cylindrical pores allows for consistent trace detection of mid ppb ($500) for BT analyte, and a record limit of detection of low ppb ($3) for MNA vapors with an estimated achievable limit of detection of approximately 600 ppt. The dispersed AgNC aggregates do not saturate at higher ppb concentrations, providing an avenue to distinguish between higher ppb concentrations and increase the effective range of the SERS substrate design. A comparison between the AgNC substrate and an electroless deposition substrate with silver quasi-nanospheres (PAM-AgNS) also demonstrates a higher SERS activity, and better detection limit, by the nanocube aggregates. This is supported by FDTD electromagnetic simulations that suggest that the higher integrated electromagnetic field intensity of the hot spots and the large specific interfacial areas impart greatly improved SERS for the AgNCs. Moreover, we demonstrated that the AgNC substrate can be reused multiple times without significant loss of SERS activity which opens up new avenues for in-field monitoring.

We demonstrate the fabrication of highly open spherical cages with large through pores using high aspect ratio cellulose nanocrystals with "haystack" shell morphology. In contrast to traditional ultrathin shell polymer microcapsules with random porous morphology and pore sizes below 10 nm with limited molecular permeability of individual macromolecules, the resilient cage-like microcapsules show a remarkable open network morphology that facilitates across-shell transport of large solid particles with a diameter from 30 to 100 nm. Moreover, the transport properties of solid nanoparticles through these shells can be pH-triggered without disassembly of these shells. Such behavior allows for the controlled loading and unloading of solid nanoparticles with much larger dimensions than molecular objects reported for conventional polymeric microcapsules.

A facile one‐step fabrication of large‐area multicolored emissive photopatterns in mixed quantum dot‐polymer films is demonstrated. This is in sharp contrast to the current photopatterning approaches that utilize only a single quantum dot (QD) component for single‐color patterns. Strategies are presented that allow for either selective or collective modification of specific predetermined photoluminescent peaks of green and red QDs during photopattern development. These strategies yield novel patterns and allow for unprecedented control over how the color contrast of the photopattern evolves with continuous light illumination. These results clearly show that the evolution of the emission spectra of a multicolor mixed QD‐polymer film can be readily tailored during pattern development, either by careful selection of the excitation wavelength or through combinations of controllably unstable and stable QDs with different recovery rates. Notably, these strategies are simple, fast, and robust, yielding high‐resolution microscopic patterns over large areas (up to fractions of a cm2). Furthermore, the flexibility and capabilities of these strategies greatly expand the potential applications of multicolor emissive photopatterns, particularly in the areas of sensing, imaging, and lasing systems where it is important to exert delicate control over the intensity of selected colors within specific spatial regions.

Proper selection of the quantum dot ligand allows for controllable enhancement of optical gain characteristics (threshold, magnitude, and stability) in quantum dot films.