Yue Bian

Recently, InGaAs/InP multiple quantum well nanowires grown by selective area epitaxy have been demonstrated with uniform morphology and high optical quality. The InGaAs quantum wells wrapping around the nanowire core are formed with both axial and radial components. As such the radial quantum well configuration presents a unique advantage for the realization of intraband absorption of normal-incidence light in the nanowires, which cannot be achieved in conventional planar quantum well structures due to polarization selection rules. We report here mid-infrared intraband transitions within the atmospheric window (3–5 μm) in InP nanowire arrays embedded with five InGaAs quantum wells under normal-incidence light. The light absorption coefficient of the quantum wells is modeled, and the absorption peak indicates a bound-to-continuum transition. The intraband photocurrent shows a linear dependence on the incident power, while the interband photoresponse is sublinear due to the surface states of the nanowires. These nanowires with radial quantum wells open up great opportunities for developing next-generation mid- to long-wavelength infrared photodetectors and focal plane arrays.

Crystalline nanowire (NWire) cross‐section shapes are known to vary considerably in experiment; an accurate analytic evaluation of NWire cross‐sections from a thermodynamic perspective is still missing. Building on previous work, analytic descriptions are given for zincblende (zb) NWire cross‐section morphing to arbitrary convex hexagonal shapes in order to evaluate the crystallographic‐structural stability of experimental NWire cross‐sections. The maximum of the ratio of NWire‐internal bonds per NWire atom describes the most stable crystallographic and thermodynamic shape of the NWire as far as internal forces are concerned. This maximum occurs when the first derivative of the above ratio , with presenting respective optimum morphing indices to obtain . The stability evaluation is then carried out by comparing derived from the experimental image over the complete morphing range of the NWire cross‐section represented by . This user‐friendly analytic approach allows to calculate the optimum morphing indices and thus all follow‐on parameters, such as , , the number of interface bonds and the NWire cross‐section area . Three examples with experimental data demonstrate the versatility and detailed insight the stability evaluation provides to any zb‐ and diamond‐lattice NWire cross‐section.

Solar‐powered interfacial evaporation, a cost‐effective and ecofriendly way to obtain freshwater from contaminated water, provides a promising path to ease the global water crisis. However, solute accumulation has severely impacted efficient light‐to‐heat‐to‐vapor generation in conventional solar evaporators. Here, it is demonstrated that an interfacial solar thermal photo‐vapor generator is an efficient light‐to‐heat photo‐vapor generator that can evaporate water stably in the presence of solute accumulation. An energy downconversion strategy which shifts sunlight energy from visible‐near infrared to mid infrared‐far infrared bands turns water from transparent to its own absorber, thus changing the fixed evaporation surface (black absorber) in a traditional solar evaporator to a dynamic front (solute surface). Light reflected from the solute can be recycled to drive evaporation. The prototype evaporator can evaporate at a high speed of 1.94 kg m⁻² h⁻¹ during a persistent solute accumulation process for 32 h. Such an ability to produce purified water while recycle valuable heavy metals from waste water containing heavy metal ions can inspire more advanced solar‐driven water treatment devices.

It has long been an aspirational goal to create artificial evaporators that allow omnidirectional energy absorptance, adequate water supply, and fast vapor transportation, replicating the feat of plant transpiration, to solve the global water crisis. This work reveals that magnolia fruits, as a kind of tree‐like living organism, can be outstanding 3D tree‐like evaporators through a simple carbonization process. The arterial pumping, branched diffusion, and confined evaporation are achieved by the “trunk,” “branches,” and “leaves,” respectively, of the mini tree. The mini tree possesses omnidirectional high light absorptance with minimized heat loss and gains energy from the environment. Water confined in the fruit possesses reduced vaporization enthalpy and transports quickly following the Murray's law. A record‐high vapor generation rate of 1.22 kg m⁻² h⁻¹ in dark and 3.15 kg m⁻² h⁻¹ under 1 sun illumination is achieved under the assistance of the gully‐like furry surface. The “absorption of nutrients” enables the fruit to recover valuable heavy metals as well as to produce clean water from wastewater efficiently. These findings not only reveal the hidden talent of magnolia fruits as cheap materials for vapor generation but also inspire future development of high‐performance, full‐time, and all‐weather vapor generation and water treatment devices.