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Light is a common source of energy in sustainable technologies for photocurrent generation. To date, in such light‐harvesting applications, the excited electrons generate the photocurrent. Here, we introduce a new mechanism for photocurrent generation that is based on excited state proton transfer (ESPT) of photoacids and photobases that can donate or accept a proton, respectively, but only after excitation. We show that the formed ions following ESPT can either serve as electron donors or acceptors with the electrodes, or modify the kinetics of mass transport across the diffuse layer, both resulting in photocurrent generation. We further show that control of the current polarity is obtained by switching the irradiation between the photoacid and the photobase. Our study represents a new approach in photoelectrochemistry by introducing ESPT processes, which can be further utilized in light‐responsive energy production or energy storage. [ABSTRACT FROM AUTHOR]

Nature demonstrates many examples of response and adaptation to external stimuli. Here, this study focuses on self-propulsion (motion) while presenting several self-propelling droplet systems responsive to pH gradients. Light is used as the gating source to gain reversibility, avoid the formation of chemical wastes, and control the self-propulsion remotely. To achieve light-stimuli ultrafast response, photoacids and photobases are used, capable of donating or capturing a proton, respectively, in their excited state. The movement and directionality of the droplet's self-propulsion are controlled by introducing the photoacid/base either in bulk solution, on the surface of the droplet, or inside the droplet. It is shown that proton transfer between the photoacid/base and the droplet results in a rapid change in the droplet's surface tension, which induces the self-propulsion movement. The high versatility of the systems together with a record-breaking ultrafast response to light makes them highly attractive for the design of various controlled cargo-carrier systems. [ABSTRACT FROM AUTHOR]

Light is a convenient source of energy and the heart of light‐harvesting natural systems and devices. Here, we show light‐modulation of both the chemical nature and ionic charge carrier concentration within a protein‐based biopolymer that was covalently functionalized with photoacids or photobases. We explore the capability of the biopolymer‐tethered photoacids and photobases to undergo excited‐state proton transfer and capture, respectively. Electrical measurements show that both the photoacid‐ and photobase‐functionalized biopolymers exhibit an impressive light‐modulated increase in ionic conductivity. Whereas cationic protons are the charge carriers for the photoacid‐functionalized biopolymer, water‐derived anionic hydroxides are the suggested charge carriers for the photobase‐functionalized biopolymer. Our work introduces a versatile toolbox to photomodulate both protons and hydroxides as charge carriers in polymers, which can be of interest for a variety of applications. [ABSTRACT FROM AUTHOR]

Fluorescent dyes are common tools for tracking biological membranes. In this work, we introduce a new ratiometric fluorescent probe for membranes based on a surface‐sensitive photoacid. As all other probes, it lights up within membranes, and furthermore, it has different ratios of fluorescent peaks for different membranes. The main unique feature of the probe is its ability to sense events taking place in the membrane far away from its actual location. This is due to the photoacidity of the probe, and the associated kinetics of its excited‐state proton release and capture that are highly sensitive to the lateral proton diffusion on the surface of the membrane. We show here that minor disruptions to the membrane integrity, induced by the Triton X‐100 surfactant at low concentration (surfactant:lipid ratio of 0.02), can be sensed by our probe using steady‐state fluorescence, while other probes are invisible to them. Time‐resolved fluorescence reveals that the surfactant insertion affects the lateral proton diffusion and accordingly the measured proton recombination of the photoacid. [ABSTRACT FROM AUTHOR]