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In the context of information explosion, neuromorphic and hardware‐based security devices have garnered significant attention for their capacity to facilitate parallel computing and not be vulnerable to hacking, respectively. A demonstration of a dual photosynaptic (DPS) and physically unclonable function (PUF) devices characterized by ternary TiO2‐x nanorods (NRs)/Pentacene/C60 heterostructure are simultaneously presented. For the DPS device, the ternary heterostructure leads to parallel‐operating DPS characteristics: i) wavelength‐dependent (WD) synapse and ii) stimulus‐moment‐dependent (SMD) synapse. Each synaptic characteristic demonstrates a remarkable degree of plasticity, which signifies a smooth transition from short‐term potentiation (STP) to long‐term potentiation (LTP). Moreover, The face recognition assessments have unveiled recognition rates of 83.3% for 2 operational modes. Notably, the DPS device maintains stable performance on the business card, even after a rigorous 49‐day testing period and undergoing 1 000 bending cycles. Regarding the PUF device, the security keys with unique patterns are created due to random current distribution induced by placement‐dependent doping effects of SnO2 quantum dots (QDs). Moreover, near‐ideal inter‐hamming distances (inter‐HDs), uniformities, and entropies are verified for all cryptographic keys. These findings introduce a pioneering concept of photonic synapses with their successful integration onto various substrates, including the hardware‐based security PUF device. [ABSTRACT FROM AUTHOR]

The Si‐based self‐powered broadband photodiode (SSBP) is prized for its ability to swiftly detect light across a wide spectrum without requiring an external voltage. However, boosting its efficiency remains challenging due to its high refractive index and limited UV light penetration. A combination of Si with ZnGa2O4, an ultra‐wide‐bandgap spinel material, can bring new opportunities to address these shortcomings of SSBP. In this study, a ZnGa2O4/p‐Si heterojunction photodiode is presented, which is capable of detecting UV to near‐infrared light autonomously. Operating without bias, this device exhibits excellent rectification and detects wavelengths from 265 to 1000 nm, achieving impressive performance metrics such as a photo‐to‐dark current ratio of 5.8 × 104, response speed of less than 3 ms, responsivity of 117 mA W−1, and specific detectivity of 5.5 × 1012 Jones while the photodiode demonstrates exceptional stability and durability under harsh conditions. The versatility of this device is demonstrated by applying it to the optical imaging sensors and physically unclonable security devices. This study provides new inspirations for the development of the energy‐efficient and emerging optical sensing technologies. [ABSTRACT FROM AUTHOR]

Highlights: Blue micro-light-emitting diodes (μLED)-integrated gas sensors were fabricated as monolithic structure by directly loading sensing materials onto the μLED. SnO2 nanoparticles are activated by blue μLED and exhibit outstanding sensitivity to NO2 at μ-Watt power levels. Noble metal (Au, Pd, Pt)-decorated SnO2 showed the tunable gas selectivity for 4 target gases under blue light illumination. Micro-light-emitting diodes (μLEDs) have gained significant interest as an activation source for gas sensors owing to their advantages, including room temperature operation and low power consumption. However, despite these benefits, challenges still exist such as a limited range of detectable gases and slow response. In this study, we present a blue μLED-integrated light-activated gas sensor array based on SnO2 nanoparticles (NPs) that exhibit excellent sensitivity, tunable selectivity, and rapid detection with micro-watt level power consumption. The optimal power for μLED is observed at the highest gas response, supported by finite-difference time-domain simulation. Additionally, we first report the visible light-activated selective detection of reducing gases using noble metal-decorated SnO2 NPs. The noble metals induce catalytic interaction with reducing gases, clearly distinguishing NH3, H2, and C2H5OH. Real-time gas monitoring based on a fully hardware-implemented light-activated sensing array was demonstrated, opening up new avenues for advancements in light-activated electronic nose technologies. [ABSTRACT FROM AUTHOR]

Open green innovation is essential to accelerate decarbonization in Africa. The dearth of empirical evidence on the current trajectory of green innovation in Africa often hinders appropriate green innovation policy design. This study investigates the incidence of collaboration in inventive activities within Africa using the 'designation of the inventor' in the online European Patent database. We identify and assess open and closed climate adaptation and mitigation inventions using explorative and network analysis techniques. Our research shows that even though climate change adaptation technologies are more valuable, climate change mitigation technologies are more responsive to open innovation. We also discovered that the number of green inventions is slightly increasing, but there are very few collaborative open green inventions in Africa as many of the inventions are closed. These results accentuate the fragmented national innovation systems in many African countries. The lack of collaboration and the disconnect between universities and firms shows that most African knowledge institutions have not evolved into vibrant sources of firm learning for national economic development. [ABSTRACT FROM AUTHOR]

This work investigates the stability conditions for linear systems with time-varying delays via an augmented Lyapunov–Krasovskii functional (LKF). Two types of augmented LKFs with cross terms in integrals are suggested to improve the stability conditions for interval time-varying linear systems. In this work, the compositions of the LKFs are considered to enhance the feasible region of the stability criterion for linear systems. Mathematical tools such as Wirtinger-based integral inequality (WBII), zero equalities, reciprocally convex approach, and Finsler's lemma are utilized to solve the problem of stability criteria. Two sufficient conditions are derived to guarantee the asymptotic stability of the systems using linear matrix inequality (LMI). First, asymptotic stability criteria are induced by constructing the new augmented LKFs in Theorem 1. Then, simplified LKFs in Corollary 1 are proposed to show the effectiveness of Theorem 1. Second, asymmetric LKFs are shown to reduce the conservatism and the number of decision variables in Theorem 2. Finally, the advantages of the proposed criteria are verified by comparing maximum delay bounds in four examples. Four numerical examples show that the proposed Theorems 1 and 2 obtain less conservative results than existing outcomes. Particularly, Example 2 shows that the asymmetric LKF methods of Theorem 2 can provide larger delay bounds and fewer decision variables than Theorem 1 in some specific systems. [ABSTRACT FROM AUTHOR]

Global climate crises are the most significant challenges to be solved these days. As one of the technological endeavors to tackle the issue, radiative cooling is amongst the most attractive approaches for sustainable heat energy regulation, which involves maximizing solar heat reflection and thermal heat emission. These green technologies inevitably require architectural applicability, considering that building facades take a large proportion of the heat‐radiating surfaces. For mass‐production suitability and durability, radiative coolers (RCs) fabricated in a fully ceramic context are recently suggested, featuring scalable, thermally insulative, and non‐shrinking advantages. However, the visual effects are also imperative for architectural instances but are seldom accounted for. In this context, this article suggests the enhanced color‐preserving radiative cooling (ECRC) structure for practical architectural applications of glass‐infiltrated ceramic RCs. By simply blending ceramic pigment into the uppermost porous alumina layer, the ECRC structure can maintain the physical, and thermal features of all‐ceramic RC, while exhibiting color by visible reflectance adjustment. ECRCs exhibit an additional cooling performance of up to ≈17.3 °C depending on their color, compared to their conventional counterparts. With additional chromatic features, ECRC can further enhance the availability of radiative cooling technology for practically realizing the energy‐saving structures in real‐world architectural circumstances. [ABSTRACT FROM AUTHOR]

Nano-structural optical filters embedded in elastomers having high mechanical tunability provide the geometric degree of freedom for selective light manipulation. The active control of spectral information in typical structural optical filters is highly limited due to the substrate rigidity. Herein, we present mechanochromic transmissive optical filters by employing flexible and stretchable polymer-embedded silicon nanostructures. Si-based nanowire arrays (Si-NWAs) have been introduced to exhibit parametric resonance characteristics by controlling the period and/or diameter. Furthermore, the spectral shift phenomenon by increased diffraction efficiency was observed after the application of a uniaxial tensile force, which depends on the period of Si-NWAs with a large index contrast between the silicon nanowire and elastomer. The strain-sensitive properties of tunable Si-NWAs filters induced by light diffraction were calculated by simulation based on wave optics. The spectral tunability and light filtering features were simply demonstrated by stretching the Si-NWAs’ optical filters. Our proposed structure provides potential opportunities for a wide variety of applications, including dynamic color display, visual strain sensor and anti-counterfeiting.