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Phase imaging is widely used in biomedical imaging, sensing, and material characterization, among other fields. However, direct imaging of phase objects with subwavelength resolution remains a challenge. Here, we demonstrate subwavelength imaging of phase and amplitude objects based on all-optical diffractive encoding and decoding. To resolve subwavelength features of an object, the diffractive imager uses a thin, high-index solid-immersion layer to transmit high-frequency information of the object to a spatially-optimized diffractive encoder, which converts/encodes high-frequency information of the input into low-frequency spatial modes for transmission through air. The subsequent diffractive decoder layers (in air) are jointly designed with the encoder using deep-learning-based optimization, and communicate with the encoder layer to create magnified images of input objects at its output, revealing subwavelength features that would otherwise be washed away due to diffraction limit. We demonstrate that this all-optical collaboration between a diffractive solid-immersion encoder and the following decoder layers in air can resolve subwavelength phase and amplitude features of input objects in a highly compact design. To experimentally demonstrate its proof-of-concept, we used terahertz radiation and developed a fabrication method for creating monolithic multi-layer diffractive processors. Through these monolithically fabricated diffractive encoder-decoder pairs, we demonstrated phase-to-intensity (P → I) transformations and all-optically reconstructed subwavelength phase features of input objects (with linewidths of ~ λ/3.4, where λ is the illumination wavelength) by directly transforming them into magnified intensity features at the output. This solid-immersion-based diffractive imager, with its compact and cost-effective design, can find wide-ranging applications in bioimaging, endoscopy, sensing and materials characterization. [ABSTRACT FROM AUTHOR]

Nonlinear optical processing of ambient natural light is highly desired for computational imaging and sensing. Strong optical nonlinear response under weak broadband incoherent light is essential for this purpose. By merging 2D transparent phototransistors (TPTs) with liquid crystal (LC) modulators, we create an optoelectronic neuron array that allows self-amplitude modulation of spatially incoherent light, achieving a large nonlinear contrast over a broad spectrum at orders-of-magnitude lower intensity than achievable in most optical nonlinear materials. We fabricated a 10,000-pixel array of optoelectronic neurons, and experimentally demonstrated an intelligent imaging system that instantly attenuates intense glares while retaining the weaker-intensity objects captured by a cellphone camera. This intelligent glare-reduction is important for various imaging applications, including autonomous driving, machine vision, and security cameras. The rapid nonlinear processing of incoherent broadband light might also find applications in optical computing, where nonlinear activation functions for ambient light conditions are highly sought.Merging 2D transparent phototransistors and liquid crystal modulators, authors report an optoelectronic neuron array for self-amplitude modulation of spatially incoherent light, achieving a large nonlinear contrast over a broad spectrum at orders-of-magnitude lower intensity. [ABSTRACT FROM AUTHOR]

Structured optical materials create new computing paradigms using photons, with transformative impact on various fields, including machine learning, computer vision, imaging, telecommunications, and sensing. This Perspective sheds light on the potential of free-space optical systems based on engineered surfaces for advancing optical computing. Manipulating light in unprecedented ways, emerging structured surfaces enable all-optical implementation of various mathematical functions and machine learning tasks. Diffractive networks, in particular, bring deep-learning principles into the design and operation of free-space optical systems to create new functionalities. Metasurfaces consisting of deeply subwavelength units are achieving exotic optical responses that provide independent control over different properties of light and can bring major advances in computational throughput and data-transfer bandwidth of free-space optical processors. Unlike integrated photonics-based optoelectronic systems that demand preprocessed inputs, free-space optical processors have direct access to all the optical degrees of freedom that carry information about an input scene/object without needing digital recovery or preprocessing of information. To realize the full potential of free-space optical computing architectures, diffractive surfaces and metasurfaces need to advance symbiotically and co-evolve in their designs, 3D fabrication/integration, cascadability, and computing accuracy to serve the needs of next-generation machine vision, computational imaging, mathematical computing, and telecommunication technologies. Optical computing via free-space-based structured optical materials allows to access optical information without the need for preprocessing or optoelectronic conversion. In this Perspective, the authors describe opportunities and challenges in their use for optical computing, information processing, computational imaging and sensing. [ABSTRACT FROM AUTHOR]

The reaction mechanisms for the atmospheric hydroxylation of n-butyl vinyl ether ( n-BVE), iso-butyl vinyl ether ( i-BVE), and tert-butyl vinyl ether ( t-BVE) were investigated by using quantum chemical method in this paper. The geometry optimizations and frequency calculations were carried out at the MPWB1K/6-31+G(d,p) level, and the accurate energetic parameters were obtained by the MPWB1K/6-311++g(3df,2p) method. The reaction mechanisms for the title reactions have been presented. Ten possible reaction channels were discussed for the primary hydroxylation of n-BVE and t-BVE, while fourteen pathways for i-BVE. Three favorable reaction pathways were chosen for each isomer to undergo further investigation. Major products are n-butyl formate, iso-butyl formate, tert-butyl formate, and HCHO. The rate constants of the primary reactions were calculated over the temperature range of 200-400 K and the pressure range of 100-2,000 Torr by employing MESMER program. At 298 K and 760 Torr, the whole rate constants of n-BVE + OH, i-BVE + OH, and t-BVE + OH are 12.3 × 10, 9.32 × 10 and 5.75 × 10cmmolecules, respectively. Additionally, the lifetimes of the three isomers with respect to OH radical are $$\tau$$ = 1.13 h, $$\tau$$ = 1.49 h, and $$\tau$$ = 2.41 h. [ABSTRACT FROM AUTHOR]

The potential energy surface (PES) and mechanism of the reaction of allyl acetate (AAC) with O are investigated by using density functional theory (DFT) and ab initio (MP2 and CCSD(T)) methods. The kinetics and main product branching ratios over the temperature range of (200-2,000 K) and at various pressures are obtained by employing multichannel Rice-Ramsperger-Kassel-Marcus (RRKM) theory. The results show that the main products are 2-oxoethyl acetate and formaldehyde. Two channels are found for the decomposition of primary ozonides: one path is corresponding to the 2-oxoethyl acetate + CHOO formation (R1); the other channel products formaldehyde + CHC(O)OCHCHOO (R2). In the whole temperature range, R1 is calculated to be preferable and its product yield accounts for 60-77% of the total while R2 is found to contribute 20-40% to the total product yield. The overall rate constants show pressure independence and strong positive temperature dependence. [ABSTRACT FROM AUTHOR]

Nanosized zero-valent iron (NZVI) supported on the cation exchange resin was synthesized and applied to decompose some water soluble azo dyes. The decomposition efficiency for azo dyes was evaluated by using the aqueous suspensions and parked column of this material. Batch experiments indicated that this novel material exhibited excellent degradation ability for 0.05 g·L−1 of Acid Orange 7, Acid Orange 8, Acid Orange 10, Sunset Yellow, and Methyl Orange, with decolorization ratio up to 95% in 4 min; pH value was the key factor for degradation and H+ was one of the reactants; adsorption of azo dyes onto the material existed at the beginning but reduced gradually until disappearing completely. For the packed column system, 58%∼90% of azo dyes were decomposed in the 1st circle of solution passing through the column, and the adsorption onto the materials could accelerate the degradation azo dyes with the increasing reaction time. During the degradation process, Fe2+, the product of NZVI, was exchanged to the resin again and could be reduced to Fe0 by KBH4 for reusing. The 10th refreshed NZVI possessed reductive activity up to 90% of the newly systhesized NZVI. Decomposing pollutants in the aqueous solution with columns packed with NZVI immobilized on the cation exchange resin is a promising technology that can solve the reclaiming and refreshing problem of NZVI. [ABSTRACT FROM AUTHOR]

A headspace solid phase microextraction coupled with gas chromatography mass spectrometry (HS-SPME/GC-MS) method was established for analyzing nitrobenzene, benzene and aniline in environmental water samples simultaneously. Factors affecting extraction efficiency (SPME fiber selection, acidity, temperature, salt addition, extraction time, headspace, etc) were verified. Under optimal extraction conditions, the detection limits are 0.50, 0.11 and 1.00 µg/L for nitrobenzene, benzene and aniline, respectively. The results indicate that this method is capable of making sensitive and accuracy analyses on nitrobenzene, benzene and aniline in environmental water samples. [ABSTRACT FROM AUTHOR]

The fluorescence system of the Eu3+ (or/and Sm3+)-2-benzoyl-indane-1,3-dione(BID)-cetyltrimethylammonium bromide (CTMAB) was investigated at excitation wavelengths of 350 nm, and emission wavelengths at 612 nm for europium and 565, 606 and 650 nm for samarium, respectively. The system was used for the determination of Eu and Sm in rare earth oxides and of BID in water. Europium or/and samarium could be determined in the range of 1.0 × 10–9–1.0 × 10–5 mol/L and 2.0 × 10–8–5.0 × 10–5 mol/L, respectively; 1.0 × 10–6–2.0 × 10–5 mol/L of BID could also be determined. [ABSTRACT FROM AUTHOR]