Broad Spectral Region Research Articles

Spectroscopic and Thermographic Qualities of Praseodymium-Doped Oxyfluorotellurite Glasses.

The thermal stability of oxyfluorotellurite glass systems, (65-x)TeO2-20ZnF2-12PbO-3Nb2O5-xPr2O3, doped with praseodymium was examined. The different concentrations of praseodymium oxide (x = 0.5 and 2 mol%) were applied to verify the thermal, optical and luminescence properties of the materials under study. The relatively high values of the Dietzel (ΔT) and Saad-Poulain (S or H') thermal stability factors determined using a differential thermal analysis (DTA) indicate the good thermal stability of the glass matrix, which gradually improves with the content of the active dopant. The temperature dependence of optical spectra in the temperature range 300-675 K for the VIS-NIR region was investigated. The involved Pr3+ optical transition intensities and relaxation dynamic of the praseodymium luminescent level were determined. The ultrashort femtosecond pulses were utilized to examine a dynamic relaxation of the praseodymium luminescent levels. Although the measured emission of the Pr3+ active ions in the studied glass encompasses the quite broad spectral region, the observed luminescence may only be attributed to 3PJ excited states. As a result, the observed decrease in the experimental lifetime for the 3P0 level along with the increasing activator content was identified as an intensification of the Pr-Pr interplay and the associated self-quenching process. The maximum relative sensitivities (Sr) estimated over a relatively wide temperature range are ~0.46% K-1 (at 300 K) for FIR (I530/I497) and 0.20% K-1 (at 600 K) for FIR (I630/I497), which seems to confirm the possibility of using investigated glasses in optical temperature sensors.

Nanosecond laser induced periodic silicon microstructures for broadband antireflective applications

Laser-driven micro/nano-texturing is a remarkably efficient and cost-effective technique, having diverse applicability in the realm of photonics, optoelectronics, and photovoltaics. Here, we demonstrate the high-intensity nanosecond laser-matter interactions for periodic micro/nanostructures on silicon, exclusively to emphasize the effects of laser parameters for large-scale integration. A wide range of periodic structure rapid fabrication over a wafer level is systematically studied for optimised parameters using nanosecond laser pulses (1064 nm, 50 ns) at different pulse repetition rates ranging from 10 to 40 kHz. A comprehensive understanding based on physical, structural, and optical studies reveals a strong correlation between the formation of nano/microstructure morphology and the laser parameters. The laser-matter interactions result in trench-like periodic patterns, formation of nanostructure agglomerations as light-trap-centres on the silicon surface. Such nano/micro periodic structures provide a dominant reduction in reflection losses of up to 80 % over a broad UV-NIR spectral region. The studies further demonstrate that the periodic structural patterns could also be potentially utilised for large-scale optical diffraction applications. In addition, the extra layer coating of Silicon Nitride (Si3N4) on the textured silicon further reduces the reflection losses, which is an added advantage of integrated silicon technology. The present work could open a commercial pathway for the rapid fabrication of nanosecond laser-based nanotexturing and periodic grating structures, enabling significantly reduced reflection and improved light trapping in large-scale Silicon-based applications due to its speed, repeatability, and high precision.

A Carbon‐Caged Rhodamine Generating Nitrosoperoxycarbonate for Photoimmunotherapy

AbstractPhotoimmunotherapy is a promising cancer treatment modality. While potent 1‐e− oxidative species are known to induce immunogenic cell death (ICD), they are also associated with unspecific oxidation and collateral tissue damage. This difficulty may be addressed by post‐generation radical reinforcement. Namely, non‐oxidative radicals are first generated and subsequently activated into powerful oxidative radicals to induce ICD. Here, we developed a photo‐triggered molecular donor (NPCD565) of nitrosoperoxycarbonate (ONOOCO2−), the first of its class to our knowledge, and further evaluated its feasibility for immunotherapy. Upon irradiation of NPCD565 by light within a broad spectral region from ultraviolet to red, ONOOCO2− is released along with a bright rhodamine dye (RD565), whose fluorescence is a reliable and convenient build‐in reporter for the localization, kinetics, and dose of ONOOCO2− generation. Upon photolysis of NPCD565 in 4T1 cells, damage‐associated molecular patterns (DAMPs) indicative of ICD were observed and confirmed to exhibit immunogenicity by induced maturation of dendritic cells. In vivo studies with a bilateral tumor‐bearing mouse model showcased the potent tumor‐killing capability of NPCD565 of the primary tumors and growth suppression of the distant tumors. This work unveils the potent immunogenicity of ONOOCO2−, and its donor (NPCD565) has broad potential for photo‐immunotherapy of cancer.

A Carbon-Caged Rhodamine Generating Nitrosoperoxycarbonate for Photoimmunotherapy.

Photoimmunotherapy is a promising cancer treatment modality. While potent 1-e- oxidative species are known to induce immunogenic cell death (ICD), they are also associated with unspecific oxidation and collateral tissue damage. This difficulty may be addressed by post-generation radical reinforcement. Namely, non-oxidative radicals are first generated and subsequently activated into powerful oxidative radicals to induce ICD. Here, we developed a photo-triggered molecular donor (NPCD565) of nitrosoperoxycarbonate (ONOOCO2 -), the first of its class to our knowledge, and further evaluated its feasibility for immunotherapy. Upon irradiation of NPCD565 by light within a broad spectral region from ultraviolet to red, ONOOCO2 - is released along with a bright rhodamine dye (RD565), whose fluorescence is a reliable and convenient build-in reporter for the localization, kinetics, and dose of ONOOCO2 - generation. Upon photolysis of NPCD565 in 4T1 cells, damage-associated molecular patterns (DAMPs) indicative of ICD were observed and confirmed to exhibit immunogenicity by induced maturation of dendritic cells. In vivo studies with a bilateral tumor-bearing mouse model showcased the potent tumor-killing capability of NPCD565 of the primary tumors and growth suppression of the distant tumors. This work unveils the potent immunogenicity of ONOOCO2 -, and its donor (NPCD565) has broad potential for photo-immunotherapy of cancer.

18.62%‐Efficiency Binary Organic Solar Cells with a PEDOT1:PSS2.80 Buffer Layer

AbstractBinary organic solar cells (OSCs) having a controllable phase‐separated morphology of active layers and simple solution manufacturing are desirable for organic photovoltaic adaptation. However, low hole mobility and an unbalanced hole‐ and electron transport reduce the power conversion efficiency (PCE) of the OSCs. Here, a highly efficient binary OSC with a poly(3,4‐ethylenedioxythiophene):poly(4‐styrenesulfonate) (PEDOT:PSS) buffer layer as a hole transport layer (HTL) via using a water‐soluble sulfonate to wrap the PEDOT:PSS core‐shell structures in solutions is reported. The PEDOT1:PSS2.80 buffer layers have good merits including i) a smooth, homogeneous, and hydrophilic surface for an intimate contact, ii) a high work function and raised surface potentials with much uniform distributions for an energy band alignment, and iii) a high optical transmittance in the broad spectral region from 400 to 1100 nm along with an improved electrical conductivity. Benefiting from a raised hole mobility and a better charge‐mobility balance, the solution‐processed binary OSCs yielded a high PCE of 18.62%. 18.62% is one of the highest values among these binary OSCs based on the PEDOT:PSS HTLs and PM6:L8‐BO active layers. The PEDOT1:PSS2.80 buffer layers are superior to the pristine PEDOT1:PSS2.60 buffer layers in terms of raising the OSC efficiency.

Designing a square periodic racemic helix photonic metamaterial using phase-controlled interference lithography for tailored chiral response

In this study, we propose a double exposure phase-controlled laser interference lithography (DE-PCLIL) approach in 4 + 1 beams interference to design a three-dimensional (3D) racemic helical periodic nanostructure. The explicit azimuthal rotation of each beam by π/2 between the two exposures and the resultant intensity distribution discover the racemic 3D helix structure arranged in the square unit cell. The proof of concept is experimentally demonstrated by recording a series of cross-sectional images at different z-planes of the volumetric interference pattern on a CMOS camera using a spatial light modulator (SLM). Additionally, we propose an approach to realize tapering in such a geometry through a slight variation of the interference angle in both exposures. We numerically investigated optical modes and circular dichroism (CD) characteristics of the racemic helix metamaterial. The racemic helix metamaterial structure offers an angle of incidence and polarization-insensitive coupled mode. Through numerical studies, we propose an alternative way to bring 3.4-fold CD signal enhancement by varying the phase of a particular handed helix only through modulating the local chiral field. Such 3D structure is profound with perfect absorption in broad spectral regions, potentially suited for plasmonic absorber-based photovoltaic and photo-catalysis applications.

Photocurable allyl viologens exhibiting RGB-to-black electrochromic switching for versatile heat-shielding capability

This article presents the electrochromic behaviors of three photocurable allyl viologens: diallyl-dipyridyl-ethylene bridged viologen (DA-DPyEV), diallyl-tetrapyridyl phenyl bridged viologen (DA-TPyPhV), and diallyl viologen (DAV), which were designed to achieve RGB colorations. The viologen-based ion gel was utilized to prepare single-layered electrochromic devices (ECDs), thus overcoming the leakage issues commonly associated with liquid electrolytes. The individual ECDs displayed outstanding electrochromic performance, including high transmittance differences and cyclic stability, forming a wide color gamut. Additionally, we fabricated transmissive-to-black ECDs by combining the three viologens in appropriate ratios. The black coloration was achieved through subtractive color mixing theory and showed fast switching speed and high coloration efficiency. Furthermore, we manufactured a flexible large-area ECD with a working area of 10 cm × 10 cm using PET-ITO electrodes. The prepared device exhibited excellent electrochromic performance, showing stable and repeated switching behavior over extended periods. Due to substantial absorption in broad spectral regions, the flexible ECDs demonstrated excellent heat-shielding capabilities, significantly reducing indoor temperatures. Overall, the current findings suggest the potential of photocurable allyl viologens for producing flexible color-changing film devices that generate various visible colors while blocking outdoor heat flux.

Just laser irradiation of silver benzoate water solution — A direct way of Ag nanofibers synthesis for broadband SERS detection

Highly efficient, homogeneous and reproducible substrates for surface enhanced Raman spectroscopy (SERS) are in high demand for practical broadband sensing and the detection of various analytes. The most promising SERS structures in terms of morphology are nanofibers, forming homogeneous coatings with broadband electric field enhancement. However, existing synthesis methods for the formation of nanofibers are multistage, requiring the preliminary synthesis of templates, using additional components, such as surfactants and capping agents, species extraction from the reaction mixture, washing and sedimentation onto a substrate. Here, we present a simple and scalable synthesis approach allowing the fabrication of long winding silver nanofibers directly on a substrate surface, without any additional stages. The process proposed is ecologically friendly and based on laser irradiation of a substrate–solution interface using a low intensity continuous wave unfocused laser beam with a wavelength of 448 nm. As the liquid phase, a silver benzoate water solution without any additional chemicals was used. The deposited nanofibers formed a continuous coating with an area corresponding to the laser beam, ca. 3 mm2, and were characterized by an enhancement factor as high as 107 in the broad spectral region, a low experimental detection limit of 10−11 M and high reproducibility of the SERS signal with a variation of ∼10%.

Enhanced Femtosecond Nonlinearities and Multiphoton Absorptions in Discrete Bands of Porphyrins.

Optical nonlinearities of discrete absorption energy levels of one of the typical heterocyclic aromatic molecules, free-base porphyrins, have been probed over a broad spectral region (400-1600 nm) utilizing intense femtosecond pulses. A wide range of strong one- and multiphoton-induced nonlinear absorptions of both the blue-end Soret (B) band (au → b1g) and red-end orbital mixing split quasi-allowed Q-bands (Qx(0,0; 0,1), Qy(0,0; 0,1), au → eg) are critically probed and reported. During the resonant excitation within B- (400 nm) and Q-bands (600-750 nm), the nonlinear absorption has become predominant by the saturation of absorption (SA) of the one-photon absorption (1PA) process due to ground-state bleaching. At nonresonant wavelengths, it is dominated by the reverse saturation of absorption (RSA), involving various nonlinear processes of two-, three-, and four-photon (2PA, 3PA, and 4PA) absorptions, either to B- or Q-bands (1100-1600 nm). The laser intensity-dependent nonresonant (2PA, 800 nm) excitations for the prominent B-band show a distinct cross-over from SA to RSA, contributed by the excited-state absorption (ESA) utilizing a three-photon induced (3PA) process, whereas resonant (1PA, 400 nm) excitation reveals a systematic strong SA process. Both wavelength- and intensity-dependent nonlinear refractive index studies exhibit positive electronic Kerr-based self-focusing effects, with prominent contributions of nonlinear absorption and higher-order effects. The spectrally discrete, highly intense laser probing of individual energy bands and the consequent variety of nonlinearities can be broadly generalized for many free-base porphyrins and metalloporphyrins. The present studies provide a strong foundation and new insight into the broad categories of macrocycles, such as porphyrins and phthalocyanines, for myriad applications in nonlinear optics and bio/optophotonics.

IR spectroscopic analysis of heterohedral metallofullerenes

The infrared spectroscopies (IR) and vibrational modes of ten heterohedral metallofullerenes C19M (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn) are theoretically simulated by density functional theory (DFT) method and applying high accuracy basis set 6-311G++(d,2p) with G09W. The obtained IR spectra bands from 0 cm−1 to 1400 cm−1 are classified into three broad spectral regions: 200–400 cm−1, 600–800 cm−1 and 1100–1300 cm−1 characterizing transition metal (M), bending modes of CC bonds at low frequency and stretching modes of CC bonds at high frequency, respectively. The results show that there is a direct linear relationship between the dipole moments and the intensity of IR peaks at the first spectral region 200–400 cm−1. In addition, the IR spectroscopy exhibits remarkable dependence on the type of transition metals. Thus, IR spectroscopic technique could be adopted to identify the doping element of metallofullerenes C19M effectively. Finally, the calculated IR spectra could be used to link and explain unidentified infrared bands to the interstellar spectral data.

Growth and optical properties of ZnO nanorods on the full surface of porous silicon by sol–gel method and oil bath method

A method for the preparation of composites that allow the growth of ZnO nanorod structures on the full surface of porous silicon (polished surface, pore walls, and pore bottoms) is presented. The porous silicon is obtained by electrochemical etching of P-type silicon (100). The nanorods were grown in two steps: a sol–gel method and an oil bath method. The morphology of ZnO nanorods at different concentrations of the growth solution was investigated using scanning electron microscopy. X-ray diffraction confirmed the formation of ZnO hexagonal fibrous zincite structures. UV–Vis absorption spectroscopy confirmed that the composites possess good light absorption in the broad spectral region. In the wavelength range of 300 to 400 nm, the light absorption value of the porous silicon/zinc oxide (porous Si/ZnO) nanorods was increased by ~25% compared to that of the porous Si/ZnO films. The photoluminescence spectra confirmed the luminescence performance of the composites. Finally, the optical properties of the composites were further verified by simulation calculations.

Nonreciprocity of Optical Absorption in the Magnetoelectric Antiferromagnet CuB2O4

The change in the absorption spectra due to reversal of the direction of light propagation (nonreciprocity of absorption) is a consequence of a simultaneous violation of both time-reversal and spatial-inversion symmetries. Here, we report on a high-resolution spectroscopic study of absorption nonreciprocity in the noncentrosymmetric multiferroic CuB2O4 below the antiferromagnetic transition temperature TN = 21 K in the commensurate phase in magnetic fields up to 0.5 T. The study was performed in a broad spectral region covering several exciton transitions, which all are followed by an anomalously rich structure due to the multiple exciton-magnon-phonon satellites. Two components were resolved for the spectral line near 1.4 eV corresponding to the exciton transition between the ground and the first excited state. A quantitative theory of the optical absorption and nonreciprocity at this line was developed. The theory takes into account the interference between the electric and magnetic dipole contributions to the absorption and gives an adequate explanation of the relevant effects.

Optical dispersion and bandgap of ultralow expansion glass

The thermal-optical property of an ultralow expansion (ULE®) 7973 glass wafer was assessed using spectrophotometers and variable angle spectroscopic ellipsometers. By modeling both the spectral transmission and the ellipsometric data, we derived optical dispersion of the glass over a broad spectral region from 180 nm up to 12 μm. Our results indicate that the transparency region of the glass is terminated by two fundamental absorption edges in the ultraviolet (UV) and the infrared (IR). The UV and IR absorption edges are dominated by the titania and silica constituents, respectively. The exponential absorption tail, the Urbach energy, in the UV increases linearly with the temperature ranging from room temperature to 650°C, whereas the optical bandgap decreases linearly over the same temperature range. The temperature-dependent coefficient is 18 μeV / ° C for the Urbach energy and −0.7 meV / ° C for the optical bandgap.

Gain recovery dynamics in active type-II semiconductor heterostructures

Type-II heterostructures as active layers for semiconductor laser devices combine the advantages of a spectrally broad, temperature stable, and efficient gain with the potential for electrical injection pumping. Their intrinsic charge carrier relaxation dynamics limit the maximum achievable repetition rates beyond any constraints of cavity design or heat dissipation. Of particular interest are the initial build up of gain after high-energy injection and the gain recovery dynamics following depletion through a stimulated emission process. The latter simulates the operation condition of a pulsed laser or semiconductor optical amplifier. An optical pump pulse injects hot charge carriers that eventually build up broad spectral gain in a model (Ga,In)As/GaAs/Ga(As,Sb) heterostructure. The surplus energies of the optical pump mimic the electron energies typical for electrical injection. Subsequently, a second laser pulse tuned to the broad spectral gain region depletes the population inversion through stimulated emission. The spectrally resolved nonlinear transmission dynamics reveal gain recovery times as fast as 5 ps. These data define the intrinsic limit for the highest laser repetition rate possible with this material system in the range of 100 GHz. The experimental results are analyzed using a microscopic many-body theory identifying the origins of the broad gain spectrum.

Studies on Femtosecond Laser Textured Broadband Anti-reflective Hierarchical a-SiNx:H Thin Films for Photovoltaic Applications

Simple ultrafast laser writing for the fabrication of hierarchical silicon nitride (a-SiNx:H) microstructures is demonstrated as an effective antireflection coating. A wide range of Si-rich to N-rich a-SiNx:H thin films, having varied optical band gap (2.32–5.94 eV) and refractive index (2.8–1.7) of wavelength-ordered (∼λ/4) thickness, are deposited using the plasma-enhanced chemical vapor deposition technique. The high-intensity femtosecond laser (800 nm, 120 fs, 1 kHz) interaction with a-SiNx:H films resulted in diverse nano-/microstructures with systematic width and depth born out of nonlinear light–matter interactions. These experimentally demonstrated the extremely disordered micro–nano structures over a large area of ∼ 1 cm2 that exhibit significant light trapping and absorption capabilities over a broad spectral region of 200–1000 nm. The extensive reduction of reflection losses from 30 to 2.8% from pre- to post-laser texturing is a favorable condition for broadband anti-reflective coatings for enhanced light harvesting from prefabricated photovoltaic devices.

Research on spectroscopic ellipsometry in China with future challenges

Following the fast and advanced development of technologies worldwide in the early 1970s, especially focusing on industry and academic applications, research on spectroscopic ellipsometry (SE) has been significantly performed in many universities and institutes in China, which is a typical developing country. Through strong international cooperation, various SE configurations have been proposed and achieved in real and practical applications. Improvements in SE instrumentation have been stimulated and approached in the broad spectral region, providing powerful tools to study the optical properties of materials and micro/nanostructures under variable experimental conditions. Thus, a brief review of the historical research and development of SE in China is presented, and future challenges are discussed.

The radiative processes involving ion-atom alkali systems: The case of hydrogen and potassium

The importance of the symmetric as well as non-symmetric ion-atom absorption processes in broad spectral region within a model of solar photosphere and also within the corresponding sunspot models, has been previously emphasized. This motivated us to study the photo-association, charge-exchange and photo-dissociation absorption processes in the cases of non-symmetric and symmetric systems involving hydrogen and potassium atoms, ions, molecules and molecular-ions. We have calculated the data for molecules and molecular state characterizations needed for current computation. We determined the partial and average cross-sections and corresponding spectral absorption rate coefficients, as the functions of wavelengths, and temperatures (100 nm ⩽λ⩽1000 nm, 400 K ⩽T⩽10 000 K). Our calculations are performed for conditions that exist in different layers of weakly ionized stellar atmospheres. The obtained data are potentially of high impact and may have broad further applications, e.g., for modelling of laboratory plasmas and various astrophysical objects including geocosmical ones.

A Rainbow Structural Color by Stretchable Photonic Crystal for Saccharide Identification.

Photonic crystals (PCs) with fascinating structural color nanomaterials present effectively spontaneous emission modulation and selectively optical signal amplification. Stretchability or elasticity could enable the feasible tunability for structural colors. Aimed at the regulation of structural colors, we endeavored to achieve the PC nanomatrix evolution and optical property during stretching. In this work, a rainbow structural color by stretchable PCs was exploited to provide abundant optical information for multianalyte recognition. The finite element analysis proved the electric field distribution in the PC matrix, which completely matched with the phenomenon of the measured PC spectra. By simply employing analysis of the multistate PC during stretching, the mono PC matrix chip can differentially enhance fluorescence signals in broad spectral regions, resulting in diverse sensing information for high-efficiency multianalysis. The stretchable PC chip can facilely discriminate 14 similar structured saccharides with a minimum concentration of 10-7 M using only one fluorescence complex. Furthermore, saccharides in different concentrations, mixtures, and real samples (beverages and sweets) also can be successfully distinguished. The exploration on fluorescent stretch dependence behavior of the photonic crystal contributes the biomatching optical platform for wearable devices, dynamic environment, clinical, or health monitoring auxiliary.

A Fermi resonance and a parallel-proton-transfer overtone in the Raman spectrum of linear centrosymmetric N4H+: A polarizability-driven first principles molecular dynamics study.

We present molecular dynamics (MD), polarizability driven MD (α-DMD), and pump-probe simulations of Raman spectra of the protonated nitrogen dimer N4H+, and some of its isotopologues, using the explicitly correlated coupled-cluster singles and doubles with perturbative triples [CCSD(T)]-F12b/aug-cc-pVTZ based potential energy surface in permutationally invariant polynomials (PIPs) of Yu et al. [J. Phys. Chem. A 119, 11623 (2015)] and a corresponding PIP-derived CCSD(T)/aug-cc-pVTZ-tr (N:spd, H:sp) polarizability tensor surface (PTS), the latter reported here for the first time. To represent the PTS in terms of a PIP basis, we utilize a recently described formulation for computing the polarizability using a many-body expansion in the orders of dipole-dipole interactions while generating a training set using a novel approach based on linear regression for potential energy distributions. The MD/α-DMD simulations reveal (i) a strong Raman activity at 260 and 2400cm-1, corresponding to the symmetric N-N⋯H bend and symmetric N-N stretch modes, respectively; (ii) a very broad spectral region in the 500-2000cm-1 range, assignable to the parallel N⋯H+⋯N proton transfer overtone; and (iii) the presence of a Fermi-like resonance in the Raman spectrum near 2400cm-1 between the Σg + N-N stretch fundamental and the Πu overtone corresponding to perpendicular N⋯H+⋯N proton transfer.

S-scheme CoTiO3/Cd9.51Zn0.49S10 heterostructures for visible-light driven photocatalytic CO2 reduction

• Hierarchial CoTiO 3 /Cd 9.51 Zn 0.49 S 10 heterostructures were fabricated by growing Cd 9.51 Zn 0.49 S 10 nanowires on CoTiO 3 microprism in situ via a hydrothermal method. • The transfer path of photogenerated charge carriers in CoTiO 3 /Cd 9.51 Zn 0.49 S 10 heterostructure follows a S-scheme mechanism. • The CoTiO 3 /Cd 9.51 Zn 0.49 S 10 hybrids manifest high activity and good stability for photocatalytic CO 2 reduction, achieving an AQE of 7.27% at 420 nm. Cd 1− x Zn x S solid solutions with strong light absorption are promising materials for solar-driven CO 2 reduction; however, their relatively weak redox ability and intrinsic photo-corrosion limit their further development as a photocatalyst. The addition of a second photocatalyst with a suitable band structure to construct a S-scheme photocatalytic system can solve both problems simultaneously. Here, we report a S-scheme photocatalyst based on the heterostructure of CoTiO 3 /Cd 9.51 Zn 0.49 S 10 (abbreviated as CoTiO 3 /CdZnS) that enables the efficient photocatalytic reduction of CO 2 . Detailed physicochemical characterization resolves the S-scheme charge transfer mechanism in this composite photocatalyst. With the well-designed structure of particles and desirable band offsets, this hybrid system offers visible light absorption in a broad spectral region, large surface area, strong redox ability, and fast carrier separation and transportation. Under visible-light illumination, the CoTiO 3 /CdZnS hybrid system displays a CO formation rate of about 11 mmol h −1 g −1 combined with a long-term operational stability. Besides, a high apparent quantum efficiency (AQE) of 7.27% is realized for the CO 2 -to-CO reduction reaction by the optimized CoTiO 3 /CdZnS hybrid under 420 nm monochromatic light irradiation.