Selective Metallization on Ordinary Polymer Substrates by Laser Direct Activation of Copper Phosphate or Nickel Phosphate

In recent years, selective metallization on polymer surfaces has attracted considerable attention due to its excellent properties and wide applications. This paper reports that copper phosphate (Cu₃(PO₄)₂) or nickel phosphate (Ni₃(PO₄)₂) was selected as laser-active material to successfully fabricate metallic patterns on ordinary polymer substrates by laser direct activation and electroless plating. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were utilized to characterize the interaction mechanism between a nanosecond-pulsed laser (355 and 1064 nm wavelengths) and Cu₃(PO₄)₂ or Ni₃(PO₄)₂. It was found that after 355 or 1064 nm laser activation with appropriate parameters, Cu⁺ was generated from Cu₃(PO₄)₂, and NiO was generated from Ni₃(PO₄)₂. At the same time, Cu⁺ or NiO adsorbed on the porous sponge-like microstructure of modified polycarbonate (PC), respectively, and acted as catalytic active centers to realize selective copper deposition in the laser-activated zone. Furthermore, the obtained copper layers were confirmed to possess good selectivity, electrical conductivity, and high adhesion strength (the highest grade of 5B). Moreover, from comparisons of Cu₃(PO₄)₂ with Ni₃(PO₄)₂ and of 355 nm laser activation with 1064 nm laser activation, the 1064 nm laser activation of Cu₃(PO₄)₂ produced the most catalytic seeds (Cu⁺) and had the best catalytic effect.

Enhanced photo-fenton and photoelectrochemical activities in nitrogen doped brownmillerite KBiFe2O5

Visible-light-driven photo-fenton-like catalytic activity and photoelectrochemical (PEC) performance of nitrogen-doped brownmillerite KBiFe₂O₅ (KBFO) are investigated. The effective optical bandgap of KBFO reduces from 1.67 to 1.60 eV post N-doping, enabling both enhancement of visible light absorption and photoactivity. The photo-fenton activity of KBFO and N-doped KBFO samples were analysed by degrading effluents like Methylene Blue (MB), Bisphenol-A (BPA) and antibiotics such as Norfloxacin (NOX) and Doxycycline (DOX). 20 mmol of Nitrogen-doped KBFO (20N-KBFO) exhibits enhanced catalytic activity while degrading MB. 20N-KBFO sample is further tested for degradation of Bisphenol-A and antibiotics in the presence of H₂O₂ and chelating agent L-cysteine. Under optimum conditions, MB, BPA, and NOX, and DOX are degraded by 99.5% (0.042 min^-1), 83% (0.016 min^-1), 72% (0.011 min^-1) and 95% (0.026 min^-1) of its initial concentration respectively. Photocurrent density of 20N-KBFO improves to 8.83 mA/cm² from 4.31 mA/cm² for pure KBFO. Photocatalytic and photoelectrochemical (PEC) properties of N-doped KBFO make it a promising candidate for energy and environmental applications.

Near-Infrared-Responsive Photocatalysts

Broadening the absorption of light to the near-infrared (NIR) region is important in photocatalysis to achieve efficient solar-to-fuel conversion. NIR-responsive photocatalysts that can utilize diffusive solar energy are attractive for alleviating the energy crisis and environmental pollution. Over the past few years, considerable progress on the component and structural design of NIR-responsive photocatalysts have been reported. This study aims to systematically summarize recent progress toward the material design and mechanism optimization of NIR-responsive photocatalysts in this area. Depending on the main strategies for harvesting NIR photons, NIR-responsive photocatalysts can be categorized as direct NIR-light photocatalysts, indirect NIR-light photocatalysts, and photothermal photocatalysts. Furthermore, the construction and application of different NIR-responsive photocatalytic systems are summarized. Conclusions and perspectives are presented to further explore the potential of NIR-responsive photocatalysts in this field.

Tuning electron transfer by crystal facet engineering of BiVO4 for boosting visible-light driven photocatalytic reduction of bromate

Removal of bromate (BrO₃^-) has gained increasing attention in drinking water treatment process. Photocatalysis technology is an effective strategy for bromate removal. During the photocatalytic reduction of bromate process, the photo-generated electrons are reductive species toward bromate reduction and photo-generated holes responsible for water oxidation. In this study, the monoclinic bismuth vanadate (BiVO₄) single crystal was developed as a visible photocatalyst for the effective removal of bromate. The as-synthesized BiVO₄ photocatalyst with optimized {010} and {110} facets ratio could achieve almost 100% removal efficiency of BrO₃^- driven by visible light with a first-order kinetic constant of 0.0368 min^-1. As demonstrated by the electron scavenger experiment and density functional theory (DFT) calculations, the exposed facets of BiVO₄ should account for the high photocatalytic reduction efficiency. Under visible light illumination, the photo-generated electron and holes were spatially transferred to {010} facets and {110} facets, respectively. The BiVO₄ single crystal photocatalyst may serve as an attractive photocatalyst by virtue of its response to the visible light, spatially charge transfer and separation as well as high photocatalytic activity, which will make the removal of BrO₃^- in water much easier, more economical and more sustainable.

Elemental red phosphorus-based materials for photocatalytic water purification and hydrogen production

Semiconductor-based photocatalysis is a renewable and sustainable technology to solve global environmental pollution and energy shortage problems. It is essential to exploit highly efficient photocatalyst materials. Recently, Earth-abundant elemental red phosphorus (RP) with broader light-harvesting and appropriate band structure characteristics has been widely studied in photocatalysis. In this review, the crystal and electronic structures of RP (e.g., amorphous, Hittorf's and fibrous phosphorus) materials are firstly summarized along with the current advancement in the synthesis strategies of RP and RP-based materials in photocatalysis accompanied by a thorough discussion of the applications of RP-based materials in photocatalytic pollutant degradation, bacterial inactivation, and water splitting. Finally, this review also offers some guidance and perspectives for the future design of efficient visible-light-driven photocatalysts.

The electronic structures and magnetic properties of mixed-valence Fe-based metal–organic VNU-15 frameworks: a theoretical study from linear response DFT+U calculations

The crystal symmetries, electronic structures, and magnetic properties of metal–organic VNU-15 frameworks (VNU = Vietnam National University) were investigated using density functional calculations (DFT) with an on-site Coulomb repulsion approximation, U_eff, of 4.30 eV, determined via the linear response method. Two different orientations of dimethylammonium (DMA⁺) cations in VNU-15 were investigated. Antiferromagnetic configurations were predicted to be the ground states, with Fe ions in high-spin states for both phases. Furthermore, VNU-15 had intrinsic semiconductor electronic behavior with a small band gap of about 1.20 eV. The change in the orientation of DMA⁺ led to changes in the dispersion of the band structure, the band gap, and the Fe contributions to the valence band and conduction band. A fascinating feature was found involving exchange of oxidation numbers between two adjacent Fe atoms in the two phases. Our results revealed that VNU-15 has strong oxidation activity and predicted the important role of an anisotropic effect on the hole and electron effective masses. The findings presented that the electronic and magnetic properties could be controlled via hydrogen bonds and proved VNU-15 to be a prospective material for photocatalytic applications.

The effects of DMA⁺ cation orientation on the electronic structures and magnetic properties of the metal–organic framework VNU-15 are investigated, and VNU-15 is proved to be a prospective material for photocatalytic applications.

Challenges and implication of full solar spectrum-driven photocatalyst

Conventional metal oxide and its composites embrace the long-standing problem of using the combined visible and near-infrared (NIR) light. Doping with suitable impurities of metal, nonmetal, or its combinations for visible light enhancement is very well studied. However, the quantum efficiency of these photocatalysts does not produce an exciting appearance toward visible and NIR light when irradiated through either artificial or natural light. Furthermore, owing to the limited availability of solar light, challenges arise from the implication of these developed nano-photocatalysts. Therefore, the hybridized concept was developed for the effective use of either full or partial solar spectrum, even functioning in dark conditions. The present review focuses on the challenges of hybridized photocatalysts in storing and discharging the harvested photons obtained from the solar spectrum. The review vividly emphasizes the evolution of light-driven nanomaterials since its innovation and significant breakthroughs in brief, while a detailed presentation of the implications of hybrid photocatalysts for full solar applications, including the mechanistic features, charging-discharging characteristics, work function, charge carrier mobility, and interactions, follows. The article also delivers the substantial contribution of these materials in regard to energy and environmental application.

Photoactive Brownmillerite Multiferroic KBiFe2O5 and Its Potential Application in Sunlight-Driven Photocatalysis

KBiFe₂O₅ (KBFO) is an upcoming promising brownmillerite-structured multiferroic photoactive material for next-generation photovoltaic and photocatalytic applications. In the present work, KBFO has been developed using multistep thermal treatment method to reduce the volatility of constituent elements and improve the stability of compound. The band gap of KBFO (found to be ∼1.68 eV) extends to the near-infrared region compared to traditional perovskite-structured multiferroics. The magnetic and dielectric transitions occur in the same temperature range (740 K-800 K), reflecting the existence of magneto-dielectric effect in the as-synthesized sample. It also shows promising photocatalytic activity by degrading organic effluents under natural sunlight compared to regular perovskite BiFeO₃ photocatalyst (operating under visible light). A new application of brownmillerite multiferroic KBFO photocatalyst in environmental and energy applications has been explored by integrating the structural, optical, magnetic, and dielectric properties of the same.

Visible-to-NIR Photon Harvesting: Progressive Engineering of Catalysts for Solar-Powered Environmental Purification and Fuel Production

Utilization of diffusive solar energy through photocatalytic processes for environmental purification and fuel production has long been pursued. However, efficient capture of visible-near-infrared (NIR) photons, especially for those with wavelengths longer than 600 nm, is a demanding quest in photocatalysis owing to their relatively low energy. In recent years, benefiting from the advances in photoactive material design, photocatalytic reaction system optimization, and new emerging mechanisms for long-wavelength photon activation, increasing numbers of studies on the harnessing of visible-NIR light for solar-to-chemical energy conversion have been reported. Here, the aim is to comprehensively summarize the progress in this area. The main strategies of the long-wavelength visible-NIR photon capture and the explicitly engineered material systems, i.e., narrow optical gap, photosensitizers, upconversion, and photothermal materials, are elaborated. In addition, the advances in long-wavelength light-driven photo- and photothermal-catalytic environmental remediation and fuel production are discussed. It is anticipated that this review presents the forefront achievements in visible-NIR photon capture and at the same time promotes the development of novel visible-NIR photon harnessing catalysts toward efficient solar energy utilization.

Internal Polarization Modulation in Bi2 MoO6 for Photocatalytic Performance Enhancement under Visible-Light Illumination

A built-in electric field from polarization inside polar photocatalysts could provide the driving force for photogenerated electrons and holes to move in opposite directions for better separation to improve their photocatalytic performance. The photocatalytic performance of a polar photocatalyst of Bi₂ MoO₆ has been enhanced through the precise control of its structure to increase internal polarization. DFT calculations predicted that a shortened crystal lattice parameter b in Bi₂ MoO₆ could induce larger internal polarization, which was achieved by the modulation of the pH of the reaction solution during a solvothermal synthetic process. A series of Bi₂ MoO₆ samples were created with reaction solutions of pH≈1, 4, and 8; the crystal lattice parameter b was found to decrease gradually with increasing solution pH. Accordingly, these Bi₂ MoO₆ samples demonstrated a gradually enhanced photocatalytic performance with decreasing crystal lattice parameter b, as demonstrated by the photocatalytic degradation of sulfamethoxazole/phenol and disinfection of Staphylococcus aureus bacteria under visible-light illumination due to improved photogenerated charge-carrier separation. This study demonstrates an innovative design strategy for materials to further enhance the photocatalytic performance of polar photocatalysts for a broad range of technical applications.

Cu2(OH)PO4/reduced graphene oxide nanocomposites for enhanced photocatalytic degradation of 2,4-dichlorophenol under infrared light irradiation

Sparked by the growing environmental crises, photocatalytic degradation of chlorophenols with inexhaustible solar energy is expected to be converted into actual applications. Here, we report the preparation of the nanocomposite of Cu₂(OH)PO₄ and reduced graphene oxide (Cu₂(OH)PO₄/rGO) through a one-step hydrothermal method and examined its infrared-light photocatalytic activity in the degradation of 2,4-dichlorophenol (2,4-DCP). As evidenced by the absorption spectra and the degradation of 2,4-DCP, Cu₂(OH)PO₄/rGO exhibited enhanced infrared light-driven photocatalytic activity compared to pure Cu₂(OH)PO₄ and was very stable even after repeated cycling. More importantly, the introduction of hydrogen peroxide (H₂O₂) could combine the photocatalytic and photo-Fenton effects into one reaction system and maximize the infrared light photocatalytic efficiency. Typically, the rate constant of Cu₂(OH)PO₄/rGO and H₂O₂ was more than 6.25 times higher than that of only Cu₂(OH)PO₄/rGO, and almost 10 times greater than the value for pure Cu₂(OH)PO₄. Further, a plausible mechanism for the enhanced photocatalytic properties of Cu₂(OH)PO₄/rGO has been discussed. These findings may help the development of novel hybrid photocatalysts with enhanced infrared light photocatalytic activity for applications in the treatment of chlorophenol-contaminated wastewater.

Nanocomposites of Cu₂(OH)PO₄ and rGO exhibit the maximized infrared light photocatalytic activity for the degradation of 2,4-DCP due to the combination of the photocatalytic and photo-Fenton effects into one reaction system.

Fabricating Metallic Circuit Patterns on Polymer Substrates through Laser and Selective Metallization

Nowadays, with the rapid development of portable electronics, wearable electronics, LEDs, microelectronics, and bioelectronics, the fabrication of metallic circuits onto polymer substrates with strong adhesion property is an ever-increasing challenge. In this study, the high-resolution and well-defined metallic circuits were successfully prepared on the polymer surface via laser direct structuring (LDS) based on copper hydroxyl phosphate [Cu₂(OH)PO₄], and the key mechanism of the selective metallization was systematically investigated. XPS confirmed that Cu⁰ (elemental copper) was formed through photochemical reduction reaction of Cu₂(OH)PO₄, after 1064 nm NIR pulsed laser irradiation. During the electroless plating, because it is the important active catalytic center, this newly formed Cu⁰ was the key factor to achieve the successful selective metallization. SEM revealed that after the electroless plating, the copper layer actually physically anchored into the polymer substrate, giving an excellent mechanical adhesion property of the obtained metallic patterns. In addition, the micro-Raman surface imaging approved the generation of the amorphous carbon on the polymer composites' surface after NIR laser irradiation, and the chemical reaction region caused by the pulsed laser spot was found at approximately 40 μm. This environmentally friendly and effective strategy for fabricating circuit patterns on the polymer surface has a possible application in the printed circuit plate (PCB) industry.

MnPSe3 Monolayer: A Promising 2D Visible-Light Photohydrolytic Catalyst with High Carrier Mobility

The 2D material single-layer MnPSe₃ would be a promising photocatalyst for water splitting, as indicated by the proper positions of band edges, strong absorption in visible-light spectrum, broad applicability (pH = 0 - 7), and high carrier mobility.

Bi(1-x)La(x)CuSeO as New Tunable Full Solar Light Active Photocatalysts

Photocatalysis is attracting enormous interest driven by the great promise of addressing current energy and environmental crises by converting solar light directly into chemical energy. However, efficiently harvesting solar energy for photocatalysis remains a pressing challenge, and the charge kinetics and mechanism of the photocatalytic process is far from being well understood. Here we report a new full solar spectrum driven photocatalyst in the system of a layered oxyselenide BiCuSeO with good photocatalytic activity for degradation of organic pollutants and chemical stability under light irradiation, and the photocatalytic performance of BiCuSeO can be further improved by band gap engineering with introduction of La. Our measurements and density-functional-theory calculations reveal that the effective mass and mobility of the carriers in BiCuSeO can be tuned by the La-doping, which are responsible for the tunable photocatalytic activity. Our findings may offer new perspectives for understanding the mechanism of photocatalysis through modulating the charge mobility and the effective mass of carriers and provide a guidance for designing efficient photocatalyts.

Co3(OH)2(HPO4)2 as a novel photocatalyst for O2 evolution under visible-light irradiation

Co₃(OH)₂(HPO₄)₂ was proved to be a novel visible-light-driven photocatalyst for O₂ evolution due to the unique characteristics of Co²⁺ octahedra.

Dramatic activities of vanadate intercalated bismuth doped LDH for solar light photocatalysis

To harvest solar energy efficiently, a series of Zn/Bi layered double hydroxide (LDH) photocatalysts with different molar ratios of Zn/Bi (2 : 1, 3 : 1, 4 : 1) has been synthesized by a coprecipitation method at constant pH. All the Bi doped LDH samples displayed hydrotalcite-like structure with interlayer carbonate, in which crystallinity decreases as the bismuth content increases. The Zn/Bi (4 : 1) LDH with a small amount of bismuth in the brucite layer and possessing high crystallinity was further modified hydrothermally by intercalating decavanadate and it showed high photochemical stability and photocatalytic activity for the degradation of different organic pollutants for practical applications under solar light irradiation. The structural integrity of the materials has been successfully characterized by studying their structural, morphological, electronic and optical properties by various physico-chemical techniques. The present study provided an insight into oxo-bridged MMCT of the LDH and established that the Zn(II)-O-Bi(III) units resulted in the generation of superoxide radicals which is clearly observed by the EPR technique. The ˙OH radicals formed during photocatalysis were revealed by means of the terephthalic acid fluorescence probe method. The photoelectrochemical measurement confirmed that the intercalated vanadate anion was crucial to obtain an optimal synergistic effect for the degradation of organic pollutants. The prolonged lifetime of photogenerated charges and improved charge transfer capability were confirmed by time-resolved fluorescence emission spectra. Furthermore, a detailed mechanism for the enhanced photocatalytic activity was discussed.

Ionic liquid-assisted fabrication of copper hydroxyphosphate nanocrystals with exposed {100} facets for enhanced photocatalytic activity

Libethenite Cu2PO4OH nanocrystals with different morphologies were prepared by an ionic liquid-assisted hydrothermal route, and were further investigated as photocatalysts under visible-light irradiation. The Cu2PO4OH elongated truncated bipyramids exposing {100} facets exhibit superior photocatalytic activity compared to other particles, which can be attributed to the presence of 100% Cu5c atoms on {100} facets. It is highly expect this research can provide a useful fundamental understanding of shape-dependent photocatalytic performance of copper hydroxyphosphate.

From UV to near-infrared, WS2 nanosheet: a novel photocatalyst for full solar light spectrum photodegradation

Narrow-bandgap semiconductor WS2 nanosheets are active photocatalysts, either under visible or under NIR irradiation. The photocatalyst functions are confirmed via photogeneration of an electron-hole pair, with a low rate of recombination.

The synergistic effect between effective mass and built-in electric field for the transfer of carriers in nonlinear optical materials

The transfer of carriers is promoted by the synergistic effect between effective masses and built-in electric field in K₃B₆O₁₀X (X = Br, Cl).

Vis/NIR light driven mild and clean synthesis of disulfides in the presence of Cu2(OH)PO4 under aerobic conditions

A highly efficient one-pot strategy has been developed for the synthesis of disulfide in the presence of air under the irradiation of Vis/NIR light.

N,F-monodoping and N/F-codoping effects on the electronic structures and optical performances of Zn2GeO4

With N/F codoping, the optical absorption property of Zn₂GeO₄was improved under visible-light irradiation, which may promote the photocatalytic activity.