Silver Peroxide Research Articles

Nanozyme-reinforced hydrogel coatings for prevention of catheter-associated urinary tract infection

Catheter-associated urinary tract infection (CAUTI) presents a significant clinical challenge globally, given its elevated infection risk, substantial treatment costs, and the emergence of drug-resistant strains. Despite extensive clinical endeavors, such as the development of antimicrobial catheters and prophylactic approaches, addressing CAUTI remains intricate due to the microenvironment complexity, sustained antimicrobial requirements, the necessity for antibiofilm strategies, and concurrent inflammatory responses. Herein, an innovative solution involving an ultra-low loading gold/iron co-doped silver peroxide nanozyme-reinforced hydrogel coating is introduced for the prevention of CAUTI. The silicone urinary catheter is modified through a straightforward and cost-effective chemical process to impart multienzyme-like activities, including peroxidase- and catalase-like functions, which exhibit antimicrobial, antibiofilm, and anti-inflammatory properties tailored to the unique urinary tract microenvironment. Additionally, the hydrogel coating enhances the hydrophilicity of catheter, thereby improving patient comfort. In vitro and in vivo experiments substantiate the efficacy of the modified catheter in inhibiting bacterial colonization, curtailing biofilm formation, enhancing oxygen supply, and modulating immune responses. This study not only proposes an alternative strategy for prevention and treatment of CAUTI but also provides a promising therapy that addresses multifaceted therapeutic needs through the utilization of multienzyme-like nanozymes.

In Situ Fabrication of Silver Peroxide Hybrid Ultrathin Co-Based Metal-Organic Frameworks for Enhanced Chemodynamic Antibacterial Therapy.

Bacterial-induced infectious diseases have always caused an unavoidable problem and lead to an increasing threat to human health. Hence, there is an urgent need for effective antibacterial strategies to treat infectious diseases. Current methods are often ineffective and require large amounts of hydrogen peroxide (H2O2), with harmful effects on normal healthy tissue. Chemodynamic therapy (CDT) provides an ideal infection microenvironment (IME)-activated paradigm to tackle bacterial-related diseases. To take full advantage of the specificity of IME and enhanced CDT for wounds with bacterial infection, we have designed an intelligent antibacterial system that exploits nanocatalytic ZIF-67@Ag2O2 nanosheets. In this system, silver peroxide nanoparticles (Ag2O2 NPs) were grown on ultrathin zeolitic imidazolate framework-67 (ZIF-67) nanosheets by in situ oxidation, and then, ZIF-67@Ag2O2 nanosheets with the ability to self-generate H2O2 were triggered by the mildly acidic environment of IME. Lamellar ZIF-67 nanosheets were shown to rapidly degrade and release Co2+, allowing the conversion of less reactive H2O2 into the highly toxic reactive oxygen species hydroxyl radicals (•OH) for enhanced CDT antibacterial properties. In vivo results revealed that the ZIF-67@Ag2O2 nanosheet system exhibits excellent antibacterial performance against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. The proposed hybrid strategy demonstrates a promising therapeutic strategy to enable antibacterial agents with IME-responsive nanocatalytic activity to circumvent antibiotic resistance against bacterial infections.

Oxidation and oriented attachment growth of colloidal nanoparticles during electrophoretic deposition

• The electrophoretic deposition can be a chemical oxidization and oriented attachment process. • The charge type of the Ag nanoparticles changes during electrophoretic deposition. • Ag 2 O 2 nanocubes are assembled from Ag 2 O 2 nanoparticles oxidized from Ag nanoparticles. Electrophoretic deposition (EPD) has been widely used to assemble nanoparticles into dense nanoparticle films. Here, we discovered that the EPD might be not necessarily the widely accepted physical pile-up process, but a chemical oxidization and oriented attachment growth process. During EPD of silver colloids prepared by laser ablation of a piece of silver plate in pure water without any chemicals introduced, we observed formation of sub-microscale well-defined silver peroxide (Ag 2 O 2 ) cuboids on the anode electrode surface. The Ag 2 O 2 nanoparticles were oxidized from the Ag nanoparticles during EPD. Fusion between neighbouring Ag 2 O 2 nanoparticles through oriented attachment and Ostwald ripening process rendered the formation of the Ag 2 O 2 cuboids. This study revealed a new growth mechanism during EPD, strengthening the capability of EPD during designing micro/nanostructures.

Serial transcriptional changes of Flammulina filiformis (winter mushroom) mycelia infected by Pseudomonas migulae

Flammulina filiformis, an industrially cultivated edible mushroom worldwide, suffers serious losses in yield and quality owing to bacterial diseases. Here, we reported the mycelial sluggish growth disease (MSGD), a new bacteriosis on F. filiformis. Pseudomonas migulae was identified as the pathogen by 16S rRNA gene phylogenetic analysis and morphologic observation. Hydrogen peroxide silver disinfectant (HPSD) was shown to effectively inhibit P. migulae and alleviate the disease symptoms at 10.00 g/L concentration. Furthermore, the molecular mechanism of F. filiformis in response to P. migulae infection was elucidated by transcriptome analysis. In the early infection stage, the infection signals are transducted into the mycelia, thus activating a series of stress defense responses, including peroxidase activity, antibiotic synthesis, and drug catabolism. In the middle and late infection stages, the apoptosis signal is transducted through the mitochondrial pathway, causing damage to DNA in the cell nucleus, resulting in DNA repair, gene silencing, and negative regulation of macromolecule synthesis. Finally, proteins and polysaccharides are strongly hydrolyzed to accelerate cell senescence, death, and mycelial growth retardation. These findings provide references for understanding the interaction mechanism between edible mushroom and pathogenic bacterium and for controlling mushroom bacterial diseases.

Colloidal Silver Hydrogen Peroxide: New Generation Molecule for Management of Phytopathogens

Plant pathogenic fungi and bacteria are a significant threat to global commercial crop production resulting in increased cost of production, reduced crop establishment and productivity. An effort was made to study the antimicrobial activity of silver hydrogen peroxide (SHP) against selected plant pathogenic fungi and bacteria under in vitro conditions. Higher antibacterial activity of SHP was observed against Xanthomonas axonopodis pv. citri (Xac; 39.67 mm), Xanthomonas citri pv. punicae (Xap; 39.00 mm), and Ralstonia solanacearum (Rs; 36.67 mm) at 500 ppm concentration. SHP was superior to streptocycline (500 ppm) against Xac (25.33 mm) and Xcp (22.67 mm) at 100 ppm. The soil-borne fungi viz., Pythium aphanidermatum and Fusarium solani failed to initiate mycelium growth on PDA at the concentration of 5000 ppm and above. The average size of SHP particles was 462 nm in diameter, and 73.40% of particles had the size of 378 nm, which reflects the particles present in SHP solution in the form of colloids. The effective doses (100–5000 ppm) did not show any phytotoxicity symptoms in plants, while leaf necrosis was noticed at 10,000 ppm after four days of application. SHP (≤5000 ppm) can be used to effectively manage both fungal and bacterial plant pathogens by a single application. Further field studies need to be conducted for validation and commercial use of SHP.

Silver Peroxide Nanoparticles for Combined Antibacterial Sonodynamic and Photothermal Therapy.

Metal peroxide nanoparticles designed to elevate the oxidative stress are considered a promising nanotherapeutics in biomedical applications, including chemotherapy, photodynamic therapy, and bacterial disinfection. However, their lack of specificity towards the therapeutic target can cause toxic side effects to healthy tissues. Here, silver peroxide nanoparticles (Ag2 O2 NPs) capable of controlled reactive oxygen species (ROS) release are synthesized. The release of bactericidal Ag+ ions and ROS is strictly regulated by external stimuli of ultrasound (US) and near-infrared (NIR) light. In vitro and in vivo investigations show that the Ag2 O2 NPs present enhanced antibacterial and antibiofilm capabilities with a killing efficiency >99.9999% in 10min, significantly accelerate multi-drug resistant Staphylococcus aureus infected skin wound closure with excellent cytocompatibility and hemocompatibility. This work not only provides the first paradigm for fabricating silver peroxide nanoparticle but also introduces a highly efficient noninvasive and safe therapeutic modality for combating bacterial infectious diseases.

Unique electrochemical behavior of a silver–zinc secondary battery at high rates and low temperatures

This study investigates an unusual charging phenomenon observed in silver–zinc secondary batteries. In the case of general secondary batteries, the specific capacity and coulombic efficiency decrease with increasing battery charging rate because of a concomitant increase in overvoltage. However, this study reveals that, at room temperature and within a specific charging-rate range, the discharge capacity and coulombic efficiency of silver–zinc batteries increase with increasing charging rate. To elucidate this unusual behavior, the charge/discharge characteristics of silver–zinc batteries were systematically analyzed at different charging rates and operating temperatures. In addition, the structural and compositional evolution of the silver cathode with the state of charge of the battery were investigated. The experimental results demonstrated that the phase transformation kinetics of silver oxide to silver peroxide governs the electrochemical performance of silver–zinc batteries and the kinetically unfavorable formation of silver peroxide ironically enables fast-chargeable silver–zinc batteries with high capacity and efficiency. Furthermore, it was confirmed that the suppression of water hydrolysis at low temperatures promotes the silver peroxide formation, resulting in high capacity during low temperature operation. This study provides an effective charge strategy, which could help achieve high-capacity, high-efficiency silver–zinc secondary batteries.

Biological Characterization and Antagonist Screening of Cladosporium anthropophilum, a Novel Pathogen Causing Stipe Black Rot on Commercial Medicinal Mushroom, Flammulina filiformis (Agaricomycetes).

We report a new fungal disease, named stipe black rot, in a cultivation factory of Flammulina filiformis (an edible mushroom cultivated worldwide) in China. The pathogen was identified as Cladosporium anthropophilum by phylogenetic analysis and morphology characterization. C. anthropophilum was characterized to mainly infect the stipe bottom and cause stipe blackening and rot, with its optimal mycelial growth conditions consisting of 25°C, pH 7, and carbon and nitrogen sources of soluble starch and sodium nitrate, respectively. Furthermore, inhibitory evaluation showed that hydrogen peroxide silver disinfectant (HPSD) can efficiently inhibit the mycelial growth of C. anthropophilum, followed by the aqueous extracts of garlic and onion. This study identified C. anthropophilum as the pathogen for the new F. filiformis black rot disease and HPSD as an effective antagonist against the pathogen, which facilitates the understanding of fungal diseases and their control in edible mushrooms.

Marine Actinomycetes Derived Pyrrolo Compounds Mediated Green Synthesis of AgO and Ag2O3 Nanoparticles and its Antidermatophytic Activity

Background: Antimicrobial potential of silver nanoparticles synthesised by using various biological sources was already been reported by many researchers. The green synthesis of silver nanoparticles using microbial sources has been proved to be more effective. Methods: In this study, anti-dermatophytic silver nanoparticles were synthesised by using pyrrolo metabolites producing actinomycetes as a green catalyst. Different characterization methods such as UV-Visible, XRD, and AFM were used to identify the physiochemical characteristics of synthesised nanoparticles. Results: The synthesised nanoparticles showed λ-max at 427 nm and 402 nm, respectively. The XRD analysis based on the JCPDS database identified the two synthesized nanoparticles as silver oxide nanoparticles (AgO NPs) and silver peroxide nanoparticles (Ag2O3 NPs). The size of these nanoparticles was found to be in the range of 40-44 nm (AgO NPs) and 23-25 nm (Ag2O3 NPs), respectively. The synthesized nanoparticles demonstrated significant anti-fungal activity against dermatophytic fungi Trichophyton mentagrophyes with the zone of inhibition of 38 mm by AgO NP and 17 mm by Ag2O3 NPs. Conclusion: Screening of marine actinomycetes LG003 and LG005 revealed the presence of pyrrolo derivatives as the major metabolites, suggesting that these pyrrolo derivatives could be responsible for synthesis and stabilization of AgO and Ag2O3NPs. Among the synthesized NPs, the AgO NPs showed great potential as an anti-dermatophytic agent. This study provides further research opportunities for AgONPs as anti-fungal agents.

Fabrication of Silver Peroxide– Zinc Rechargeable Battery

Electrochemical energy sources especially rechargeable batteries hold a great promise for meeting the ever-growing demand for energy. Though lead acid and lithium ion batteries have been highly successful commercially, the safety issues in using them have led to the development of alternate rechargeable systems. In this regard, silver peroxide-zinc rechargeable batteries are of great importance especially as energy sources for biomedical devices as they can be tuned to obtain low power discharge over prolonged time duration. This study focuses on the electrochemical synthesis of silver peroxide on silver electrodes and its use as the cathode for rechargeable battery. Synthesis parameters were optimized for the formation of silver peroxide and the oxide thus formed was characterized using XRD, EDS, IR spectroscopy, FESEM and AFM. Two different prototypes of batteries (two compartment and pouch model) were fabricated using zinc as the anode and silver peroxide as cathode. The prototypes were able to provide potential of 1.5 V with a power rating of 150 µW and 3.3 µW for the two compartments and pouch model respectively. Both the models were rechargeable and are having low internal resistance

Legionella Survey in the Plumbing System of a Sparse Academic Campus: A Case Study at the University of Perugia

We have monitored the presence of bacteria belonging to the genus Legionella in the plumbing of buildings at the University of Perugia (Italy). More than 300 water samples were collected from 156 control-point taps in 41 buildings comprised in the eight campuses of the University. Legionella was absent in most samples, while it was found in only 12 buildings (29% of the total). Molecular analysis indicated the presence of L. pneumophila (serogroups 1, 8 and 6–10), L. taurinensis and L. anisa. In only three cases contamination levels were above the limit at which remedial actions are required, according to international guidelines. In two buildings, where the water temperature could be raised and maintained above 60 °C, thermal disinfection was effective in eradicating Legionella. Conversely, in buildings where contaminations were caused by heat exchangers that produced hot water at a maximum temperature of 50 °C, a chemical disinfection with silver hydrogen peroxide was carried out but was effective only in the short term. In this case study, Legionella contaminations and remediation effectiveness strongly depended on the network and heating-system characteristics, indicating how a multidisciplinary approach that integrates microbiological analysis with hydraulic surveys is necessary for an effective definition of Legionella prevention and control strategies.

Can 2% Hydrogen Peroxide-Silver be an Effective Natural Disinfectant in the Dental Office?

Background and aim: Dentists and healthcare workers are commonly in contact with microorganisms present in blood and saliva which may potentially transfer infectious diseases. Use of methods to remove and or decrease the number of contaminants on instruments and tabletops are of paramount importance. Important properties of a good disinfectant aside from the ability to kill microbes include being safe, noncorrosive or damaging to instruments, odorless, colorless, economical and eco-friendly. This study was done to assess effectiveness and longevity of 2% hydrogen peroxide-silver for disinfection. Materials and methods: Using sterilized physiological serum a spore suspension of Bacillus subtilis of 1×10 cfu/ ml was prepared on McFarland standard media. A sterilized capped tube was used for preparation of the suspension; 2 ml of a newly opened bottle of 2% hydrogen peroxide silver was poured in the test tube using a sterilized pipette and the tube was recapped. Then, 1 ml of the spore suspension was added to the test tube (test group).On the first day eight cultures were taken (at 30’, 60’, 120’, 180’, 240’, 300’, 360’ and 420’) and repeated twice each time. Also the same number of cultures was taken from the suspension at all the aforementioned time points without addition of hydrogen peroxide silver (control group). Then the samples were transferred to the culture medium after the required time points elapsed. All cultures were placed in the incubator for 24 hours at 37°C and assessed for growth. This procedure was the repeated using the same batch of 2%hydrogen peroxide silver until it was no longer effective on the organism. Results: The batch of 2% hydrogen peroxide silver re-opened daily was effective on Bacillus subtilis up to 4 days of repeated daily use after contact for 180 min. There was no effect on day 4. All controls showed viability and growth of Bacillus subtilis. Conclusion: Instruments should be soaked in 2% hydrogen peroxide –silver for at least 3 hours before being sterilized in an autoclave; 2% hydrogen peroxide silver will not disinfect after 3 days of use. A fresh bottle should be used daily for greater guarantee of disinfection.

In vitro activity of antimicrobial agents against Pseudomonas tolaasii, pathogen of cultivated button mushroom

In vitro antibacterial activity tests of seven biofungicides (Ekstrasol, Bisolbisan, Bisolbifit, Serenade, Sonata, Timorex, F-Stop) and two disinfectants (colloidal silver alone and in combination with hydrogen peroxide) against the Pseudomonas tolaasii strain (NS3B6) were carried out by the disc-diffusion, broth microdilution and broth macrodilution method. Biofungicides tested in this study did not exhibit any antimicrobial activity in neither one of the methods used. Disc diffusion method revealed high sensitivity of the tested P. tolaasii strain to Ecocute based on colloidal silver and hydrogen peroxide. Both microdilution and macrodilution methods identified the same MICs and MBCs of Ecocute (0.19 mg/L) for P. tolaasii strain. MICs and MBCs values of silver alone were much higher (10 mg/L) compared to silver in combination with hydrogen peroxide.

Preparation of Silver Nano-Particles by CO(NH<sub>2</sub>)<sub>2</sub>·H<sub>2</sub>O<sub>2</sub>

This article will present using chemical reduction to prepare silver nano-particles, which is a certain improvement base on the traditional hydrogen peroxide (H2O2) Silver ammonia by using a new reductant urea peroxide (CO (NH2) 2•H2O2) to replace hydrogen peroxide. Hydrogen Peroxide silver ammonia is widely used in the nano-silver particles Preparation, however, the nano-silver particles prepared in traditional ways is not homogeneous and very easy agglomerated, therefore, in this experimental by using of urea peroxide as a reductant, under condition of temperature 30°C, 45 nm homogeneous nano-silver particles is successfully prepared. The detection instrument used in the experimental is transmission electron microscopy and laser particle size analyzer.

Efficacy of Colloidal Silver-Hydrogen Peroxide and 2-Bromo-2-nitroporopane-1,3-diol Compounds Against Different Serogroups of Legionella pneumophila Strains

Cooling towers are considered as amplifier and disseminator sources for Legionella spp. despite preventive treatments. Information which was obtained from biocidal tests could improve the effectiveness of treatments. Therefore, the choice of appropriate biocides and the applying of biocides in correct dosages and contact times are important. Various oxidizing and non-oxidizing biocides have been investigated in vitro for their effectiveness against legionellae. Colloidal silver-hydrogen peroxide (CSHP) and 2-bromo-2-nitroporopane-1,3-diol (BNPD) biocides were selected as an example for oxidizing and non-oxidizing agents, respectively, in view of bactericidal action against different serogroups of L. pneumophila strains [serogroup 1 (S1) and serogroup 2-14 (S2)] which are isolated different cooling towers in the vicinity of Istanbul, Turkey and reference strain. In the current study, oxidizing biocide was found more effective than non-oxidizing biocide in terms of contact times, log reductions and recommended dosages. At the recommended concentrations for cooling towers (100ppm), while CSHP compound killed all strains in 3h contact time, BNPD compound killed S2 and reference strain in the same contact time, S1 strain after 6h contact time. The results of the present study showed that effective biocide applications can be achieved by pre-determining minimum inhibitory concentration (MIC) and minimum contact time of different biocides to kill target bacteria.

Silver(II) Oxide or Silver(I,III) Oxide?

The often called silver peroxide and silver(II) oxide, AgO or Ag2O2, is actually a mixed oxidation state silver(I,III) oxide. A thermochemical cycle, with lattice energies calculated within the volume-based thermodynamic approach, explain why the silver(I,III) oxide is more stable than the hypothetical silver(II) oxide. The coordination geometries of silver and copper in their known oxides correlate with those associated to their electron configurations in coordination compounds. The second ionization energy is higher for Ag than for Cu, which can be related to the small size of 3d orbitals and the resulting high electron repulsion for the first transition series elements.

Study on Improving Stainless Steel Antibacterial Capability

A new method was studied for improving stainless steel antibacterial capability. The Na2FeO4 coating was prepared on steel surface throughout NaOH treatment, then steel samples were immersed into the solution coantaining Ag+, Zn2+ and TiO2. The antibacterial-ions were fixated firmly on the stainless steel with chemical bond. Scanning electronic microscopy(SEM), X-ray(XRD) and atomic absoption spectroscopy(AAS) were employed to analyze the materials, and the results showed that the antibacterial membrane included silver citrate and silver peroxide. Quinn test was also carried out, in which Staphylococus and E.coli. the results showed that the steel has a bacteriostasis rate of 99.48% to Staphylococus, and 99.09% to E.coli.

Environmentally friendly disinfectant: Production, disinfectant action and efficiency

Silver is a known disinfectant from ancient times, and it has been widely used for various purposes: for food and water disinfection, curing of wounds and as a universal antibiotic for a wide spectrum of diseases - until the Second World War and the discovery of penicillin. Until recently, it was assumed that silver, being a heavy metal, was toxic for humans and living beings. However, the newest research provides facts that the usage of silver, even for drinking water disinfection, is benign if it is added in small concentrations (in parts per billion). It has been shown in the newer scientific and technical literature that silver in colloidal form is a powerful (secondary) disinfectant for drinking water, that it can be effectively used for the disinfection of water containers including swimming pools, installations in food industry, medicine, etc. Particularly, it has been shown that colloidal silver combined with hydrogen peroxide shows synergism having strong bactericidal and antiviral effects. The combination can be successfully used as a disinfectant in agriculture, food production and medicine. The original electrochemical process of production, the mechanism of physical-chemical reactions in that process and the mechanism of the antiseptic affect of the environmentally friendly disinfectant, based on the synergism of colloidal silver and hydrogen peroxide and the activity of electrochemically activated water, is shown. The starting solution was anolyte, obtained in electrochemical activation by water electrolysis of a highly diluted solution of K-tartarate in demineralized water (5.5-1CT4 M). The problem of electrolysis of very dilute aqueous solutions in membrane cells was particularly treated. It was shown that the efficiency of the electrolysis depends on the competition between the two processes: the rates of the processes of hydrogen and oxygen generation at the electrodes and the process of diffusion of hydrogen and hydroxyl ions through the cell membrane. Relatively strong disinfectant and sterilization action on standard races of gram-positive and gram-negative bacteria, blast spores and spores, as well as the safety of implementation of an environmentally friendly disinfectant was certified in a relevant institution, the Military Academy of Medicine in Belgrade.

The interaction of silver ions and hydrogen peroxide in the inactivation of E. coli: A preliminary evaluation of a new long acting residual drinking water disinfectant

The inactivation efficiencies of silver ions, hydrogen peroxide and their combination was studied as part of a performance evaluation of the combined disinfectant for drinking water applications. The major advantages of such combined disinfectant include, low toxicity of its components, long lasting residual effect and low disinfection by product formation. Specific strains of E. coli (E. coli-B (SR-9) and E. coli K-12) were used in this study as target microorganisms and the separate and combined inactivation efficiencies of silver and hydrogen peroxide were evaluated at different concentrations and exposure durations. Both, silver and hydrogen peroxide exhibited a significant inactivation performance even at concentrations that do not pose any health risk according to the EEC, WHO and the USEPA (the USEPA Maximum Contaminant Level (MCL) of silver is 90 ppb, and currently, there is no MCL for hydrogen peroxide but it is approved as a food additive in the USA). Combinations of 1:1000 silverhydrogen peroxide (w) exhibited higher inactivation performance as compared with each of the disinfectants alone and in some cases a synergistic effect was observed, i.e., the combined disinfectant exhibited higher inactivation performance than the sum of the inactivation levels of the separate disinfectants. Thus, for example, one hour exposure to 30 ppb silver, 30 ppm hydrogen peroxide and their combination yielded 2.87, 0.65 and 5 logs of inactivation respectively. While the rate of inactivation shown by this combined disinfectant, now available commercially in a stabilized formulation is relatively slow, it may well hold promise as a secondary disinfectant providing long lasting residuals and biofilm control required for distribution systems. Its disinfection action may be similar to chloramines, the use of which has been recently outlawed in France and in Germany and which are now under careful scrutiny in other countries due to the formation of undesirable by-products.

Some optical properties of silver peroxide (AgO) and silver oxide (Ag2O) films produced by chemical-bath deposition

Thin films of silver peroxide and silver oxide have been prepared by the chemical-bath-deposition technique. Peroxide of silver was deposited as thin films on glass substrates from a solution obtained by dissolving bulk silver hydroxide in triethanolamine. Annealing of these films in air above 125°C yielded oxide films. Transmittance and reflectance data have been used to calculate the spectral variation of their optical constants. Thickness of the films varied between 0.05 and 0.1 μm. Electrical conductivity measurements show that both films are insulating. Breakdown voltages of about 625 V/mm and 500 V/mm have been obtained for AgO and Ag2O, respectively, on placing silver print electrodes on the films at various spacings. In their conducting state they have resistivities of the order of 50.0 Ω m. Ag2O films have a band gap of 2.25 eV, while AgO films transmit in the UV and visible regions.